1 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
2 * This Source Code Form is subject to the terms of the Mozilla Public
3 * License, v. 2.0. If a copy of the MPL was not distributed with this
4 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
6 #ifndef GFX_SKIP_CHARS_H
7 #define GFX_SKIP_CHARS_H
12 * gfxSkipChars is a data structure representing a list of characters that
13 * have been skipped. The initial string is called the "original string"
14 * and after skipping some characters, the result is called the "skipped string".
15 * gfxSkipChars provides efficient ways to translate between offsets in the
16 * original string and the skipped string. It is used by textrun code to keep
17 * track of offsets before and after text transformations such as whitespace
18 * compression and control code deletion.
22 * The gfxSkipChars is represented as a sorted array of skipped ranges.
24 * A freshly-created gfxSkipChars means "all chars kept".
28 friend struct SkippedRangeStartComparator
;
29 friend struct SkippedRangeOffsetComparator
;
35 SkippedRange(uint32_t aOffset
, uint32_t aLength
, uint32_t aDelta
)
36 : mOffset(aOffset
), mLength(aLength
), mDelta(aDelta
)
39 uint32_t Start() const
46 return mOffset
+ mLength
;
49 uint32_t Length() const
54 uint32_t SkippedOffset() const
56 return mOffset
- mDelta
;
59 uint32_t Delta() const
64 uint32_t NextDelta() const
66 return mDelta
+ mLength
;
69 void Extend(uint32_t aChars
)
75 uint32_t mOffset
; // original-string offset at which we want to skip
76 uint32_t mLength
; // number of skipped chars at this offset
77 uint32_t mDelta
; // sum of lengths of preceding skipped-ranges
85 void SkipChars(uint32_t aChars
)
87 NS_ASSERTION(mCharCount
+ aChars
> mCharCount
,
88 "Character count overflow");
89 uint32_t rangeCount
= mRanges
.Length();
92 SkippedRange
& lastRange
= mRanges
[rangeCount
- 1];
93 if (lastRange
.End() == mCharCount
) {
94 lastRange
.Extend(aChars
);
98 delta
= lastRange
.NextDelta();
100 mRanges
.AppendElement(SkippedRange(mCharCount
, aChars
, delta
));
101 mCharCount
+= aChars
;
104 void KeepChars(uint32_t aChars
)
106 NS_ASSERTION(mCharCount
+ aChars
> mCharCount
,
107 "Character count overflow");
108 mCharCount
+= aChars
;
121 void TakeFrom(gfxSkipChars
* aSkipChars
)
123 mRanges
.SwapElements(aSkipChars
->mRanges
);
124 mCharCount
= aSkipChars
->mCharCount
;
125 aSkipChars
->mCharCount
= 0;
128 int32_t GetOriginalCharCount() const
133 const SkippedRange
& LastRange() const
135 // this is only valid if mRanges is non-empty; no assertion here
136 // because nsTArray will already assert if we abuse it
137 return mRanges
[mRanges
.Length() - 1];
140 friend class gfxSkipCharsIterator
;
143 nsTArray
<SkippedRange
> mRanges
;
148 * A gfxSkipCharsIterator represents a position in the original string. It lets you
149 * map efficiently to and from positions in the string after skipped characters
150 * have been removed. You can also specify an offset that is added to all
151 * incoming original string offsets and subtracted from all outgoing original
152 * string offsets --- useful when the gfxSkipChars corresponds to something
153 * offset from the original DOM coordinates, which it often does for gfxTextRuns.
155 * The current positions (in both the original and skipped strings) are
156 * always constrained to be >= 0 and <= the string length. When the position
157 * is equal to the string length, it is at the end of the string. The current
158 * positions do not include any aOriginalStringToSkipCharsOffset.
160 * When the position in the original string corresponds to a skipped character,
161 * the skipped-characters offset is the offset of the next unskipped character,
162 * or the skipped-characters string length if there is no next unskipped character.
164 class gfxSkipCharsIterator
168 * @param aOriginalStringToSkipCharsOffset add this to all incoming and
169 * outgoing original string offsets
171 gfxSkipCharsIterator(const gfxSkipChars
& aSkipChars
,
172 int32_t aOriginalStringToSkipCharsOffset
,
173 int32_t aOriginalStringOffset
)
174 : mSkipChars(&aSkipChars
),
175 mOriginalStringOffset(0),
176 mSkippedStringOffset(0),
177 mCurrentRangeIndex(-1),
178 mOriginalStringToSkipCharsOffset(aOriginalStringToSkipCharsOffset
)
180 SetOriginalOffset(aOriginalStringOffset
);
183 explicit gfxSkipCharsIterator(const gfxSkipChars
& aSkipChars
,
184 int32_t aOriginalStringToSkipCharsOffset
= 0)
185 : mSkipChars(&aSkipChars
),
186 mOriginalStringOffset(0),
187 mSkippedStringOffset(0),
188 mCurrentRangeIndex(-1),
189 mOriginalStringToSkipCharsOffset(aOriginalStringToSkipCharsOffset
)
192 gfxSkipCharsIterator(const gfxSkipCharsIterator
& aIterator
)
193 : mSkipChars(aIterator
.mSkipChars
),
194 mOriginalStringOffset(aIterator
.mOriginalStringOffset
),
195 mSkippedStringOffset(aIterator
.mSkippedStringOffset
),
196 mCurrentRangeIndex(aIterator
.mCurrentRangeIndex
),
197 mOriginalStringToSkipCharsOffset(aIterator
.mOriginalStringToSkipCharsOffset
)
201 * The empty constructor creates an object that is useless until it is assigned.
203 gfxSkipCharsIterator()
204 : mSkipChars(nullptr)
208 * Return true if this iterator is properly initialized and usable.
212 return mSkipChars
!= nullptr;
216 * Set the iterator to aOriginalStringOffset in the original string.
217 * This can efficiently move forward or backward from the current position.
218 * aOriginalStringOffset is clamped to [0,originalStringLength].
220 void SetOriginalOffset(int32_t aOriginalStringOffset
);
223 * Set the iterator to aSkippedStringOffset in the skipped string.
224 * This can efficiently move forward or backward from the current position.
225 * aSkippedStringOffset is clamped to [0,skippedStringLength].
227 void SetSkippedOffset(uint32_t aSkippedStringOffset
);
229 uint32_t ConvertOriginalToSkipped(int32_t aOriginalStringOffset
)
231 SetOriginalOffset(aOriginalStringOffset
);
232 return GetSkippedOffset();
235 uint32_t ConvertSkippedToOriginal(int32_t aSkippedStringOffset
)
237 SetSkippedOffset(aSkippedStringOffset
);
238 return GetOriginalOffset();
242 * Test if the character at the current position in the original string
243 * is skipped or not. If aRunLength is non-null, then *aRunLength is set
244 * to a number of characters all of which are either skipped or not, starting
245 * at this character. When the current position is at the end of the original
246 * string, we return true and *aRunLength is set to zero.
248 bool IsOriginalCharSkipped(int32_t* aRunLength
= nullptr) const;
250 void AdvanceOriginal(int32_t aDelta
)
252 SetOriginalOffset(GetOriginalOffset() + aDelta
);
255 void AdvanceSkipped(int32_t aDelta
)
257 SetSkippedOffset(GetSkippedOffset() + aDelta
);
261 * @return the offset within the original string
263 int32_t GetOriginalOffset() const
265 return mOriginalStringOffset
- mOriginalStringToSkipCharsOffset
;
269 * @return the offset within the skipped string corresponding to the
270 * current position in the original string. If the current position
271 * in the original string is a character that is skipped, then we return
272 * the position corresponding to the first non-skipped character in the
273 * original string after the current position, or the length of the skipped
274 * string if there is no such character.
276 uint32_t GetSkippedOffset() const
278 return mSkippedStringOffset
;
281 int32_t GetOriginalEnd() const
283 return mSkipChars
->GetOriginalCharCount() -
284 mOriginalStringToSkipCharsOffset
;
288 const gfxSkipChars
* mSkipChars
;
291 int32_t mOriginalStringOffset
;
292 uint32_t mSkippedStringOffset
;
294 // Index of the last skippedRange that precedes or contains the current
295 // position in the original string.
296 // If index == -1 then we are before the first skipped char.
297 int32_t mCurrentRangeIndex
;
299 // This offset is added to map from "skipped+unskipped characters in
300 // the original DOM string" character space to "skipped+unskipped
301 // characters in the textrun's gfxSkipChars" character space
302 int32_t mOriginalStringToSkipCharsOffset
;
305 #endif /*GFX_SKIP_CHARS_H*/