scanner.cc revision 3fb3ca8c7ca439d408449a395897395c0faae8d1 
1// Copyright 2011 the V8 project authors. All rights reserved.
2// Redistribution and use in source and binary forms, with or without
3// modification, are permitted provided that the following conditions are
4// met:
5//
6//     * Redistributions of source code must retain the above copyright
7//       notice, this list of conditions and the following disclaimer.
8//     * Redistributions in binary form must reproduce the above
9//       copyright notice, this list of conditions and the following
10//       disclaimer in the documentation and/or other materials provided
11//       with the distribution.
12//     * Neither the name of Google Inc. nor the names of its
13//       contributors may be used to endorse or promote products derived
14//       from this software without specific prior written permission.
15//
16// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27
28#include "v8.h"
29
30#include "ast.h"
31#include "handles.h"
32#include "scanner.h"
33#include "unicode-inl.h"
34
35namespace v8 {
36namespace internal {
37
38// ----------------------------------------------------------------------------
39// BufferedUC16CharacterStreams
40
41BufferedUC16CharacterStream::BufferedUC16CharacterStream()
42    : UC16CharacterStream(),
43      pushback_limit_(NULL) {
44  // Initialize buffer as being empty. First read will fill the buffer.
45  buffer_cursor_ = buffer_;
46  buffer_end_ = buffer_;
47}
48
49BufferedUC16CharacterStream::~BufferedUC16CharacterStream() { }
50
51void BufferedUC16CharacterStream::PushBack(uc32 character) {
52  if (character == kEndOfInput) {
53    pos_--;
54    return;
55  }
56  if (pushback_limit_ == NULL && buffer_cursor_ > buffer_) {
57    // buffer_ is writable, buffer_cursor_ is const pointer.
58    buffer_[--buffer_cursor_ - buffer_] = static_cast<uc16>(character);
59    pos_--;
60    return;
61  }
62  SlowPushBack(static_cast<uc16>(character));
63}
64
65
66void BufferedUC16CharacterStream::SlowPushBack(uc16 character) {
67  // In pushback mode, the end of the buffer contains pushback,
68  // and the start of the buffer (from buffer start to pushback_limit_)
69  // contains valid data that comes just after the pushback.
70  // We NULL the pushback_limit_ if pushing all the way back to the
71  // start of the buffer.
72
73  if (pushback_limit_ == NULL) {
74    // Enter pushback mode.
75    pushback_limit_ = buffer_end_;
76    buffer_end_ = buffer_ + kBufferSize;
77    buffer_cursor_ = buffer_end_;
78  }
79  // Ensure that there is room for at least one pushback.
80  ASSERT(buffer_cursor_ > buffer_);
81  ASSERT(pos_ > 0);
82  buffer_[--buffer_cursor_ - buffer_] = character;
83  if (buffer_cursor_ == buffer_) {
84    pushback_limit_ = NULL;
85  } else if (buffer_cursor_ < pushback_limit_) {
86    pushback_limit_ = buffer_cursor_;
87  }
88  pos_--;
89}
90
91
92bool BufferedUC16CharacterStream::ReadBlock() {
93  buffer_cursor_ = buffer_;
94  if (pushback_limit_ != NULL) {
95    // Leave pushback mode.
96    buffer_end_ = pushback_limit_;
97    pushback_limit_ = NULL;
98    // If there were any valid characters left at the
99    // start of the buffer, use those.
100    if (buffer_cursor_ < buffer_end_) return true;
101    // Otherwise read a new block.
102  }
103  unsigned length = FillBuffer(pos_, kBufferSize);
104  buffer_end_ = buffer_ + length;
105  return length > 0;
106}
107
108
109unsigned BufferedUC16CharacterStream::SlowSeekForward(unsigned delta) {
110  // Leave pushback mode (i.e., ignore that there might be valid data
111  // in the buffer before the pushback_limit_ point).
112  pushback_limit_ = NULL;
113  return BufferSeekForward(delta);
114}
115
116// ----------------------------------------------------------------------------
117// GenericStringUC16CharacterStream
118
119
120GenericStringUC16CharacterStream::GenericStringUC16CharacterStream(
121    Handle<String> data,
122    unsigned start_position,
123    unsigned end_position)
124    : string_(data),
125      length_(end_position) {
126  ASSERT(end_position >= start_position);
127  buffer_cursor_ = buffer_;
128  buffer_end_ = buffer_;
129  pos_ = start_position;
130}
131
132
133GenericStringUC16CharacterStream::~GenericStringUC16CharacterStream() { }
134
135
136unsigned GenericStringUC16CharacterStream::BufferSeekForward(unsigned delta) {
137  unsigned old_pos = pos_;
138  pos_ = Min(pos_ + delta, length_);
139  ReadBlock();
140  return pos_ - old_pos;
141}
142
143
144unsigned GenericStringUC16CharacterStream::FillBuffer(unsigned from_pos,
145                                                      unsigned length) {
146  if (from_pos >= length_) return 0;
147  if (from_pos + length > length_) {
148    length = length_ - from_pos;
149  }
150  String::WriteToFlat<uc16>(*string_, buffer_, from_pos, from_pos + length);
151  return length;
152}
153
154
155// ----------------------------------------------------------------------------
156// Utf8ToUC16CharacterStream
157Utf8ToUC16CharacterStream::Utf8ToUC16CharacterStream(const byte* data,
158                                                     unsigned length)
159    : BufferedUC16CharacterStream(),
160      raw_data_(data),
161      raw_data_length_(length),
162      raw_data_pos_(0),
163      raw_character_position_(0) {
164  ReadBlock();
165}
166
167
168Utf8ToUC16CharacterStream::~Utf8ToUC16CharacterStream() { }
169
170
171unsigned Utf8ToUC16CharacterStream::BufferSeekForward(unsigned delta) {
172  unsigned old_pos = pos_;
173  unsigned target_pos = pos_ + delta;
174  SetRawPosition(target_pos);
175  pos_ = raw_character_position_;
176  ReadBlock();
177  return pos_ - old_pos;
178}
179
180
181unsigned Utf8ToUC16CharacterStream::FillBuffer(unsigned char_position,
182                                               unsigned length) {
183  static const unibrow::uchar kMaxUC16Character = 0xffff;
184  SetRawPosition(char_position);
185  if (raw_character_position_ != char_position) {
186    // char_position was not a valid position in the stream (hit the end
187    // while spooling to it).
188    return 0u;
189  }
190  unsigned i = 0;
191  while (i < length) {
192    if (raw_data_pos_ == raw_data_length_) break;
193    unibrow::uchar c = raw_data_[raw_data_pos_];
194    if (c <= unibrow::Utf8::kMaxOneByteChar) {
195      raw_data_pos_++;
196    } else {
197      c =  unibrow::Utf8::CalculateValue(raw_data_ + raw_data_pos_,
198                                         raw_data_length_ - raw_data_pos_,
199                                         &raw_data_pos_);
200      // Don't allow characters outside of the BMP.
201      if (c > kMaxUC16Character) {
202        c = unibrow::Utf8::kBadChar;
203      }
204    }
205    buffer_[i++] = static_cast<uc16>(c);
206  }
207  raw_character_position_ = char_position + i;
208  return i;
209}
210
211
212static const byte kUtf8MultiByteMask = 0xC0;
213static const byte kUtf8MultiByteCharStart = 0xC0;
214static const byte kUtf8MultiByteCharFollower = 0x80;
215
216
217#ifdef DEBUG
218static bool IsUtf8MultiCharacterStart(byte first_byte) {
219  return (first_byte & kUtf8MultiByteMask) == kUtf8MultiByteCharStart;
220}
221#endif
222
223
224static bool IsUtf8MultiCharacterFollower(byte later_byte) {
225  return (later_byte & kUtf8MultiByteMask) == kUtf8MultiByteCharFollower;
226}
227
228
229// Move the cursor back to point at the preceding UTF-8 character start
230// in the buffer.
231static inline void Utf8CharacterBack(const byte* buffer, unsigned* cursor) {
232  byte character = buffer[--*cursor];
233  if (character > unibrow::Utf8::kMaxOneByteChar) {
234    ASSERT(IsUtf8MultiCharacterFollower(character));
235    // Last byte of a multi-byte character encoding. Step backwards until
236    // pointing to the first byte of the encoding, recognized by having the
237    // top two bits set.
238    while (IsUtf8MultiCharacterFollower(buffer[--*cursor])) { }
239    ASSERT(IsUtf8MultiCharacterStart(buffer[*cursor]));
240  }
241}
242
243
244// Move the cursor forward to point at the next following UTF-8 character start
245// in the buffer.
246static inline void Utf8CharacterForward(const byte* buffer, unsigned* cursor) {
247  byte character = buffer[(*cursor)++];
248  if (character > unibrow::Utf8::kMaxOneByteChar) {
249    // First character of a multi-byte character encoding.
250    // The number of most-significant one-bits determines the length of the
251    // encoding:
252    //  110..... - (0xCx, 0xDx) one additional byte (minimum).
253    //  1110.... - (0xEx) two additional bytes.
254    //  11110... - (0xFx) three additional bytes (maximum).
255    ASSERT(IsUtf8MultiCharacterStart(character));
256    // Additional bytes is:
257    // 1 if value in range 0xC0 .. 0xDF.
258    // 2 if value in range 0xE0 .. 0xEF.
259    // 3 if value in range 0xF0 .. 0xF7.
260    // Encode that in a single value.
261    unsigned additional_bytes =
262        ((0x3211u) >> (((character - 0xC0) >> 2) & 0xC)) & 0x03;
263    *cursor += additional_bytes;
264    ASSERT(!IsUtf8MultiCharacterFollower(buffer[1 + additional_bytes]));
265  }
266}
267
268
269void Utf8ToUC16CharacterStream::SetRawPosition(unsigned target_position) {
270  if (raw_character_position_ > target_position) {
271    // Spool backwards in utf8 buffer.
272    do {
273      Utf8CharacterBack(raw_data_, &raw_data_pos_);
274      raw_character_position_--;
275    } while (raw_character_position_ > target_position);
276    return;
277  }
278  // Spool forwards in the utf8 buffer.
279  while (raw_character_position_ < target_position) {
280    if (raw_data_pos_ == raw_data_length_) return;
281    Utf8CharacterForward(raw_data_, &raw_data_pos_);
282    raw_character_position_++;
283  }
284}
285
286
287// ----------------------------------------------------------------------------
288// ExternalTwoByteStringUC16CharacterStream
289
290ExternalTwoByteStringUC16CharacterStream::
291    ~ExternalTwoByteStringUC16CharacterStream() { }
292
293
294ExternalTwoByteStringUC16CharacterStream
295    ::ExternalTwoByteStringUC16CharacterStream(
296        Handle<ExternalTwoByteString> data,
297        int start_position,
298        int end_position)
299    : UC16CharacterStream(),
300      source_(data),
301      raw_data_(data->GetTwoByteData(start_position)) {
302  buffer_cursor_ = raw_data_,
303  buffer_end_ = raw_data_ + (end_position - start_position);
304  pos_ = start_position;
305}
306
307
308// ----------------------------------------------------------------------------
309// Scanner::LiteralScope
310
311Scanner::LiteralScope::LiteralScope(Scanner* self)
312    : scanner_(self), complete_(false) {
313  self->StartLiteral();
314}
315
316
317Scanner::LiteralScope::~LiteralScope() {
318  if (!complete_) scanner_->DropLiteral();
319}
320
321
322void Scanner::LiteralScope::Complete() {
323  scanner_->TerminateLiteral();
324  complete_ = true;
325}
326
327} }  // namespace v8::internal
328