v8/src/scanner-character-streams.cc
2012-03-12 12:35:28 +00:00

324 lines
11 KiB
C++

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