tor-browser

translit.cpp (63071B)

---

// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
**********************************************************************
*   Copyright (C) 1999-2016, International Business Machines
*   Corporation and others.  All Rights Reserved.
**********************************************************************
*   Date        Name        Description
*   11/17/99    aliu        Creation.
**********************************************************************
*/

#include "utypeinfo.h"  // for 'typeid' to work

#include "unicode/utypes.h"

#if !UCONFIG_NO_TRANSLITERATION

#include "unicode/putil.h"
#include "unicode/translit.h"
#include "unicode/locid.h"
#include "unicode/msgfmt.h"
#include "unicode/rep.h"
#include "unicode/resbund.h"
#include "unicode/unifilt.h"
#include "unicode/uniset.h"
#include "unicode/uscript.h"
#include "unicode/strenum.h"
#include "unicode/utf16.h"
#include "cpdtrans.h"
#include "nultrans.h"
#include "rbt_data.h"
#include "rbt_pars.h"
#include "rbt.h"
#include "transreg.h"
#include "name2uni.h"
#include "nortrans.h"
#include "remtrans.h"
#include "titletrn.h"
#include "tolowtrn.h"
#include "toupptrn.h"
#include "uni2name.h"
#include "brktrans.h"
#include "esctrn.h"
#include "unesctrn.h"
#include "tridpars.h"
#include "anytrans.h"
#include "util.h"
#include "hash.h"
#include "mutex.h"
#include "ucln_in.h"
#include "uassert.h"
#include "cmemory.h"
#include "cstring.h"
#include "uinvchar.h"

static const char16_t TARGET_SEP  = 0x002D; /*-*/
static const char16_t ID_DELIM    = 0x003B; /*;*/
static const char16_t VARIANT_SEP = 0x002F; // '/'

/**
* Prefix for resource bundle key for the display name for a
* transliterator.  The ID is appended to this to form the key.
* The resource bundle value should be a String.
*/
static const char RB_DISPLAY_NAME_PREFIX[] = "%Translit%%";

/**
* Prefix for resource bundle key for the display name for a
* transliterator SCRIPT.  The ID is appended to this to form the key.
* The resource bundle value should be a String.
*/
static const char RB_SCRIPT_DISPLAY_NAME_PREFIX[] = "%Translit%";

/**
* Resource bundle key for display name pattern.
* The resource bundle value should be a String forming a
* MessageFormat pattern, e.g.:
* "{0,choice,0#|1#{1} Transliterator|2#{1} to {2} Transliterator}".
*/
static const char RB_DISPLAY_NAME_PATTERN[] = "TransliteratorNamePattern";

/**
* Resource bundle key for the list of RuleBasedTransliterator IDs.
* The resource bundle value should be a String[] with each element
* being a valid ID.  The ID will be appended to RB_RULE_BASED_PREFIX
* to obtain the class name in which the RB_RULE key will be sought.
*/
static const char RB_RULE_BASED_IDS[] = "RuleBasedTransliteratorIDs";

/**
* The mutex controlling access to registry object.
*/
static icu::UMutex registryMutex;

/**
* System transliterator registry; non-null when initialized.
*/
static icu::TransliteratorRegistry* registry = nullptr;

// Macro to check/initialize the registry. ONLY USE WITHIN
// MUTEX. Avoids function call when registry is initialized.
#define HAVE_REGISTRY(status) (registry!=0 || initializeRegistry(status))

U_NAMESPACE_BEGIN

UOBJECT_DEFINE_ABSTRACT_RTTI_IMPLEMENTATION(Transliterator)

/**
* Return true if the given UTransPosition is valid for text of
* the given length.
*/
static inline UBool positionIsValid(UTransPosition& index, int32_t len) {
   return !(index.contextStart < 0 ||
            index.start < index.contextStart ||
            index.limit < index.start ||
            index.contextLimit < index.limit ||
            len < index.contextLimit);
}

/**
* Default constructor.
* @param theID the string identifier for this transliterator
* @param theFilter the filter.  Any character for which
* <tt>filter.contains()</tt> returns <tt>false</tt> will not be
* altered by this transliterator.  If <tt>filter</tt> is
* <tt>null</tt> then no filtering is applied.
*/
Transliterator::Transliterator(const UnicodeString& theID,
                              UnicodeFilter* adoptedFilter) :
   UObject(), ID(theID), filter(adoptedFilter),
   maximumContextLength(0)
{
   // NUL-terminate the ID string, which is a non-aliased copy.
   ID.append(static_cast<char16_t>(0));
   ID.truncate(ID.length()-1);
}

/**
* Destructor.
*/
Transliterator::~Transliterator() {
   delete filter;
}

/**
* Copy constructor.
*/
Transliterator::Transliterator(const Transliterator& other) :
   UObject(other), ID(other.ID), filter(nullptr),
   maximumContextLength(other.maximumContextLength)
{
   // NUL-terminate the ID string, which is a non-aliased copy.
   ID.append(static_cast<char16_t>(0));
   ID.truncate(ID.length()-1);

   if (other.filter != nullptr) {
       // We own the filter, so we must have our own copy
       filter = other.filter->clone();
   }
}

Transliterator* Transliterator::clone() const {
   return nullptr;
}

/**
* Assignment operator.
*/
Transliterator& Transliterator::operator=(const Transliterator& other) {
   if (this == &other) { return *this; }  // self-assignment: no-op
   ID = other.ID;
   // NUL-terminate the ID string
   ID.getTerminatedBuffer();

   maximumContextLength = other.maximumContextLength;
   adoptFilter(other.filter == nullptr ? nullptr : other.filter->clone());
   return *this;
}

/**
* Transliterates a segment of a string.  <code>Transliterator</code> API.
* @param text the string to be transliterated
* @param start the beginning index, inclusive; <code>0 <= start
* <= limit</code>.
* @param limit the ending index, exclusive; <code>start <= limit
* <= text.length()</code>.
* @return the new limit index, or -1
*/
int32_t Transliterator::transliterate(Replaceable& text,
                                     int32_t start, int32_t limit) const {
   if (start < 0 ||
       limit < start ||
       text.length() < limit) {
       return -1;
   }

   UTransPosition offsets;
   offsets.contextStart= start;
   offsets.contextLimit = limit;
   offsets.start = start;
   offsets.limit = limit;
   filteredTransliterate(text, offsets, false, true);
   return offsets.limit;
}

/**
* Transliterates an entire string in place. Convenience method.
* @param text the string to be transliterated
*/
void Transliterator::transliterate(Replaceable& text) const {
   transliterate(text, 0, text.length());
}

/**
* Transliterates the portion of the text buffer that can be
* transliterated unambiguosly after new text has been inserted,
* typically as a result of a keyboard event.  The new text in
* <code>insertion</code> will be inserted into <code>text</code>
* at <code>index.contextLimit</code>, advancing
* <code>index.contextLimit</code> by <code>insertion.length()</code>.
* Then the transliterator will try to transliterate characters of
* <code>text</code> between <code>index.start</code> and
* <code>index.contextLimit</code>.  Characters before
* <code>index.start</code> will not be changed.
*
* <p>Upon return, values in <code>index</code> will be updated.
* <code>index.contextStart</code> will be advanced to the first
* character that future calls to this method will read.
* <code>index.start</code> and <code>index.contextLimit</code> will
* be adjusted to delimit the range of text that future calls to
* this method may change.
*
* <p>Typical usage of this method begins with an initial call
* with <code>index.contextStart</code> and <code>index.contextLimit</code>
* set to indicate the portion of <code>text</code> to be
* transliterated, and <code>index.start == index.contextStart</code>.
* Thereafter, <code>index</code> can be used without
* modification in future calls, provided that all changes to
* <code>text</code> are made via this method.
*
* <p>This method assumes that future calls may be made that will
* insert new text into the buffer.  As a result, it only performs
* unambiguous transliterations.  After the last call to this
* method, there may be untransliterated text that is waiting for
* more input to resolve an ambiguity.  In order to perform these
* pending transliterations, clients should call {@link
* #finishKeyboardTransliteration} after the last call to this
* method has been made.
* 
* @param text the buffer holding transliterated and untransliterated text
* @param index an array of three integers.
*
* <ul><li><code>index.contextStart</code>: the beginning index,
* inclusive; <code>0 <= index.contextStart <= index.contextLimit</code>.
*
* <li><code>index.contextLimit</code>: the ending index, exclusive;
* <code>index.contextStart <= index.contextLimit <= text.length()</code>.
* <code>insertion</code> is inserted at
* <code>index.contextLimit</code>.
*
* <li><code>index.start</code>: the next character to be
* considered for transliteration; <code>index.contextStart <=
* index.start <= index.contextLimit</code>.  Characters before
* <code>index.start</code> will not be changed by future calls
* to this method.</ul>
*
* @param insertion text to be inserted and possibly
* transliterated into the translation buffer at
* <code>index.contextLimit</code>.  If <code>null</code> then no text
* is inserted.
* @see #START
* @see #LIMIT
* @see #CURSOR
* @see #handleTransliterate
* @exception IllegalArgumentException if <code>index</code>
* is invalid
*/
void Transliterator::transliterate(Replaceable& text,
                                  UTransPosition& index,
                                  const UnicodeString& insertion,
                                  UErrorCode &status) const {
   _transliterate(text, index, &insertion, status);
}

/**
* Transliterates the portion of the text buffer that can be
* transliterated unambiguosly after a new character has been
* inserted, typically as a result of a keyboard event.  This is a
* convenience method; see {@link
* #transliterate(Replaceable, int[], String)} for details.
* @param text the buffer holding transliterated and
* untransliterated text
* @param index an array of three integers.  See {@link
* #transliterate(Replaceable, int[], String)}.
* @param insertion text to be inserted and possibly
* transliterated into the translation buffer at
* <code>index.contextLimit</code>.
* @see #transliterate(Replaceable, int[], String)
*/
void Transliterator::transliterate(Replaceable& text,
                                  UTransPosition& index,
                                  UChar32 insertion,
                                  UErrorCode& status) const {
   UnicodeString str(insertion);
   _transliterate(text, index, &str, status);
}

/**
* Transliterates the portion of the text buffer that can be
* transliterated unambiguosly.  This is a convenience method; see
* {@link #transliterate(Replaceable, int[], String)} for
* details.
* @param text the buffer holding transliterated and
* untransliterated text
* @param index an array of three integers.  See {@link
* #transliterate(Replaceable, int[], String)}.
* @see #transliterate(Replaceable, int[], String)
*/
void Transliterator::transliterate(Replaceable& text,
                                  UTransPosition& index,
                                  UErrorCode& status) const {
   _transliterate(text, index, nullptr, status);
}

/**
* Finishes any pending transliterations that were waiting for
* more characters.  Clients should call this method as the last
* call after a sequence of one or more calls to
* <code>transliterate()</code>.
* @param text the buffer holding transliterated and
* untransliterated text.
* @param index the array of indices previously passed to {@link
* #transliterate}
*/
void Transliterator::finishTransliteration(Replaceable& text,
                                          UTransPosition& index) const {
   if (!positionIsValid(index, text.length())) {
       return;
   }

   filteredTransliterate(text, index, false, true);
}

/**
* This internal method does keyboard transliteration.  If the
* 'insertion' is non-null then we append it to 'text' before
* proceeding.  This method calls through to the pure virtual
* framework method handleTransliterate() to do the actual
* work.
*/
void Transliterator::_transliterate(Replaceable& text,
                                   UTransPosition& index,
                                   const UnicodeString* insertion,
                                   UErrorCode &status) const {
   if (U_FAILURE(status)) {
       return;
   }

   if (!positionIsValid(index, text.length())) {
       status = U_ILLEGAL_ARGUMENT_ERROR;
       return;
   }

//    int32_t originalStart = index.contextStart;
   if (insertion != nullptr) {
       text.handleReplaceBetween(index.limit, index.limit, *insertion);
       index.limit += insertion->length();
       index.contextLimit += insertion->length();
   }

   if (index.limit > 0 &&
       U16_IS_LEAD(text.charAt(index.limit - 1))) {
       // Oops, there is a dangling lead surrogate in the buffer.
       // This will break most transliterators, since they will
       // assume it is part of a pair.  Don't transliterate until
       // more text comes in.
       return;
   }

   filteredTransliterate(text, index, true, true);

#if 0
   // TODO
   // I CAN'T DO what I'm attempting below now that the Kleene star
   // operator is supported.  For example, in the rule

   //   ([:Lu:]+) { x } > $1;

   // what is the maximum context length?  getMaximumContextLength()
   // will return 1, but this is just the length of the ante context
   // part of the pattern string -- 1 character, which is a standin
   // for a Quantifier, which contains a StringMatcher, which
   // contains a UnicodeSet.

   // There is a complicated way to make this work again, and that's
   // to add a "maximum left context" protocol into the
   // UnicodeMatcher hierarchy.  At present I'm not convinced this is
   // worth it.

   // ---

   // The purpose of the code below is to keep the context small
   // while doing incremental transliteration.  When part of the left
   // context (between contextStart and start) is no longer needed,
   // we try to advance contextStart past that portion.  We use the
   // maximum context length to do so.
   int32_t newCS = index.start;
   int32_t n = getMaximumContextLength();
   while (newCS > originalStart && n-- > 0) {
       --newCS;
       newCS -= U16_LENGTH(text.char32At(newCS)) - 1;
   }
   index.contextStart = uprv_max(newCS, originalStart);
#endif
}

/**
* This method breaks up the input text into runs of unfiltered
* characters.  It passes each such run to
* <subclass>.handleTransliterate().  Subclasses that can handle the
* filter logic more efficiently themselves may override this method.
*
* All transliteration calls in this class go through this method.
*/
void Transliterator::filteredTransliterate(Replaceable& text,
                                          UTransPosition& index,
                                          UBool incremental,
                                          UBool rollback) const {
   // Short circuit path for transliterators with no filter in
   // non-incremental mode.
   if (filter == nullptr && !rollback) {
       handleTransliterate(text, index, incremental);
       return;
   }

   //----------------------------------------------------------------------
   // This method processes text in two groupings:
   //
   // RUNS -- A run is a contiguous group of characters which are contained
   // in the filter for this transliterator (filter.contains(ch) == true).
   // Text outside of runs may appear as context but it is not modified.
   // The start and limit Position values are narrowed to each run.
   //
   // PASSES (incremental only) -- To make incremental mode work correctly,
   // each run is broken up into n passes, where n is the length (in code
   // points) of the run.  Each pass contains the first n characters.  If a
   // pass is completely transliterated, it is committed, and further passes
   // include characters after the committed text.  If a pass is blocked,
   // and does not transliterate completely, then this method rolls back
   // the changes made during the pass, extends the pass by one code point,
   // and tries again.
   //----------------------------------------------------------------------
   
   // globalLimit is the limit value for the entire operation.  We
   // set index.limit to the end of each unfiltered run before
   // calling handleTransliterate(), so we need to maintain the real
   // value of index.limit here.  After each transliteration, we
   // update globalLimit for insertions or deletions that have
   // happened.
   int32_t globalLimit = index.limit;
   
   // If there is a non-null filter, then break the input text up.  Say the
   // input text has the form:
   //   xxxabcxxdefxx
   // where 'x' represents a filtered character (filter.contains('x') ==
   // false).  Then we break this up into:
   //   xxxabc xxdef xx
   // Each pass through the loop consumes a run of filtered
   // characters (which are ignored) and a subsequent run of
   // unfiltered characters (which are transliterated).
   
   for (;;) {

       if (filter != nullptr) {
           // Narrow the range to be transliterated to the first segment
           // of unfiltered characters at or after index.start.

           // Advance past filtered chars
           UChar32 c;
           while (index.start < globalLimit &&
                  !filter->contains(c=text.char32At(index.start))) {
               index.start += U16_LENGTH(c);
           }

           // Find the end of this run of unfiltered chars
           index.limit = index.start;
           while (index.limit < globalLimit &&
                  filter->contains(c=text.char32At(index.limit))) {
               index.limit += U16_LENGTH(c);
           }
       }

       // Check to see if the unfiltered run is empty.  This only
       // happens at the end of the string when all the remaining
       // characters are filtered.
       if (index.limit == index.start) {
           // assert(index.start == globalLimit);
           break;
       }

       // Is this run incremental?  If there is additional
       // filtered text (if limit < globalLimit) then we pass in
       // an incremental value of false to force the subclass to
       // complete the transliteration for this run.
       UBool isIncrementalRun =
           (index.limit < globalLimit ? false : incremental);
       
       int32_t delta;

       // Implement rollback.  To understand the need for rollback,
       // consider the following transliterator:
       //
       //  "t" is "a > A;"
       //  "u" is "A > b;"
       //  "v" is a compound of "t; NFD; u" with a filter [:Ll:]
       //
       // Now apply "c" to the input text "a".  The result is "b".  But if
       // the transliteration is done incrementally, then the NFD holds
       // things up after "t" has already transformed "a" to "A".  When
       // finishTransliterate() is called, "A" is _not_ processed because
       // it gets excluded by the [:Ll:] filter, and the end result is "A"
       // -- incorrect.  The problem is that the filter is applied to a
       // partially-transliterated result, when we only want it to apply to
       // input text.  Although this example hinges on a compound
       // transliterator containing NFD and a specific filter, it can
       // actually happen with any transliterator which may do a partial
       // transformation in incremental mode into characters outside its
       // filter.
       //
       // To handle this, when in incremental mode we supply characters to
       // handleTransliterate() in several passes.  Each pass adds one more
       // input character to the input text.  That is, for input "ABCD", we
       // first try "A", then "AB", then "ABC", and finally "ABCD".  If at
       // any point we block (upon return, start < limit) then we roll
       // back.  If at any point we complete the run (upon return start ==
       // limit) then we commit that run.

       if (rollback && isIncrementalRun) {

           int32_t runStart = index.start;
           int32_t runLimit = index.limit;
           int32_t runLength =  runLimit - runStart;

           // Make a rollback copy at the end of the string
           int32_t rollbackOrigin = text.length();
           text.copy(runStart, runLimit, rollbackOrigin);

           // Variables reflecting the commitment of completely
           // transliterated text.  passStart is the runStart, advanced
           // past committed text.  rollbackStart is the rollbackOrigin,
           // advanced past rollback text that corresponds to committed
           // text.
           int32_t passStart = runStart;
           int32_t rollbackStart = rollbackOrigin;

           // The limit for each pass; we advance by one code point with
           // each iteration.
           int32_t passLimit = index.start;

           // Total length, in 16-bit code units, of uncommitted text.
           // This is the length to be rolled back.
           int32_t uncommittedLength = 0;

           // Total delta (change in length) for all passes
           int32_t totalDelta = 0;

           // PASS MAIN LOOP -- Start with a single character, and extend
           // the text by one character at a time.  Roll back partial
           // transliterations and commit complete transliterations.
           for (;;) {
               // Length of additional code point, either one or two
               int32_t charLength = U16_LENGTH(text.char32At(passLimit));
               passLimit += charLength;
               if (passLimit > runLimit) {
                   break;
               }
               uncommittedLength += charLength;

               index.limit = passLimit;

               // Delegate to subclass for actual transliteration.  Upon
               // return, start will be updated to point after the
               // transliterated text, and limit and contextLimit will be
               // adjusted for length changes.
               handleTransliterate(text, index, true);

               delta = index.limit - passLimit; // change in length

               // We failed to completely transliterate this pass.
               // Roll back the text.  Indices remain unchanged; reset
               // them where necessary.
               if (index.start != index.limit) {
                   // Find the rollbackStart, adjusted for length changes
                   // and the deletion of partially transliterated text.
                   int32_t rs = rollbackStart + delta - (index.limit - passStart);

                   // Delete the partially transliterated text
                   text.handleReplaceBetween(passStart, index.limit, UnicodeString());

                   // Copy the rollback text back
                   text.copy(rs, rs + uncommittedLength, passStart);

                   // Restore indices to their original values
                   index.start = passStart;
                   index.limit = passLimit;
                   index.contextLimit -= delta;
               }

               // We did completely transliterate this pass.  Update the
               // commit indices to record how far we got.  Adjust indices
               // for length change.
               else {
                   // Move the pass indices past the committed text.
                   passStart = passLimit = index.start;

                   // Adjust the rollbackStart for length changes and move
                   // it past the committed text.  All characters we've
                   // processed to this point are committed now, so zero
                   // out the uncommittedLength.
                   rollbackStart += delta + uncommittedLength;
                   uncommittedLength = 0;

                   // Adjust indices for length changes.
                   runLimit += delta;
                   totalDelta += delta;
               }
           }

           // Adjust overall limit and rollbackOrigin for insertions and
           // deletions.  Don't need to worry about contextLimit because
           // handleTransliterate() maintains that.
           rollbackOrigin += totalDelta;
           globalLimit += totalDelta;

           // Delete the rollback copy
           text.handleReplaceBetween(rollbackOrigin, rollbackOrigin + runLength, UnicodeString());

           // Move start past committed text
           index.start = passStart;
       }

       else {
           // Delegate to subclass for actual transliteration.
           int32_t limit = index.limit;
           handleTransliterate(text, index, isIncrementalRun);
           delta = index.limit - limit; // change in length

           // In a properly written transliterator, start == limit after
           // handleTransliterate() returns when incremental is false.
           // Catch cases where the subclass doesn't do this, and throw
           // an exception.  (Just pinning start to limit is a bad idea,
           // because what's probably happening is that the subclass
           // isn't transliterating all the way to the end, and it should
           // in non-incremental mode.)
           if (!incremental && index.start != index.limit) {
               // We can't throw an exception, so just fudge things
               index.start = index.limit;
           }

           // Adjust overall limit for insertions/deletions.  Don't need
           // to worry about contextLimit because handleTransliterate()
           // maintains that.
           globalLimit += delta;
       }

       if (filter == nullptr || isIncrementalRun) {
           break;
       }

       // If we did completely transliterate this
       // run, then repeat with the next unfiltered run.
   }

   // Start is valid where it is.  Limit needs to be put back where
   // it was, modulo adjustments for deletions/insertions.
   index.limit = globalLimit;
}

void Transliterator::filteredTransliterate(Replaceable& text,
                                          UTransPosition& index,
                                          UBool incremental) const {
   filteredTransliterate(text, index, incremental, false);
}

/**
* Method for subclasses to use to set the maximum context length.
* @see #getMaximumContextLength
*/
void Transliterator::setMaximumContextLength(int32_t maxContextLength) {
   maximumContextLength = maxContextLength;
}

/**
* Returns a programmatic identifier for this transliterator.
* If this identifier is passed to <code>getInstance()</code>, it
* will return this object, if it has been registered.
* @see #registerInstance
* @see #getAvailableIDs
*/
const UnicodeString& Transliterator::getID() const {
   return ID;
}

/**
* Returns a name for this transliterator that is appropriate for
* display to the user in the default locale.  See {@link
* #getDisplayName(Locale)} for details.
*/
UnicodeString& U_EXPORT2 Transliterator::getDisplayName(const UnicodeString& ID,
                                             UnicodeString& result) {
   return getDisplayName(ID, Locale::getDefault(), result);
}

/**
* Returns a name for this transliterator that is appropriate for
* display to the user in the given locale.  This name is taken
* from the locale resource data in the standard manner of the
* <code>java.text</code> package.
*
* <p>If no localized names exist in the system resource bundles,
* a name is synthesized using a localized
* <code>MessageFormat</code> pattern from the resource data.  The
* arguments to this pattern are an integer followed by one or two
* strings.  The integer is the number of strings, either 1 or 2.
* The strings are formed by splitting the ID for this
* transliterator at the first TARGET_SEP.  If there is no TARGET_SEP, then the
* entire ID forms the only string.
* @param inLocale the Locale in which the display name should be
* localized.
* @see java.text.MessageFormat
*/
UnicodeString& U_EXPORT2 Transliterator::getDisplayName(const UnicodeString& id,
                                             const Locale& inLocale,
                                             UnicodeString& result) {
   UErrorCode status = U_ZERO_ERROR;

   ResourceBundle bundle(U_ICUDATA_TRANSLIT, inLocale, status);

   // Suspend checking status until later...

   result.truncate(0);

   // Normalize the ID
   UnicodeString source, target, variant;
   UBool sawSource;
   TransliteratorIDParser::IDtoSTV(id, source, target, variant, sawSource);
   if (target.length() < 1) {
       // No target; malformed id
       return result;
   }
   if (variant.length() > 0) { // Change "Foo" to "/Foo"
       variant.insert(0, VARIANT_SEP);
   }
   UnicodeString ID(source);
   ID.append(TARGET_SEP).append(target).append(variant);

   // build the char* key
   if (uprv_isInvariantUString(ID.getBuffer(), ID.length())) {
       char key[200];
       uprv_strcpy(key, RB_DISPLAY_NAME_PREFIX);
       int32_t length = static_cast<int32_t>(uprv_strlen(RB_DISPLAY_NAME_PREFIX));
       ID.extract(0, static_cast<int32_t>(sizeof(key) - length), key + length, static_cast<int32_t>(sizeof(key) - length), US_INV);

       // Try to retrieve a UnicodeString from the bundle.
       UnicodeString resString = bundle.getStringEx(key, status);

       if (U_SUCCESS(status) && resString.length() != 0) {
           return result = resString; // [sic] assign & return
       }

#if !UCONFIG_NO_FORMATTING
       // We have failed to get a name from the locale data.  This is
       // typical, since most transliterators will not have localized
       // name data.  The next step is to retrieve the MessageFormat
       // pattern from the locale data and to use it to synthesize the
       // name from the ID.

       status = U_ZERO_ERROR;
       resString = bundle.getStringEx(RB_DISPLAY_NAME_PATTERN, status);

       if (U_SUCCESS(status) && resString.length() != 0) {
           MessageFormat msg(resString, inLocale, status);
           // Suspend checking status until later...

           // We pass either 2 or 3 Formattable objects to msg.
           Formattable args[3];
           int32_t nargs;
           args[0].setLong(2); // # of args to follow
           args[1].setString(source);
           args[2].setString(target);
           nargs = 3;

           // Use display names for the scripts, if they exist
           UnicodeString s;
           length = static_cast<int32_t>(uprv_strlen(RB_SCRIPT_DISPLAY_NAME_PREFIX));
           for (int j=1; j<=2; ++j) {
               status = U_ZERO_ERROR;
               uprv_strcpy(key, RB_SCRIPT_DISPLAY_NAME_PREFIX);
               args[j].getString(s);
               if (uprv_isInvariantUString(s.getBuffer(), s.length())) {
                   s.extract(0, sizeof(key) - length - 1, key + length, static_cast<int32_t>(sizeof(key)) - length - 1, US_INV);

                   resString = bundle.getStringEx(key, status);

                   if (U_SUCCESS(status)) {
                       args[j] = resString;
                   }
               }
           }

           status = U_ZERO_ERROR;
           FieldPosition pos; // ignored by msg
           msg.format(args, nargs, result, pos, status);
           if (U_SUCCESS(status)) {
               result.append(variant);
               return result;
           }
       }
#endif
   }

   // We should not reach this point unless there is something
   // wrong with the build or the RB_DISPLAY_NAME_PATTERN has
   // been deleted from the root RB_LOCALE_ELEMENTS resource.
   result = ID;
   return result;
}

/**
* Returns the filter used by this transliterator, or <tt>null</tt>
* if this transliterator uses no filter.  Caller musn't delete
* the result!
*/
const UnicodeFilter* Transliterator::getFilter() const {
   return filter;
}

/**
* Returns the filter used by this transliterator, or
* <tt>nullptr</tt> if this transliterator uses no filter.  The
* caller must eventually delete the result.  After this call,
* this transliterator's filter is set to <tt>nullptr</tt>.
*/
UnicodeFilter* Transliterator::orphanFilter() {
   UnicodeFilter *result = filter;
   filter = nullptr;
   return result;
}

/**
* Changes the filter used by this transliterator.  If the filter
* is set to <tt>null</tt> then no filtering will occur.
*
* <p>Callers must take care if a transliterator is in use by
* multiple threads.  The filter should not be changed by one
* thread while another thread may be transliterating.
*/
void Transliterator::adoptFilter(UnicodeFilter* filterToAdopt) {
   delete filter;
   filter = filterToAdopt;
}

/**
* Returns this transliterator's inverse.  See the class
* documentation for details.  This implementation simply inverts
* the two entities in the ID and attempts to retrieve the
* resulting transliterator.  That is, if <code>getID()</code>
* returns "A-B", then this method will return the result of
* <code>getInstance("B-A")</code>, or <code>null</code> if that
* call fails.
*
* <p>This method does not take filtering into account.  The
* returned transliterator will have no filter.
*
* <p>Subclasses with knowledge of their inverse may wish to
* override this method.
*
* @return a transliterator that is an inverse, not necessarily
* exact, of this transliterator, or <code>null</code> if no such
* transliterator is registered.
* @see #registerInstance
*/
Transliterator* Transliterator::createInverse(UErrorCode& status) const {
   UParseError parseError;
   return Transliterator::createInstance(ID, UTRANS_REVERSE,parseError,status);
}

Transliterator* U_EXPORT2
Transliterator::createInstance(const UnicodeString& ID,
                               UTransDirection dir,
                               UErrorCode& status)
{
   UParseError parseError;
   return createInstance(ID, dir, parseError, status);
}

/**
* Returns a <code>Transliterator</code> object given its ID.
* The ID must be either a system transliterator ID or a ID registered
* using <code>registerInstance()</code>.
*
* @param ID a valid ID, as enumerated by <code>getAvailableIDs()</code>
* @return A <code>Transliterator</code> object with the given ID
* @see #registerInstance
* @see #getAvailableIDs
* @see #getID
*/
Transliterator* U_EXPORT2
Transliterator::createInstance(const UnicodeString& ID,
                               UTransDirection dir,
                               UParseError& parseError,
                               UErrorCode& status)
{
   if (U_FAILURE(status)) {
       return nullptr;
   }

   UnicodeString canonID;
   UVector list(status);
   if (U_FAILURE(status)) {
       return nullptr;
   }

   UnicodeSet* globalFilter = nullptr;
   // TODO add code for parseError...currently unused, but
   // later may be used by parsing code...
   if (!TransliteratorIDParser::parseCompoundID(ID, dir, canonID, list, globalFilter)) {
       status = U_INVALID_ID;
       delete globalFilter;
       return nullptr;
   }
   LocalPointer<UnicodeSet> lpGlobalFilter(globalFilter);
   
   TransliteratorIDParser::instantiateList(list, status);
   if (U_FAILURE(status)) {
       return nullptr;
   }
   
   U_ASSERT(list.size() > 0);
   Transliterator* t = nullptr;
   
   if (list.size() > 1 || canonID.indexOf(ID_DELIM) >= 0) {
       // [NOTE: If it's a compoundID, we instantiate a CompoundTransliterator even if it only
       // has one child transliterator.  This is so that toRules() will return the right thing
       // (without any inactive ID), but our main ID still comes out correct.  That is, if we
       // instantiate "(Lower);Latin-Greek;", we want the rules to come out as "::Latin-Greek;"
       // even though the ID is "(Lower);Latin-Greek;".
       t = new CompoundTransliterator(list, parseError, status);
   }
   else {
       t = static_cast<Transliterator*>(list.elementAt(0));
   }
   // Check null pointer
   if (t != nullptr) {
       t->setID(canonID);
       if (lpGlobalFilter.isValid()) {
           t->adoptFilter(lpGlobalFilter.orphan());
       }
   }
   else if (U_SUCCESS(status)) {
       status = U_MEMORY_ALLOCATION_ERROR;
   }
   return t;
}

/**
* Create a transliterator from a basic ID.  This is an ID
* containing only the forward direction source, target, and
* variant.
* @param id a basic ID of the form S-T or S-T/V.
* @return a newly created Transliterator or null if the ID is
* invalid.
*/
Transliterator* Transliterator::createBasicInstance(const UnicodeString& id,
                                                   const UnicodeString* canon) {
   UParseError pe;
   UErrorCode ec = U_ZERO_ERROR;
   TransliteratorAlias* alias = nullptr;
   Transliterator* t = nullptr;

   umtx_lock(&registryMutex);
   if (HAVE_REGISTRY(ec)) {
       t = registry->get(id, alias, ec);
   }
   umtx_unlock(&registryMutex);

   if (U_FAILURE(ec)) {
       delete t;
       delete alias;
       return nullptr;
   }

   // We may have not gotten a transliterator:  Because we can't
   // instantiate a transliterator from inside TransliteratorRegistry::
   // get() (that would deadlock), we sometimes pass back an alias.  This
   // contains the data we need to finish the instantiation outside the
   // registry mutex.  The alias may, in turn, generate another alias, so
   // we handle aliases in a loop.  The max times through the loop is two.
   // [alan]
   while (alias != nullptr) {
       U_ASSERT(t==0);
       // Rule-based aliases are handled with TransliteratorAlias::
       // parse(), followed by TransliteratorRegistry::reget().
       // Other aliases are handled with TransliteratorAlias::create().
       if (alias->isRuleBased()) {
           // Step 1. parse
           TransliteratorParser parser(ec);
           alias->parse(parser, pe, ec);
           delete alias;
           alias = nullptr;

           // Step 2. reget
           umtx_lock(&registryMutex);
           if (HAVE_REGISTRY(ec)) {
               t = registry->reget(id, parser, alias, ec);
           }
           umtx_unlock(&registryMutex);

           // Step 3. Loop back around!
       } else {
           t = alias->create(pe, ec);
           delete alias;
           alias = nullptr;
           break;
       }
       if (U_FAILURE(ec)) {
           delete t;
           delete alias;
           t = nullptr;
           break;
       }
   }

   if (t != nullptr && canon != nullptr) {
       t->setID(*canon);
   }

   return t;
}

/**
* Returns a <code>Transliterator</code> object constructed from
* the given rule string.  This will be a RuleBasedTransliterator,
* if the rule string contains only rules, or a
* CompoundTransliterator, if it contains ID blocks, or a
* NullTransliterator, if it contains ID blocks which parse as
* empty for the given direction.
*/
Transliterator* U_EXPORT2
Transliterator::createFromRules(const UnicodeString& ID,
                               const UnicodeString& rules,
                               UTransDirection dir,
                               UParseError& parseError,
                               UErrorCode& status)
{
   Transliterator* t = nullptr;

   TransliteratorParser parser(status);
   parser.parse(rules, dir, parseError, status);

   if (U_FAILURE(status)) {
       return nullptr;
   }

   // NOTE: The logic here matches that in TransliteratorRegistry.
   if (parser.idBlockVector.size() == 0 && parser.dataVector.size() == 0) {
       t = new NullTransliterator();
   }
   else if (parser.idBlockVector.size() == 0 && parser.dataVector.size() == 1) {
       t = new RuleBasedTransliterator(ID, static_cast<TransliterationRuleData*>(parser.dataVector.orphanElementAt(0)), true);
   }
   else if (parser.idBlockVector.size() == 1 && parser.dataVector.size() == 0) {
       // idBlock, no data -- this is an alias.  The ID has
       // been munged from reverse into forward mode, if
       // necessary, so instantiate the ID in the forward
       // direction.
       if (parser.compoundFilter != nullptr) {
           UnicodeString filterPattern;
           parser.compoundFilter->toPattern(filterPattern, false);
           t = createInstance(filterPattern + UnicodeString(ID_DELIM)
                   + *static_cast<UnicodeString*>(parser.idBlockVector.elementAt(0)), UTRANS_FORWARD, parseError, status);
       }
       else
           t = createInstance(*static_cast<UnicodeString*>(parser.idBlockVector.elementAt(0)), UTRANS_FORWARD, parseError, status);


       if (t != nullptr) {
           t->setID(ID);
       }
   }
   else {
       UVector transliterators(status);
       // TODO ICU-21701 missing U_FAILURE check here.
       //      Error and nullptr checking through this whole block looks suspect.
       int32_t passNumber = 1;

       int32_t limit = parser.idBlockVector.size();
       if (parser.dataVector.size() > limit)
           limit = parser.dataVector.size();

       for (int32_t i = 0; i < limit; i++) {
           if (i < parser.idBlockVector.size()) {
               UnicodeString* idBlock = static_cast<UnicodeString*>(parser.idBlockVector.elementAt(i));
               if (!idBlock->isEmpty()) {
                   Transliterator* temp = createInstance(*idBlock, UTRANS_FORWARD, parseError, status);
                   if (U_FAILURE(status)) {
                       delete temp;
                       return nullptr;
                   }
                   if (temp != nullptr && typeid(*temp) != typeid(NullTransliterator)) {
                       transliterators.addElement(temp, status);
                       if (U_FAILURE(status)) {
                           delete temp;
                           return nullptr;
                       }
                   } else {
                       delete temp;
                   }
               }
           }
           if (!parser.dataVector.isEmpty()) {
               TransliterationRuleData* data = static_cast<TransliterationRuleData*>(parser.dataVector.orphanElementAt(0));
               // TODO: Should passNumber be turned into a decimal-string representation (1 -> "1")?
               RuleBasedTransliterator* temprbt = new RuleBasedTransliterator(UnicodeString(CompoundTransliterator::PASS_STRING) + UnicodeString(passNumber++),
                       data, true);
               // Check if nullptr before adding it to transliterators to avoid future usage of nullptr pointer.
               if (temprbt == nullptr) {
                   if (U_SUCCESS(status)) {
                       status = U_MEMORY_ALLOCATION_ERROR;
                   }
                   return t;
               }
               transliterators.addElement(temprbt, status);
               if (U_FAILURE(status)) {
                   delete temprbt;
                   return t;
               }
               // TODO: ICU-21701 the transliterators vector will leak its contents if anything goes wrong.
               //       Under normal operation, the CompoundTransliterator constructor adopts the
               //       the contents of the vector.
           }
       }

       t = new CompoundTransliterator(transliterators, passNumber - 1, parseError, status);
       // Null pointer check
       if (t != nullptr) {
           t->setID(ID);
           t->adoptFilter(parser.orphanCompoundFilter());
       }
   }
   if (U_SUCCESS(status) && t == nullptr) {
       status = U_MEMORY_ALLOCATION_ERROR;
   }
   return t;
}

UnicodeString& Transliterator::toRules(UnicodeString& rulesSource,
                                      UBool escapeUnprintable) const {
   // The base class implementation of toRules munges the ID into
   // the correct format.  That is: foo => ::foo
   if (escapeUnprintable) {
       rulesSource.truncate(0);
       UnicodeString id = getID();
       for (int32_t i=0; i<id.length();) {
           UChar32 c = id.char32At(i);
           if (!ICU_Utility::escapeUnprintable(rulesSource, c)) {
               rulesSource.append(c);
           }
           i += U16_LENGTH(c);
       }
   } else {
       rulesSource = getID();
   }
   // KEEP in sync with rbt_pars
   rulesSource.insert(0, UNICODE_STRING_SIMPLE("::"));
   rulesSource.append(ID_DELIM);
   return rulesSource;
}

int32_t Transliterator::countElements() const {
   const CompoundTransliterator* ct = dynamic_cast<const CompoundTransliterator*>(this);
   return ct != nullptr ? ct->getCount() : 0;
}

const Transliterator& Transliterator::getElement(int32_t index, UErrorCode& ec) const {
   if (U_FAILURE(ec)) {
       return *this;
   }
   const CompoundTransliterator* cpd = dynamic_cast<const CompoundTransliterator*>(this);
   int32_t n = (cpd == nullptr) ? 1 : cpd->getCount();
   if (index < 0 || index >= n) {
       ec = U_INDEX_OUTOFBOUNDS_ERROR;
       return *this;
   } else {
       return (n == 1) ? *this : cpd->getTransliterator(index);
   }
}

UnicodeSet& Transliterator::getSourceSet(UnicodeSet& result) const {
   handleGetSourceSet(result);
   if (filter != nullptr) {
       UnicodeSet* filterSet = dynamic_cast<UnicodeSet*>(filter);
       UBool deleteFilterSet = false;
       // Most, but not all filters will be UnicodeSets.  Optimize for
       // the high-runner case.
       if (filterSet == nullptr) {
           filterSet = new UnicodeSet();
           // Check null pointer
           if (filterSet == nullptr) {
               return result;
           }
           deleteFilterSet = true;
           filter->addMatchSetTo(*filterSet);
       }
       result.retainAll(*filterSet);
       if (deleteFilterSet) {
           delete filterSet;
       }
   }
   return result;
}

void Transliterator::handleGetSourceSet(UnicodeSet& result) const {
   result.clear();
}

UnicodeSet& Transliterator::getTargetSet(UnicodeSet& result) const {
   return result.clear();
}

// For public consumption
void U_EXPORT2 Transliterator::registerFactory(const UnicodeString& id,
                                    Transliterator::Factory factory,
                                    Transliterator::Token context) {
   Mutex lock(&registryMutex);
   UErrorCode ec = U_ZERO_ERROR;
   if (HAVE_REGISTRY(ec)) {
       _registerFactory(id, factory, context);
   }
}

// To be called only by Transliterator subclasses that are called
// to register themselves by initializeRegistry().
void Transliterator::_registerFactory(const UnicodeString& id,
                                     Transliterator::Factory factory,
                                     Transliterator::Token context) {
   UErrorCode ec = U_ZERO_ERROR;
   registry->put(id, factory, context, true, ec);
}

// To be called only by Transliterator subclasses that are called
// to register themselves by initializeRegistry().
void Transliterator::_registerSpecialInverse(const UnicodeString& target,
                                            const UnicodeString& inverseTarget,
                                            UBool bidirectional) {
   UErrorCode status = U_ZERO_ERROR;
   TransliteratorIDParser::registerSpecialInverse(target, inverseTarget, bidirectional, status);
}

/**
* Registers a instance <tt>obj</tt> of a subclass of
* <code>Transliterator</code> with the system.  This object must
* implement the <tt>clone()</tt> method.  When
* <tt>getInstance()</tt> is called with an ID string that is
* equal to <tt>obj.getID()</tt>, then <tt>obj.clone()</tt> is
* returned.
*
* @param obj an instance of subclass of
* <code>Transliterator</code> that defines <tt>clone()</tt>
* @see #getInstance
* @see #unregister
*/
void U_EXPORT2 Transliterator::registerInstance(Transliterator* adoptedPrototype) {
   Mutex lock(&registryMutex);
   UErrorCode ec = U_ZERO_ERROR;
   if (HAVE_REGISTRY(ec)) {
       _registerInstance(adoptedPrototype);
   }
}

void Transliterator::_registerInstance(Transliterator* adoptedPrototype) {
   UErrorCode ec = U_ZERO_ERROR;
   registry->put(adoptedPrototype, true, ec);
}

void U_EXPORT2 Transliterator::registerAlias(const UnicodeString& aliasID,
                                            const UnicodeString& realID) {
   Mutex lock(&registryMutex);
   UErrorCode ec = U_ZERO_ERROR;
   if (HAVE_REGISTRY(ec)) {
       _registerAlias(aliasID, realID);
   }
}

void Transliterator::_registerAlias(const UnicodeString& aliasID,
                                   const UnicodeString& realID) {
   UErrorCode ec = U_ZERO_ERROR;
   registry->put(aliasID, realID, false, true, ec);
}

/**
* Unregisters a transliterator or class.  This may be either
* a system transliterator or a user transliterator or class.
* 
* @param ID the ID of the transliterator or class
* @see #registerInstance

*/
void U_EXPORT2 Transliterator::unregister(const UnicodeString& ID) {
   Mutex lock(&registryMutex);
   UErrorCode ec = U_ZERO_ERROR;
   if (HAVE_REGISTRY(ec)) {
       registry->remove(ID);
   }
}

/**
* == OBSOLETE - remove in ICU 3.4 ==
* Return the number of IDs currently registered with the system.
* To retrieve the actual IDs, call getAvailableID(i) with
* i from 0 to countAvailableIDs() - 1.
*/
int32_t U_EXPORT2 Transliterator::countAvailableIDs() {
   int32_t retVal = 0;
   Mutex lock(&registryMutex);
   UErrorCode ec = U_ZERO_ERROR;
   if (HAVE_REGISTRY(ec)) {
       retVal = registry->countAvailableIDs();
   }
   return retVal;
}

/**
* == OBSOLETE - remove in ICU 3.4 ==
* Return the index-th available ID.  index must be between 0
* and countAvailableIDs() - 1, inclusive.  If index is out of
* range, the result of getAvailableID(0) is returned.
*/
const UnicodeString& U_EXPORT2 Transliterator::getAvailableID(int32_t index) {
   const UnicodeString* result = nullptr;
   umtx_lock(&registryMutex);
   UErrorCode ec = U_ZERO_ERROR;
   if (HAVE_REGISTRY(ec)) {
       result = &registry->getAvailableID(index);
   }
   umtx_unlock(&registryMutex);
   U_ASSERT(result != nullptr); // fail if no registry
   return *result;
}

StringEnumeration* U_EXPORT2 Transliterator::getAvailableIDs(UErrorCode& ec) {
   if (U_FAILURE(ec)) return nullptr;
   StringEnumeration* result = nullptr;
   umtx_lock(&registryMutex);
   if (HAVE_REGISTRY(ec)) {
       result = registry->getAvailableIDs();
   }
   umtx_unlock(&registryMutex);
   if (result == nullptr) {
       ec = U_INTERNAL_TRANSLITERATOR_ERROR;
   }
   return result;
}

int32_t U_EXPORT2 Transliterator::countAvailableSources() {
   Mutex lock(&registryMutex);
   UErrorCode ec = U_ZERO_ERROR;
   return HAVE_REGISTRY(ec) ? _countAvailableSources() : 0;
}

UnicodeString& U_EXPORT2 Transliterator::getAvailableSource(int32_t index,
                                                 UnicodeString& result) {
   Mutex lock(&registryMutex);
   UErrorCode ec = U_ZERO_ERROR;
   if (HAVE_REGISTRY(ec)) {
       _getAvailableSource(index, result);
   }
   return result;
}

int32_t U_EXPORT2 Transliterator::countAvailableTargets(const UnicodeString& source) {
   Mutex lock(&registryMutex);
   UErrorCode ec = U_ZERO_ERROR;
   return HAVE_REGISTRY(ec) ? _countAvailableTargets(source) : 0;
}

UnicodeString& U_EXPORT2 Transliterator::getAvailableTarget(int32_t index,
                                                 const UnicodeString& source,
                                                 UnicodeString& result) {
   Mutex lock(&registryMutex);
   UErrorCode ec = U_ZERO_ERROR;
   if (HAVE_REGISTRY(ec)) {
       _getAvailableTarget(index, source, result);
   }
   return result;
}

int32_t U_EXPORT2 Transliterator::countAvailableVariants(const UnicodeString& source,
                                              const UnicodeString& target) {
   Mutex lock(&registryMutex);
   UErrorCode ec = U_ZERO_ERROR;
   return HAVE_REGISTRY(ec) ? _countAvailableVariants(source, target) : 0;
}

UnicodeString& U_EXPORT2 Transliterator::getAvailableVariant(int32_t index,
                                                  const UnicodeString& source,
                                                  const UnicodeString& target,
                                                  UnicodeString& result) {
   Mutex lock(&registryMutex);
   UErrorCode ec = U_ZERO_ERROR;
   if (HAVE_REGISTRY(ec)) {
       _getAvailableVariant(index, source, target, result);
   }
   return result;
}

int32_t Transliterator::_countAvailableSources() {
   return registry->countAvailableSources();
}

UnicodeString& Transliterator::_getAvailableSource(int32_t index,
                                                 UnicodeString& result) {
   return registry->getAvailableSource(index, result);
}

int32_t Transliterator::_countAvailableTargets(const UnicodeString& source) {
   return registry->countAvailableTargets(source);
}

UnicodeString& Transliterator::_getAvailableTarget(int32_t index,
                                                 const UnicodeString& source,
                                                 UnicodeString& result) {
   return registry->getAvailableTarget(index, source, result);
}

int32_t Transliterator::_countAvailableVariants(const UnicodeString& source,
                                              const UnicodeString& target) {
   return registry->countAvailableVariants(source, target);
}

UnicodeString& Transliterator::_getAvailableVariant(int32_t index,
                                                  const UnicodeString& source,
                                                  const UnicodeString& target,
                                                  UnicodeString& result) {
   return registry->getAvailableVariant(index, source, target, result);
}

#ifdef U_USE_DEPRECATED_TRANSLITERATOR_API

/**
* Method for subclasses to use to obtain a character in the given
* string, with filtering.
* @deprecated the new architecture provides filtering at the top
* level.  This method will be removed Dec 31 2001.
*/
char16_t Transliterator::filteredCharAt(const Replaceable& text, int32_t i) const {
   char16_t c;
   const UnicodeFilter* localFilter = getFilter();
   return (localFilter == 0) ? text.charAt(i) :
       (localFilter->contains(c = text.charAt(i)) ? c : (char16_t)0xFFFE);
}

#endif

/**
* If the registry is initialized, return true.  If not, initialize it
* and return true.  If the registry cannot be initialized, return
* false (rare).
*
* IMPORTANT: Upon entry, registryMutex must be LOCKED.  The entire
* initialization is done with the lock held.  There is NO REASON to
* unlock, since no other thread that is waiting on the registryMutex
* cannot itself proceed until the registry is initialized.
*/
UBool Transliterator::initializeRegistry(UErrorCode &status) {
   if (registry != nullptr) {
       return true;
   }

   registry = new TransliteratorRegistry(status);
   if (registry == nullptr || U_FAILURE(status)) {
       delete registry;
       registry = nullptr;
       return false; // can't create registry, no recovery
   }

   /* The following code parses the index table located in
    * icu/data/translit/root.txt.  The index is an n x 4 table
    * that follows this format:
    *  <id>{
    *      file{
    *          resource{"<resource>"}
    *          direction{"<direction>"}
    *      }
    *  }
    *  <id>{
    *      internal{
    *          resource{"<resource>"}
    *          direction{"<direction"}
    *       }
    *  }
    *  <id>{
    *      alias{"<getInstanceArg"}
    *  }
    * <id> is the ID of the system transliterator being defined.  These
    * are public IDs enumerated by Transliterator.getAvailableIDs(),
    * unless the second field is "internal".
    * 
    * <resource> is a ResourceReader resource name.  Currently these refer
    * to file names under com/ibm/text/resources.  This string is passed
    * directly to ResourceReader, together with <encoding>.
    * 
    * <direction> is either "FORWARD" or "REVERSE".
    * 
    * <getInstanceArg> is a string to be passed directly to
    * Transliterator.getInstance().  The returned Transliterator object
    * then has its ID changed to <id> and is returned.
    *
    * The extra blank field on "alias" lines is to make the array square.
    */
   //static const char translit_index[] = "translit_index";

   UErrorCode lstatus = U_ZERO_ERROR;
   UResourceBundle *bundle, *transIDs, *colBund;
   bundle = ures_open(U_ICUDATA_TRANSLIT, nullptr/*open default locale*/, &lstatus);
   transIDs = ures_getByKey(bundle, RB_RULE_BASED_IDS, nullptr, &lstatus);
   const UnicodeString T_PART = UNICODE_STRING_SIMPLE("-t-");

   int32_t row, maxRows;
   if (lstatus == U_MEMORY_ALLOCATION_ERROR) {
       delete registry;
       registry = nullptr;
       status = U_MEMORY_ALLOCATION_ERROR;
       return false;
   }
   if (U_SUCCESS(lstatus)) {
       maxRows = ures_getSize(transIDs);
       for (row = 0; row < maxRows; row++) {
           colBund = ures_getByIndex(transIDs, row, nullptr, &lstatus);
           if (U_SUCCESS(lstatus)) {
               UnicodeString id(ures_getKey(colBund), -1, US_INV);
               if(id.indexOf(T_PART) != -1) {
                   ures_close(colBund);
                   continue;
               }
               UResourceBundle* res = ures_getNextResource(colBund, nullptr, &lstatus);
               const char* typeStr = ures_getKey(res);
               char16_t type;
               u_charsToUChars(typeStr, &type, 1);

               if (U_SUCCESS(lstatus)) {
                   int32_t len = 0;
                   const char16_t *resString;
                   switch (type) {
                   case 0x66: // 'f'
                   case 0x69: // 'i'
                       // 'file' or 'internal';
                       // row[2]=resource, row[3]=direction
                       {
                           
                           resString = ures_getStringByKey(res, "resource", &len, &lstatus);
                           UBool visible = (type == 0x0066 /*f*/);
                           UTransDirection dir = 
                               (ures_getUnicodeStringByKey(res, "direction", &lstatus).charAt(0) ==
                                0x0046 /*F*/) ?
                               UTRANS_FORWARD : UTRANS_REVERSE;
                           registry->put(id, UnicodeString(true, resString, len), dir, true, visible, lstatus);
                       }
                       break;
                   case 0x61: // 'a'
                       // 'alias'; row[2]=createInstance argument
                       resString = ures_getString(res, &len, &lstatus);
                       registry->put(id, UnicodeString(true, resString, len), true, true, lstatus);
                       break;
                   }
               }
               ures_close(res);
           }
           ures_close(colBund);
       }
   }

   ures_close(transIDs);
   ures_close(bundle);

   // Manually add prototypes that the system knows about to the
   // cache.  This is how new non-rule-based transliterators are
   // added to the system.
   
   // This is to allow for null pointer check
   NullTransliterator* tempNullTranslit = new NullTransliterator();
   LowercaseTransliterator* tempLowercaseTranslit = new LowercaseTransliterator();
   UppercaseTransliterator* tempUppercaseTranslit = new UppercaseTransliterator();
   TitlecaseTransliterator* tempTitlecaseTranslit = new TitlecaseTransliterator();
   UnicodeNameTransliterator* tempUnicodeTranslit = new UnicodeNameTransliterator();
   NameUnicodeTransliterator* tempNameUnicodeTranslit = new NameUnicodeTransliterator();
#if !UCONFIG_NO_BREAK_ITERATION
    // TODO: could or should these transliterators be referenced polymorphically once constructed?
    BreakTransliterator* tempBreakTranslit         = new BreakTransliterator();
#endif
   // Check for null pointers
   if (tempNullTranslit == nullptr || tempLowercaseTranslit == nullptr || tempUppercaseTranslit == nullptr ||
       tempTitlecaseTranslit == nullptr || tempUnicodeTranslit == nullptr || 
#if !UCONFIG_NO_BREAK_ITERATION
       tempBreakTranslit == nullptr ||
#endif
       tempNameUnicodeTranslit == nullptr )
   {
       delete tempNullTranslit;
       delete tempLowercaseTranslit;
       delete tempUppercaseTranslit;
       delete tempTitlecaseTranslit;
       delete tempUnicodeTranslit;
       delete tempNameUnicodeTranslit;
#if !UCONFIG_NO_BREAK_ITERATION
       delete tempBreakTranslit;
#endif
       // Since there was an error, remove registry
       delete registry;
       registry = nullptr;

       status = U_MEMORY_ALLOCATION_ERROR;
       return 0;
   }

   registry->put(tempNullTranslit, true, status);
   registry->put(tempLowercaseTranslit, true, status);
   registry->put(tempUppercaseTranslit, true, status);
   registry->put(tempTitlecaseTranslit, true, status);
   registry->put(tempUnicodeTranslit, true, status);
   registry->put(tempNameUnicodeTranslit, true, status);
#if !UCONFIG_NO_BREAK_ITERATION
   registry->put(tempBreakTranslit, false, status);   // false means invisible.
#endif

   RemoveTransliterator::registerIDs(); // Must be within mutex
   EscapeTransliterator::registerIDs();
   UnescapeTransliterator::registerIDs();
   NormalizationTransliterator::registerIDs();
   AnyTransliterator::registerIDs();

   _registerSpecialInverse(UNICODE_STRING_SIMPLE("Null"),
                           UNICODE_STRING_SIMPLE("Null"), false);
   _registerSpecialInverse(UNICODE_STRING_SIMPLE("Upper"),
                           UNICODE_STRING_SIMPLE("Lower"), true);
   _registerSpecialInverse(UNICODE_STRING_SIMPLE("Title"),
                           UNICODE_STRING_SIMPLE("Lower"), false);

   ucln_i18n_registerCleanup(UCLN_I18N_TRANSLITERATOR, utrans_transliterator_cleanup);

   return true;
}

U_NAMESPACE_END

// Defined in transreg.h:

/**
* Release all static memory held by transliterator.  This will
* necessarily invalidate any rule-based transliterators held by the
* user, because RBTs hold pointers to common data objects.
*/
U_CFUNC UBool utrans_transliterator_cleanup() {
   U_NAMESPACE_USE
   TransliteratorIDParser::cleanup();
   if (registry) {
       delete registry;
       registry = nullptr;
   }
   return true;
}

#endif /* #if !UCONFIG_NO_TRANSLITERATION */

//eof