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SpanningCellSorter.h (2890B)

      1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
      2 // vim:cindent:ts=4:et:sw=4:
      3 /* This Source Code Form is subject to the terms of the Mozilla Public
      4 * License, v. 2.0. If a copy of the MPL was not distributed with this
      5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
      6 
      7 #ifndef SpanningCellSorter_h
      8 #define SpanningCellSorter_h
      9 
     10 /*
     11 * Code to sort cells by their colspan, used by BasicTableLayoutStrategy.
     12 */
     13 
     14 #include "PLDHashTable.h"
     15 #include "StackArena.h"
     16 #include "nsDebug.h"
     17 #include "nsTArray.h"
     18 
     19 /**
     20 * The SpanningCellSorter is responsible for accumulating lists of cells
     21 * with colspans so that those cells can later be enumerated, sorted
     22 * from lowest number of columns spanned to highest.  It does not use a
     23 * stable sort (in fact, it currently reverses).
     24 */
     25 class MOZ_STACK_CLASS SpanningCellSorter {
     26 public:
     27  SpanningCellSorter();
     28  ~SpanningCellSorter();
     29 
     30  struct Item {
     31    int32_t row, col;
     32    Item* next;
     33  };
     34 
     35  /**
     36   * Add a cell to the sorter.  Returns false on out of memory.
     37   * aColSpan is the number of columns spanned, and aRow/aCol are the
     38   * position of the cell in the table (for GetCellInfoAt).
     39   */
     40  bool AddCell(int32_t aColSpan, int32_t aRow, int32_t aCol);
     41 
     42  /**
     43   * Get the next *list* of cells.  Each list contains all the cells
     44   * for a colspan value, and the lists are given in order from lowest
     45   * to highest colspan.  The colspan value is filled in to *aColSpan.
     46   */
     47  Item* GetNext(int32_t* aColSpan);
     48 
     49 private:
     50  enum State { ADDING, ENUMERATING_ARRAY, ENUMERATING_HASH, DONE };
     51  State mState;
     52 
     53  // store small colspans in an array for fast sorting and
     54  // enumeration, and large colspans in a hash table
     55 
     56  enum { ARRAY_BASE = 2 };
     57  enum { ARRAY_SIZE = 8 };
     58  Item* mArray[ARRAY_SIZE];
     59  int32_t SpanToIndex(int32_t aSpan) { return aSpan - ARRAY_BASE; }
     60  int32_t IndexToSpan(int32_t aIndex) { return aIndex + ARRAY_BASE; }
     61  bool UseArrayForSpan(int32_t aSpan) {
     62    NS_ASSERTION(SpanToIndex(aSpan) >= 0, "cell without colspan");
     63    return SpanToIndex(aSpan) < ARRAY_SIZE;
     64  }
     65 
     66  PLDHashTable mHashTable;
     67  struct HashTableEntry : public PLDHashEntryHdr {
     68    int32_t mColSpan;
     69    Item* mItems;
     70  };
     71 
     72  static const PLDHashTableOps HashTableOps;
     73 
     74  static PLDHashNumber HashTableHashKey(const void* key);
     75  static bool HashTableMatchEntry(const PLDHashEntryHdr* hdr, const void* key);
     76 
     77  static int CompareHashTableEntry(HashTableEntry* a, HashTableEntry* b);
     78 
     79  /* state used only during enumeration */
     80  uint32_t mEnumerationIndex;  // into mArray or mSortedHashTable
     81  nsTArray<HashTableEntry*> mSortedHashTable;
     82 
     83  /*
     84   * operator new is forbidden since we use the pres shell's stack
     85   * memory, which much be pushed and popped at points matching a
     86   * push/pop on the C++ stack.
     87   */
     88  void* operator new(size_t sz) noexcept(true) { return nullptr; }
     89 };
     90 
     91 #endif