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/* -*- Mode: C++; tab-width: 20; 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 GFX_SKIP_CHARS_H
#define GFX_SKIP_CHARS_H
#include "nsTArray.h"
/*
* gfxSkipChars is a data structure representing a list of characters that
* have been skipped. The initial string is called the "original string"
* and after skipping some characters, the result is called the "skipped
* string". gfxSkipChars provides efficient ways to translate between offsets in
* the original string and the skipped string. It is used by textrun code to
* keep track of offsets before and after text transformations such as
* whitespace compression and control code deletion.
*/
/**
* The gfxSkipChars is represented as a sorted array of skipped ranges.
*
* A freshly-created gfxSkipChars means "all chars kept".
*/
class gfxSkipChars {
friend struct SkippedRangeStartComparator;
friend struct SkippedRangeOffsetComparator;
private:
class SkippedRange {
public:
SkippedRange(uint32_t aOffset, uint32_t aLength, uint32_t aDelta)
: mOffset(aOffset), mLength(aLength), mDelta(aDelta) {}
uint32_t Start() const { return mOffset; }
uint32_t End() const { return mOffset + mLength; }
uint32_t Length() const { return mLength; }
uint32_t SkippedOffset() const { return mOffset - mDelta; }
uint32_t Delta() const { return mDelta; }
uint32_t NextDelta() const { return mDelta + mLength; }
void Extend(uint32_t aChars) { mLength += aChars; }
private:
uint32_t mOffset; // original-string offset at which we want to skip
uint32_t mLength; // number of skipped chars at this offset
uint32_t mDelta; // sum of lengths of preceding skipped-ranges
};
public:
gfxSkipChars() : mCharCount(0) {}
void SkipChars(uint32_t aChars) {
NS_ASSERTION(mCharCount + aChars > mCharCount, "Character count overflow");
uint32_t rangeCount = mRanges.Length();
uint32_t delta = 0;
if (rangeCount > 0) {
SkippedRange& lastRange = mRanges[rangeCount - 1];
if (lastRange.End() == mCharCount) {
lastRange.Extend(aChars);
mCharCount += aChars;
return;
}
delta = lastRange.NextDelta();
}
mRanges.AppendElement(SkippedRange(mCharCount, aChars, delta));
mCharCount += aChars;
}
void KeepChars(uint32_t aChars) {
NS_ASSERTION(mCharCount + aChars > mCharCount, "Character count overflow");
mCharCount += aChars;
}
void SkipChar() { SkipChars(1); }
void KeepChar() { KeepChars(1); }
void TakeFrom(gfxSkipChars* aSkipChars) {
mRanges = std::move(aSkipChars->mRanges);
mCharCount = aSkipChars->mCharCount;
aSkipChars->mCharCount = 0;
}
int32_t GetOriginalCharCount() const { return mCharCount; }
const SkippedRange& LastRange() const {
// this is only valid if mRanges is non-empty; no assertion here
// because nsTArray will already assert if we abuse it
return mRanges[mRanges.Length() - 1];
}
friend class gfxSkipCharsIterator;
private:
nsTArray<SkippedRange> mRanges;
uint32_t mCharCount;
};
/**
* A gfxSkipCharsIterator represents a position in the original string. It lets
* you map efficiently to and from positions in the string after skipped
* characters have been removed. You can also specify an offset that is added to
* all incoming original string offsets and subtracted from all outgoing
* original string offsets --- useful when the gfxSkipChars corresponds to
* something offset from the original DOM coordinates, which it often does for
* gfxTextRuns.
*
* The current positions (in both the original and skipped strings) are
* always constrained to be >= 0 and <= the string length. When the position
* is equal to the string length, it is at the end of the string. The current
* positions do not include any aOriginalStringToSkipCharsOffset.
*
* When the position in the original string corresponds to a skipped character,
* the skipped-characters offset is the offset of the next unskipped character,
* or the skipped-characters string length if there is no next unskipped
* character.
*/
class gfxSkipCharsIterator {
public:
/**
* @param aOriginalStringToSkipCharsOffset add this to all incoming and
* outgoing original string offsets
*/
gfxSkipCharsIterator(const gfxSkipChars& aSkipChars,
int32_t aOriginalStringToSkipCharsOffset,
int32_t aOriginalStringOffset)
: mSkipChars(&aSkipChars),
mOriginalStringOffset(0),
mSkippedStringOffset(0),
mCurrentRangeIndex(-1),
mOriginalStringToSkipCharsOffset(aOriginalStringToSkipCharsOffset) {
SetOriginalOffset(aOriginalStringOffset);
}
explicit gfxSkipCharsIterator(const gfxSkipChars& aSkipChars,
int32_t aOriginalStringToSkipCharsOffset = 0)
: mSkipChars(&aSkipChars),
mOriginalStringOffset(0),
mSkippedStringOffset(0),
mOriginalStringToSkipCharsOffset(aOriginalStringToSkipCharsOffset) {
mCurrentRangeIndex =
mSkipChars->mRanges.IsEmpty() || mSkipChars->mRanges[0].Start() > 0 ? -1
: 0;
}
gfxSkipCharsIterator(const gfxSkipCharsIterator& aIterator) = default;
/**
* The empty constructor creates an object that is useless until it is
* assigned.
*/
gfxSkipCharsIterator()
: mSkipChars(nullptr),
mOriginalStringOffset(0),
mSkippedStringOffset(0),
mCurrentRangeIndex(0),
mOriginalStringToSkipCharsOffset(0) {}
/**
* Return true if this iterator is properly initialized and usable.
*/
bool IsInitialized() const { return mSkipChars != nullptr; }
/**
* Set the iterator to aOriginalStringOffset in the original string.
* This can efficiently move forward or backward from the current position.
* aOriginalStringOffset is clamped to [0,originalStringLength].
*/
void SetOriginalOffset(int32_t aOriginalStringOffset);
/**
* Set the iterator to aSkippedStringOffset in the skipped string.
* This can efficiently move forward or backward from the current position.
* aSkippedStringOffset is clamped to [0,skippedStringLength].
*/
void SetSkippedOffset(uint32_t aSkippedStringOffset);
uint32_t ConvertOriginalToSkipped(int32_t aOriginalStringOffset) {
SetOriginalOffset(aOriginalStringOffset);
return GetSkippedOffset();
}
int32_t ConvertSkippedToOriginal(uint32_t aSkippedStringOffset) {
SetSkippedOffset(aSkippedStringOffset);
return GetOriginalOffset();
}
/**
* Test if the character at the current position in the original string
* is skipped or not. If aRunLength is non-null, then *aRunLength is set
* to a number of characters all of which are either skipped or not, starting
* at this character. When the current position is at the end of the original
* string, we return true and *aRunLength is set to zero.
*/
bool IsOriginalCharSkipped(int32_t* aRunLength = nullptr) const;
void AdvanceOriginal(int32_t aDelta) {
SetOriginalOffset(GetOriginalOffset() + aDelta);
}
void AdvanceSkipped(int32_t aDelta) {
SetSkippedOffset(GetSkippedOffset() + aDelta);
}
/**
* @return the offset within the original string
*/
int32_t GetOriginalOffset() const {
return mOriginalStringOffset - mOriginalStringToSkipCharsOffset;
}
/**
* @return the offset within the skipped string corresponding to the
* current position in the original string. If the current position
* in the original string is a character that is skipped, then we return
* the position corresponding to the first non-skipped character in the
* original string after the current position, or the length of the skipped
* string if there is no such character.
*/
uint32_t GetSkippedOffset() const { return mSkippedStringOffset; }
int32_t GetOriginalEnd() const {
return mSkipChars->GetOriginalCharCount() -
mOriginalStringToSkipCharsOffset;
}
private:
const gfxSkipChars* mSkipChars;
// Current position
int32_t mOriginalStringOffset;
uint32_t mSkippedStringOffset;
// Index of the last skippedRange that precedes or contains the current
// position in the original string.
// If index == -1 then we are before the first skipped char.
int32_t mCurrentRangeIndex;
// This offset is added to map from "skipped+unskipped characters in
// the original DOM string" character space to "skipped+unskipped
// characters in the textrun's gfxSkipChars" character space
int32_t mOriginalStringToSkipCharsOffset;
};
#endif /*GFX_SKIP_CHARS_H*/