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unicode-decoder.h
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74 lines (61 loc) · 2.26 KB
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// Copyright 2014 the V8 project 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 V8_STRINGS_UNICODE_DECODER_H_
#define V8_STRINGS_UNICODE_DECODER_H_
#include "src/strings/unicode.h"
#include "src/utils/vector.h"
namespace v8 {
namespace internal {
// The return value may point to the first aligned word containing the first
// non-one-byte character, rather than directly to the non-one-byte character.
// If the return value is >= the passed length, the entire string was
// one-byte.
inline int NonAsciiStart(const uint8_t* chars, int length) {
const uint8_t* start = chars;
const uint8_t* limit = chars + length;
if (static_cast<size_t>(length) >= kIntptrSize) {
// Check unaligned bytes.
while (!IsAligned(reinterpret_cast<intptr_t>(chars), kIntptrSize)) {
if (*chars > unibrow::Utf8::kMaxOneByteChar) {
return static_cast<int>(chars - start);
}
++chars;
}
// Check aligned words.
DCHECK_EQ(unibrow::Utf8::kMaxOneByteChar, 0x7F);
const uintptr_t non_one_byte_mask = kUintptrAllBitsSet / 0xFF * 0x80;
while (chars + sizeof(uintptr_t) <= limit) {
if (*reinterpret_cast<const uintptr_t*>(chars) & non_one_byte_mask) {
return static_cast<int>(chars - start);
}
chars += sizeof(uintptr_t);
}
}
// Check remaining unaligned bytes.
while (chars < limit) {
if (*chars > unibrow::Utf8::kMaxOneByteChar) {
return static_cast<int>(chars - start);
}
++chars;
}
return static_cast<int>(chars - start);
}
class V8_EXPORT_PRIVATE Utf8Decoder final {
public:
enum class Encoding : uint8_t { kAscii, kLatin1, kUtf16 };
explicit Utf8Decoder(const Vector<const uint8_t>& chars);
bool is_ascii() const { return encoding_ == Encoding::kAscii; }
bool is_one_byte() const { return encoding_ <= Encoding::kLatin1; }
int utf16_length() const { return utf16_length_; }
int non_ascii_start() const { return non_ascii_start_; }
template <typename Char>
V8_EXPORT_PRIVATE void Decode(Char* out, const Vector<const uint8_t>& data);
private:
Encoding encoding_;
int non_ascii_start_;
int utf16_length_;
};
} // namespace internal
} // namespace v8
#endif // V8_STRINGS_UNICODE_DECODER_H_