neovim

fold.c (101436B)

---

// vim: set fdm=marker fdl=1 fdc=3

// fold.c: code for folding

#include <assert.h>
#include <inttypes.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "klib/kvec.h"
#include "nvim/api/extmark.h"
#include "nvim/api/private/defs.h"
#include "nvim/api/private/helpers.h"
#include "nvim/ascii_defs.h"
#include "nvim/buffer_defs.h"
#include "nvim/buffer_updates.h"
#include "nvim/change.h"
#include "nvim/charset.h"
#include "nvim/cursor.h"
#include "nvim/decoration.h"
#include "nvim/diff.h"
#include "nvim/drawscreen.h"
#include "nvim/errors.h"
#include "nvim/eval.h"
#include "nvim/eval/typval.h"
#include "nvim/eval/vars.h"
#include "nvim/ex_session.h"
#include "nvim/extmark.h"
#include "nvim/extmark_defs.h"
#include "nvim/fold.h"
#include "nvim/garray.h"
#include "nvim/garray_defs.h"
#include "nvim/gettext_defs.h"
#include "nvim/globals.h"
#include "nvim/indent.h"
#include "nvim/mark.h"
#include "nvim/mark_defs.h"
#include "nvim/mbyte.h"
#include "nvim/memline.h"
#include "nvim/memory.h"
#include "nvim/message.h"
#include "nvim/move.h"
#include "nvim/ops.h"
#include "nvim/option_defs.h"
#include "nvim/option_vars.h"
#include "nvim/os/input.h"
#include "nvim/plines.h"
#include "nvim/pos_defs.h"
#include "nvim/search.h"
#include "nvim/state_defs.h"
#include "nvim/strings.h"
#include "nvim/syntax.h"
#include "nvim/types_defs.h"
#include "nvim/undo.h"
#include "nvim/vim_defs.h"

// local declarations. {{{1
// typedef fold_T {{{2

// The toplevel folds for each window are stored in the w_folds growarray.
// Each toplevel fold can contain an array of second level folds in the
// fd_nested growarray.
// The info stored in both growarrays is the same: An array of fold_T.

typedef struct {
 linenr_T fd_top;              // first line of fold; for nested fold
                               // relative to parent
 linenr_T fd_len;              // number of lines in the fold
 garray_T fd_nested;           // array of nested folds
 char fd_flags;                // see below
 TriState fd_small;            // kTrue, kFalse, or kNone: fold smaller than
                               // 'foldminlines'; kNone applies to nested
                               // folds too
} fold_T;

enum {
 FD_OPEN = 0,    // fold is open (nested ones can be closed)
 FD_CLOSED = 1,  // fold is closed
 FD_LEVEL = 2,   // depends on 'foldlevel' (nested folds too)
};

#define MAX_LEVEL       20      // maximum fold depth

// Define "fline_T", passed to get fold level for a line. {{{2
typedef struct {
 win_T *wp;              // window
 linenr_T lnum;                // current line number
 linenr_T off;                 // offset between lnum and real line number
 linenr_T lnum_save;           // line nr used by foldUpdateIEMSRecurse()
 int lvl;                      // current level (-1 for undefined)
 int lvl_next;                 // level used for next line
 int start;                    // number of folds that are forced to start at
                               // this line.
 int end;                      // level of fold that is forced to end below
                               // this line
 int had_end;                  // level of fold that is forced to end above
                               // this line (copy of "end" of prev. line)
} fline_T;

// Flag is set when redrawing is needed.
static bool fold_changed;

// Function used by foldUpdateIEMSRecurse
typedef void (*LevelGetter)(fline_T *);

// static functions {{{2

#include "fold.c.generated.h"
static const char *e_nofold = N_("E490: No fold found");

// While updating the folds lines between invalid_top and invalid_bot have an
// undefined fold level.  Only used for the window currently being updated.
static linenr_T invalid_top = 0;
static linenr_T invalid_bot = 0;

// When using 'foldexpr' we sometimes get the level of the next line, which
// calls foldlevel() to get the level of the current line, which hasn't been
// stored yet.  To get around this chicken-egg problem the level of the
// previous line is stored here when available.  prev_lnum is zero when the
// level is not available.
static linenr_T prev_lnum = 0;
static int prev_lnum_lvl = -1;

// Flags used for "done" argument of setManualFold.
#define DONE_NOTHING    0
#define DONE_ACTION     1       // did close or open a fold
#define DONE_FOLD       2       // did find a fold

static size_t foldstartmarkerlen;
static char *foldendmarker;
static size_t foldendmarkerlen;

// Exported folding functions. {{{1
// copyFoldingState() {{{2
/// Copy that folding state from window "wp_from" to window "wp_to".
void copyFoldingState(win_T *wp_from, win_T *wp_to)
{
 wp_to->w_fold_manual = wp_from->w_fold_manual;
 wp_to->w_foldinvalid = wp_from->w_foldinvalid;
 cloneFoldGrowArray(&wp_from->w_folds, &wp_to->w_folds);
}

// hasAnyFolding() {{{2
/// @return  true if there may be folded lines in window "win".
int hasAnyFolding(win_T *win)
{
 // very simple now, but can become more complex later
 return !win->w_buffer->terminal && win->w_p_fen
        && (!foldmethodIsManual(win) || !GA_EMPTY(&win->w_folds));
}

// hasFolding() {{{2
/// When returning true, *firstp and *lastp are set to the first and last
/// lnum of the sequence of folded lines (skipped when NULL).
///
/// @return  true if line "lnum" in window "win" is part of a closed fold.
bool hasFolding(win_T *win, linenr_T lnum, linenr_T *firstp, linenr_T *lastp)
{
 return hasFoldingWin(win, lnum, firstp, lastp, true, NULL);
}

// hasFoldingWin() {{{2
/// Search folds starting at lnum
/// @param lnum first line to search
/// @param[out] first first line of fold containing lnum
/// @param[out] lastp last line with a fold
/// @param cache when true: use cached values of window
/// @param[out] infop where to store fold info
///
/// @return true if range contains folds
bool hasFoldingWin(win_T *const win, const linenr_T lnum, linenr_T *const firstp,
                  linenr_T *const lastp, const bool cache, foldinfo_T *const infop)
{
 checkupdate(win);

 // Return quickly when there is no folding at all in this window.
 if (!hasAnyFolding(win)) {
   if (infop != NULL) {
     infop->fi_level = 0;
   }
   return false;
 }

 bool had_folded = false;
 linenr_T first = 0;
 linenr_T last = 0;

 if (cache) {
   // First look in cached info for displayed lines.  This is probably
   // the fastest, but it can only be used if the entry is still valid.
   const int x = find_wl_entry(win, lnum);
   if (x >= 0) {
     first = win->w_lines[x].wl_lnum;
     last = win->w_lines[x].wl_foldend;
     had_folded = win->w_lines[x].wl_folded;
   }
 }

 linenr_T lnum_rel = lnum;
 int level = 0;
 int low_level = 0;
 fold_T *fp;
 bool maybe_small = false;
 bool use_level = false;

 if (first == 0) {
   // Recursively search for a fold that contains "lnum".
   garray_T *gap = &win->w_folds;
   while (true) {
     if (!foldFind(gap, lnum_rel, &fp)) {
       break;
     }

     // Remember lowest level of fold that starts in "lnum".
     if (lnum_rel == fp->fd_top && low_level == 0) {
       low_level = level + 1;
     }

     first += fp->fd_top;
     last += fp->fd_top;

     // is this fold closed?
     had_folded = check_closed(win, fp, &use_level, level,
                               &maybe_small, lnum - lnum_rel);
     if (had_folded) {
       // Fold closed: Set last and quit loop.
       last += fp->fd_len - 1;
       break;
     }

     // Fold found, but it's open: Check nested folds.  Line number is
     // relative to containing fold.
     gap = &fp->fd_nested;
     lnum_rel -= fp->fd_top;
     level++;
   }
 }

 if (!had_folded) {
   if (infop != NULL) {
     infop->fi_level = level;
     infop->fi_lnum = lnum - lnum_rel;
     infop->fi_low_level = low_level == 0 ? level : low_level;
   }
   return false;
 }

 last = MIN(last, win->w_buffer->b_ml.ml_line_count);
 if (lastp != NULL) {
   *lastp = last;
 }
 if (firstp != NULL) {
   *firstp = first;
 }
 if (infop != NULL) {
   infop->fi_level = level + 1;
   infop->fi_lnum = first;
   infop->fi_low_level = low_level == 0 ? level + 1 : low_level;
 }
 return true;
}

// foldLevel() {{{2
/// @return  fold level at line number "lnum" in the current window.
static int foldLevel(linenr_T lnum)
{
 // While updating the folds lines between invalid_top and invalid_bot have
 // an undefined fold level.  Otherwise update the folds first.
 if (invalid_top == 0) {
   checkupdate(curwin);
 } else if (lnum == prev_lnum && prev_lnum_lvl >= 0) {
   return prev_lnum_lvl;
 } else if (lnum >= invalid_top && lnum <= invalid_bot) {
   return -1;
 }

 // Return quickly when there is no folding at all in this window.
 if (!hasAnyFolding(curwin)) {
   return 0;
 }

 return foldLevelWin(curwin, lnum);
}

// lineFolded() {{{2
/// Low level function to check if a line is folded.  Doesn't use any caching.
///
/// @return  true if line is folded or,
///          false if line is not folded.
bool lineFolded(win_T *const win, const linenr_T lnum)
{
 return fold_info(win, lnum).fi_lines != 0;
}

// fold_info() {{{2
///
/// Count the number of lines that are folded at line number "lnum".
/// Normally "lnum" is the first line of a possible fold, and the returned
/// number is the number of lines in the fold.
/// Doesn't use caching from the displayed window.
///
/// @return with the fold level info.
///         fi_lines = number of folded lines from "lnum",
///                    or 0 if line is not folded.
foldinfo_T fold_info(win_T *win, linenr_T lnum)
{
 foldinfo_T info;
 linenr_T last;

 if (hasFoldingWin(win, lnum, NULL, &last, false, &info)) {
   info.fi_lines = (last - lnum + 1);
 } else {
   info.fi_lines = 0;
 }

 return info;
}

// foldmethodIsManual() {{{2
/// @return  true if 'foldmethod' is "manual"
bool foldmethodIsManual(win_T *wp)
{
 return (wp->w_p_fdm[0] != NUL && wp->w_p_fdm[3] == 'u');
}

// foldmethodIsIndent() {{{2
/// @return  true if 'foldmethod' is "indent"
bool foldmethodIsIndent(win_T *wp)
{
 return wp->w_p_fdm[0] == 'i';
}

// foldmethodIsExpr() {{{2
/// @return  true if 'foldmethod' is "expr"
bool foldmethodIsExpr(win_T *wp)
{
 return (wp->w_p_fdm[0] != NUL && wp->w_p_fdm[1] == 'x');
}

// foldmethodIsMarker() {{{2
/// @return  true if 'foldmethod' is "marker"
bool foldmethodIsMarker(win_T *wp)
{
 return (wp->w_p_fdm[0] != NUL && wp->w_p_fdm[2] == 'r');
}

// foldmethodIsSyntax() {{{2
/// @return  true if 'foldmethod' is "syntax"
bool foldmethodIsSyntax(win_T *wp)
{
 return wp->w_p_fdm[0] == 's';
}

// foldmethodIsDiff() {{{2
/// @return  true if 'foldmethod' is "diff"
bool foldmethodIsDiff(win_T *wp)
{
 return wp->w_p_fdm[0] == 'd';
}

// closeFold() {{{2
/// Close fold for current window at position "pos".
/// Repeat "count" times.
void closeFold(pos_T pos, int count)
{
 setFoldRepeat(pos, count, false);
}

// closeFoldRecurse() {{{2
/// Close fold for current window at position `pos` recursively.
void closeFoldRecurse(pos_T pos)
{
 setManualFold(pos, false, true, NULL);
}

// opFoldRange() {{{2
///
/// Open or Close folds for current window in lines "first" to "last".
/// Used for "zo", "zO", "zc" and "zC" in Visual mode.
///
/// @param opening     true to open, false to close
/// @param recurse     true to do it recursively
/// @param had_visual  true when Visual selection used
void opFoldRange(pos_T firstpos, pos_T lastpos, int opening, int recurse, bool had_visual)
{
 int done = DONE_NOTHING;              // avoid error messages
 linenr_T first = firstpos.lnum;
 linenr_T last = lastpos.lnum;
 linenr_T lnum_next;

 for (linenr_T lnum = first; lnum <= last; lnum = lnum_next + 1) {
   pos_T temp = { lnum, 0, 0 };
   lnum_next = lnum;
   // Opening one level only: next fold to open is after the one going to
   // be opened.
   if (opening && !recurse) {
     hasFolding(curwin, lnum, NULL, &lnum_next);
   }
   setManualFold(temp, opening, recurse, &done);
   // Closing one level only: next line to close a fold is after just
   // closed fold.
   if (!opening && !recurse) {
     hasFolding(curwin, lnum, NULL, &lnum_next);
   }
 }
 if (done == DONE_NOTHING) {
   emsg(_(e_nofold));
 }
 // Force a redraw to remove the Visual highlighting.
 if (had_visual) {
   redraw_curbuf_later(UPD_INVERTED);
 }
}

// openFold() {{{2
/// Open fold for current window at position "pos".
/// Repeat "count" times.
void openFold(pos_T pos, int count)
{
 setFoldRepeat(pos, count, true);
}

// openFoldRecurse() {{{2
/// Open fold for current window at position `pos` recursively.
void openFoldRecurse(pos_T pos)
{
 setManualFold(pos, true, true, NULL);
}

// foldOpenCursor() {{{2
/// Open folds until the cursor line is not in a closed fold.
void foldOpenCursor(void)
{
 checkupdate(curwin);
 if (hasAnyFolding(curwin)) {
   while (true) {
     int done = DONE_NOTHING;
     setManualFold(curwin->w_cursor, true, false, &done);
     if (!(done & DONE_ACTION)) {
       break;
     }
   }
 }
}

// newFoldLevel() {{{2
/// Set new foldlevel for current window.
void newFoldLevel(void)
{
 newFoldLevelWin(curwin);

 if (foldmethodIsDiff(curwin) && curwin->w_p_scb) {
   // Set the same foldlevel in other windows in diff mode.
   FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
     if (wp != curwin && foldmethodIsDiff(wp) && wp->w_p_scb) {
       wp->w_p_fdl = curwin->w_p_fdl;
       newFoldLevelWin(wp);
     }
   }
 }
}

static void newFoldLevelWin(win_T *wp)
{
 checkupdate(wp);
 if (wp->w_fold_manual) {
   // Set all flags for the first level of folds to FD_LEVEL.  Following
   // manual open/close will then change the flags to FD_OPEN or
   // FD_CLOSED for those folds that don't use 'foldlevel'.
   fold_T *fp = (fold_T *)wp->w_folds.ga_data;
   for (int i = 0; i < wp->w_folds.ga_len; i++) {
     fp[i].fd_flags = FD_LEVEL;
   }
   wp->w_fold_manual = false;
 }
 changed_window_setting(wp);
}

// foldCheckClose() {{{2
/// Apply 'foldlevel' to all folds that don't contain the cursor.
void foldCheckClose(void)
{
 if (*p_fcl == NUL) {
   return;
 }

 // 'foldclose' can only be "all" right now
 checkupdate(curwin);
 if (checkCloseRec(&curwin->w_folds, curwin->w_cursor.lnum,
                   (int)curwin->w_p_fdl)) {
   changed_window_setting(curwin);
 }
}

// checkCloseRec() {{{2
static bool checkCloseRec(garray_T *gap, linenr_T lnum, int level)
{
 bool retval = false;

 fold_T *fp = (fold_T *)gap->ga_data;
 for (int i = 0; i < gap->ga_len; i++) {
   // Only manually opened folds may need to be closed.
   if (fp[i].fd_flags == FD_OPEN) {
     if (level <= 0 && (lnum < fp[i].fd_top
                        || lnum >= fp[i].fd_top + fp[i].fd_len)) {
       fp[i].fd_flags = FD_LEVEL;
       retval = true;
     } else {
       retval |= checkCloseRec(&fp[i].fd_nested, lnum - fp[i].fd_top,
                               level - 1);
     }
   }
 }
 return retval;
}

// foldManualAllowed() {{{2
/// @return  true if it's allowed to manually create or delete a fold or,
///          give an error message and return false if not.
int foldManualAllowed(bool create)
{
 if (foldmethodIsManual(curwin) || foldmethodIsMarker(curwin)) {
   return true;
 }
 if (create) {
   emsg(_("E350: Cannot create fold with current 'foldmethod'"));
 } else {
   emsg(_("E351: Cannot delete fold with current 'foldmethod'"));
 }
 return false;
}

// foldCreate() {{{2
/// Create a fold from line "start" to line "end" (inclusive) in the current
/// window.
void foldCreate(win_T *wp, pos_T start, pos_T end)
{
 bool use_level = false;
 bool closed = false;
 int level = 0;
 pos_T start_rel = start;
 pos_T end_rel = end;

 if (start.lnum > end.lnum) {
   // reverse the range
   end = start_rel;
   start = end_rel;
   start_rel = start;
   end_rel = end;
 }

 // When 'foldmethod' is "marker" add markers, which creates the folds.
 if (foldmethodIsMarker(wp)) {
   foldCreateMarkers(wp, start, end);
   return;
 }

 checkupdate(wp);

 int i;

 // Find the place to insert the new fold
 garray_T *gap = &wp->w_folds;
 if (gap->ga_len == 0) {
   i = 0;
 } else {
   fold_T *fp;
   while (true) {
     if (!foldFind(gap, start_rel.lnum, &fp)) {
       break;
     }
     if (fp->fd_top + fp->fd_len > end_rel.lnum) {
       // New fold is completely inside this fold: Go one level deeper.
       gap = &fp->fd_nested;
       start_rel.lnum -= fp->fd_top;
       end_rel.lnum -= fp->fd_top;
       if (use_level || fp->fd_flags == FD_LEVEL) {
         use_level = true;
         if (level >= wp->w_p_fdl) {
           closed = true;
         }
       } else if (fp->fd_flags == FD_CLOSED) {
         closed = true;
       }
       level++;
     } else {
       // This fold and new fold overlap: Insert here and move some folds
       // inside the new fold.
       break;
     }
   }
   if (gap->ga_len == 0) {
     i = 0;
   } else {
     i = (int)(fp - (fold_T *)gap->ga_data);
   }
 }

 ga_grow(gap, 1);
 {
   fold_T *fp = (fold_T *)gap->ga_data + i;
   garray_T fold_ga;
   ga_init(&fold_ga, (int)sizeof(fold_T), 10);

   // Count number of folds that will be contained in the new fold.
   int cont;
   for (cont = 0; i + cont < gap->ga_len; cont++) {
     if (fp[cont].fd_top > end_rel.lnum) {
       break;
     }
   }
   if (cont > 0) {
     ga_grow(&fold_ga, cont);
     // If the first fold starts before the new fold, let the new fold
     // start there.  Otherwise the existing fold would change.
     start_rel.lnum = MIN(start_rel.lnum, fp->fd_top);

     // When last contained fold isn't completely contained, adjust end
     // of new fold.
     end_rel.lnum = MAX(end_rel.lnum, fp[cont - 1].fd_top + fp[cont - 1].fd_len - 1);
     // Move contained folds to inside new fold
     memmove(fold_ga.ga_data, fp, sizeof(fold_T) * (size_t)cont);
     fold_ga.ga_len += cont;
     i += cont;

     // Adjust line numbers in contained folds to be relative to the
     // new fold.
     for (int j = 0; j < cont; j++) {
       ((fold_T *)fold_ga.ga_data)[j].fd_top -= start_rel.lnum;
     }
   }
   // Move remaining entries to after the new fold.
   if (i < gap->ga_len) {
     memmove(fp + 1, (fold_T *)gap->ga_data + i,
             sizeof(fold_T) * (size_t)(gap->ga_len - i));
   }
   gap->ga_len = gap->ga_len + 1 - cont;

   // insert new fold
   fp->fd_nested = fold_ga;
   fp->fd_top = start_rel.lnum;
   fp->fd_len = end_rel.lnum - start_rel.lnum + 1;

   // We want the new fold to be closed.  If it would remain open because
   // of using 'foldlevel', need to adjust fd_flags of containing folds.
   if (use_level && !closed && level < wp->w_p_fdl) {
     closeFold(start, 1);
   }
   if (!use_level) {
     wp->w_fold_manual = true;
   }
   fp->fd_flags = FD_CLOSED;
   fp->fd_small = kNone;

   // redraw
   changed_window_setting(wp);
 }
}

// deleteFold() {{{2
/// @param start delete all folds from start to end when not 0
/// @param end delete all folds from start to end when not 0
/// @param recursive delete recursively if true
/// @param had_visual true when Visual selection used
void deleteFold(win_T *const wp, const linenr_T start, const linenr_T end, const int recursive,
               const bool had_visual)
{
 fold_T *found_fp = NULL;
 linenr_T found_off = 0;
 bool maybe_small = false;
 int level = 0;
 linenr_T lnum = start;
 bool did_one = false;
 linenr_T first_lnum = MAXLNUM;
 linenr_T last_lnum = 0;

 checkupdate(wp);

 while (lnum <= end) {
   // Find the deepest fold for "start".
   garray_T *gap = &wp->w_folds;
   garray_T *found_ga = NULL;
   linenr_T lnum_off = 0;
   bool use_level = false;
   while (true) {
     fold_T *fp;
     if (!foldFind(gap, lnum - lnum_off, &fp)) {
       break;
     }
     // lnum is inside this fold, remember info
     found_ga = gap;
     found_fp = fp;
     found_off = lnum_off;

     // if "lnum" is folded, don't check nesting
     if (check_closed(wp, fp, &use_level, level,
                      &maybe_small, lnum_off)) {
       break;
     }

     // check nested folds
     gap = &fp->fd_nested;
     lnum_off += fp->fd_top;
     level++;
   }
   if (found_ga == NULL) {
     lnum++;
   } else {
     lnum = found_fp->fd_top + found_fp->fd_len + found_off;

     if (foldmethodIsManual(wp)) {
       deleteFoldEntry(wp, found_ga,
                       (int)(found_fp - (fold_T *)found_ga->ga_data),
                       recursive);
     } else {
       first_lnum = MIN(first_lnum, found_fp->fd_top + found_off);
       last_lnum = MAX(last_lnum, lnum);
       if (!did_one) {
         parseMarker(wp);
       }
       deleteFoldMarkers(wp, found_fp, recursive, found_off);
     }
     did_one = true;

     // redraw window
     changed_window_setting(wp);
   }
 }
 if (!did_one) {
   emsg(_(e_nofold));
   // Force a redraw to remove the Visual highlighting.
   if (had_visual) {
     redraw_buf_later(wp->w_buffer, UPD_INVERTED);
   }
 } else {
   // Deleting markers may make cursor column invalid
   check_cursor_col(wp);
 }

 if (last_lnum > 0) {
   changed_lines(wp->w_buffer, first_lnum, 0, last_lnum, 0, false);

   // send one nvim_buf_lines_event at the end
   // last_lnum is the line *after* the last line of the outermost fold
   // that was modified. Note also that deleting a fold might only require
   // the modification of the *first* line of the fold, but we send through a
   // notification that includes every line that was part of the fold
   int64_t num_changed = last_lnum - first_lnum;
   buf_updates_send_changes(wp->w_buffer, first_lnum, num_changed, num_changed);
 }
}

// clearFolding() {{{2
/// Remove all folding for window "win".
void clearFolding(win_T *win)
{
 deleteFoldRecurse(win->w_buffer, &win->w_folds);
 win->w_foldinvalid = false;
}

// foldUpdate() {{{2
/// Update folds for changes in the buffer of a window.
/// Note that inserted/deleted lines must have already been taken care of by
/// calling foldMarkAdjust().
/// The changes in lines from top to bot (inclusive).
void foldUpdate(win_T *wp, linenr_T top, linenr_T bot)
{
 if (disable_fold_update || (State & MODE_INSERT && !foldmethodIsIndent(wp))) {
   return;
 }

 if (need_diff_redraw) {
   // will update later
   return;
 }

 if (wp->w_folds.ga_len > 0) {
   // Mark all folds from top to bot (or bot to top) as maybe-small.
   linenr_T maybe_small_start = MIN(top, bot);
   linenr_T maybe_small_end = MAX(top, bot);

   fold_T *fp;
   foldFind(&wp->w_folds, maybe_small_start, &fp);
   while (fp < (fold_T *)wp->w_folds.ga_data + wp->w_folds.ga_len
          && fp->fd_top <= maybe_small_end) {
     fp->fd_small = kNone;
     fp++;
   }
 }

 if (foldmethodIsIndent(wp)
     || foldmethodIsExpr(wp)
     || foldmethodIsMarker(wp)
     || foldmethodIsDiff(wp)
     || foldmethodIsSyntax(wp)) {
   int save_got_int = got_int;

   // reset got_int here, otherwise it won't work
   got_int = false;
   foldUpdateIEMS(wp, top, bot);
   got_int |= save_got_int;
 }
}

/// Updates folds when leaving insert-mode.
void foldUpdateAfterInsert(void)
{
 if (foldmethodIsManual(curwin)  // foldmethod=manual: No need to update.
     // These foldmethods are too slow, do not auto-update on insert-leave.
     || foldmethodIsSyntax(curwin) || foldmethodIsExpr(curwin)) {
   return;
 }

 foldUpdateAll(curwin);
 foldOpenCursor();
}

// foldUpdateAll() {{{2
/// Update all lines in a window for folding.
/// Used when a fold setting changes or after reloading the buffer.
/// The actual updating is postponed until fold info is used, to avoid doing
/// every time a setting is changed or a syntax item is added.
void foldUpdateAll(win_T *win)
{
 win->w_foldinvalid = true;
 redraw_later(win, UPD_NOT_VALID);
}

// foldMoveTo() {{{2
///
/// If "updown" is false: Move to the start or end of the fold.
/// If "updown" is true: move to fold at the same level.
/// @return FAIL if not moved.
///
/// @param dir  FORWARD or BACKWARD
int foldMoveTo(const bool updown, const int dir, const int count)
{
 int retval = FAIL;
 fold_T *fp;

 checkupdate(curwin);

 // Repeat "count" times.
 for (int n = 0; n < count; n++) {
   // Find nested folds.  Stop when a fold is closed.  The deepest fold
   // that moves the cursor is used.
   linenr_T lnum_off = 0;
   garray_T *gap = &curwin->w_folds;
   if (gap->ga_len == 0) {
     break;
   }
   bool use_level = false;
   bool maybe_small = false;
   linenr_T lnum_found = curwin->w_cursor.lnum;
   int level = 0;
   bool last = false;
   while (true) {
     if (!foldFind(gap, curwin->w_cursor.lnum - lnum_off, &fp)) {
       if (!updown || gap->ga_len == 0) {
         break;
       }

       // When moving up, consider a fold above the cursor; when
       // moving down consider a fold below the cursor.
       if (dir == FORWARD) {
         if (fp - (fold_T *)gap->ga_data >= gap->ga_len) {
           break;
         }
         fp--;
       } else {
         if (fp == (fold_T *)gap->ga_data) {
           break;
         }
       }
       // don't look for contained folds, they will always move
       // the cursor too far.
       last = true;
     }

     if (!last) {
       // Check if this fold is closed.
       if (check_closed(curwin, fp, &use_level, level,
                        &maybe_small, lnum_off)) {
         last = true;
       }

       // "[z" and "]z" stop at closed fold
       if (last && !updown) {
         break;
       }
     }

     if (updown) {
       if (dir == FORWARD) {
         // to start of next fold if there is one
         if (fp + 1 - (fold_T *)gap->ga_data < gap->ga_len) {
           linenr_T lnum = fp[1].fd_top + lnum_off;
           if (lnum > curwin->w_cursor.lnum) {
             lnum_found = lnum;
           }
         }
       } else {
         // to end of previous fold if there is one
         if (fp > (fold_T *)gap->ga_data) {
           linenr_T lnum = fp[-1].fd_top + lnum_off + fp[-1].fd_len - 1;
           if (lnum < curwin->w_cursor.lnum) {
             lnum_found = lnum;
           }
         }
       }
     } else {
       // Open fold found, set cursor to its start/end and then check
       // nested folds.
       if (dir == FORWARD) {
         linenr_T lnum = fp->fd_top + lnum_off + fp->fd_len - 1;
         if (lnum > curwin->w_cursor.lnum) {
           lnum_found = lnum;
         }
       } else {
         linenr_T lnum = fp->fd_top + lnum_off;
         if (lnum < curwin->w_cursor.lnum) {
           lnum_found = lnum;
         }
       }
     }

     if (last) {
       break;
     }

     // Check nested folds (if any).
     gap = &fp->fd_nested;
     lnum_off += fp->fd_top;
     level++;
   }
   if (lnum_found != curwin->w_cursor.lnum) {
     if (retval == FAIL) {
       setpcmark();
     }
     curwin->w_cursor.lnum = lnum_found;
     curwin->w_cursor.col = 0;
     retval = OK;
   } else {
     break;
   }
 }

 return retval;
}

// foldInitWin() {{{2
/// Init the fold info in a new window.
void foldInitWin(win_T *new_win)
{
 ga_init(&new_win->w_folds, (int)sizeof(fold_T), 10);
}

// find_wl_entry() {{{2
/// Find an entry in the win->w_lines[] array for buffer line "lnum".
/// Only valid entries are considered (for entries where wl_valid is false the
/// line number can be wrong).
///
/// @return  index of entry or -1 if not found.
int find_wl_entry(win_T *win, linenr_T lnum)
{
 for (int i = 0; i < win->w_lines_valid; i++) {
   if (win->w_lines[i].wl_valid) {
     if (lnum < win->w_lines[i].wl_lnum) {
       return -1;
     }
     if (lnum <= win->w_lines[i].wl_foldend) {
       return i;
     }
   }
 }
 return -1;
}

// foldAdjustVisual() {{{2
/// Adjust the Visual area to include any fold at the start or end completely.
void foldAdjustVisual(void)
{
 if (!VIsual_active || !hasAnyFolding(curwin)) {
   return;
 }

 pos_T *start, *end;

 if (ltoreq(VIsual, curwin->w_cursor)) {
   start = &VIsual;
   end = &curwin->w_cursor;
 } else {
   start = &curwin->w_cursor;
   end = &VIsual;
 }
 if (hasFolding(curwin, start->lnum, &start->lnum, NULL)) {
   start->col = 0;
 }

 if (!hasFolding(curwin, end->lnum, NULL, &end->lnum)) {
   return;
 }

 end->col = ml_get_len(end->lnum);
 if (end->col > 0 && *p_sel == 'o') {
   end->col--;
 }
 // prevent cursor from moving on the trail byte
 mb_adjust_cursor();
}

// foldAdjustCursor() {{{2
/// Move the cursor to the first line of a closed fold.
void foldAdjustCursor(win_T *wp)
{
 hasFolding(wp, wp->w_cursor.lnum, &wp->w_cursor.lnum, NULL);
}

// Internal functions for "fold_T" {{{1
// cloneFoldGrowArray() {{{2
/// Will "clone" (i.e deep copy) a garray_T of folds.
void cloneFoldGrowArray(garray_T *from, garray_T *to)
{
 ga_init(to, from->ga_itemsize, from->ga_growsize);

 if (GA_EMPTY(from)) {
   return;
 }

 ga_grow(to, from->ga_len);

 fold_T *from_p = (fold_T *)from->ga_data;
 fold_T *to_p = (fold_T *)to->ga_data;

 for (int i = 0; i < from->ga_len; i++) {
   to_p->fd_top = from_p->fd_top;
   to_p->fd_len = from_p->fd_len;
   to_p->fd_flags = from_p->fd_flags;
   to_p->fd_small = from_p->fd_small;
   cloneFoldGrowArray(&from_p->fd_nested, &to_p->fd_nested);
   to->ga_len++;
   from_p++;
   to_p++;
 }
}

// foldFind() {{{2
/// Search for line "lnum" in folds of growarray "gap".
/// Set "*fpp" to the fold struct for the fold that contains "lnum" or
/// the first fold below it (careful: it can be beyond the end of the array!).
///
/// @return  false when there is no fold that contains "lnum".
static bool foldFind(const garray_T *gap, linenr_T lnum, fold_T **fpp)
{
 if (gap->ga_len == 0) {
   *fpp = NULL;
   return false;
 }

 // Perform a binary search.
 // "low" is lowest index of possible match.
 // "high" is highest index of possible match.
 fold_T *fp = (fold_T *)gap->ga_data;
 linenr_T low = 0;
 linenr_T high = gap->ga_len - 1;
 while (low <= high) {
   linenr_T i = (low + high) / 2;
   if (fp[i].fd_top > lnum) {
     // fold below lnum, adjust high
     high = i - 1;
   } else if (fp[i].fd_top + fp[i].fd_len <= lnum) {
     // fold above lnum, adjust low
     low = i + 1;
   } else {
     // lnum is inside this fold
     *fpp = fp + i;
     return true;
   }
 }
 *fpp = fp + low;
 return false;
}

// foldLevelWin() {{{2
/// @return  fold level at line number "lnum" in window "wp".
static int foldLevelWin(win_T *wp, linenr_T lnum)
{
 fold_T *fp;
 linenr_T lnum_rel = lnum;
 int level = 0;

 // Recursively search for a fold that contains "lnum".
 garray_T *gap = &wp->w_folds;
 while (true) {
   if (!foldFind(gap, lnum_rel, &fp)) {
     break;
   }
   // Check nested folds.  Line number is relative to containing fold.
   gap = &fp->fd_nested;
   lnum_rel -= fp->fd_top;
   level++;
 }

 return level;
}

// checkupdate() {{{2
/// Check if the folds in window "wp" are invalid and update them if needed.
static void checkupdate(win_T *wp)
{
 if (!wp->w_foldinvalid) {
   return;
 }

 foldUpdate(wp, 1, (linenr_T)MAXLNUM);     // will update all
 wp->w_foldinvalid = false;
}

// setFoldRepeat() {{{2
/// Open or close fold for current window at position `pos`.
/// Repeat "count" times.
static void setFoldRepeat(pos_T pos, int count, int do_open)
{
 for (int n = 0; n < count; n++) {
   int done = DONE_NOTHING;
   setManualFold(pos, do_open, false, &done);
   if (!(done & DONE_ACTION)) {
     // Only give an error message when no fold could be opened.
     if (n == 0 && !(done & DONE_FOLD)) {
       emsg(_(e_nofold));
     }
     break;
   }
 }
}

// setManualFold() {{{2
/// Open or close the fold in the current window which contains "lnum".
/// Also does this for other windows in diff mode when needed.
///
/// @param opening  true when opening, false when closing
/// @param recurse  true when closing/opening recursive
static linenr_T setManualFold(pos_T pos, bool opening, bool recurse, int *donep)
{
 if (foldmethodIsDiff(curwin) && curwin->w_p_scb) {
   linenr_T dlnum;

   // Do the same operation in other windows in diff mode.  Calculate the
   // line number from the diffs.
   FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
     if (wp != curwin && foldmethodIsDiff(wp) && wp->w_p_scb) {
       dlnum = diff_lnum_win(curwin->w_cursor.lnum, wp);
       if (dlnum != 0) {
         setManualFoldWin(wp, dlnum, opening, recurse, NULL);
       }
     }
   }
 }

 return setManualFoldWin(curwin, pos.lnum, opening, recurse, donep);
}

// setManualFoldWin() {{{2
/// Open or close the fold in window "wp" which contains "lnum".
/// "donep", when not NULL, points to flag that is set to DONE_FOLD when some
/// fold was found and to DONE_ACTION when some fold was opened or closed.
/// When "donep" is NULL give an error message when no fold was found for
/// "lnum", but only if "wp" is "curwin".
///
/// @param opening  true when opening, false when closing
/// @param recurse  true when closing/opening recursive
///
/// @return         the line number of the next line that could be closed.
///                 It's only valid when "opening" is true!
static linenr_T setManualFoldWin(win_T *wp, linenr_T lnum, bool opening, bool recurse, int *donep)
{
 fold_T *fp;
 fold_T *fp2;
 fold_T *found = NULL;
 int level = 0;
 bool use_level = false;
 bool found_fold = false;
 linenr_T next = MAXLNUM;
 linenr_T off = 0;
 int done = 0;

 checkupdate(wp);

 // Find the fold, open or close it.
 garray_T *gap = &wp->w_folds;
 while (true) {
   if (!foldFind(gap, lnum, &fp)) {
     // If there is a following fold, continue there next time.
     if (fp != NULL && fp < (fold_T *)gap->ga_data + gap->ga_len) {
       next = fp->fd_top + off;
     }
     break;
   }

   // lnum is inside this fold
   found_fold = true;

   // If there is a following fold, continue there next time.
   if (fp + 1 < (fold_T *)gap->ga_data + gap->ga_len) {
     next = fp[1].fd_top + off;
   }

   // Change from level-dependent folding to manual.
   if (use_level || fp->fd_flags == FD_LEVEL) {
     use_level = true;
     fp->fd_flags = level >= wp->w_p_fdl ? FD_CLOSED : FD_OPEN;
     fp2 = (fold_T *)fp->fd_nested.ga_data;
     for (int j = 0; j < fp->fd_nested.ga_len; j++) {
       fp2[j].fd_flags = FD_LEVEL;
     }
   }

   // Simple case: Close recursively means closing the fold.
   if (!opening && recurse) {
     if (fp->fd_flags != FD_CLOSED) {
       done |= DONE_ACTION;
       fp->fd_flags = FD_CLOSED;
     }
   } else if (fp->fd_flags == FD_CLOSED) {
     // When opening, open topmost closed fold.
     if (opening) {
       fp->fd_flags = FD_OPEN;
       done |= DONE_ACTION;
       if (recurse) {
         foldOpenNested(fp);
       }
     }
     break;
   }

   // fold is open, check nested folds
   found = fp;
   gap = &fp->fd_nested;
   lnum -= fp->fd_top;
   off += fp->fd_top;
   level++;
 }
 if (found_fold) {
   // When closing and not recurse, close deepest open fold.
   if (!opening && found != NULL) {
     found->fd_flags = FD_CLOSED;
     done |= DONE_ACTION;
   }
   wp->w_fold_manual = true;
   if (done & DONE_ACTION) {
     changed_window_setting(wp);
   }
   done |= DONE_FOLD;
 } else if (donep == NULL && wp == curwin) {
   emsg(_(e_nofold));
 }

 if (donep != NULL) {
   *donep |= done;
 }

 return next;
}

// foldOpenNested() {{{2
/// Open all nested folds in fold "fpr" recursively.
static void foldOpenNested(fold_T *fpr)
{
 fold_T *fp = (fold_T *)fpr->fd_nested.ga_data;
 for (int i = 0; i < fpr->fd_nested.ga_len; i++) {
   foldOpenNested(&fp[i]);
   fp[i].fd_flags = FD_OPEN;
 }
}

// deleteFoldEntry() {{{2
/// Delete fold "idx" from growarray "gap".
///
/// @param recursive  when true, also delete all the folds contained in it.
///                   when false, contained folds are moved one level up.
static void deleteFoldEntry(win_T *const wp, garray_T *const gap, const int idx,
                           const bool recursive)
{
 fold_T *fp = (fold_T *)gap->ga_data + idx;
 if (recursive || GA_EMPTY(&fp->fd_nested)) {
   // recursively delete the contained folds
   deleteFoldRecurse(wp->w_buffer, &fp->fd_nested);
   gap->ga_len--;
   if (idx < gap->ga_len) {
     memmove(fp, fp + 1, sizeof(*fp) * (size_t)(gap->ga_len - idx));
   }
 } else {
   // Move nested folds one level up, to overwrite the fold that is
   // deleted.
   int moved = fp->fd_nested.ga_len;
   ga_grow(gap, moved - 1);
   {
     // Get "fp" again, the array may have been reallocated.
     fp = (fold_T *)gap->ga_data + idx;

     // adjust fd_top and fd_flags for the moved folds
     fold_T *nfp = (fold_T *)fp->fd_nested.ga_data;
     for (int i = 0; i < moved; i++) {
       nfp[i].fd_top += fp->fd_top;
       if (fp->fd_flags == FD_LEVEL) {
         nfp[i].fd_flags = FD_LEVEL;
       }
       if (fp->fd_small == kNone) {
         nfp[i].fd_small = kNone;
       }
     }

     // move the existing folds down to make room
     if (idx + 1 < gap->ga_len) {
       memmove(fp + moved, fp + 1,
               sizeof(*fp) * (size_t)(gap->ga_len - (idx + 1)));
     }
     // move the contained folds one level up
     memmove(fp, nfp, sizeof(*fp) * (size_t)moved);
     xfree(nfp);
     gap->ga_len += moved - 1;
   }
 }
}

// deleteFoldRecurse() {{{2
/// Delete nested folds in a fold.
void deleteFoldRecurse(buf_T *bp, garray_T *gap)
{
#define DELETE_FOLD_NESTED(fd) deleteFoldRecurse(bp, &((fd)->fd_nested))
 GA_DEEP_CLEAR(gap, fold_T, DELETE_FOLD_NESTED);
}

// foldMarkAdjust() {{{2
/// Update line numbers of folds for inserted/deleted lines.
///
/// We are adjusting the folds in the range from line1 til line2,
/// make sure that line2 does not get smaller than line1
void foldMarkAdjust(win_T *wp, linenr_T line1, linenr_T line2, linenr_T amount,
                   linenr_T amount_after)
{
 // If deleting marks from line1 to line2, but not deleting all those
 // lines, set line2 so that only deleted lines have their folds removed.
 if (amount == MAXLNUM && line2 >= line1 && line2 - line1 >= -amount_after) {
   line2 = line1 - amount_after - 1;
 }
 if (line2 < line1) {
   line2 = line1;
 }
 // If appending a line in Insert mode, it should be included in the fold
 // just above the line.
 if ((State & MODE_INSERT) && amount == 1 && line2 == MAXLNUM) {
   line1--;
 }
 foldMarkAdjustRecurse(wp, &wp->w_folds, line1, line2, amount, amount_after);
}

// foldMarkAdjustRecurse() {{{2
static void foldMarkAdjustRecurse(win_T *wp, garray_T *gap, linenr_T line1, linenr_T line2,
                                 linenr_T amount, linenr_T amount_after)
{
 if (gap->ga_len == 0) {
   return;
 }

 // In Insert mode an inserted line at the top of a fold is considered part
 // of the fold, otherwise it isn't.
 linenr_T top = ((State & MODE_INSERT) && amount == 1 && line2 == MAXLNUM)
                ? line1 + 1
                : line1;

 // Find the fold containing or just below "line1".
 fold_T *fp;
 foldFind(gap, line1, &fp);

 // Adjust all folds below "line1" that are affected.
 for (int i = (int)(fp - (fold_T *)gap->ga_data); i < gap->ga_len; i++, fp++) {
   // Check for these situations:
   //    1  2  3
   //    1  2  3
   // line1     2      3  4  5
   //       2  3  4  5
   //       2  3  4  5
   // line2     2      3  4  5
   //          3     5  6
   //          3     5  6

   linenr_T last = fp->fd_top + fp->fd_len - 1;     // last line of fold

   // 1. fold completely above line1: nothing to do
   if (last < line1) {
     continue;
   }

   // 6. fold below line2: only adjust for amount_after
   if (fp->fd_top > line2) {
     if (amount_after == 0) {
       break;
     }
     fp->fd_top += amount_after;
   } else {
     if (fp->fd_top >= top && last <= line2) {
       // 4. fold completely contained in range
       if (amount == MAXLNUM) {
         // Deleting lines: delete the fold completely
         deleteFoldEntry(wp, gap, i, true);
         i--;              // adjust index for deletion
         fp--;
       } else {
         fp->fd_top += amount;
       }
     } else {
       if (fp->fd_top < top) {
         // 2 or 3: need to correct nested folds too
         foldMarkAdjustRecurse(wp, &fp->fd_nested, line1 - fp->fd_top,
                               line2 - fp->fd_top, amount, amount_after);
         if (last <= line2) {
           // 2. fold contains line1, line2 is below fold
           if (amount == MAXLNUM) {
             fp->fd_len = line1 - fp->fd_top;
           } else {
             fp->fd_len += amount;
           }
         } else {
           // 3. fold contains line1 and line2
           fp->fd_len += amount_after;
         }
       } else {
         // 5. fold is below line1 and contains line2; need to
         // correct nested folds too
         if (amount == MAXLNUM) {
           foldMarkAdjustRecurse(wp, &fp->fd_nested, 0, line2 - fp->fd_top,
                                 amount, amount_after + (fp->fd_top - top));
           fp->fd_len -= line2 - fp->fd_top + 1;
           fp->fd_top = line1;
         } else {
           foldMarkAdjustRecurse(wp, &fp->fd_nested, 0, line2 - fp->fd_top,
                                 amount, amount_after - amount);
           fp->fd_len += amount_after - amount;
           fp->fd_top += amount;
         }
       }
     }
   }
 }
}

// getDeepestNesting() {{{2
/// Get the lowest 'foldlevel' value that makes the deepest nested fold in
/// window `wp`.
int getDeepestNesting(win_T *wp)
{
 checkupdate(wp);
 return getDeepestNestingRecurse(&wp->w_folds);
}

static int getDeepestNestingRecurse(garray_T *gap)
{
 int maxlevel = 0;

 fold_T *fp = (fold_T *)gap->ga_data;
 for (int i = 0; i < gap->ga_len; i++) {
   int level = getDeepestNestingRecurse(&fp[i].fd_nested) + 1;
   maxlevel = MAX(maxlevel, level);
 }

 return maxlevel;
}

// check_closed() {{{2
/// Check if a fold is closed and update the info needed to check nested folds.
///
/// @param[in,out] use_levelp true: outer fold had FD_LEVEL
/// @param[in,out] fp fold to check
/// @param level folding depth
/// @param[out] maybe_smallp true: outer this had fd_small == kNone
/// @param lnum_off line number offset for fp->fd_top
/// @return true if fold is closed
static bool check_closed(win_T *const wp, fold_T *const fp, bool *const use_levelp, const int level,
                        bool *const maybe_smallp, const linenr_T lnum_off)
{
 bool closed = false;

 // Check if this fold is closed.  If the flag is FD_LEVEL this
 // fold and all folds it contains depend on 'foldlevel'.
 if (*use_levelp || fp->fd_flags == FD_LEVEL) {
   *use_levelp = true;
   if (level >= wp->w_p_fdl) {
     closed = true;
   }
 } else if (fp->fd_flags == FD_CLOSED) {
   closed = true;
 }

 // Small fold isn't closed anyway.
 if (fp->fd_small == kNone) {
   *maybe_smallp = true;
 }
 if (closed) {
   if (*maybe_smallp) {
     fp->fd_small = kNone;
   }
   checkSmall(wp, fp, lnum_off);
   if (fp->fd_small == kTrue) {
     closed = false;
   }
 }
 return closed;
}

// checkSmall() {{{2
/// Update fd_small field of fold "fp".
///
/// @param lnum_off  offset for fp->fd_top
static void checkSmall(win_T *const wp, fold_T *const fp, const linenr_T lnum_off)
{
 if (fp->fd_small != kNone) {
   return;
 }

 // Mark any nested folds to maybe-small
 setSmallMaybe(&fp->fd_nested);

 if (fp->fd_len > wp->w_p_fml) {
   fp->fd_small = kFalse;
 } else {
   int count = 0;
   for (int n = 0; n < fp->fd_len; n++) {
     count += plines_win_nofold(wp, fp->fd_top + lnum_off + n);
     if (count > wp->w_p_fml) {
       fp->fd_small = kFalse;
       return;
     }
   }
   fp->fd_small = kTrue;
 }
}

// setSmallMaybe() {{{2
/// Set small flags in "gap" to kNone.
static void setSmallMaybe(garray_T *gap)
{
 fold_T *fp = (fold_T *)gap->ga_data;
 for (int i = 0; i < gap->ga_len; i++) {
   fp[i].fd_small = kNone;
 }
}

// foldCreateMarkers() {{{2
/// Create a fold from line "start" to line "end" (inclusive) in window `wp`
/// by adding markers.
static void foldCreateMarkers(win_T *wp, pos_T start, pos_T end)
{
 buf_T *buf = wp->w_buffer;
 if (!MODIFIABLE(buf)) {
   emsg(_(e_modifiable));
   return;
 }
 parseMarker(wp);

 foldAddMarker(buf, start, wp->w_p_fmr, foldstartmarkerlen);
 foldAddMarker(buf, end, foldendmarker, foldendmarkerlen);

 // Update both changes here, to avoid all folds after the start are
 // changed when the start marker is inserted and the end isn't.
 changed_lines(buf, start.lnum, 0, end.lnum, 0, false);

 // Note: foldAddMarker() may not actually change start and/or end if
 // u_save() is unable to save the buffer line, but we send the
 // nvim_buf_lines_event anyway since it won't do any harm.
 int64_t num_changed = 1 + end.lnum - start.lnum;
 buf_updates_send_changes(buf, start.lnum, num_changed, num_changed);
}

// foldAddMarker() {{{2
/// Add "marker[markerlen]" in 'commentstring' to position `pos`.
static void foldAddMarker(buf_T *buf, pos_T pos, const char *marker, size_t markerlen)
{
 char *cms = buf->b_p_cms;
 char *p = strstr(buf->b_p_cms, "%s");
 bool line_is_comment = false;
 linenr_T lnum = pos.lnum;

 // Allocate a new line: old-line + 'cms'-start + marker + 'cms'-end
 char *line = ml_get_buf(buf, lnum);
 size_t line_len = (size_t)ml_get_buf_len(buf, lnum);
 size_t added = 0;

 if (u_save(lnum - 1, lnum + 1) != OK) {
   return;
 }

 // Check if the line ends with an unclosed comment
 skip_comment(line, false, false, &line_is_comment);
 char *newline = xmalloc(line_len + markerlen + strlen(cms) + 1);
 STRCPY(newline, line);
 // Append the marker to the end of the line
 if (p == NULL || line_is_comment) {
   xmemcpyz(newline + line_len, marker, markerlen);
   added = markerlen;
 } else {
   STRCPY(newline + line_len, cms);
   memcpy(newline + line_len + (p - cms), marker, markerlen);
   STRCPY(newline + line_len + (p - cms) + markerlen, p + 2);
   added = markerlen + strlen(cms) - 2;
 }
 ml_replace_buf(buf, lnum, newline, false, false);
 if (added) {
   extmark_splice_cols(buf, (int)lnum - 1, (int)line_len,
                       0, (int)added, kExtmarkUndo);
 }
}

// deleteFoldMarkers() {{{2
/// Delete the markers for a fold, causing it to be deleted.
///
/// @param lnum_off  offset for fp->fd_top
static void deleteFoldMarkers(win_T *wp, fold_T *fp, bool recursive, linenr_T lnum_off)
{
 if (recursive) {
   for (int i = 0; i < fp->fd_nested.ga_len; i++) {
     deleteFoldMarkers(wp, (fold_T *)fp->fd_nested.ga_data + i, true,
                       lnum_off + fp->fd_top);
   }
 }
 foldDelMarker(wp->w_buffer, fp->fd_top + lnum_off, wp->w_p_fmr,
               foldstartmarkerlen);
 foldDelMarker(wp->w_buffer, fp->fd_top + lnum_off + fp->fd_len - 1,
               foldendmarker, foldendmarkerlen);
}

// foldDelMarker() {{{2
/// Delete marker "marker[markerlen]" at the end of line "lnum".
/// Delete 'commentstring' if it matches.
/// If the marker is not found, there is no error message.  Could be a missing
/// close-marker.
static void foldDelMarker(buf_T *buf, linenr_T lnum, char *marker, size_t markerlen)
{
 // end marker may be missing and fold extends below the last line
 if (lnum > buf->b_ml.ml_line_count) {
   return;
 }

 char *cms = buf->b_p_cms;
 char *line = ml_get_buf(buf, lnum);
 for (char *p = line; *p != NUL; p++) {
   if (strncmp(p, marker, markerlen) != 0) {
     continue;
   }
   // Found the marker, include a digit if it's there.
   size_t len = markerlen;
   if (ascii_isdigit(p[len])) {
     len++;
   }
   if (*cms != NUL) {
     // Also delete 'commentstring' if it matches.
     char *cms2 = strstr(cms, "%s");
     if (cms2 != NULL && p - line >= cms2 - cms
         && strncmp(p - (cms2 - cms), cms, (size_t)(cms2 - cms)) == 0
         && strncmp(p + len, cms2 + 2, strlen(cms2 + 2)) == 0) {
       p -= cms2 - cms;
       len += strlen(cms) - 2;
     }
   }
   if (u_save(lnum - 1, lnum + 1) == OK) {
     // Make new line: text-before-marker + text-after-marker
     char *newline = xmalloc((size_t)ml_get_buf_len(buf, lnum) - len + 1);
     assert(p >= line);
     memcpy(newline, line, (size_t)(p - line));
     STRCPY(newline + (p - line), p + len);
     ml_replace_buf(buf, lnum, newline, false, false);
     extmark_splice_cols(buf, (int)lnum - 1, (int)(p - line),
                         (int)len, 0, kExtmarkUndo);
   }
   break;
 }
}

// get_foldtext() {{{2
/// Generates text to display
///
/// @param buf allocated memory of length FOLD_TEXT_LEN. Used when 'foldtext'
///            isn't set puts the result in "buf[FOLD_TEXT_LEN]".
/// @param at line "lnum", with last line "lnume".
/// @return the text for a closed fold
///
/// Otherwise the result is in allocated memory.
char *get_foldtext(win_T *wp, linenr_T lnum, linenr_T lnume, foldinfo_T foldinfo, char *buf,
                  VirtText *vt)
 FUNC_ATTR_NONNULL_ALL
{
 char *text = NULL;
 // an error occurred when evaluating 'fdt' setting
 static bool got_fdt_error = false;
 int save_did_emsg = did_emsg;
 static win_T *last_wp = NULL;
 static linenr_T last_lnum = 0;

 if (last_wp == NULL || last_wp != wp || last_lnum > lnum || last_lnum == 0) {
   // window changed, try evaluating foldtext setting once again
   got_fdt_error = false;
 }

 if (!got_fdt_error) {
   // a previous error should not abort evaluating 'foldexpr'
   did_emsg = false;
 }

 if (*wp->w_p_fdt != NUL) {
   char dashes[MAX_LEVEL + 2];

   // Set "v:foldstart" and "v:foldend".
   set_vim_var_nr(VV_FOLDSTART, (varnumber_T)lnum);
   set_vim_var_nr(VV_FOLDEND, (varnumber_T)lnume);

   // Set "v:folddashes" to a string of "level" dashes.
   // Set "v:foldlevel" to "level".
   int level = MIN(foldinfo.fi_level, (int)sizeof(dashes) - 1);
   memset(dashes, '-', (size_t)level);
   dashes[level] = NUL;
   set_vim_var_string(VV_FOLDDASHES, dashes, -1);
   set_vim_var_nr(VV_FOLDLEVEL, (varnumber_T)level);

   // skip evaluating 'foldtext' on errors
   if (!got_fdt_error) {
     win_T *const save_curwin = curwin;
     const sctx_T saved_sctx = current_sctx;

     curwin = wp;
     curbuf = wp->w_buffer;
     current_sctx = wp->w_p_script_ctx[kWinOptFoldtext];

     emsg_off++;  // handle exceptions, but don't display errors

     Object obj = eval_foldtext(wp);
     if (obj.type == kObjectTypeArray) {
       Error err = ERROR_INIT;
       *vt = parse_virt_text(obj.data.array, &err, NULL);
       if (!ERROR_SET(&err)) {
         *buf = NUL;
         text = buf;
       }
       api_clear_error(&err);
     } else if (obj.type == kObjectTypeString) {
       text = obj.data.string.data;
       obj = NIL;
     }
     api_free_object(obj);

     emsg_off--;

     if (text == NULL || did_emsg) {
       got_fdt_error = true;
     }

     curwin = save_curwin;
     curbuf = curwin->w_buffer;
     current_sctx = saved_sctx;
   }
   last_lnum = lnum;
   last_wp = wp;
   set_vim_var_string(VV_FOLDDASHES, NULL, -1);

   if (!did_emsg && save_did_emsg) {
     did_emsg = save_did_emsg;
   }

   if (text != NULL) {
     // Replace unprintable characters, if there are any.  But
     // replace a TAB with a space.
     char *p;
     for (p = text; *p != NUL; p++) {
       int len = utfc_ptr2len(p);

       if (len > 1) {
         if (!vim_isprintc(utf_ptr2char(p))) {
           break;
         }
         p += len - 1;
       } else if (*p == TAB) {
         *p = ' ';
       } else if (ptr2cells(p) > 1) {
         break;
       }
     }
     if (*p != NUL) {
       p = transstr(text, true);
       xfree(text);
       text = p;
     }
   }
 }
 if (text == NULL) {
   int count = lnume - lnum + 1;

   vim_snprintf(buf, FOLD_TEXT_LEN,
                NGETTEXT("+--%3d line folded",
                         "+--%3d lines folded ", count),
                count);
   text = buf;
 }
 return text;
}

// foldtext_cleanup() {{{2
/// Remove 'foldmarker' and 'commentstring' from "str" (in-place).
static void foldtext_cleanup(char *str)
{
 // Ignore leading and trailing white space in 'commentstring'.
 char *cms_start = skipwhite(curbuf->b_p_cms);
 size_t cms_slen = strlen(cms_start);
 while (cms_slen > 0 && ascii_iswhite(cms_start[cms_slen - 1])) {
   cms_slen--;
 }

 // locate "%s" in 'commentstring', use the part before and after it.
 char *cms_end = strstr(cms_start, "%s");
 size_t cms_elen = 0;
 if (cms_end != NULL) {
   cms_elen = cms_slen - (size_t)(cms_end - cms_start);
   cms_slen = (size_t)(cms_end - cms_start);

   // exclude white space before "%s"
   while (cms_slen > 0 && ascii_iswhite(cms_start[cms_slen - 1])) {
     cms_slen--;
   }

   // skip "%s" and white space after it
   char *s = skipwhite(cms_end + 2);
   cms_elen -= (size_t)(s - cms_end);
   cms_end = s;
 }
 parseMarker(curwin);

 bool did1 = false;
 bool did2 = false;

 for (char *s = str; *s != NUL;) {
   size_t len = 0;
   if (strncmp(s, curwin->w_p_fmr, foldstartmarkerlen) == 0) {
     len = foldstartmarkerlen;
   } else if (strncmp(s, foldendmarker, foldendmarkerlen) == 0) {
     len = foldendmarkerlen;
   }
   if (len > 0) {
     if (ascii_isdigit(s[len])) {
       len++;
     }

     // May remove 'commentstring' start.  Useful when it's a double
     // quote and we already removed a double quote.
     char *p;
     for (p = s; p > str && ascii_iswhite(p[-1]); p--) {}
     if (p >= str + cms_slen
         && strncmp(p - cms_slen, cms_start, cms_slen) == 0) {
       len += (size_t)(s - p) + cms_slen;
       s = p - cms_slen;
     }
   } else if (cms_end != NULL) {
     if (!did1 && cms_slen > 0 && strncmp(s, cms_start, cms_slen) == 0) {
       len = cms_slen;
       did1 = true;
     } else if (!did2 && cms_elen > 0
                && strncmp(s, cms_end, cms_elen) == 0) {
       len = cms_elen;
       did2 = true;
     }
   }
   if (len != 0) {
     while (ascii_iswhite(s[len])) {
       len++;
     }
     STRMOVE(s, s + len);
   } else {
     MB_PTR_ADV(s);
   }
 }
}

// Folding by indent, expr, marker and syntax. {{{1
// Function declarations. {{{2

// foldUpdateIEMS() {{{2
/// Update the folding for window "wp", at least from lines "top" to "bot".
/// IEMS = "Indent Expr Marker Syntax"
static void foldUpdateIEMS(win_T *const wp, linenr_T top, linenr_T bot)
{
 // Avoid problems when being called recursively.
 if (invalid_top != 0) {
   return;
 }

 if (wp->w_foldinvalid) {
   // Need to update all folds.
   top = 1;
   bot = wp->w_buffer->b_ml.ml_line_count;
   wp->w_foldinvalid = false;

   // Mark all folds as maybe-small.
   setSmallMaybe(&wp->w_folds);
 }

 // add the context for "diff" folding
 if (foldmethodIsDiff(wp)) {
   if (top > diff_context) {
     top -= diff_context;
   } else {
     top = 1;
   }
   bot += diff_context;
 }

 // When deleting lines at the end of the buffer "top" can be past the end
 // of the buffer.
 top = MIN(top, wp->w_buffer->b_ml.ml_line_count);

 fline_T fline;

 fold_changed = false;
 fline.wp = wp;
 fline.off = 0;
 fline.lvl = 0;
 fline.lvl_next = -1;
 fline.start = 0;
 fline.end = MAX_LEVEL + 1;
 fline.had_end = MAX_LEVEL + 1;

 invalid_top = top;
 invalid_bot = bot;

 LevelGetter getlevel = NULL;

 if (foldmethodIsMarker(wp)) {
   getlevel = foldlevelMarker;

   // Init marker variables to speed up foldlevelMarker().
   parseMarker(wp);

   // Need to get the level of the line above top, it is used if there is
   // no marker at the top.
   if (top > 1) {
     // Get the fold level at top - 1.
     const int level = foldLevelWin(wp, top - 1);

     // The fold may end just above the top, check for that.
     fline.lnum = top - 1;
     fline.lvl = level;
     getlevel(&fline);

     // If a fold started here, we already had the level, if it stops
     // here, we need to use lvl_next.  Could also start and end a fold
     // in the same line.
     if (fline.lvl > level) {
       fline.lvl = level - (fline.lvl - fline.lvl_next);
     } else {
       fline.lvl = fline.lvl_next;
     }
   }
   fline.lnum = top;
   getlevel(&fline);
 } else {
   fline.lnum = top;
   if (foldmethodIsExpr(wp)) {
     getlevel = foldlevelExpr;
     // start one line back, because a "<1" may indicate the end of a
     // fold in the topline
     if (top > 1) {
       fline.lnum--;
     }
   } else if (foldmethodIsSyntax(wp)) {
     getlevel = foldlevelSyntax;
   } else if (foldmethodIsDiff(wp)) {
     getlevel = foldlevelDiff;
   } else {
     getlevel = foldlevelIndent;
     // Start one line back, because if the line above "top" has an
     // undefined fold level, folding it relies on the line under it,
     // which is "top".
     if (top > 1) {
       fline.lnum--;
     }
   }

   // Backup to a line for which the fold level is defined.  Since it's
   // always defined for line one, we will stop there.
   fline.lvl = -1;
   for (; !got_int; fline.lnum--) {
     // Reset lvl_next each time, because it will be set to a value for
     // the next line, but we search backwards here.
     fline.lvl_next = -1;
     getlevel(&fline);
     if (fline.lvl >= 0) {
       break;
     }
   }
 }

 // If folding is defined by the syntax, it is possible that a change in
 // one line will cause all sub-folds of the current fold to change (e.g.,
 // closing a C-style comment can cause folds in the subsequent lines to
 // appear). To take that into account we should adjust the value of "bot"
 // to point to the end of the current fold:
 if (foldlevelSyntax == getlevel) {
   garray_T *gap = &wp->w_folds;
   fold_T *fpn = NULL;
   int current_fdl = 0;
   linenr_T fold_start_lnum = 0;
   linenr_T lnum_rel = fline.lnum;

   while (current_fdl < fline.lvl) {
     if (!foldFind(gap, lnum_rel, &fpn)) {
       break;
     }
     current_fdl++;

     fold_start_lnum += fpn->fd_top;
     gap = &fpn->fd_nested;
     lnum_rel -= fpn->fd_top;
   }
   if (fpn != NULL && current_fdl == fline.lvl) {
     linenr_T fold_end_lnum = fold_start_lnum + fpn->fd_len;

     bot = MAX(bot, fold_end_lnum);
   }
 }

 linenr_T start = fline.lnum;
 linenr_T end = bot;
 // Do at least one line.
 if (start > end && end < wp->w_buffer->b_ml.ml_line_count) {
   end = start;
 }

 fold_T *fp;

 while (!got_int) {
   // Always stop at the end of the file ("end" can be past the end of
   // the file).
   if (fline.lnum > wp->w_buffer->b_ml.ml_line_count) {
     break;
   }
   if (fline.lnum > end) {
     // For "marker", "expr"  and "syntax"  methods: If a change caused
     // a fold to be removed, we need to continue at least until where
     // it ended.
     if (getlevel != foldlevelMarker
         && getlevel != foldlevelSyntax
         && getlevel != foldlevelExpr) {
       break;
     }
     if ((start <= end
          && foldFind(&wp->w_folds, end, &fp)
          && fp->fd_top + fp->fd_len - 1 > end)
         || (fline.lvl == 0
             && foldFind(&wp->w_folds, fline.lnum, &fp)
             && fp->fd_top < fline.lnum)) {
       end = fp->fd_top + fp->fd_len - 1;
     } else if (getlevel == foldlevelSyntax
                && foldLevelWin(wp, fline.lnum) != fline.lvl) {
       // For "syntax" method: Compare the foldlevel that the syntax
       // tells us to the foldlevel from the existing folds.  If they
       // don't match continue updating folds.
       end = fline.lnum;
     } else {
       break;
     }
   }

   // A level 1 fold starts at a line with foldlevel > 0.
   if (fline.lvl > 0) {
     invalid_top = fline.lnum;
     invalid_bot = end;
     end = foldUpdateIEMSRecurse(&wp->w_folds, 1, start, &fline, getlevel, end,
                                 FD_LEVEL);
     start = fline.lnum;
   } else {
     if (fline.lnum == wp->w_buffer->b_ml.ml_line_count) {
       break;
     }
     fline.lnum++;
     fline.lvl = fline.lvl_next;
     getlevel(&fline);
   }
 }

 // There can't be any folds from start until end now.
 foldRemove(wp, &wp->w_folds, start, end);

 // If some fold changed, need to redraw and position cursor.
 if (fold_changed && wp->w_p_fen) {
   changed_window_setting(wp);
 }

 // If we updated folds past "bot", need to redraw more lines.  Don't do
 // this in other situations, the changed lines will be redrawn anyway and
 // this method can cause the whole window to be updated.
 if (end != bot) {
   redraw_win_range_later(wp, top, end);
 }

 invalid_top = 0;
}

// foldUpdateIEMSRecurse() {{{2
/// Update a fold that starts at "flp->lnum".  At this line there is always a
/// valid foldlevel, and its level >= "level".
///
/// "flp" is valid for "flp->lnum" when called and it's valid when returning.
/// "flp->lnum" is set to the lnum just below the fold, if it ends before
/// "bot", it's "bot" plus one if the fold continues and it's bigger when using
/// the marker method and a text change made following folds to change.
/// When returning, "flp->lnum_save" is the line number that was used to get
/// the level when the level at "flp->lnum" is invalid.
/// Remove any folds from "startlnum" up to here at this level.
/// Recursively update nested folds.
/// Below line "bot" there are no changes in the text.
/// "flp->lnum", "flp->lnum_save" and "bot" are relative to the start of the
/// outer fold.
/// "flp->off" is the offset to the real line number in the buffer.
///
/// All this would be a lot simpler if all folds in the range would be deleted
/// and then created again.  But we would lose all information about the
/// folds, even when making changes that don't affect the folding (e.g. "vj~").
///
/// @param topflags  containing fold flags
///
/// @return  bot, which may have been increased for lines that also need to be
/// updated as a result of a detected change in the fold.
static linenr_T foldUpdateIEMSRecurse(garray_T *const gap, const int level,
                                     const linenr_T startlnum, fline_T *const flp,
                                     LevelGetter getlevel, linenr_T bot, const char topflags)
{
 fold_T *fp = NULL;

 // If using the marker method, the start line is not the start of a fold
 // at the level we're dealing with and the level is non-zero, we must use
 // the previous fold.  But ignore a fold that starts at or below
 // startlnum, it must be deleted.
 if (getlevel == foldlevelMarker && flp->start <= flp->lvl - level
     && flp->lvl > 0) {
   foldFind(gap, startlnum - 1, &fp);
   if (fp != NULL
       && (fp >= ((fold_T *)gap->ga_data) + gap->ga_len
           || fp->fd_top >= startlnum)) {
     fp = NULL;
   }
 }

 fold_T *fp2;
 int lvl = level;
 linenr_T startlnum2 = startlnum;
 const linenr_T firstlnum = flp->lnum;     // first lnum we got
 bool finish = false;
 const linenr_T linecount = flp->wp->w_buffer->b_ml.ml_line_count - flp->off;

 // Loop over all lines in this fold, or until "bot" is hit.
 // Handle nested folds inside of this fold.
 // "flp->lnum" is the current line.  When finding the end of the fold, it
 // is just below the end of the fold.
 // "*flp" contains the level of the line "flp->lnum" or a following one if
 // there are lines with an invalid fold level.  "flp->lnum_save" is the
 // line number that was used to get the fold level (below "flp->lnum" when
 // it has an invalid fold level).  When called the fold level is always
 // valid, thus "flp->lnum_save" is equal to "flp->lnum".
 flp->lnum_save = flp->lnum;
 while (!got_int) {
   // Updating folds can be slow, check for CTRL-C.
   line_breakcheck();

   // Set "lvl" to the level of line "flp->lnum".  When flp->start is set
   // and after the first line of the fold, set the level to zero to
   // force the fold to end.  Do the same when had_end is set: Previous
   // line was marked as end of a fold.
   lvl = MIN(flp->lvl, MAX_LEVEL);
   if (flp->lnum > firstlnum
       && (level > lvl - flp->start || level >= flp->had_end)) {
     lvl = 0;
   }

   if (flp->lnum > bot && !finish && fp != NULL) {
     // For "marker" and "syntax" methods:
     // - If a change caused a nested fold to be removed, we need to
     //   delete it and continue at least until where it ended.
     // - If a change caused a nested fold to be created, or this fold
     //   to continue below its original end, need to finish this fold.
     if (getlevel != foldlevelMarker
         && getlevel != foldlevelExpr
         && getlevel != foldlevelSyntax) {
       break;
     }
     int i = 0;
     fp2 = fp;
     if (lvl >= level) {
       // Compute how deep the folds currently are, if it's deeper
       // than "lvl" then some must be deleted, need to update
       // at least one nested fold.
       int ll = flp->lnum - fp->fd_top;
       while (foldFind(&fp2->fd_nested, ll, &fp2)) {
         i++;
         ll -= fp2->fd_top;
       }
     }
     if (lvl < level + i) {
       foldFind(&fp->fd_nested, flp->lnum - fp->fd_top, &fp2);
       if (fp2 != NULL) {
         bot = fp2->fd_top + fp2->fd_len - 1 + fp->fd_top;
       }
     } else if (fp->fd_top + fp->fd_len <= flp->lnum && lvl >= level) {
       finish = true;
     } else {
       break;
     }
   }

   // At the start of the first nested fold and at the end of the current
   // fold: check if existing folds at this level, before the current
   // one, need to be deleted or truncated.
   if (fp == NULL
       && (lvl != level
           || flp->lnum_save >= bot
           || flp->start != 0
           || flp->had_end <= MAX_LEVEL
           || flp->lnum == linecount)) {
     // Remove or update folds that have lines between startlnum and
     // firstlnum.
     while (!got_int) {
       // set concat to 1 if it's allowed to concatenate this fold
       // with a previous one that touches it.
       int concat = (flp->start != 0 || flp->had_end <= MAX_LEVEL) ? 0 : 1;

       // Find an existing fold to re-use.  Preferably one that
       // includes startlnum, otherwise one that ends just before
       // startlnum or starts after it.
       if (gap->ga_len > 0
           && (foldFind(gap, startlnum, &fp)
               || (fp < ((fold_T *)gap->ga_data) + gap->ga_len
                   && fp->fd_top <= firstlnum)
               || foldFind(gap, firstlnum - concat, &fp)
               || (fp < ((fold_T *)gap->ga_data) + gap->ga_len
                   && ((lvl < level && fp->fd_top < flp->lnum)
                       || (lvl >= level
                           && fp->fd_top <= flp->lnum_save))))) {
         if (fp->fd_top + fp->fd_len + concat > firstlnum) {
           // Use existing fold for the new fold.  If it starts
           // before where we started looking, extend it.  If it
           // starts at another line, update nested folds to keep
           // their position, compensating for the new fd_top.
           if (fp->fd_top == firstlnum) {
             // We have found a fold beginning exactly where we want one.
           } else if (fp->fd_top >= startlnum) {
             if (fp->fd_top > firstlnum) {
               // We will move the start of this fold up, hence we move all
               // nested folds (with relative line numbers) down.
               foldMarkAdjustRecurse(flp->wp, &fp->fd_nested,
                                     0, (linenr_T)MAXLNUM,
                                     (fp->fd_top - firstlnum), 0);
             } else {
               // Will move fold down, move nested folds relatively up.
               foldMarkAdjustRecurse(flp->wp, &fp->fd_nested,
                                     0,
                                     (firstlnum - fp->fd_top - 1),
                                     (linenr_T)MAXLNUM,
                                     (fp->fd_top - firstlnum));
             }
             fp->fd_len += fp->fd_top - firstlnum;
             fp->fd_top = firstlnum;
             fp->fd_small = kNone;
             fold_changed = true;
           } else if ((flp->start != 0 && lvl == level)
                      || (firstlnum != startlnum)) {
             // Before there was a fold spanning from above startlnum to below
             // firstlnum. This fold is valid above startlnum (because we are
             // not updating that range), but there is now a break in it.
             // If the break is because we are now forced to start a new fold
             // at the level "level" at line fline->lnum, then we need to
             // split the fold at fline->lnum.
             // If the break is because the range [startlnum, firstlnum) is
             // now at a lower indent than "level", we need to split the fold
             // in this range.
             // Any splits have to be done recursively.
             linenr_T breakstart;
             linenr_T breakend;
             if (firstlnum != startlnum) {
               breakstart = startlnum;
               breakend = firstlnum;
             } else {
               breakstart = flp->lnum;
               breakend = flp->lnum;
             }
             foldRemove(flp->wp, &fp->fd_nested, breakstart - fp->fd_top,
                        breakend - fp->fd_top);
             int i = (int)(fp - (fold_T *)gap->ga_data);
             foldSplit(flp->wp->w_buffer, gap, i, breakstart, breakend - 1);
             fp = (fold_T *)gap->ga_data + i + 1;
             // If using the "marker" or "syntax" method, we
             // need to continue until the end of the fold is
             // found.
             if (getlevel == foldlevelMarker
                 || getlevel == foldlevelExpr
                 || getlevel == foldlevelSyntax) {
               finish = true;
             }
           }
           if (fp->fd_top == startlnum && concat) {
             int i = (int)(fp - (fold_T *)gap->ga_data);
             if (i != 0) {
               fp2 = fp - 1;
               if (fp2->fd_top + fp2->fd_len == fp->fd_top) {
                 foldMerge(flp->wp, fp2, gap, fp);
                 fp = fp2;
               }
             }
           }
           break;
         }
         if (fp->fd_top >= startlnum) {
           // A fold that starts at or after startlnum and stops
           // before the new fold must be deleted.  Continue
           // looking for the next one.
           deleteFoldEntry(flp->wp, gap,
                           (int)(fp - (fold_T *)gap->ga_data), true);
         } else {
           // A fold has some lines above startlnum, truncate it
           // to stop just above startlnum.
           fp->fd_len = startlnum - fp->fd_top;
           foldMarkAdjustRecurse(flp->wp, &fp->fd_nested,
                                 fp->fd_len, (linenr_T)MAXLNUM,
                                 (linenr_T)MAXLNUM, 0);
           fold_changed = true;
         }
       } else {
         // Insert new fold.  Careful: ga_data may be NULL and it
         // may change!
         int i;
         if (gap->ga_len == 0) {
           i = 0;
         } else {
           i = (int)(fp - (fold_T *)gap->ga_data);
         }
         foldInsert(gap, i);
         fp = (fold_T *)gap->ga_data + i;
         // The new fold continues until bot, unless we find the
         // end earlier.
         fp->fd_top = firstlnum;
         fp->fd_len = bot - firstlnum + 1;
         // When the containing fold is open, the new fold is open.
         // The new fold is closed if the fold above it is closed.
         // The first fold depends on the containing fold.
         if (topflags == FD_OPEN) {
           flp->wp->w_fold_manual = true;
           fp->fd_flags = FD_OPEN;
         } else if (i <= 0) {
           fp->fd_flags = topflags;
           if (topflags != FD_LEVEL) {
             flp->wp->w_fold_manual = true;
           }
         } else {
           fp->fd_flags = (fp - 1)->fd_flags;
         }
         fp->fd_small = kNone;
         // If using the "marker", "expr" or "syntax" method, we
         // need to continue until the end of the fold is found.
         if (getlevel == foldlevelMarker
             || getlevel == foldlevelExpr
             || getlevel == foldlevelSyntax) {
           finish = true;
         }
         fold_changed = true;
         break;
       }
     }
   }

   if (lvl < level || flp->lnum > linecount) {
     // Found a line with a lower foldlevel, this fold ends just above
     // "flp->lnum".
     break;
   }

   // The fold includes the line "flp->lnum" and "flp->lnum_save".
   // Check "fp" for safety.
   if (lvl > level && fp != NULL) {
     // There is a nested fold, handle it recursively.
     // At least do one line (can happen when finish is true).
     bot = MAX(bot, flp->lnum);

     // Line numbers in the nested fold are relative to the start of
     // this fold.
     flp->lnum = flp->lnum_save - fp->fd_top;
     flp->off += fp->fd_top;
     int i = (int)(fp - (fold_T *)gap->ga_data);
     bot = foldUpdateIEMSRecurse(&fp->fd_nested, level + 1,
                                 startlnum2 - fp->fd_top, flp, getlevel,
                                 bot - fp->fd_top, fp->fd_flags);
     fp = (fold_T *)gap->ga_data + i;
     flp->lnum += fp->fd_top;
     flp->lnum_save += fp->fd_top;
     flp->off -= fp->fd_top;
     bot += fp->fd_top;
     startlnum2 = flp->lnum;

     // This fold may end at the same line, don't incr. flp->lnum.
   } else {
     // Get the level of the next line, then continue the loop to check
     // if it ends there.
     // Skip over undefined lines, to find the foldlevel after it.
     // For the last line in the file the foldlevel is always valid.
     flp->lnum = flp->lnum_save;
     int ll = flp->lnum + 1;
     while (!got_int) {
       // Make the previous level available to foldlevel().
       prev_lnum = flp->lnum;
       prev_lnum_lvl = flp->lvl;

       if (++flp->lnum > linecount) {
         break;
       }
       flp->lvl = flp->lvl_next;
       getlevel(flp);
       if (flp->lvl >= 0 || flp->had_end <= MAX_LEVEL) {
         break;
       }
     }
     prev_lnum = 0;
     if (flp->lnum > linecount) {
       break;
     }

     // leave flp->lnum_save to lnum of the line that was used to get
     // the level, flp->lnum to the lnum of the next line.
     flp->lnum_save = flp->lnum;
     flp->lnum = ll;
   }
 }

 if (fp == NULL) {     // only happens when got_int is set
   return bot;
 }

 // Get here when:
 // lvl < level: the folds ends just above "flp->lnum"
 // lvl >= level: fold continues below "bot"

 // Current fold at least extends until lnum.
 if (fp->fd_len < flp->lnum - fp->fd_top) {
   fp->fd_len = flp->lnum - fp->fd_top;
   fp->fd_small = kNone;
   fold_changed = true;
 } else if (fp->fd_top + fp->fd_len > linecount) {
   // running into the end of the buffer (deleted last line)
   fp->fd_len = linecount - fp->fd_top + 1;
 }

 // Delete contained folds from the end of the last one found until where
 // we stopped looking.
 foldRemove(flp->wp, &fp->fd_nested, startlnum2 - fp->fd_top,
            flp->lnum - 1 - fp->fd_top);

 if (lvl < level) {
   // End of fold found, update the length when it got shorter.
   if (fp->fd_len != flp->lnum - fp->fd_top) {
     if (fp->fd_top + fp->fd_len - 1 > bot) {
       // fold continued below bot
       if (getlevel == foldlevelMarker
           || getlevel == foldlevelExpr
           || getlevel == foldlevelSyntax) {
         // marker method: truncate the fold and make sure the
         // previously included lines are processed again
         bot = fp->fd_top + fp->fd_len - 1;
         fp->fd_len = flp->lnum - fp->fd_top;
       } else {
         // indent or expr method: split fold to create a new one
         // below bot
         int i = (int)(fp - (fold_T *)gap->ga_data);
         foldSplit(flp->wp->w_buffer, gap, i, flp->lnum, bot);
         fp = (fold_T *)gap->ga_data + i;
       }
     } else {
       fp->fd_len = flp->lnum - fp->fd_top;
     }
     fold_changed = true;
   }
 }

 // delete following folds that end before the current line
 while (true) {
   fp2 = fp + 1;
   if (fp2 >= (fold_T *)gap->ga_data + gap->ga_len
       || fp2->fd_top > flp->lnum) {
     break;
   }
   if (fp2->fd_top + fp2->fd_len > flp->lnum) {
     if (fp2->fd_top < flp->lnum) {
       // Make fold that includes lnum start at lnum.
       foldMarkAdjustRecurse(flp->wp, &fp2->fd_nested,
                             0, (flp->lnum - fp2->fd_top - 1),
                             (linenr_T)MAXLNUM, (fp2->fd_top - flp->lnum));
       fp2->fd_len -= flp->lnum - fp2->fd_top;
       fp2->fd_top = flp->lnum;
       fold_changed = true;
     }

     if (lvl >= level) {
       // merge new fold with existing fold that follows
       foldMerge(flp->wp, fp, gap, fp2);
     }
     break;
   }
   fold_changed = true;
   deleteFoldEntry(flp->wp, gap, (int)(fp2 - (fold_T *)gap->ga_data), true);
 }

 // Need to redraw the lines we inspected, which might be further down than
 // was asked for.
 bot = MAX(bot, flp->lnum - 1);

 return bot;
}

// foldInsert() {{{2
/// Insert a new fold in "gap" at position "i".
static void foldInsert(garray_T *gap, int i)
{
 ga_grow(gap, 1);

 fold_T *fp = (fold_T *)gap->ga_data + i;
 if (gap->ga_len > 0 && i < gap->ga_len) {
   memmove(fp + 1, fp, sizeof(fold_T) * (size_t)(gap->ga_len - i));
 }
 gap->ga_len++;
 ga_init(&fp->fd_nested, (int)sizeof(fold_T), 10);
}

// foldSplit() {{{2
/// Split the "i"th fold in "gap", which starts before "top" and ends below
/// "bot" in two pieces, one ending above "top" and the other starting below
/// "bot".
/// The caller must first have taken care of any nested folds from "top" to
/// "bot"!
static void foldSplit(buf_T *buf, garray_T *const gap, const int i, const linenr_T top,
                     const linenr_T bot)
{
 fold_T *fp2;

 // The fold continues below bot, need to split it.
 foldInsert(gap, i + 1);

 fold_T *const fp = (fold_T *)gap->ga_data + i;
 fp[1].fd_top = bot + 1;
 // check for wrap around (MAXLNUM, and 32bit)
 assert(fp[1].fd_top > bot);
 fp[1].fd_len = fp->fd_len - (fp[1].fd_top - fp->fd_top);
 fp[1].fd_flags = fp->fd_flags;
 fp[1].fd_small = kNone;
 fp->fd_small = kNone;

 // Move nested folds below bot to new fold.  There can't be
 // any between top and bot, they have been removed by the caller.
 garray_T *const gap1 = &fp->fd_nested;
 garray_T *const gap2 = &fp[1].fd_nested;
 foldFind(gap1, bot + 1 - fp->fd_top, &fp2);
 if (fp2 != NULL) {
   const int len = (int)((fold_T *)gap1->ga_data + gap1->ga_len - fp2);
   if (len > 0) {
     ga_grow(gap2, len);
     for (int idx = 0; idx < len; idx++) {
       ((fold_T *)gap2->ga_data)[idx] = fp2[idx];
       ((fold_T *)gap2->ga_data)[idx].fd_top
         -= fp[1].fd_top - fp->fd_top;
     }
     gap2->ga_len = len;
     gap1->ga_len -= len;
   }
 }
 fp->fd_len = top - fp->fd_top;
 fold_changed = true;
}

// foldRemove() {{{2
/// Remove folds within the range "top" to and including "bot".
/// Check for these situations:
///      1  2  3
///      1  2  3
/// top     2  3  4  5
///     2  3  4  5
/// bot     2  3  4  5
///        3     5  6
///        3     5  6
///
/// 1: not changed
/// 2: truncate to stop above "top"
/// 3: split in two parts, one stops above "top", other starts below "bot".
/// 4: deleted
/// 5: made to start below "bot".
/// 6: not changed
static void foldRemove(win_T *const wp, garray_T *gap, linenr_T top, linenr_T bot)
{
 if (bot < top) {
   return;             // nothing to do
 }

 fold_T *fp = NULL;

 while (gap->ga_len > 0) {
   // Find fold that includes top or a following one.
   if (foldFind(gap, top, &fp) && fp->fd_top < top) {
     // 2: or 3: need to delete nested folds
     foldRemove(wp, &fp->fd_nested, top - fp->fd_top, bot - fp->fd_top);
     if (fp->fd_top + fp->fd_len - 1 > bot) {
       // 3: need to split it.
       foldSplit(wp->w_buffer, gap,
                 (int)(fp - (fold_T *)gap->ga_data), top, bot);
     } else {
       // 2: truncate fold at "top".
       fp->fd_len = top - fp->fd_top;
     }
     fold_changed = true;
     continue;
   }
   if (gap->ga_data == NULL
       || fp >= (fold_T *)(gap->ga_data) + gap->ga_len
       || fp->fd_top > bot) {
     // 6: Found a fold below bot, can stop looking.
     break;
   }
   if (fp->fd_top >= top) {
     // Found an entry below top.
     fold_changed = true;
     if (fp->fd_top + fp->fd_len - 1 > bot) {
       // 5: Make fold that includes bot start below bot.
       foldMarkAdjustRecurse(wp, &fp->fd_nested,
                             0, (bot - fp->fd_top),
                             (linenr_T)MAXLNUM, (fp->fd_top - bot - 1));
       fp->fd_len -= bot - fp->fd_top + 1;
       fp->fd_top = bot + 1;
       break;
     }

     // 4: Delete completely contained fold.
     deleteFoldEntry(wp, gap, (int)(fp - (fold_T *)gap->ga_data), true);
   }
 }
}

// foldReverseOrder() {{{2
static void foldReverseOrder(garray_T *gap, const linenr_T start_arg, const linenr_T end_arg)
{
 linenr_T start = start_arg;
 linenr_T end = end_arg;
 for (; start < end; start++, end--) {
   fold_T *left = (fold_T *)gap->ga_data + start;
   fold_T *right = (fold_T *)gap->ga_data + end;
   fold_T tmp = *left;
   *left = *right;
   *right = tmp;
 }
}

// foldMoveRange() {{{2
/// Move folds within the inclusive range "line1" to "line2" to after "dest"
/// require "line1" <= "line2" <= "dest"
///
/// There are the following situations for the first fold at or below line1 - 1.
///       1  2  3  4
///       1  2  3  4
/// line1    2  3  4
///          2  3  4  5  6  7
/// line2       3  4  5  6  7
///             3  4     6  7  8  9
/// dest           4        7  8  9
///                4        7  8    10
///                4        7  8    10
///
/// In the following descriptions, "moved" means moving in the buffer, *and* in
/// the fold array.
/// Meanwhile, "shifted" just means moving in the buffer.
/// 1. not changed
/// 2. truncated above line1
/// 3. length reduced by  line2 - line1, folds starting between the end of 3 and
///    dest are truncated and shifted up
/// 4. internal folds moved (from [line1, line2] to dest)
/// 5. moved to dest.
/// 6. truncated below line2 and moved.
/// 7. length reduced by line2 - dest, folds starting between line2 and dest are
///    removed, top is moved down by move_len.
/// 8. truncated below dest and shifted up.
/// 9. shifted up
/// 10. not changed
static void truncate_fold(win_T *const wp, fold_T *fp, linenr_T end)
{
 // I want to stop *at here*, foldRemove() stops *above* top
 end += 1;
 foldRemove(wp, &fp->fd_nested, end - fp->fd_top, MAXLNUM);
 fp->fd_len = end - fp->fd_top;
}

#define FOLD_END(fp) ((fp)->fd_top + (fp)->fd_len - 1)
#define VALID_FOLD(fp, gap) \
 ((gap)->ga_len > 0 && (fp) < ((fold_T *)(gap)->ga_data + (gap)->ga_len))
#define FOLD_INDEX(fp, gap) ((size_t)((fp) - ((fold_T *)(gap)->ga_data)))
void foldMoveRange(win_T *const wp, garray_T *gap, const linenr_T line1, const linenr_T line2,
                  const linenr_T dest)
{
 fold_T *fp;
 const linenr_T range_len = line2 - line1 + 1;
 const linenr_T move_len = dest - line2;
 const bool at_start = foldFind(gap, line1 - 1, &fp);

 if (at_start) {
   if (FOLD_END(fp) > dest) {
     // Case 4 -- don't have to change this fold, but have to move nested
     // folds.
     foldMoveRange(wp, &fp->fd_nested, line1 - fp->fd_top, line2 -
                   fp->fd_top, dest - fp->fd_top);
     return;
   } else if (FOLD_END(fp) > line2) {
     // Case 3 -- Remove nested folds between line1 and line2 & reduce the
     // length of fold by "range_len".
     // Folds after this one must be dealt with.
     foldMarkAdjustRecurse(wp, &fp->fd_nested, line1 - fp->fd_top,
                           line2 - fp->fd_top, MAXLNUM, -range_len);
     fp->fd_len -= range_len;
   } else {
     // Case 2 -- truncate fold *above* line1.
     // Folds after this one must be dealt with.
     truncate_fold(wp, fp, line1 - 1);
   }
   // Look at the next fold, and treat that one as if it were the first after
   // "line1" (because now it is).
   fp = fp + 1;
 }

 if (!VALID_FOLD(fp, gap) || fp->fd_top > dest) {
   // No folds after "line1" and before "dest"
   // Case 10.
   return;
 } else if (fp->fd_top > line2) {
   for (; VALID_FOLD(fp, gap) && FOLD_END(fp) <= dest; fp++) {
     // Case 9. (for all case 9's) -- shift up.
     fp->fd_top -= range_len;
   }
   if (VALID_FOLD(fp, gap) && fp->fd_top <= dest) {
     // Case 8. -- ensure truncated at dest, shift up
     truncate_fold(wp, fp, dest);
     fp->fd_top -= range_len;
   }
   return;
 } else if (FOLD_END(fp) > dest) {
   // Case 7 -- remove nested folds and shrink
   foldMarkAdjustRecurse(wp, &fp->fd_nested, line2 + 1 - fp->fd_top,
                         dest - fp->fd_top, MAXLNUM, -move_len);
   fp->fd_len -= move_len;
   fp->fd_top += move_len;
   return;
 }

 // Case 5 or 6: changes rely on whether there are folds between the end of
 // this fold and "dest".
 size_t move_start = FOLD_INDEX(fp, gap);
 size_t move_end = 0;
 size_t dest_index = 0;
 for (; VALID_FOLD(fp, gap) && fp->fd_top <= dest; fp++) {
   if (fp->fd_top <= line2) {
     // 5, or 6
     if (FOLD_END(fp) > line2) {
       // 6, truncate before moving
       truncate_fold(wp, fp, line2);
     }
     fp->fd_top += move_len;
     continue;
   }

   // Record index of the first fold after the moved range.
   if (move_end == 0) {
     move_end = FOLD_INDEX(fp, gap);
   }

   if (FOLD_END(fp) > dest) {
     truncate_fold(wp, fp, dest);
   }

   fp->fd_top -= range_len;
 }
 dest_index = FOLD_INDEX(fp, gap);

 // All folds are now correct, but not necessarily in the correct order.
 // We must swap folds in the range [move_end, dest_index) with those in the
 // range [move_start, move_end).
 if (move_end == 0) {
   // There are no folds after those moved, so none were moved out of order.
   return;
 }
 foldReverseOrder(gap, (linenr_T)move_start, (linenr_T)(dest_index - 1));
 foldReverseOrder(gap, (linenr_T)move_start,
                  (linenr_T)(move_start + dest_index - move_end - 1));
 foldReverseOrder(gap, (linenr_T)(move_start + dest_index - move_end),
                  (linenr_T)(dest_index - 1));
}
#undef FOLD_END
#undef VALID_FOLD
#undef FOLD_INDEX

// foldMerge() {{{2
/// Merge two adjacent folds (and the nested ones in them).
/// This only works correctly when the folds are really adjacent!  Thus "fp1"
/// must end just above "fp2".
/// The resulting fold is "fp1", nested folds are moved from "fp2" to "fp1".
/// Fold entry "fp2" in "gap" is deleted.
static void foldMerge(win_T *const wp, fold_T *fp1, garray_T *gap, fold_T *fp2)
{
 fold_T *fp3;
 fold_T *fp4;
 garray_T *gap1 = &fp1->fd_nested;
 garray_T *gap2 = &fp2->fd_nested;

 // If the last nested fold in fp1 touches the first nested fold in fp2,
 // merge them recursively.
 if (foldFind(gap1, fp1->fd_len - 1, &fp3) && foldFind(gap2, 0, &fp4)) {
   foldMerge(wp, fp3, gap2, fp4);
 }

 // Move nested folds in fp2 to the end of fp1.
 if (!GA_EMPTY(gap2)) {
   ga_grow(gap1, gap2->ga_len);
   for (int idx = 0; idx < gap2->ga_len; idx++) {
     ((fold_T *)gap1->ga_data)[gap1->ga_len]
       = ((fold_T *)gap2->ga_data)[idx];
     ((fold_T *)gap1->ga_data)[gap1->ga_len].fd_top += fp1->fd_len;
     gap1->ga_len++;
   }
   gap2->ga_len = 0;
 }

 fp1->fd_len += fp2->fd_len;
 deleteFoldEntry(wp, gap, (int)(fp2 - (fold_T *)gap->ga_data), true);
 fold_changed = true;
}

// foldlevelIndent() {{{2
/// Low level function to get the foldlevel for the "indent" method.
/// Doesn't use any caching.
///
/// @return  a level of -1 if the foldlevel depends on surrounding lines.
static void foldlevelIndent(fline_T *flp)
{
 linenr_T lnum = flp->lnum + flp->off;

 buf_T *buf = flp->wp->w_buffer;
 char *s = skipwhite(ml_get_buf(buf, lnum));

 // empty line or lines starting with a character in 'foldignore': level
 // depends on surrounding lines
 if (*s == NUL || vim_strchr(flp->wp->w_p_fdi, (uint8_t)(*s)) != NULL) {
   // first and last line can't be undefined, use level 0
   flp->lvl = (lnum == 1 || lnum == buf->b_ml.ml_line_count) ? 0 : -1;
 } else {
   flp->lvl = get_indent_buf(buf, lnum) / get_sw_value(buf);
 }
 flp->lvl = MIN(flp->lvl, (int)MAX(0, flp->wp->w_p_fdn));
}

// foldlevelDiff() {{{2
/// Low level function to get the foldlevel for the "diff" method.
/// Doesn't use any caching.
static void foldlevelDiff(fline_T *flp)
{
 flp->lvl = (diff_infold(flp->wp, flp->lnum + flp->off)) ? 1 : 0;
}

// foldlevelExpr() {{{2
/// Low level function to get the foldlevel for the "expr" method.
/// Doesn't use any caching.
///
/// @return  a level of -1 if the foldlevel depends on surrounding lines.
static void foldlevelExpr(fline_T *flp)
{
 linenr_T lnum = flp->lnum + flp->off;

 win_T *win = curwin;
 curwin = flp->wp;
 curbuf = flp->wp->w_buffer;
 set_vim_var_nr(VV_LNUM, (varnumber_T)lnum);

 flp->start = 0;
 flp->had_end = flp->end;
 flp->end = MAX_LEVEL + 1;
 if (lnum <= 1) {
   flp->lvl = 0;
 }

 // KeyTyped may be reset to 0 when calling a function which invokes
 // do_cmdline().  To make 'foldopen' work correctly restore KeyTyped.
 const bool save_keytyped = KeyTyped;

 int c;
 const int n = eval_foldexpr(flp->wp, &c);
 KeyTyped = save_keytyped;

 switch (c) {
 // "a1", "a2", .. : add to the fold level
 case 'a':
   if (flp->lvl >= 0) {
     flp->lvl += n;
     flp->lvl_next = flp->lvl;
   }
   flp->start = n;
   break;

 // "s1", "s2", .. : subtract from the fold level
 case 's':
   if (flp->lvl >= 0) {
     if (n > flp->lvl) {
       flp->lvl_next = 0;
     } else {
       flp->lvl_next = flp->lvl - n;
     }
     flp->end = flp->lvl_next + 1;
   }
   break;

 // ">1", ">2", .. : start a fold with a certain level
 case '>':
   flp->lvl = n;
   flp->lvl_next = n;
   flp->start = 1;
   break;

 // "<1", "<2", .. : end a fold with a certain level
 case '<':
   // To prevent an unexpected start of a new fold, the next
   // level must not exceed the level of the current fold.
   flp->lvl_next = MIN(flp->lvl, n - 1);
   flp->end = n;
   break;

 // "=": No change in level
 case '=':
   flp->lvl_next = flp->lvl;
   break;

 // "-1", "0", "1", ..: set fold level
 default:
   if (n < 0) {
     // Use the current level for the next line, so that "a1"
     // will work there.
     flp->lvl_next = flp->lvl;
   } else {
     flp->lvl_next = n;
   }
   flp->lvl = n;
   break;
 }

 // If the level is unknown for the first or the last line in the file, use
 // level 0.
 if (flp->lvl < 0) {
   if (lnum <= 1) {
     flp->lvl = 0;
     flp->lvl_next = 0;
   }
   if (lnum == curbuf->b_ml.ml_line_count) {
     flp->lvl_next = 0;
   }
 }

 curwin = win;
 curbuf = curwin->w_buffer;
}

// parseMarker() {{{2
/// Parse 'foldmarker' and set "foldendmarker", "foldstartmarkerlen" and
/// "foldendmarkerlen".
/// Relies on the option value to have been checked for correctness already.
static void parseMarker(win_T *wp)
{
 foldendmarker = vim_strchr(wp->w_p_fmr, ',');
 foldstartmarkerlen = (size_t)(foldendmarker++ - wp->w_p_fmr);
 foldendmarkerlen = strlen(foldendmarker);
}

// foldlevelMarker() {{{2
/// Low level function to get the foldlevel for the "marker" method.
/// "foldendmarker", "foldstartmarkerlen" and "foldendmarkerlen" must have been
/// set before calling this.
/// Requires that flp->lvl is set to the fold level of the previous line!
/// Careful: This means you can't call this function twice on the same line.
/// Doesn't use any caching.
/// Sets flp->start when a start marker was found.
static void foldlevelMarker(fline_T *flp)
{
 int start_lvl = flp->lvl;

 // cache a few values for speed
 char *startmarker = flp->wp->w_p_fmr;
 char cstart = *startmarker;
 startmarker++;
 char cend = *foldendmarker;

 // Default: no start found, next level is same as current level
 flp->start = 0;
 flp->lvl_next = flp->lvl;

 char *s = ml_get_buf(flp->wp->w_buffer, flp->lnum + flp->off);
 while (*s) {
   if (*s == cstart
       && strncmp(s + 1, startmarker, foldstartmarkerlen - 1) == 0) {
     // found startmarker: set flp->lvl
     s += foldstartmarkerlen;
     if (ascii_isdigit(*s)) {
       int n = atoi(s);
       if (n > 0) {
         flp->lvl = n;
         flp->lvl_next = n;
         flp->start = MAX(n - start_lvl, 1);
       }
     } else {
       flp->lvl++;
       flp->lvl_next++;
       flp->start++;
     }
   } else if (*s == cend
              && strncmp(s + 1, foldendmarker + 1, foldendmarkerlen - 1) == 0) {
     // found endmarker: set flp->lvl_next
     s += foldendmarkerlen;
     if (ascii_isdigit(*s)) {
       int n = atoi(s);
       if (n > 0) {
         flp->lvl = n;
         flp->lvl_next = n - 1;
         // never start a fold with an end marker
         flp->lvl_next = MIN(flp->lvl_next, start_lvl);
       }
     } else {
       flp->lvl_next--;
     }
   } else {
     MB_PTR_ADV(s);
   }
 }

 // The level can't go negative, must be missing a start marker.
 flp->lvl_next = MAX(flp->lvl_next, 0);
}

// foldlevelSyntax() {{{2
/// Low level function to get the foldlevel for the "syntax" method.
/// Doesn't use any caching.
static void foldlevelSyntax(fline_T *flp)
{
 linenr_T lnum = flp->lnum + flp->off;

 // Use the maximum fold level at the start of this line and the next.
 flp->lvl = syn_get_foldlevel(flp->wp, lnum);
 flp->start = 0;
 if (lnum < flp->wp->w_buffer->b_ml.ml_line_count) {
   int n = syn_get_foldlevel(flp->wp, lnum + 1);
   if (n > flp->lvl) {
     flp->start = n - flp->lvl;        // fold(s) start here
     flp->lvl = n;
   }
 }
}

// functions for storing the fold state in a View {{{1
// put_folds() {{{2
/// Write commands to "fd" to restore the manual folds in window "wp".
///
/// @return  FAIL if writing fails.
int put_folds(FILE *fd, win_T *wp)
{
 if (foldmethodIsManual(wp)) {
   if (put_line(fd, "silent! normal! zE") == FAIL
       || put_folds_recurse(fd, &wp->w_folds, 0) == FAIL
       || put_line(fd, "let &fdl = &fdl") == FAIL) {
     return FAIL;
   }
 }

 // If some folds are manually opened/closed, need to restore that.
 if (wp->w_fold_manual) {
   return put_foldopen_recurse(fd, wp, &wp->w_folds, 0);
 }

 return OK;
}

// put_folds_recurse() {{{2
/// Write commands to "fd" to recreate manually created folds.
///
/// @return  FAIL when writing failed.
static int put_folds_recurse(FILE *fd, garray_T *gap, linenr_T off)
{
 fold_T *fp = (fold_T *)gap->ga_data;
 for (int i = 0; i < gap->ga_len; i++) {
   // Do nested folds first, they will be created closed.
   if (put_folds_recurse(fd, &fp->fd_nested, off + fp->fd_top) == FAIL) {
     return FAIL;
   }
   if (fprintf(fd, "sil! %" PRId64 ",%" PRId64 "fold",
               (int64_t)fp->fd_top + off,
               (int64_t)(fp->fd_top + off + fp->fd_len - 1)) < 0
       || put_eol(fd) == FAIL) {
     return FAIL;
   }
   fp++;
 }
 return OK;
}

// put_foldopen_recurse() {{{2
/// Write commands to "fd" to open and close manually opened/closed folds.
///
/// @return  FAIL when writing failed.
static int put_foldopen_recurse(FILE *fd, win_T *wp, garray_T *gap, linenr_T off)
{
 fold_T *fp = (fold_T *)gap->ga_data;
 for (int i = 0; i < gap->ga_len; i++) {
   if (fp->fd_flags != FD_LEVEL) {
     if (!GA_EMPTY(&fp->fd_nested)) {
       // open nested folds while this fold is open
       // ignore errors
       if (fprintf(fd, "%" PRId64, (int64_t)fp->fd_top + off) < 0
           || put_eol(fd) == FAIL
           || put_line(fd, "sil! normal! zo") == FAIL) {
         return FAIL;
       }
       if (put_foldopen_recurse(fd, wp, &fp->fd_nested,
                                off + fp->fd_top)
           == FAIL) {
         return FAIL;
       }
       // close the parent when needed
       if (fp->fd_flags == FD_CLOSED) {
         if (put_fold_open_close(fd, fp, off) == FAIL) {
           return FAIL;
         }
       }
     } else {
       // Open or close the leaf according to the window foldlevel.
       // Do not close a leaf that is already closed, as it will close
       // the parent.
       int level = foldLevelWin(wp, off + fp->fd_top);
       if ((fp->fd_flags == FD_CLOSED && wp->w_p_fdl >= level)
           || (fp->fd_flags != FD_CLOSED && wp->w_p_fdl < level)) {
         if (put_fold_open_close(fd, fp, off) == FAIL) {
           return FAIL;
         }
       }
     }
   }
   fp++;
 }

 return OK;
}

// put_fold_open_close() {{{2
/// Write the open or close command to "fd".
///
/// @return  FAIL when writing failed.
static int put_fold_open_close(FILE *fd, fold_T *fp, linenr_T off)
{
 if (fprintf(fd, "%" PRIdLINENR, fp->fd_top + off) < 0
     || put_eol(fd) == FAIL
     || fprintf(fd, "sil! normal! z%c",
                fp->fd_flags == FD_CLOSED ? 'c' : 'o') < 0
     || put_eol(fd) == FAIL) {
   return FAIL;
 }

 return OK;
}

// }}}1

/// "foldclosed()" and "foldclosedend()" functions
static void foldclosed_both(typval_T *argvars, typval_T *rettv, bool end)
{
 const linenr_T lnum = tv_get_lnum(argvars);
 if (lnum >= 1 && lnum <= curbuf->b_ml.ml_line_count) {
   linenr_T first;
   linenr_T last;
   if (hasFoldingWin(curwin, lnum, &first, &last, false, NULL)) {
     rettv->vval.v_number = (varnumber_T)(end ? last : first);
     return;
   }
 }
 rettv->vval.v_number = -1;
}

/// "foldclosed()" function
void f_foldclosed(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
{
 foldclosed_both(argvars, rettv, false);
}

/// "foldclosedend()" function
void f_foldclosedend(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
{
 foldclosed_both(argvars, rettv, true);
}

/// "foldlevel()" function
void f_foldlevel(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
{
 const linenr_T lnum = tv_get_lnum(argvars);
 if (lnum >= 1 && lnum <= curbuf->b_ml.ml_line_count) {
   rettv->vval.v_number = foldLevel(lnum);
 }
}

/// "foldtext()" function
void f_foldtext(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
{
 rettv->v_type = VAR_STRING;
 rettv->vval.v_string = NULL;

 linenr_T foldstart = (linenr_T)get_vim_var_nr(VV_FOLDSTART);
 linenr_T foldend = (linenr_T)get_vim_var_nr(VV_FOLDEND);
 char *dashes = get_vim_var_str(VV_FOLDDASHES);
 if (foldstart > 0 && foldend <= curbuf->b_ml.ml_line_count) {
   // Find first non-empty line in the fold.
   linenr_T lnum;
   for (lnum = foldstart; lnum < foldend; lnum++) {
     if (!linewhite(lnum)) {
       break;
     }
   }

   // Find interesting text in this line.
   char *s = skipwhite(ml_get(lnum));
   // skip C comment-start
   if (s[0] == '/' && (s[1] == '*' || s[1] == '/')) {
     s = skipwhite(s + 2);
     if (*skipwhite(s) == NUL && lnum + 1 < foldend) {
       s = skipwhite(ml_get(lnum + 1));
       if (*s == '*') {
         s = skipwhite(s + 1);
       }
     }
   }
   int count = foldend - foldstart + 1;
   char *txt = NGETTEXT("+-%s%3d line: ", "+-%s%3d lines: ", count);
   size_t len = strlen(txt)
                + strlen(dashes)  // for %s
                + 20              // for %3ld
                + strlen(s);      // concatenated
   char *r = xmalloc(len);
   snprintf(r, len, txt, dashes, count);
   len = strlen(r);
   strcat(r, s);
   // remove 'foldmarker' and 'commentstring'
   foldtext_cleanup(r + len);
   rettv->vval.v_string = r;
 }
}

/// "foldtextresult(lnum)" function
void f_foldtextresult(typval_T *argvars, typval_T *rettv, EvalFuncData fptr)
{
 char buf[FOLD_TEXT_LEN];
 static bool entered = false;

 rettv->v_type = VAR_STRING;
 rettv->vval.v_string = NULL;
 if (entered) {
   return;  // reject recursive use
 }
 entered = true;
 linenr_T lnum = tv_get_lnum(argvars);
 // Treat illegal types and illegal string values for {lnum} the same.
 lnum = MAX(lnum, 0);

 foldinfo_T info = fold_info(curwin, lnum);
 if (info.fi_lines > 0) {
   VirtText vt = VIRTTEXT_EMPTY;
   char *text = get_foldtext(curwin, lnum, lnum + info.fi_lines - 1, info, buf, &vt);
   if (text == buf) {
     text = xstrdup(text);
   }
   if (kv_size(vt) > 0) {
     assert(*text == NUL);
     for (size_t i = 0; i < kv_size(vt);) {
       int attr = 0;
       char *new_text = next_virt_text_chunk(vt, &i, &attr);
       if (new_text == NULL) {
         break;
       }
       new_text = concat_str(text, new_text);
       xfree(text);
       text = new_text;
     }
   }
   clear_virttext(&vt);
   rettv->vval.v_string = text;
 }

 entered = false;
}