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// Copyright 2011 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#include "scanner-character-streams.h"
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#include "unicode-inl.h"
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// ----------------------------------------------------------------------------
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// BufferedUtf16CharacterStreams
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BufferedUtf16CharacterStream::BufferedUtf16CharacterStream()
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: Utf16CharacterStream(),
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pushback_limit_(NULL) {
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// Initialize buffer as being empty. First read will fill the buffer.
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buffer_cursor_ = buffer_;
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buffer_end_ = buffer_;
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BufferedUtf16CharacterStream::~BufferedUtf16CharacterStream() { }
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void BufferedUtf16CharacterStream::PushBack(uc32 character) {
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if (character == kEndOfInput) {
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if (pushback_limit_ == NULL && buffer_cursor_ > buffer_) {
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// buffer_ is writable, buffer_cursor_ is const pointer.
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buffer_[--buffer_cursor_ - buffer_] = static_cast<uc16>(character);
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SlowPushBack(static_cast<uc16>(character));
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void BufferedUtf16CharacterStream::SlowPushBack(uc16 character) {
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// In pushback mode, the end of the buffer contains pushback,
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// and the start of the buffer (from buffer start to pushback_limit_)
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// contains valid data that comes just after the pushback.
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// We NULL the pushback_limit_ if pushing all the way back to the
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// start of the buffer.
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if (pushback_limit_ == NULL) {
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// Enter pushback mode.
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pushback_limit_ = buffer_end_;
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buffer_end_ = buffer_ + kBufferSize;
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buffer_cursor_ = buffer_end_;
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// Ensure that there is room for at least one pushback.
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ASSERT(buffer_cursor_ > buffer_);
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buffer_[--buffer_cursor_ - buffer_] = character;
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if (buffer_cursor_ == buffer_) {
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pushback_limit_ = NULL;
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} else if (buffer_cursor_ < pushback_limit_) {
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pushback_limit_ = buffer_cursor_;
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bool BufferedUtf16CharacterStream::ReadBlock() {
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buffer_cursor_ = buffer_;
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if (pushback_limit_ != NULL) {
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// Leave pushback mode.
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buffer_end_ = pushback_limit_;
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pushback_limit_ = NULL;
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// If there were any valid characters left at the
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// start of the buffer, use those.
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if (buffer_cursor_ < buffer_end_) return true;
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// Otherwise read a new block.
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unsigned length = FillBuffer(pos_, kBufferSize);
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buffer_end_ = buffer_ + length;
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unsigned BufferedUtf16CharacterStream::SlowSeekForward(unsigned delta) {
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// Leave pushback mode (i.e., ignore that there might be valid data
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// in the buffer before the pushback_limit_ point).
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pushback_limit_ = NULL;
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return BufferSeekForward(delta);
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// ----------------------------------------------------------------------------
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// GenericStringUtf16CharacterStream
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GenericStringUtf16CharacterStream::GenericStringUtf16CharacterStream(
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unsigned start_position,
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unsigned end_position)
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length_(end_position) {
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ASSERT(end_position >= start_position);
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buffer_cursor_ = buffer_;
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buffer_end_ = buffer_;
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pos_ = start_position;
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GenericStringUtf16CharacterStream::~GenericStringUtf16CharacterStream() { }
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unsigned GenericStringUtf16CharacterStream::BufferSeekForward(unsigned delta) {
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unsigned old_pos = pos_;
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pos_ = Min(pos_ + delta, length_);
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return pos_ - old_pos;
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unsigned GenericStringUtf16CharacterStream::FillBuffer(unsigned from_pos,
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if (from_pos >= length_) return 0;
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if (from_pos + length > length_) {
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length = length_ - from_pos;
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String::WriteToFlat<uc16>(*string_, buffer_, from_pos, from_pos + length);
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// ----------------------------------------------------------------------------
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// Utf8ToUtf16CharacterStream
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Utf8ToUtf16CharacterStream::Utf8ToUtf16CharacterStream(const byte* data,
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: BufferedUtf16CharacterStream(),
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raw_data_length_(length),
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raw_character_position_(0) {
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Utf8ToUtf16CharacterStream::~Utf8ToUtf16CharacterStream() { }
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unsigned Utf8ToUtf16CharacterStream::BufferSeekForward(unsigned delta) {
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unsigned old_pos = pos_;
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unsigned target_pos = pos_ + delta;
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SetRawPosition(target_pos);
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pos_ = raw_character_position_;
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return pos_ - old_pos;
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unsigned Utf8ToUtf16CharacterStream::FillBuffer(unsigned char_position,
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static const unibrow::uchar kMaxUtf16Character = 0xffff;
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SetRawPosition(char_position);
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if (raw_character_position_ != char_position) {
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// char_position was not a valid position in the stream (hit the end
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// while spooling to it).
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while (i < length - 1) {
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if (raw_data_pos_ == raw_data_length_) break;
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unibrow::uchar c = raw_data_[raw_data_pos_];
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if (c <= unibrow::Utf8::kMaxOneByteChar) {
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c = unibrow::Utf8::CalculateValue(raw_data_ + raw_data_pos_,
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raw_data_length_ - raw_data_pos_,
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if (c > kMaxUtf16Character) {
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buffer_[i++] = unibrow::Utf16::LeadSurrogate(c);
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buffer_[i++] = unibrow::Utf16::TrailSurrogate(c);
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buffer_[i++] = static_cast<uc16>(c);
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raw_character_position_ = char_position + i;
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static const byte kUtf8MultiByteMask = 0xC0;
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static const byte kUtf8MultiByteCharStart = 0xC0;
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static const byte kUtf8MultiByteCharFollower = 0x80;
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static bool IsUtf8MultiCharacterStart(byte first_byte) {
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return (first_byte & kUtf8MultiByteMask) == kUtf8MultiByteCharStart;
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static bool IsUtf8MultiCharacterFollower(byte later_byte) {
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return (later_byte & kUtf8MultiByteMask) == kUtf8MultiByteCharFollower;
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// Move the cursor back to point at the preceding UTF-8 character start
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static inline void Utf8CharacterBack(const byte* buffer, unsigned* cursor) {
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byte character = buffer[--*cursor];
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if (character > unibrow::Utf8::kMaxOneByteChar) {
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ASSERT(IsUtf8MultiCharacterFollower(character));
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// Last byte of a multi-byte character encoding. Step backwards until
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// pointing to the first byte of the encoding, recognized by having the
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while (IsUtf8MultiCharacterFollower(buffer[--*cursor])) { }
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ASSERT(IsUtf8MultiCharacterStart(buffer[*cursor]));
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// Move the cursor forward to point at the next following UTF-8 character start
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static inline void Utf8CharacterForward(const byte* buffer, unsigned* cursor) {
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byte character = buffer[(*cursor)++];
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if (character > unibrow::Utf8::kMaxOneByteChar) {
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// First character of a multi-byte character encoding.
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// The number of most-significant one-bits determines the length of the
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// 110..... - (0xCx, 0xDx) one additional byte (minimum).
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// 1110.... - (0xEx) two additional bytes.
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// 11110... - (0xFx) three additional bytes (maximum).
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ASSERT(IsUtf8MultiCharacterStart(character));
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// Additional bytes is:
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// 1 if value in range 0xC0 .. 0xDF.
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// 2 if value in range 0xE0 .. 0xEF.
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// 3 if value in range 0xF0 .. 0xF7.
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// Encode that in a single value.
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unsigned additional_bytes =
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((0x3211u) >> (((character - 0xC0) >> 2) & 0xC)) & 0x03;
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*cursor += additional_bytes;
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ASSERT(!IsUtf8MultiCharacterFollower(buffer[1 + additional_bytes]));
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// This can't set a raw position between two surrogate pairs, since there
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// is no position in the UTF8 stream that corresponds to that. This assumes
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// that the surrogate pair is correctly coded as a 4 byte UTF-8 sequence. If
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// it is illegally coded as two 3 byte sequences then there is no problem here.
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void Utf8ToUtf16CharacterStream::SetRawPosition(unsigned target_position) {
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if (raw_character_position_ > target_position) {
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// Spool backwards in utf8 buffer.
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int old_pos = raw_data_pos_;
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Utf8CharacterBack(raw_data_, &raw_data_pos_);
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raw_character_position_--;
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ASSERT(old_pos - raw_data_pos_ <= 4);
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// Step back over both code units for surrogate pairs.
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if (old_pos - raw_data_pos_ == 4) raw_character_position_--;
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} while (raw_character_position_ > target_position);
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// No surrogate pair splitting.
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ASSERT(raw_character_position_ == target_position);
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// Spool forwards in the utf8 buffer.
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while (raw_character_position_ < target_position) {
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if (raw_data_pos_ == raw_data_length_) return;
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int old_pos = raw_data_pos_;
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Utf8CharacterForward(raw_data_, &raw_data_pos_);
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raw_character_position_++;
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ASSERT(raw_data_pos_ - old_pos <= 4);
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if (raw_data_pos_ - old_pos == 4) raw_character_position_++;
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// No surrogate pair splitting.
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ASSERT(raw_character_position_ == target_position);
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// ----------------------------------------------------------------------------
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// ExternalTwoByteStringUtf16CharacterStream
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ExternalTwoByteStringUtf16CharacterStream::
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~ExternalTwoByteStringUtf16CharacterStream() { }
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ExternalTwoByteStringUtf16CharacterStream
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::ExternalTwoByteStringUtf16CharacterStream(
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Handle<ExternalTwoByteString> data,
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: Utf16CharacterStream(),
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raw_data_(data->GetTwoByteData(start_position)) {
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buffer_cursor_ = raw_data_,
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buffer_end_ = raw_data_ + (end_position - start_position);
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pos_ = start_position;
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} } // namespace v8::internal