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// Copyright 2019 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "third_party/blink/renderer/platform/wtf/text/text_offset_map.h"
#include "third_party/blink/renderer/platform/wtf/text/wtf_string.h"
namespace WTF {
namespace {
// Returns a negative value:
// The specified entry represents a removal of characters.
// Returns a positive value:
// The specified entry represents an addition of characters.
// Returns zero:
// The specified entry is redundant.
int ChunkLengthDifference(const Vector<TextOffsetMap::Entry>& entries,
wtf_size_t index) {
wtf_size_t previous_source = 0;
wtf_size_t previous_target = 0;
if (index > 0) {
previous_source = entries[index - 1].source;
previous_target = entries[index - 1].target;
}
const TextOffsetMap::Entry& entry = entries[index];
return (entry.target - previous_target) - (entry.source - previous_source);
}
} // namespace
std::ostream& operator<<(std::ostream& stream,
const TextOffsetMap::Entry& entry) {
return stream << "{" << entry.source << ", " << entry.target << "}";
}
std::ostream& operator<<(std::ostream& stream,
const Vector<TextOffsetMap::Entry>& entries) {
stream << "{";
for (wtf_size_t i = 0; i < entries.size(); ++i) {
if (i > 0) {
stream << ", ";
}
stream << entries[i];
}
return stream << "}";
}
TextOffsetMap::TextOffsetMap(const TextOffsetMap& map12,
const TextOffsetMap& map23) {
if (map12.IsEmpty()) {
entries_ = map23.entries_;
return;
}
if (map23.IsEmpty()) {
entries_ = map12.entries_;
return;
}
const wtf_size_t size12 = map12.entries_.size();
const wtf_size_t size23 = map23.entries_.size();
wtf_size_t index12 = 0, index23 = 0;
int offset_diff_12 = 0, offset_diff_23 = 0;
while (index12 < size12 && index23 < size23) {
const Entry& entry12 = map12.entries_[index12];
const Entry& entry23 = map23.entries_[index23];
int chunk_length_diff_12 = ChunkLengthDifference(map12.entries_, index12);
int chunk_length_diff_23 = ChunkLengthDifference(map23.entries_, index23);
if (chunk_length_diff_12 < 0 && chunk_length_diff_23 < 0 &&
entry12.target + offset_diff_23 == entry23.target) {
// No need to handle entry12 because it was overwritten by entry23.
offset_diff_12 = entry12.target - entry12.source;
++index12;
} else if (chunk_length_diff_12 > 0 && chunk_length_diff_23 > 0 &&
entry12.source == entry23.source - offset_diff_12) {
offset_diff_12 = entry12.target - entry12.source;
offset_diff_23 = entry23.target - entry23.source;
Append(entry12.source, entry23.target + chunk_length_diff_12);
++index12;
++index23;
} else if (entry12.target < entry23.source) {
Append(entry12.source, entry12.target + offset_diff_23);
offset_diff_12 = entry12.target - entry12.source;
++index12;
} else if (entry12.target == entry23.source) {
Append(entry12.source, entry23.target);
offset_diff_12 = entry12.target - entry12.source;
offset_diff_23 = entry23.target - entry23.source;
++index12;
++index23;
} else {
DCHECK_GT(entry12.target, entry23.source);
if (chunk_length_diff_12 > 0 && chunk_length_diff_23 < 0) {
// No need to append entry23 because it is included in entry12.
} else {
Append(entry23.source - offset_diff_12, entry23.target);
}
offset_diff_23 = entry23.target - entry23.source;
++index23;
}
}
for (; index12 < size12; ++index12) {
const Entry& entry12 = map12.entries_[index12];
Append(entry12.source, entry12.target + offset_diff_23);
}
for (; index23 < size23; ++index23) {
const Entry& entry23 = map23.entries_[index23];
Append(entry23.source - offset_diff_12, entry23.target);
}
}
TextOffsetMap::TextOffsetMap(wtf_size_t length1,
const TextOffsetMap& map12,
wtf_size_t length2,
const TextOffsetMap& map23,
wtf_size_t length3) {
if (map12.IsEmpty()) {
entries_ = map23.entries_;
return;
}
if (map23.IsEmpty()) {
entries_ = map12.entries_;
return;
}
Vector<Length> length_map12 = map12.CreateLengthMap(length1, length2);
Vector<Length> length_map = map23.CreateLengthMap(length2, length3);
wtf_size_t index12 = 0;
for (wtf_size_t index23 = 0; index23 < length_map.size(); ++index23) {
Length length = length_map[index23];
Length sum = 0;
bool is_starting_at_middle = length > 0 && length_map12[index12] == 0;
for (wtf_size_t i = 0; i < length; ++i) {
sum += length_map12[index12++];
}
length_map[index23] = sum;
if (is_starting_at_middle) {
length_map[index23] = 0;
length_map[index23 - 1] += sum;
}
}
wtf_size_t source_index = 0;
for (wtf_size_t dest_index = 0; dest_index < length_map.size();
++dest_index) {
wtf_size_t source_length = length_map[dest_index];
source_index += source_length;
wtf_size_t dest_length = 1;
if (source_length == 1) {
while (dest_index + 1 < length_map.size() &&
length_map[dest_index + 1] == 0u) {
++dest_index;
++dest_length;
}
}
if (source_length != dest_length) {
Append(source_index, dest_index + 1);
}
}
}
void TextOffsetMap::Append(wtf_size_t source, wtf_size_t target) {
CHECK(IsEmpty() ||
(source >= entries_.back().source && target >= entries_.back().target));
entries_.emplace_back(source, target);
}
void TextOffsetMap::Append(const icu::Edits& edits) {
DCHECK(IsEmpty());
UErrorCode error = U_ZERO_ERROR;
auto edit = edits.getFineChangesIterator();
while (edit.next(error)) {
if (!edit.hasChange() || edit.oldLength() == edit.newLength())
continue;
entries_.emplace_back(edit.sourceIndex() + edit.oldLength(),
edit.destinationIndex() + edit.newLength());
}
DCHECK(U_SUCCESS(error));
}
// Convert this TextOffsetMap to a form we can split easily.
Vector<TextOffsetMap::Length> TextOffsetMap::CreateLengthMap(
wtf_size_t old_length,
wtf_size_t new_length) const {
Vector<Length> map;
if (IsEmpty()) {
return map;
}
map.reserve(new_length);
unsigned old_offset = 0;
unsigned new_offset = 0;
for (const auto& entry : Entries()) {
unsigned old_chunk_length = entry.source - old_offset;
unsigned new_chunk_length = entry.target - new_offset;
if (old_chunk_length < new_chunk_length) {
unsigned i = 0;
for (; i < old_chunk_length; ++i) {
map.push_back(1u);
}
for (; i < new_chunk_length; ++i) {
map.push_back(0u);
}
} else if (old_chunk_length > new_chunk_length) {
CHECK_GE(new_chunk_length, 1u);
for (unsigned i = 0; i < new_chunk_length - 1; ++i) {
map.push_back(1u);
}
unsigned length = 1u + (old_chunk_length - new_chunk_length);
map.push_back(length);
} else {
for (unsigned i = 0; i < new_chunk_length; ++i) {
map.push_back(1u);
}
}
old_offset = entry.source;
new_offset = entry.target;
}
DCHECK_EQ(old_length - old_offset, new_length - new_offset);
// TODO(layout-dev): We may drop this trailing '1' sequence to save memory.
for (; new_offset < new_length; ++new_offset) {
map.push_back(1u);
}
DCHECK_EQ(map.size(), new_length);
return map;
}
} // namespace WTF
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