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317 lines
12 KiB
C++
317 lines
12 KiB
C++
/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef GFX_SKIP_CHARS_H
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#define GFX_SKIP_CHARS_H
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#include "nsAutoPtr.h"
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#include "nsTArray.h"
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/*
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* gfxSkipChars is a data structure representing a list of characters that
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* have been skipped. The initial string is called the "original string"
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* and after skipping some characters, the result is called the "skipped string".
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* gfxSkipChars provides efficient ways to translate between offsets in the
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* original string and the skipped string. It is used by textrun code to keep
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* track of offsets before and after text transformations such as whitespace
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* compression and control code deletion.
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*/
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/**
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* gfxSkipCharsBuilder is a helper class that accumulates a list of (skip, keep)
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* commands and can eventually be used to construct a real gfxSkipChars.
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* gfxSkipCharsBuilder objects are quite large so don't keep these around.
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* On the positive side, the Skip/KeepChar(s) methods are very efficient,
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* especially when you have runs of all-kept or all-skipped characters.
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*
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* mBuffer is an array of bytes; even numbered bytes represent characters kept,
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* odd numbered bytes represent characters skipped. After those characters
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* are accounted for, we have mRunCharCount characters which are kept or
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* skipped depending on the value of mRunSkipped.
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*
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* mCharCount is the sum of counts of all skipped and kept characters, i.e.,
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* the length of the original string.
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*/
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class gfxSkipCharsBuilder {
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public:
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gfxSkipCharsBuilder() :
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mCharCount(0), mRunCharCount(0), mRunSkipped(false), mInErrorState(false)
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{}
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void SkipChars(uint32_t aChars) {
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DoChars(aChars, true);
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}
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void KeepChars(uint32_t aChars) {
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DoChars(aChars, false);
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}
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void SkipChar() {
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SkipChars(1);
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}
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void KeepChar() {
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KeepChars(1);
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}
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void DoChars(uint32_t aChars, bool aSkipped) {
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if (aSkipped != mRunSkipped && aChars > 0) {
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FlushRun();
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}
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NS_ASSERTION(mRunCharCount + aChars > mRunCharCount,
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"Character count overflow");
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mRunCharCount += aChars;
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}
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bool IsOK() { return !mInErrorState; }
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uint32_t GetCharCount() { return mCharCount + mRunCharCount; }
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bool GetAllCharsKept() { return mBuffer.Length() == 0; }
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friend class gfxSkipChars;
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private:
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typedef AutoFallibleTArray<uint8_t,256> Buffer;
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/**
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* Moves mRunCharCount/mRunSkipped to the buffer (updating mCharCount),
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* sets mRunCharCount to zero and toggles mRunSkipped.
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*/
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void FlushRun();
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Buffer mBuffer;
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uint32_t mCharCount;
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uint32_t mRunCharCount;
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bool mRunSkipped; // == mBuffer.Length()&1
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bool mInErrorState;
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};
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/**
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* The gfxSkipChars list is represented as a list of bytes of the form
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* [chars to keep, chars to skip, chars to keep, chars to skip, ...]
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* In the special case where all chars are to be kept, the list is length
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* zero.
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*
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* A freshly-created gfxSkipChars means "all chars kept".
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*/
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class gfxSkipChars {
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public:
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gfxSkipChars() : mListLength(0), mCharCount(0) {}
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void TakeFrom(gfxSkipChars* aSkipChars) {
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mList = aSkipChars->mList.forget();
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mListLength = aSkipChars->mListLength;
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mCharCount = aSkipChars->mCharCount;
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aSkipChars->mCharCount = 0;
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aSkipChars->mListLength = 0;
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BuildShortcuts();
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}
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void TakeFrom(gfxSkipCharsBuilder* aSkipCharsBuilder) {
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if (!aSkipCharsBuilder->mBuffer.Length()) {
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NS_ASSERTION(!aSkipCharsBuilder->mRunSkipped, "out of sync");
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// all characters kept
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mCharCount = aSkipCharsBuilder->mRunCharCount;
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mList = nullptr;
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mListLength = 0;
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} else {
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aSkipCharsBuilder->FlushRun();
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mCharCount = aSkipCharsBuilder->mCharCount;
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mList = new uint8_t[aSkipCharsBuilder->mBuffer.Length()];
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if (!mList) {
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mListLength = 0;
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} else {
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mListLength = aSkipCharsBuilder->mBuffer.Length();
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memcpy(mList, aSkipCharsBuilder->mBuffer.Elements(), mListLength);
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}
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}
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aSkipCharsBuilder->mBuffer.Clear();
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aSkipCharsBuilder->mCharCount = 0;
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aSkipCharsBuilder->mRunCharCount = 0;
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aSkipCharsBuilder->mRunSkipped = false;
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BuildShortcuts();
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}
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void SetAllKeep(uint32_t aLength) {
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mCharCount = aLength;
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mList = nullptr;
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mListLength = 0;
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}
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int32_t GetOriginalCharCount() const { return mCharCount; }
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friend class gfxSkipCharsIterator;
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private:
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struct Shortcut {
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uint32_t mListPrefixLength;
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uint32_t mListPrefixCharCount;
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uint32_t mListPrefixKeepCharCount;
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Shortcut() {}
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Shortcut(uint32_t aListPrefixLength, uint32_t aListPrefixCharCount,
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uint32_t aListPrefixKeepCharCount) :
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mListPrefixLength(aListPrefixLength),
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mListPrefixCharCount(aListPrefixCharCount),
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mListPrefixKeepCharCount(aListPrefixKeepCharCount) {}
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};
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void BuildShortcuts();
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nsAutoArrayPtr<uint8_t> mList;
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nsAutoArrayPtr<Shortcut> mShortcuts;
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uint32_t mListLength;
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uint32_t mCharCount;
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};
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/**
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* A gfxSkipCharsIterator represents a position in the original string. It lets you
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* map efficiently to and from positions in the string after skipped characters
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* have been removed. You can also specify an offset that is added to all
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* incoming original string offsets and subtracted from all outgoing original
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* string offsets --- useful when the gfxSkipChars corresponds to something
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* offset from the original DOM coordinates, which it often does for gfxTextRuns.
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*
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* The current positions (in both the original and skipped strings) are
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* always constrained to be >= 0 and <= the string length. When the position
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* is equal to the string length, it is at the end of the string. The current
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* positions do not include any aOriginalStringToSkipCharsOffset.
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*
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* When the position in the original string corresponds to a skipped character,
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* the skipped-characters offset is the offset of the next unskipped character,
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* or the skipped-characters string length if there is no next unskipped character.
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*/
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class gfxSkipCharsIterator {
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public:
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/**
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* @param aOriginalStringToSkipCharsOffset add this to all incoming and
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* outgoing original string offsets
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*/
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gfxSkipCharsIterator(const gfxSkipChars& aSkipChars,
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int32_t aOriginalStringToSkipCharsOffset,
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int32_t aOriginalStringOffset)
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: mSkipChars(&aSkipChars),
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mOriginalStringToSkipCharsOffset(aOriginalStringToSkipCharsOffset),
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mListPrefixLength(0), mListPrefixCharCount(0), mListPrefixKeepCharCount(0) {
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SetOriginalOffset(aOriginalStringOffset);
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}
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gfxSkipCharsIterator(const gfxSkipChars& aSkipChars,
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int32_t aOriginalStringToSkipCharsOffset = 0)
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: mSkipChars(&aSkipChars),
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mOriginalStringOffset(0), mSkippedStringOffset(0),
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mOriginalStringToSkipCharsOffset(aOriginalStringToSkipCharsOffset),
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mListPrefixLength(0), mListPrefixCharCount(0), mListPrefixKeepCharCount(0) {
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}
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gfxSkipCharsIterator(const gfxSkipCharsIterator& aIterator)
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: mSkipChars(aIterator.mSkipChars),
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mOriginalStringOffset(aIterator.mOriginalStringOffset),
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mSkippedStringOffset(aIterator.mSkippedStringOffset),
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mOriginalStringToSkipCharsOffset(aIterator.mOriginalStringToSkipCharsOffset),
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mListPrefixLength(aIterator.mListPrefixLength),
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mListPrefixCharCount(aIterator.mListPrefixCharCount),
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mListPrefixKeepCharCount(aIterator.mListPrefixKeepCharCount)
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{}
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/**
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* The empty constructor creates an object that is useless until it is assigned.
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*/
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gfxSkipCharsIterator() : mSkipChars(nullptr) {}
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/**
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* Return true if this iterator is properly initialized and usable.
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*/
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bool IsInitialized() { return mSkipChars != nullptr; }
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/**
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* Set the iterator to aOriginalStringOffset in the original string.
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* This can efficiently move forward or backward from the current position.
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* aOriginalStringOffset is clamped to [0,originalStringLength].
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*/
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void SetOriginalOffset(int32_t aOriginalStringOffset) {
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SetOffsets(aOriginalStringOffset + mOriginalStringToSkipCharsOffset, true);
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}
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/**
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* Set the iterator to aSkippedStringOffset in the skipped string.
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* This can efficiently move forward or backward from the current position.
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* aSkippedStringOffset is clamped to [0,skippedStringLength].
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*/
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void SetSkippedOffset(uint32_t aSkippedStringOffset) {
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SetOffsets(aSkippedStringOffset, false);
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}
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uint32_t ConvertOriginalToSkipped(int32_t aOriginalStringOffset) {
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SetOriginalOffset(aOriginalStringOffset);
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return GetSkippedOffset();
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}
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uint32_t ConvertSkippedToOriginal(int32_t aSkippedStringOffset) {
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SetSkippedOffset(aSkippedStringOffset);
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return GetOriginalOffset();
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}
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/**
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* Test if the character at the current position in the original string
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* is skipped or not. If aRunLength is non-null, then *aRunLength is set
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* to a number of characters all of which are either skipped or not, starting
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* at this character. When the current position is at the end of the original
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* string, we return true and *aRunLength is set to zero.
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*/
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bool IsOriginalCharSkipped(int32_t* aRunLength = nullptr) const;
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void AdvanceOriginal(int32_t aDelta) {
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SetOffsets(mOriginalStringOffset + aDelta, true);
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}
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void AdvanceSkipped(int32_t aDelta) {
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SetOffsets(mSkippedStringOffset + aDelta, false);
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}
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/**
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* @return the offset within the original string
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*/
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int32_t GetOriginalOffset() const {
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return mOriginalStringOffset - mOriginalStringToSkipCharsOffset;
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}
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/**
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* @return the offset within the skipped string corresponding to the
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* current position in the original string. If the current position
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* in the original string is a character that is skipped, then we return
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* the position corresponding to the first non-skipped character in the
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* original string after the current position, or the length of the skipped
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* string if there is no such character.
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*/
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uint32_t GetSkippedOffset() const { return mSkippedStringOffset; }
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int32_t GetOriginalEnd() const {
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return mSkipChars->GetOriginalCharCount() -
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mOriginalStringToSkipCharsOffset;
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}
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private:
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void SetOffsets(uint32_t aOffset, bool aInOriginalString);
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const gfxSkipChars* mSkipChars;
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int32_t mOriginalStringOffset;
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uint32_t mSkippedStringOffset;
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// This offset is added to map from "skipped+unskipped characters in
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// the original DOM string" character space to "skipped+unskipped
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// characters in the textrun's gfxSkipChars" character space
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int32_t mOriginalStringToSkipCharsOffset;
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/*
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* This is used to speed up cursor-style traversal. The invariant is that
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* the first mListPrefixLength bytes of mSkipChars.mList sum to
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* mListPrefixCharCount, and the even-indexed bytes in that prefix sum to
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* mListPrefixKeepCharCount.
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* Also, 0 <= mListPrefixLength < mSkipChars.mListLength, or else
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* mSkipChars.mListLength is zero.
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* Also, mListPrefixCharCount <= mOriginalStringOffset (and therefore
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* mListPrefixKeepCharCount < mSkippedStringOffset).
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*/
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uint32_t mListPrefixLength;
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uint32_t mListPrefixCharCount;
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uint32_t mListPrefixKeepCharCount;
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};
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#endif /*GFX_SKIP_CHARS_H*/
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