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// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_UTF16_RAGEL_ITERATOR_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_UTF16_RAGEL_ITERATOR_H_
#include <unicode/uchar.h>
#include "base/check_op.h"
#include "third_party/blink/renderer/platform/platform_export.h"
#include "third_party/blink/renderer/platform/wtf/allocator/allocator.h"
namespace blink {
// UTF16RagelIterator is set up on top of a UTF-16 UChar* buffer iterating over
// a Blink internal text string and as such is used as an adapter between Blink
// strings and the Ragel-based emoji scanner. It supports forwarding and
// reversing using arithmetic operators. Dereferencing the iterator means
// retrieving a character class as defined in the Ragel grammar of
// third-party/emoji-segmenter. The dereferenced character category is cached
// since Ragel dereferences multiple times without moving the iterator's cursor.
class PLATFORM_EXPORT UTF16RagelIterator {
DISALLOW_NEW();
public:
UTF16RagelIterator() : buffer_(nullptr), buffer_size_(0), cursor_(0) {}
UTF16RagelIterator(const UChar* buffer,
unsigned buffer_size,
unsigned cursor = 0)
: buffer_(buffer),
buffer_size_(buffer_size),
cursor_(cursor),
cached_category_(kMaxEmojiScannerCategory) {
UpdateCachedCategory();
}
UTF16RagelIterator end() {
UTF16RagelIterator ret = *this;
ret.cursor_ = buffer_size_;
return ret;
}
UTF16RagelIterator& SetCursor(unsigned new_cursor);
unsigned Cursor() { return cursor_; }
UTF16RagelIterator& operator+=(int v) {
if (v > 0) {
U16_FWD_N(buffer_, cursor_, buffer_size_, v);
} else if (v < 0) {
U16_BACK_N(buffer_, 0, cursor_, -v);
}
UpdateCachedCategory();
return *this;
}
UTF16RagelIterator& operator-=(int v) { return *this += -v; }
UTF16RagelIterator operator+(int v) {
UTF16RagelIterator ret = *this;
return ret += v;
}
UTF16RagelIterator operator-(int v) { return *this + -v; }
int operator-(const UTF16RagelIterator& other) {
DCHECK_EQ(buffer_, other.buffer_);
return cursor_ - other.cursor_;
}
UTF16RagelIterator& operator++() {
DCHECK_LT(cursor_, buffer_size_);
U16_FWD_1(buffer_, cursor_, buffer_size_);
UpdateCachedCategory();
return *this;
}
UTF16RagelIterator& operator--() {
DCHECK_GT(cursor_, 0u);
U16_BACK_1(buffer_, 0, cursor_);
UpdateCachedCategory();
return *this;
}
UTF16RagelIterator operator++(int) {
UTF16RagelIterator ret = *this;
++(*this);
return ret;
}
UTF16RagelIterator operator--(int) {
UTF16RagelIterator ret = *this;
--(*this);
return ret;
}
UTF16RagelIterator operator=(int v) {
// We need this integer assignment operator because Ragel has initialization
// code for assigning 0 to ts, te.
DCHECK_EQ(v, 0);
UTF16RagelIterator ret = *this;
ret.cursor_ = v;
return ret;
}
UChar32 operator*() {
CHECK(buffer_size_);
return cached_category_;
}
bool operator==(const UTF16RagelIterator& other) const {
return buffer_ == other.buffer_ && buffer_size_ == other.buffer_size_ &&
cursor_ == other.cursor_;
}
bool operator!=(const UTF16RagelIterator& other) const {
return !(*this == other);
}
// Must match the categories defined in third-party/emoji-segmenter/.
// TODO(drott): Add static asserts once emoji-segmenter is imported to
// third-party.
enum EmojiScannerCharacterClass {
EMOJI = 0,
EMOJI_TEXT_PRESENTATION = 1,
EMOJI_EMOJI_PRESENTATION = 2,
EMOJI_MODIFIER_BASE = 3,
EMOJI_MODIFIER = 4,
EMOJI_VS_BASE = 5,
REGIONAL_INDICATOR = 6,
KEYCAP_BASE = 7,
COMBINING_ENCLOSING_KEYCAP = 8,
COMBINING_ENCLOSING_CIRCLE_BACKSLASH = 9,
ZWJ = 10,
VS15 = 11,
VS16 = 12,
TAG_BASE = 13,
TAG_SEQUENCE = 14,
TAG_TERM = 15,
kMaxEmojiScannerCategory = 16
};
private:
UChar32 Codepoint() const {
DCHECK_GT(buffer_size_, 0u);
UChar32 output;
U16_GET(buffer_, 0, cursor_, buffer_size_, output);
return output;
}
void UpdateCachedCategory();
const UChar* buffer_;
unsigned buffer_size_;
unsigned cursor_;
unsigned char cached_category_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_FONTS_UTF16_RAGEL_ITERATOR_H_
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