Corrected implementation of TwoByteExternalBufferedStream.

src/parsing/scanner-character-streams.cc

 // Copyright 2011 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.
 
 #include "src/parsing/scanner-character-streams.h"
 
 #include "include/v8.h"
 #include "src/globals.h"
 #include "src/handles.h"
 #include "src/objects-inl.h"
@@ skipping 519 matching lines @@
 size_t OneByteExternalStreamingStream::FillBuffer(size_t position) {
   const Chunk& chunk = chunks_[FindChunk(chunks_, source_, position)];
   if (chunk.byte_length == 0) return 0;
 
   size_t start_pos = position - chunk.byte_pos;
   size_t len = i::Min(kBufferSize, chunk.byte_length - start_pos);
   i::CopyCharsUnsigned(buffer_, chunk.data + start_pos, len);
   return len;
 }
 
-#if !(V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64 || V8_TARGET_ARCH_ARM)
+#if !(V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64)
 // ----------------------------------------------------------------------------
 // TwoByteExternalStreamingStream
 //
 // A stream of ucs-2 data, delivered in chunks. Chunks may be 'cut' into the
 // middle of characters (or even contain only one byte), which adds a bit
 // of complexity. This stream avoid all data copying, except for characters
 // that cross chunk boundaries.
 
 class TwoByteExternalStreamingStream : public Utf16CharacterStream {
  public:
@@ skipping 145 matching lines @@
   // architectures. Otherwise read characters from memory directly.
   if (!odd_start) {
     buffer_start_ = reinterpret_cast<const uint16_t*>(current.data);
     size_t number_chars = current.byte_length / 2;
     buffer_end_ = buffer_start_ + number_chars;
     buffer_pos_ = current.byte_pos / 2;
     buffer_cursor_ = buffer_start_ + (position - buffer_pos_);
     DCHECK_EQ(position, pos());
     return true;
   } else {
+    buffer_start_ = buffer_;
     buffer_pos_ = position;
     buffer_cursor_ = buffer_;
     buffer_end_ = buffer_ + FillBuffer(position, chunk_no);
     DCHECK_EQ(pos(), position);
     DCHECK_LE(buffer_end_, buffer_start_ + kBufferSize);
     return buffer_cursor_ < buffer_end_;
   }
 }
 
 size_t TwoByteExternalBufferedStream::FillBuffer(size_t position,
                                                  size_t chunk_no) {
+  DCHECK_EQ(chunks_[chunk_no].byte_pos % 2, 1);
+  bool odd_start = true;
   // Align buffer_pos_ to the size of the buffer.
   {
     size_t new_pos = position / kBufferSize * kBufferSize;
     if (new_pos != position) {
       chunk_no = FindChunk(chunks_, source_, 2 * new_pos + 1);
       buffer_pos_ = new_pos;
       buffer_cursor_ = buffer_start_ + (position - buffer_pos_);
       position = new_pos;
+      odd_start = chunks_[chunk_no].byte_pos % 2;
     }
   }
 
   Chunk* current = &chunks_[chunk_no];
 
   // Annoying edge case: Chunks may not be 2-byte aligned, meaning that a
   // character may be split between the previous and the current chunk.
   // If we find such a lonely byte at the beginning of the chunk, we'll copy
   // it to the first byte in buffer_.
   size_t totalLength = 0;
   bool lonely_byte = (current->byte_pos == (2 * position + 1));
   if (lonely_byte) {
     DCHECK_NE(chunk_no, 0);
     Chunk& previous_chunk = chunks_[chunk_no - 1];
     *reinterpret_cast<uint8_t*>(buffer_) =
         previous_chunk.data[previous_chunk.byte_length - 1];
     totalLength++;
   }
 
   // Common case: character is in current chunk.
-  DCHECK_LE(current->byte_pos, 2 * position + 1);
+  DCHECK_LE(current->byte_pos, 2 * position + odd_start);
   DCHECK_LT(2 * position + 1, current->byte_pos + current->byte_length);
 
   // Copy characters from current chunk starting from chunk_pos to the end of
   // buffer or chunk.
   size_t chunk_pos = position - current->byte_pos / 2;
-  bool middle_of_chunk = chunk_pos != 0;
+  size_t start_offset = odd_start && chunk_pos != 0;
   size_t bytes_to_move =
-      i::Min(2 * kBufferSize - !middle_of_chunk,
-             current->byte_length - 2 * chunk_pos + middle_of_chunk);
-  i::MemMove(reinterpret_cast<uint8_t*>(buffer_) + !middle_of_chunk,
-             current->data + 2 * chunk_pos - middle_of_chunk, bytes_to_move);
+      i::Min(2 * kBufferSize - lonely_byte,
+             current->byte_length - 2 * chunk_pos + start_offset);
+  i::MemMove(reinterpret_cast<uint8_t*>(buffer_) + lonely_byte,
+             current->data + 2 * chunk_pos - start_offset, bytes_to_move);
 
   // Fill up the rest of the buffer if there is space and data left.
   totalLength += bytes_to_move;
   position = (current->byte_pos + current->byte_length) / 2;
   if (position - buffer_pos_ < kBufferSize) {
     chunk_no = FindChunk(chunks_, source_, 2 * position + 1);
     current = &chunks_[chunk_no];
+    odd_start = current->byte_pos % 2;
     bytes_to_move = i::Min(2 * kBufferSize - totalLength, current->byte_length);
-    while (bytes_to_move && current->byte_pos % 2) {
+    while (bytes_to_move) {
       // Common case: character is in current chunk.
-      DCHECK_LE(current->byte_pos, 2 * position + 1);
+      DCHECK_LE(current->byte_pos, 2 * position + odd_start);
       DCHECK_LT(2 * position + 1, current->byte_pos + current->byte_length);
 
       i::MemMove(reinterpret_cast<uint8_t*>(buffer_) + totalLength,
                  current->data, bytes_to_move);
       totalLength += bytes_to_move;
       position = (current->byte_pos + current->byte_length) / 2;
       chunk_no = FindChunk(chunks_, source_, 2 * position + 1);
       current = &chunks_[chunk_no];
+      odd_start = current->byte_pos % 2;
       bytes_to_move =
           i::Min(2 * kBufferSize - totalLength, current->byte_length);
     }
   }
   return totalLength / 2;
 }
 #endif
 
 // ----------------------------------------------------------------------------
 // ScannerStream: Create stream instances.
@@ skipping 27 matching lines @@
     const char* data, size_t length) {
   return std::unique_ptr<Utf16CharacterStream>(
       new ExternalOneByteStringUtf16CharacterStream(data, length));
 }
 
 Utf16CharacterStream* ScannerStream::For(
     ScriptCompiler::ExternalSourceStream* source_stream,
     v8::ScriptCompiler::StreamedSource::Encoding encoding) {
   switch (encoding) {
     case v8::ScriptCompiler::StreamedSource::TWO_BYTE:
-#if !(V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64 || V8_TARGET_ARCH_ARM)
+#if !(V8_TARGET_ARCH_MIPS || V8_TARGET_ARCH_MIPS64)
       return new TwoByteExternalStreamingStream(source_stream);
 #else
       return new TwoByteExternalBufferedStream(source_stream);
 #endif
     case v8::ScriptCompiler::StreamedSource::ONE_BYTE:
       return new OneByteExternalStreamingStream(source_stream);
     case v8::ScriptCompiler::StreamedSource::UTF8:
       return new Utf8ExternalStreamingStream(source_stream);
   }
   UNREACHABLE();
   return nullptr;
 }
 
 }  // namespace internal
 }  // namespace v8