The Tor Browser: comparison layout/base/nsBidi.h

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+/* -*- Mode: C; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+*
+* This Source Code Form is subject to the terms of the Mozilla Public
+* License, v. 2.0. If a copy of the MPL was not distributed with this
+* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef nsBidi_h__
+#define nsBidi_h__
+#include "nsBidiUtils.h"
+// Bidi reordering engine from ICU
+/*
+* javadoc-style comments are intended to be transformed into HTML
+* using DOC++ - see
+* http://www.zib.de/Visual/software/doc++/index.html .
+*
+* The HTML documentation is created with
+*  doc++ -H nsIBidi.h
+*/
+/**
+* @mainpage BIDI algorithm for Mozilla (from ICU)
+*
+* <h2>BIDI algorithm for Mozilla</h2>
+*
+* This is an implementation of the Unicode Bidirectional algorithm.
+* The algorithm is defined in the
+* <a href="http://www.unicode.org/unicode/reports/tr9/">Unicode Technical Report 9</a>,
+* version 5, also described in The Unicode Standard, Version 3.0 .<p>
+*
+* <h3>General remarks about the API:</h3>
+*
+* The <quote>limit</quote> of a sequence of characters is the position just after their
+* last character, i.e., one more than that position.<p>
+*
+* Some of the API functions provide access to <quote>runs</quote>.
+* Such a <quote>run</quote> is defined as a sequence of characters
+* that are at the same embedding level
+* after performing the BIDI algorithm.<p>
+*
+* @author Markus W. Scherer. Ported to Mozilla by Simon Montagu
+* @version 1.0
+*/
+/**
+* nsBidiLevel is the type of the level values in this
+* Bidi implementation.
+* It holds an embedding level and indicates the visual direction
+* by its bit 0 (even/odd value).<p>
+*
+* It can also hold non-level values for the
+* <code>aParaLevel</code> and <code>aEmbeddingLevels</code>
+* arguments of <code>SetPara</code>; there:
+* <ul>
+* <li>bit 7 of an <code>aEmbeddingLevels[]</code>
+* value indicates whether the using application is
+* specifying the level of a character to <i>override</i> whatever the
+* Bidi implementation would resolve it to.</li>
+* <li><code>aParaLevel</code> can be set to the
+* pseudo-level values <code>NSBIDI_DEFAULT_LTR</code>
+* and <code>NSBIDI_DEFAULT_RTL</code>.</li></ul>
+*
+* @see nsIBidi::SetPara
+*
+* <p>The related constants are not real, valid level values.
+* <code>NSBIDI_DEFAULT_XXX</code> can be used to specify
+* a default for the paragraph level for
+* when the <code>SetPara</code> function
+* shall determine it but there is no
+* strongly typed character in the input.<p>
+*
+* Note that the value for <code>NSBIDI_DEFAULT_LTR</code> is even
+* and the one for <code>NSBIDI_DEFAULT_RTL</code> is odd,
+* just like with normal LTR and RTL level values -
+* these special values are designed that way. Also, the implementation
+* assumes that NSBIDI_MAX_EXPLICIT_LEVEL is odd.
+*
+* @see NSBIDI_DEFAULT_LTR
+* @see NSBIDI_DEFAULT_RTL
+* @see NSBIDI_LEVEL_OVERRIDE
+* @see NSBIDI_MAX_EXPLICIT_LEVEL
+*/
+typedef uint8_t nsBidiLevel;
+/** Paragraph level setting.
+*  If there is no strong character, then set the paragraph level to 0 (left-to-right).
+*/
+#define NSBIDI_DEFAULT_LTR 0xfe
+/** Paragraph level setting.
+*  If there is no strong character, then set the paragraph level to 1 (right-to-left).
+*/
+#define NSBIDI_DEFAULT_RTL 0xff
+/**
+* Maximum explicit embedding level.
+* (The maximum resolved level can be up to <code>NSBIDI_MAX_EXPLICIT_LEVEL+1</code>).
+*
+*/
+#define NSBIDI_MAX_EXPLICIT_LEVEL 61
+/** Bit flag for level input.
+*  Overrides directional properties.
+*/
+#define NSBIDI_LEVEL_OVERRIDE 0x80
+/**
+* <code>nsBidiDirection</code> values indicate the text direction.
+*/
+enum nsBidiDirection {
+/** All left-to-right text This is a 0 value. */
+NSBIDI_LTR,
+/** All right-to-left text This is a 1 value. */
+NSBIDI_RTL,
+/** Mixed-directional text. */
+NSBIDI_MIXED
+};
+typedef enum nsBidiDirection nsBidiDirection;
+/* miscellaneous definitions ------------------------------------------------ */
+/** option flags for WriteReverse() */
+/**
+* option bit for WriteReverse():
+* keep combining characters after their base characters in RTL runs
+*
+* @see WriteReverse
+*/
+#define NSBIDI_KEEP_BASE_COMBINING       1
+/**
+* option bit for WriteReverse():
+* replace characters with the "mirrored" property in RTL runs
+* by their mirror-image mappings
+*
+* @see WriteReverse
+*/
+#define NSBIDI_DO_MIRRORING              2
+/**
+* option bit for WriteReverse():
+* remove Bidi control characters
+*
+* @see WriteReverse
+*/
+#define NSBIDI_REMOVE_BIDI_CONTROLS      8
+/* helper macros for each allocated array member */
+#define GETDIRPROPSMEMORY(length) \
+GetMemory((void **)&mDirPropsMemory, &mDirPropsSize, \
+mMayAllocateText, (length))
+#define GETLEVELSMEMORY(length) \
+GetMemory((void **)&mLevelsMemory, &mLevelsSize, \
+mMayAllocateText, (length))
+#define GETRUNSMEMORY(length) \
+GetMemory((void **)&mRunsMemory, &mRunsSize, \
+mMayAllocateRuns, (length)*sizeof(Run))
+/* additional macros used by constructor - always allow allocation */
+#define GETINITIALDIRPROPSMEMORY(length) \
+GetMemory((void **)&mDirPropsMemory, &mDirPropsSize, \
+true, (length))
+#define GETINITIALLEVELSMEMORY(length) \
+GetMemory((void **)&mLevelsMemory, &mLevelsSize, \
+true, (length))
+#define GETINITIALRUNSMEMORY(length) \
+GetMemory((void **)&mRunsMemory, &mRunsSize, \
+true, (length)*sizeof(Run))
+/*
+* Sometimes, bit values are more appropriate
+* to deal with directionality properties.
+* Abbreviations in these macro names refer to names
+* used in the Bidi algorithm.
+*/
+typedef uint8_t DirProp;
+#define DIRPROP_FLAG(dir) (1UL<<(dir))
+/* special flag for multiple runs from explicit embedding codes */
+#define DIRPROP_FLAG_MULTI_RUNS (1UL<<31)
+/* are there any characters that are LTR or RTL? */
+#define MASK_LTR (DIRPROP_FLAG(L)|DIRPROP_FLAG(EN)|DIRPROP_FLAG(AN)|DIRPROP_FLAG(LRE)|DIRPROP_FLAG(LRO))
+#define MASK_RTL (DIRPROP_FLAG(R)|DIRPROP_FLAG(AL)|DIRPROP_FLAG(RLE)|DIRPROP_FLAG(RLO))
+/* explicit embedding codes */
+#define MASK_LRX (DIRPROP_FLAG(LRE)|DIRPROP_FLAG(LRO))
+#define MASK_RLX (DIRPROP_FLAG(RLE)|DIRPROP_FLAG(RLO))
+#define MASK_OVERRIDE (DIRPROP_FLAG(LRO)|DIRPROP_FLAG(RLO))
+#define MASK_EXPLICIT (MASK_LRX|MASK_RLX|DIRPROP_FLAG(PDF))
+#define MASK_BN_EXPLICIT (DIRPROP_FLAG(BN)|MASK_EXPLICIT)
+/* paragraph and segment separators */
+#define MASK_B_S (DIRPROP_FLAG(B)|DIRPROP_FLAG(S))
+/* all types that are counted as White Space or Neutral in some steps */
+#define MASK_WS (MASK_B_S|DIRPROP_FLAG(WS)|MASK_BN_EXPLICIT)
+#define MASK_N (DIRPROP_FLAG(O_N)|MASK_WS)
+/* all types that are included in a sequence of European Terminators for (W5) */
+#define MASK_ET_NSM_BN (DIRPROP_FLAG(ET)|DIRPROP_FLAG(NSM)|MASK_BN_EXPLICIT)
+/* types that are neutrals or could becomes neutrals in (Wn) */
+#define MASK_POSSIBLE_N (DIRPROP_FLAG(CS)|DIRPROP_FLAG(ES)|DIRPROP_FLAG(ET)|MASK_N)
+/*
+* These types may be changed to "e",
+* the embedding type (L or R) of the run,
+* in the Bidi algorithm (N2)
+*/
+#define MASK_EMBEDDING (DIRPROP_FLAG(NSM)|MASK_POSSIBLE_N)
+/* the dirProp's L and R are defined to 0 and 1 values in nsCharType */
+#define GET_LR_FROM_LEVEL(level) ((DirProp)((level)&1))
+#define IS_DEFAULT_LEVEL(level) (((level)&0xfe)==0xfe)
+/* handle surrogate pairs --------------------------------------------------- */
+#define IS_FIRST_SURROGATE(uchar) (((uchar)&0xfc00)==0xd800)
+#define IS_SECOND_SURROGATE(uchar) (((uchar)&0xfc00)==0xdc00)
+/* get the UTF-32 value directly from the surrogate pseudo-characters */
+#define SURROGATE_OFFSET ((0xd800<<10UL)+0xdc00-0x10000)
+#define GET_UTF_32(first, second) (((first)<<10UL)+(second)-SURROGATE_OFFSET)
+#define UTF_ERROR_VALUE 0xffff
+/* definitions with forward iteration --------------------------------------- */
+/*
+* all the macros that go forward assume that
+* the initial offset is 0<=i<length;
+* they update the offset
+*/
+/* fast versions, no error-checking */
+#define UTF16_APPEND_CHAR_UNSAFE(s, i, c){ \
+if((uint32_t)(c)<=0xffff) { \
+(s)[(i)++]=(char16_t)(c); \
+} else { \
+(s)[(i)++]=(char16_t)((c)>>10)+0xd7c0; \
+(s)[(i)++]=(char16_t)(c)&0x3ff|0xdc00; \
+} \
+}
+/* safe versions with error-checking and optional regularity-checking */
+#define UTF16_APPEND_CHAR_SAFE(s, i, length, c) { \
+if((PRUInt32)(c)<=0xffff) { \
+(s)[(i)++]=(char16_t)(c); \
+} else if((PRUInt32)(c)<=0x10ffff) { \
+if((i)+1<(length)) { \
+(s)[(i)++]=(char16_t)((c)>>10)+0xd7c0; \
+(s)[(i)++]=(char16_t)(c)&0x3ff|0xdc00; \
+} else /* not enough space */ { \
+(s)[(i)++]=UTF_ERROR_VALUE; \
+} \
+} else /* c>0x10ffff, write error value */ { \
+(s)[(i)++]=UTF_ERROR_VALUE; \
+} \
+}
+/* definitions with backward iteration -------------------------------------- */
+/*
+* all the macros that go backward assume that
+* the valid buffer range starts at offset 0
+* and that the initial offset is 0<i<=length;
+* they update the offset
+*/
+/* fast versions, no error-checking */
+/*
+* Get a single code point from an offset that points behind the last
+* of the code units that belong to that code point.
+* Assume 0<=i<length.
+*/
+#define UTF16_PREV_CHAR_UNSAFE(s, i, c) { \
+(c)=(s)[--(i)]; \
+if(IS_SECOND_SURROGATE(c)) { \
+(c)=GET_UTF_32((s)[--(i)], (c)); \
+} \
+}
+#define UTF16_BACK_1_UNSAFE(s, i) { \
+if(IS_SECOND_SURROGATE((s)[--(i)])) { \
+--(i); \
+} \
+}
+#define UTF16_BACK_N_UNSAFE(s, i, n) { \
+int32_t __N=(n); \
+while(__N>0) { \
+UTF16_BACK_1_UNSAFE(s, i); \
+--__N; \
+} \
+}
+/* safe versions with error-checking and optional regularity-checking */
+#define UTF16_PREV_CHAR_SAFE(s, start, i, c, strict) { \
+(c)=(s)[--(i)]; \
+if(IS_SECOND_SURROGATE(c)) { \
+char16_t __c2; \
+if((i)>(start) && IS_FIRST_SURROGATE(__c2=(s)[(i)-1])) { \
+--(i); \
+(c)=GET_UTF_32(__c2, (c)); \
+/* strict: ((c)&0xfffe)==0xfffe is caught by UTF_IS_ERROR() */ \
+} else if(strict) {\
+/* unmatched second surrogate */ \
+(c)=UTF_ERROR_VALUE; \
+} \
+} else if(strict && IS_FIRST_SURROGATE(c)) { \
+/* unmatched first surrogate */ \
+(c)=UTF_ERROR_VALUE; \
+/* else strict: (c)==0xfffe is caught by UTF_IS_ERROR() */ \
+} \
+}
+#define UTF16_BACK_1_SAFE(s, start, i) { \
+if(IS_SECOND_SURROGATE((s)[--(i)]) && (i)>(start) && IS_FIRST_SURROGATE((s)[(i)-1])) { \
+--(i); \
+} \
+}
+#define UTF16_BACK_N_SAFE(s, start, i, n) { \
+int32_t __N=(n); \
+while(__N>0 && (i)>(start)) { \
+UTF16_BACK_1_SAFE(s, start, i); \
+--__N; \
+} \
+}
+#define UTF_PREV_CHAR_UNSAFE(s, i, c)                UTF16_PREV_CHAR_UNSAFE(s, i, c)
+#define UTF_PREV_CHAR_SAFE(s, start, i, c, strict)   UTF16_PREV_CHAR_SAFE(s, start, i, c, strict)
+#define UTF_BACK_1_UNSAFE(s, i)                      UTF16_BACK_1_UNSAFE(s, i)
+#define UTF_BACK_1_SAFE(s, start, i)                 UTF16_BACK_1_SAFE(s, start, i)
+#define UTF_BACK_N_UNSAFE(s, i, n)                   UTF16_BACK_N_UNSAFE(s, i, n)
+#define UTF_BACK_N_SAFE(s, start, i, n)              UTF16_BACK_N_SAFE(s, start, i, n)
+#define UTF_APPEND_CHAR_UNSAFE(s, i, c)              UTF16_APPEND_CHAR_UNSAFE(s, i, c)
+#define UTF_APPEND_CHAR_SAFE(s, i, length, c)        UTF16_APPEND_CHAR_SAFE(s, i, length, c)
+#define UTF_PREV_CHAR(s, start, i, c)                UTF_PREV_CHAR_SAFE(s, start, i, c, false)
+#define UTF_BACK_1(s, start, i)                      UTF_BACK_1_SAFE(s, start, i)
+#define UTF_BACK_N(s, start, i, n)                   UTF_BACK_N_SAFE(s, start, i, n)
+#define UTF_APPEND_CHAR(s, i, length, c)             UTF_APPEND_CHAR_SAFE(s, i, length, c)
+/* Run structure for reordering --------------------------------------------- */
+typedef struct Run {
+int32_t logicalStart,  /* first character of the run; b31 indicates even/odd level */
+visualLimit;  /* last visual position of the run +1 */
+} Run;
+/* in a Run, logicalStart will get this bit set if the run level is odd */
+#define INDEX_ODD_BIT (1UL<<31)
+#define MAKE_INDEX_ODD_PAIR(index, level) (index|((uint32_t)level<<31))
+#define ADD_ODD_BIT_FROM_LEVEL(x, level)  ((x)|=((uint32_t)level<<31))
+#define REMOVE_ODD_BIT(x)          ((x)&=~INDEX_ODD_BIT)
+#define GET_INDEX(x)   (x&~INDEX_ODD_BIT)
+#define GET_ODD_BIT(x) ((uint32_t)x>>31)
+#define IS_ODD_RUN(x)  ((x&INDEX_ODD_BIT)!=0)
+#define IS_EVEN_RUN(x) ((x&INDEX_ODD_BIT)==0)
+typedef uint32_t Flags;
+/**
+* This class holds information about a paragraph of text
+* with Bidi-algorithm-related details, or about one line of
+* such a paragraph.<p>
+* Reordering can be done on a line, or on a paragraph which is
+* then interpreted as one single line.<p>
+*
+* On construction, the class is initially empty. It is assigned
+* the Bidi properties of a paragraph by <code>SetPara</code>
+* or the Bidi properties of a line of a paragraph by
+* <code>SetLine</code>.<p>
+* A Bidi class can be reused for as long as it is not deallocated
+* by calling its destructor.<p>
+* <code>SetPara</code> will allocate additional memory for
+* internal structures as necessary.
+*/
+class nsBidi
+{
+public:
+/** @brief Default constructor.
+*
+* The nsBidi object is initially empty. It is assigned
+* the Bidi properties of a paragraph by <code>SetPara()</code>
+* or the Bidi properties of a line of a paragraph by
+* <code>GetLine()</code>.<p>
+* This object can be reused for as long as it is not destroyed.<p>
+* <code>SetPara()</code> will allocate additional memory for
+* internal structures as necessary.
+*
+*/
+nsBidi();
+/** @brief Destructor. */
+virtual ~nsBidi();
+/**
+* Perform the Unicode Bidi algorithm. It is defined in the
+* <a href="http://www.unicode.org/unicode/reports/tr9/">Unicode Technical Report 9</a>,
+* version 5,
+* also described in The Unicode Standard, Version 3.0 .<p>
+*
+* This function takes a single plain text paragraph with or without
+* externally specified embedding levels from <quote>styled</quote> text
+* and computes the left-right-directionality of each character.<p>
+*
+* If the entire paragraph consists of text of only one direction, then
+* the function may not perform all the steps described by the algorithm,
+* i.e., some levels may not be the same as if all steps were performed.
+* This is not relevant for unidirectional text.<br>
+* For example, in pure LTR text with numbers the numbers would get
+* a resolved level of 2 higher than the surrounding text according to
+* the algorithm. This implementation may set all resolved levels to
+* the same value in such a case.<p>
+*
+* The text must be externally split into separate paragraphs (rule P1).
+* Paragraph separators (B) should appear at most at the very end.
+*
+* @param aText is a pointer to the single-paragraph text that the
+*      Bidi algorithm will be performed on
+*      (step (P1) of the algorithm is performed externally).
+*      <strong>The text must be (at least) <code>aLength</code> long.</strong>
+*
+* @param aLength is the length of the text; if <code>aLength==-1</code> then
+*      the text must be zero-terminated.
+*
+* @param aParaLevel specifies the default level for the paragraph;
+*      it is typically 0 (LTR) or 1 (RTL).
+*      If the function shall determine the paragraph level from the text,
+*      then <code>aParaLevel</code> can be set to
+*      either <code>NSBIDI_DEFAULT_LTR</code>
+*      or <code>NSBIDI_DEFAULT_RTL</code>;
+*      if there is no strongly typed character, then
+*      the desired default is used (0 for LTR or 1 for RTL).
+*      Any other value between 0 and <code>NSBIDI_MAX_EXPLICIT_LEVEL</code> is also valid,
+*      with odd levels indicating RTL.
+*
+* @param aEmbeddingLevels (in) may be used to preset the embedding and override levels,
+*      ignoring characters like LRE and PDF in the text.
+*      A level overrides the directional property of its corresponding
+*      (same index) character if the level has the
+*      <code>NSBIDI_LEVEL_OVERRIDE</code> bit set.<p>
+*      Except for that bit, it must be
+*      <code>aParaLevel<=aEmbeddingLevels[]<=NSBIDI_MAX_EXPLICIT_LEVEL</code>.<p>
+*      <strong>Caution: </strong>A copy of this pointer, not of the levels,
+*      will be stored in the <code>nsBidi</code> object;
+*      the <code>aEmbeddingLevels</code> array must not be
+*      deallocated before the <code>nsBidi</code> object is destroyed or reused,
+*      and the <code>aEmbeddingLevels</code>
+*      should not be modified to avoid unexpected results on subsequent Bidi operations.
+*      However, the <code>SetPara</code> and
+*      <code>SetLine</code> functions may modify some or all of the levels.<p>
+*      After the <code>nsBidi</code> object is reused or destroyed, the caller
+*      must take care of the deallocation of the <code>aEmbeddingLevels</code> array.<p>
+*      <strong>The <code>aEmbeddingLevels</code> array must be
+*      at least <code>aLength</code> long.</strong>
+*/
+nsresult SetPara(const char16_t *aText, int32_t aLength, nsBidiLevel aParaLevel, nsBidiLevel *aEmbeddingLevels);
+/**
+* Get the directionality of the text.
+*
+* @param aDirection receives a <code>NSBIDI_XXX</code> value that indicates if the entire text
+*       represented by this object is unidirectional,
+*       and which direction, or if it is mixed-directional.
+*
+* @see nsBidiDirection
+*/
+nsresult GetDirection(nsBidiDirection* aDirection);
+/**
+* Get the paragraph level of the text.
+*
+* @param aParaLevel receives a <code>NSBIDI_XXX</code> value indicating the paragraph level
+*
+* @see nsBidiLevel
+*/
+nsresult GetParaLevel(nsBidiLevel* aParaLevel);
+#ifdef FULL_BIDI_ENGINE
+/**
+* <code>SetLine</code> sets an <code>nsBidi</code> to
+* contain the reordering information, especially the resolved levels,
+* for all the characters in a line of text. This line of text is
+* specified by referring to an <code>nsBidi</code> object representing
+* this information for a paragraph of text, and by specifying
+* a range of indexes in this paragraph.<p>
+* In the new line object, the indexes will range from 0 to <code>aLimit-aStart</code>.<p>
+*
+* This is used after calling <code>SetPara</code>
+* for a paragraph, and after line-breaking on that paragraph.
+* It is not necessary if the paragraph is treated as a single line.<p>
+*
+* After line-breaking, rules (L1) and (L2) for the treatment of
+* trailing WS and for reordering are performed on
+* an <code>nsBidi</code> object that represents a line.<p>
+*
+* <strong>Important:</strong> the line <code>nsBidi</code> object shares data with
+* <code>aParaBidi</code>.
+* You must destroy or reuse this object before <code>aParaBidi</code>.
+* In other words, you must destroy or reuse the <code>nsBidi</code> object for a line
+* before the object for its parent paragraph.
+*
+* @param aParaBidi is the parent paragraph object.
+*
+* @param aStart is the line's first index into the paragraph text.
+*
+* @param aLimit is just behind the line's last index into the paragraph text
+*      (its last index +1).<br>
+*      It must be <code>0<=aStart<=aLimit<=</code>paragraph length.
+*
+* @see SetPara
+*/
+nsresult SetLine(nsIBidi* aParaBidi, int32_t aStart, int32_t aLimit);
+/**
+* Get the length of the text.
+*
+* @param aLength receives the length of the text that the nsBidi object was created for.
+*/
+nsresult GetLength(int32_t* aLength);
+/**
+* Get the level for one character.
+*
+* @param aCharIndex the index of a character.
+*
+* @param aLevel receives the level for the character at aCharIndex.
+*
+* @see nsBidiLevel
+*/
+nsresult GetLevelAt(int32_t aCharIndex,  nsBidiLevel* aLevel);
+/**
+* Get an array of levels for each character.<p>
+*
+* Note that this function may allocate memory under some
+* circumstances, unlike <code>GetLevelAt</code>.
+*
+* @param aLevels receives a pointer to the levels array for the text,
+*       or <code>nullptr</code> if an error occurs.
+*
+* @see nsBidiLevel
+*/
+nsresult GetLevels(nsBidiLevel** aLevels);
+#endif // FULL_BIDI_ENGINE
+/**
+* Get the bidirectional type for one character.
+*
+* @param aCharIndex the index of a character.
+*
+* @param aType receives the bidirectional type of the character at aCharIndex.
+*/
+nsresult GetCharTypeAt(int32_t aCharIndex,  nsCharType* aType);
+/**
+* Get a logical run.
+* This function returns information about a run and is used
+* to retrieve runs in logical order.<p>
+* This is especially useful for line-breaking on a paragraph.
+*
+* @param aLogicalStart is the first character of the run.
+*
+* @param aLogicalLimit will receive the limit of the run.
+*      The l-value that you point to here may be the
+*      same expression (variable) as the one for
+*      <code>aLogicalStart</code>.
+*      This pointer can be <code>nullptr</code> if this
+*      value is not necessary.
+*
+* @param aLevel will receive the level of the run.
+*      This pointer can be <code>nullptr</code> if this
+*      value is not necessary.
+*/
+nsresult GetLogicalRun(int32_t aLogicalStart, int32_t* aLogicalLimit, nsBidiLevel* aLevel);
+/**
+* Get the number of runs.
+* This function may invoke the actual reordering on the
+* <code>nsBidi</code> object, after <code>SetPara</code>
+* may have resolved only the levels of the text. Therefore,
+* <code>CountRuns</code> may have to allocate memory,
+* and may fail doing so.
+*
+* @param aRunCount will receive the number of runs.
+*/
+nsresult CountRuns(int32_t* aRunCount);
+/**
+* Get one run's logical start, length, and directionality,
+* which can be 0 for LTR or 1 for RTL.
+* In an RTL run, the character at the logical start is
+* visually on the right of the displayed run.
+* The length is the number of characters in the run.<p>
+* <code>CountRuns</code> should be called
+* before the runs are retrieved.
+*
+* @param aRunIndex is the number of the run in visual order, in the
+*      range <code>[0..CountRuns-1]</code>.
+*
+* @param aLogicalStart is the first logical character index in the text.
+*      The pointer may be <code>nullptr</code> if this index is not needed.
+*
+* @param aLength is the number of characters (at least one) in the run.
+*      The pointer may be <code>nullptr</code> if this is not needed.
+*
+* @param aDirection will receive the directionality of the run,
+*       <code>NSBIDI_LTR==0</code> or <code>NSBIDI_RTL==1</code>,
+*       never <code>NSBIDI_MIXED</code>.
+*
+* @see CountRuns<p>
+*
+* Example:
+* @code
+*  int32_t i, count, logicalStart, visualIndex=0, length;
+*  nsBidiDirection dir;
+*  pBidi->CountRuns(&count);
+*  for(i=0; i<count; ++i) {
+*    pBidi->GetVisualRun(i, &logicalStart, &length, &dir);
+*    if(NSBIDI_LTR==dir) {
+*      do { // LTR
+*        show_char(text[logicalStart++], visualIndex++);
+*      } while(--length>0);
+*    } else {
+*      logicalStart+=length;  // logicalLimit
+*      do { // RTL
+*        show_char(text[--logicalStart], visualIndex++);
+*      } while(--length>0);
+*    }
+*  }
+* @endcode
+*
+* Note that in right-to-left runs, code like this places
+* modifier letters before base characters and second surrogates
+* before first ones.
+*/
+nsresult GetVisualRun(int32_t aRunIndex, int32_t* aLogicalStart, int32_t* aLength, nsBidiDirection* aDirection);
+#ifdef FULL_BIDI_ENGINE
+/**
+* Get the visual position from a logical text position.
+* If such a mapping is used many times on the same
+* <code>nsBidi</code> object, then calling
+* <code>GetLogicalMap</code> is more efficient.<p>
+*
+* Note that in right-to-left runs, this mapping places
+* modifier letters before base characters and second surrogates
+* before first ones.
+*
+* @param aLogicalIndex is the index of a character in the text.
+*
+* @param aVisualIndex will receive the visual position of this character.
+*
+* @see GetLogicalMap
+* @see GetLogicalIndex
+*/
+nsresult GetVisualIndex(int32_t aLogicalIndex, int32_t* aVisualIndex);
+/**
+* Get the logical text position from a visual position.
+* If such a mapping is used many times on the same
+* <code>nsBidi</code> object, then calling
+* <code>GetVisualMap</code> is more efficient.<p>
+*
+* This is the inverse function to <code>GetVisualIndex</code>.
+*
+* @param aVisualIndex is the visual position of a character.
+*
+* @param aLogicalIndex will receive the index of this character in the text.
+*
+* @see GetVisualMap
+* @see GetVisualIndex
+*/
+nsresult GetLogicalIndex(int32_t aVisualIndex, int32_t* aLogicalIndex);
+/**
+* Get a logical-to-visual index map (array) for the characters in the nsBidi
+* (paragraph or line) object.
+*
+* @param aIndexMap is a pointer to an array of <code>GetLength</code>
+*      indexes which will reflect the reordering of the characters.
+*      The array does not need to be initialized.<p>
+*      The index map will result in <code>aIndexMap[aLogicalIndex]==aVisualIndex</code>.<p>
+*
+* @see GetVisualMap
+* @see GetVisualIndex
+*/
+nsresult GetLogicalMap(int32_t *aIndexMap);
+/**
+* Get a visual-to-logical index map (array) for the characters in the nsBidi
+* (paragraph or line) object.
+*
+* @param aIndexMap is a pointer to an array of <code>GetLength</code>
+*      indexes which will reflect the reordering of the characters.
+*      The array does not need to be initialized.<p>
+*      The index map will result in <code>aIndexMap[aVisualIndex]==aLogicalIndex</code>.<p>
+*
+* @see GetLogicalMap
+* @see GetLogicalIndex
+*/
+nsresult GetVisualMap(int32_t *aIndexMap);
+/**
+* This is a convenience function that does not use a nsBidi object.
+* It is intended to be used for when an application has determined the levels
+* of objects (character sequences) and just needs to have them reordered (L2).
+* This is equivalent to using <code>GetLogicalMap</code> on a
+* <code>nsBidi</code> object.
+*
+* @param aLevels is an array with <code>aLength</code> levels that have been determined by
+*      the application.
+*
+* @param aLength is the number of levels in the array, or, semantically,
+*      the number of objects to be reordered.
+*      It must be <code>aLength>0</code>.
+*
+* @param aIndexMap is a pointer to an array of <code>aLength</code>
+*      indexes which will reflect the reordering of the characters.
+*      The array does not need to be initialized.<p>
+*      The index map will result in <code>aIndexMap[aLogicalIndex]==aVisualIndex</code>.
+*/
+static nsresult ReorderLogical(const nsBidiLevel *aLevels, int32_t aLength, int32_t *aIndexMap);
+#endif // FULL_BIDI_ENGINE
+/**
+* This is a convenience function that does not use a nsBidi object.
+* It is intended to be used for when an application has determined the levels
+* of objects (character sequences) and just needs to have them reordered (L2).
+* This is equivalent to using <code>GetVisualMap</code> on a
+* <code>nsBidi</code> object.
+*
+* @param aLevels is an array with <code>aLength</code> levels that have been determined by
+*      the application.
+*
+* @param aLength is the number of levels in the array, or, semantically,
+*      the number of objects to be reordered.
+*      It must be <code>aLength>0</code>.
+*
+* @param aIndexMap is a pointer to an array of <code>aLength</code>
+*      indexes which will reflect the reordering of the characters.
+*      The array does not need to be initialized.<p>
+*      The index map will result in <code>aIndexMap[aVisualIndex]==aLogicalIndex</code>.
+*/
+static nsresult ReorderVisual(const nsBidiLevel *aLevels, int32_t aLength, int32_t *aIndexMap);
+#ifdef FULL_BIDI_ENGINE
+/**
+* Invert an index map.
+* The one-to-one index mapping of the first map is inverted and written to
+* the second one.
+*
+* @param aSrcMap is an array with <code>aLength</code> indexes
+*      which define the original mapping.
+*
+* @param aDestMap is an array with <code>aLength</code> indexes
+*      which will be filled with the inverse mapping.
+*
+* @param aLength is the length of each array.
+*/
+nsresult InvertMap(const int32_t *aSrcMap, int32_t *aDestMap, int32_t aLength);
+#endif // FULL_BIDI_ENGINE
+/**
+* Reverse a Right-To-Left run of Unicode text.
+*
+* This function preserves the integrity of characters with multiple
+* code units and (optionally) modifier letters.
+* Characters can be replaced by mirror-image characters
+* in the destination buffer. Note that "real" mirroring has
+* to be done in a rendering engine by glyph selection
+* and that for many "mirrored" characters there are no
+* Unicode characters as mirror-image equivalents.
+* There are also options to insert or remove Bidi control
+* characters; see the description of the <code>aDestSize</code>
+* and <code>aOptions</code> parameters and of the option bit flags.
+*
+* Since no Bidi controls are inserted here, this function will never
+* write more than <code>aSrcLength</code> characters to <code>aDest</code>.
+*
+* @param aSrc A pointer to the RTL run text.
+*
+* @param aSrcLength The length of the RTL run.
+*                 If the <code>NSBIDI_REMOVE_BIDI_CONTROLS</code> option
+*                 is set, then the destination length may be less than
+*                 <code>aSrcLength</code>.
+*                 If this option is not set, then the destination length
+*                 will be exactly <code>aSrcLength</code>.
+*
+* @param aDest A pointer to where the reordered text is to be copied.
+*             <code>aSrc[aSrcLength]</code> and <code>aDest[aSrcLength]</code>
+*             must not overlap.
+*
+* @param aOptions A bit set of options for the reordering that control
+*                how the reordered text is written.
+*
+* @param aDestSize will receive the number of characters that were written to <code>aDest</code>.
+*/
+nsresult WriteReverse(const char16_t *aSrc, int32_t aSrcLength, char16_t *aDest, uint16_t aOptions, int32_t *aDestSize);
+protected:
+friend class nsBidiPresUtils;
+/** length of the current text */
+int32_t mLength;
+/** memory sizes in bytes */
+size_t mDirPropsSize, mLevelsSize, mRunsSize;
+/** allocated memory */
+DirProp* mDirPropsMemory;
+nsBidiLevel* mLevelsMemory;
+Run* mRunsMemory;
+/** indicators for whether memory may be allocated after construction */
+bool mMayAllocateText, mMayAllocateRuns;
+const DirProp* mDirProps;
+nsBidiLevel* mLevels;
+/** the paragraph level */
+nsBidiLevel mParaLevel;
+/** flags is a bit set for which directional properties are in the text */
+Flags mFlags;
+/** the overall paragraph or line directionality - see nsBidiDirection */
+nsBidiDirection mDirection;
+/** characters after trailingWSStart are WS and are */
+/* implicitly at the paraLevel (rule (L1)) - levels may not reflect that */
+int32_t mTrailingWSStart;
+/** fields for line reordering */
+int32_t mRunCount;     /* ==-1: runs not set up yet */
+Run* mRuns;
+/** for non-mixed text, we only need a tiny array of runs (no malloc()) */
+Run mSimpleRuns[1];
+private:
+void Init();
+bool GetMemory(void **aMemory, size_t* aSize, bool aMayAllocate, size_t aSizeNeeded);
+void Free();
+void GetDirProps(const char16_t *aText);
+nsBidiDirection ResolveExplicitLevels();
+nsresult CheckExplicitLevels(nsBidiDirection *aDirection);
+nsBidiDirection DirectionFromFlags(Flags aFlags);
+void ResolveImplicitLevels(int32_t aStart, int32_t aLimit, DirProp aSOR, DirProp aEOR);
+void AdjustWSLevels();
+void SetTrailingWSStart();
+bool GetRuns();
+void GetSingleRun(nsBidiLevel aLevel);
+void ReorderLine(nsBidiLevel aMinLevel, nsBidiLevel aMaxLevel);
+static bool PrepareReorder(const nsBidiLevel *aLevels, int32_t aLength, int32_t *aIndexMap, nsBidiLevel *aMinLevel, nsBidiLevel *aMaxLevel);
+int32_t doWriteReverse(const char16_t *src, int32_t srcLength,
+char16_t *dest, uint16_t options);
+};
+#endif // _nsBidi_h_

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layout/base/nsBidi.h