libwebp: update snapshot to v0.3.0-rc6

third_party/libwebp/dec/vp8l.c

 // Copyright 2012 Google Inc. All Rights Reserved.
 //
 // This code is licensed under the same terms as WebM:
 //  Software License Agreement:  http://www.webmproject.org/license/software/
 //  Additional IP Rights Grant:  http://www.webmproject.org/license/additional/
 // -----------------------------------------------------------------------------
 //
 // main entry for the decoder
 //
 // Authors: Vikas Arora (vikaas.arora@gmail.com)
@@ skipping 131 matching lines @@
     const int yoffset = dist_code >> 4;
     const int xoffset = 8 - (dist_code & 0xf);
     const int dist = yoffset * xsize + xoffset;
     return (dist >= 1) ? dist : 1;
   }
 }
 
 //------------------------------------------------------------------------------
 // Decodes the next Huffman code from bit-stream.
 // FillBitWindow(br) needs to be called at minimum every second call
-// to ReadSymbolUnsafe.
-static int ReadSymbolUnsafe(const HuffmanTree* tree, VP8LBitReader* const br) {
+// to ReadSymbol, in order to pre-fetch enough bits.
+static WEBP_INLINE int ReadSymbol(const HuffmanTree* tree,
+                                  VP8LBitReader* const br) {
   const HuffmanTreeNode* node = tree->root_;
+  int num_bits = 0;
+  uint32_t bits = VP8LPrefetchBits(br);
   assert(node != NULL);
   while (!HuffmanTreeNodeIsLeaf(node)) {
-    node = HuffmanTreeNextNode(node, VP8LReadOneBitUnsafe(br));
+    node = HuffmanTreeNextNode(node, bits & 1);
+    bits >>= 1;
+    ++num_bits;
   }
+  VP8LDiscardBits(br, num_bits);
   return node->symbol_;
 }
 
-static WEBP_INLINE int ReadSymbol(const HuffmanTree* tree,
-                                  VP8LBitReader* const br) {
-  const int read_safe = (br->pos_ + 8 > br->len_);
-  if (!read_safe) {
-    return ReadSymbolUnsafe(tree, br);
-  } else {
-    const HuffmanTreeNode* node = tree->root_;
-    assert(node != NULL);
-    while (!HuffmanTreeNodeIsLeaf(node)) {
-      node = HuffmanTreeNextNode(node, VP8LReadOneBit(br));
-    }
-    return node->symbol_;
-  }
-}
-
 static int ReadHuffmanCodeLengths(
     VP8LDecoder* const dec, const int* const code_length_code_lengths,
     int num_symbols, int* const code_lengths) {
   int ok = 0;
   VP8LBitReader* const br = &dec->br_;
   int symbol;
   int max_symbol;
   int prev_code_len = DEFAULT_CODE_LENGTH;
   HuffmanTree tree;
 
@@ skipping 133 matching lines @@
     const int huffman_ysize = VP8LSubSampleSize(ysize, huffman_precision);
     const int huffman_pixs = huffman_xsize * huffman_ysize;
     if (!DecodeImageStream(huffman_xsize, huffman_ysize, 0, dec,
                            &huffman_image)) {
       dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
       goto Error;
     }
     hdr->huffman_subsample_bits_ = huffman_precision;
     for (i = 0; i < huffman_pixs; ++i) {
       // The huffman data is stored in red and green bytes.
-      const int index = (huffman_image[i] >> 8) & 0xffff;
-      huffman_image[i] = index;
-      if (index >= num_htree_groups) {
-        num_htree_groups = index + 1;
+      const int group = (huffman_image[i] >> 8) & 0xffff;
+      huffman_image[i] = group;
+      if (group >= num_htree_groups) {
+        num_htree_groups = group + 1;
       }
     }
   }
 
   if (br->error_) goto Error;
 
   assert(num_htree_groups <= 0x10000);
   htree_groups =
       (HTreeGroup*)WebPSafeCalloc((uint64_t)num_htree_groups,
                                   sizeof(*htree_groups));
@@ skipping 264 matching lines @@
                                       hdr->huffman_subsample_bits_, x, y);
   assert(meta_index < hdr->num_htree_groups_);
   return hdr->htree_groups_ + meta_index;
 }
 
 //------------------------------------------------------------------------------
 // Main loop, with custom row-processing function
 
 typedef void (*ProcessRowsFunc)(VP8LDecoder* const dec, int row);
 
-static void ApplyTransforms(VP8LDecoder* const dec, int num_rows,
-                            const uint32_t* const rows) {
+static void ApplyInverseTransforms(VP8LDecoder* const dec, int num_rows,
+                                   const uint32_t* const rows) {
   int n = dec->next_transform_;
   const int cache_pixs = dec->width_ * num_rows;
-  uint32_t* rows_data = dec->argb_cache_;
   const int start_row = dec->last_row_;
   const int end_row = start_row + num_rows;
+  const uint32_t* rows_in = rows;
+  uint32_t* const rows_out = dec->argb_cache_;
 
   // Inverse transforms.
   // TODO: most transforms only need to operate on the cropped region only.
-  memcpy(rows_data, rows, cache_pixs * sizeof(*rows_data));
+  memcpy(rows_out, rows_in, cache_pixs * sizeof(*rows_out));
   while (n-- > 0) {
     VP8LTransform* const transform = &dec->transforms_[n];
-    VP8LInverseTransform(transform, start_row, end_row, rows, rows_data);
+    VP8LInverseTransform(transform, start_row, end_row, rows_in, rows_out);
+    rows_in = rows_out;
   }
 }
 
 // Processes (transforms, scales & color-converts) the rows decoded after the
 // last call.
 static void ProcessRows(VP8LDecoder* const dec, int row) {
   const uint32_t* const rows = dec->argb_ + dec->width_ * dec->last_row_;
   const int num_rows = row - dec->last_row_;
 
   if (num_rows <= 0) return;  // Nothing to be done.
-  ApplyTransforms(dec, num_rows, rows);
+  ApplyInverseTransforms(dec, num_rows, rows);
 
   // Emit output.
   {
     VP8Io* const io = dec->io_;
     const uint32_t* rows_data = dec->argb_cache_;
     if (!SetCropWindow(io, dec->last_row_, row, &rows_data, io->width)) {
       // Nothing to output (this time).
     } else {
       const WebPDecBuffer* const output = dec->output_;
       const int in_stride = io->width * sizeof(*rows_data);
@@ skipping 137 matching lines @@
 }
 
 // -----------------------------------------------------------------------------
 // VP8LTransform
 
 static void ClearTransform(VP8LTransform* const transform) {
   free(transform->data_);
   transform->data_ = NULL;
 }
 
-static void ApplyInverseTransforms(VP8LDecoder* const dec, int start_idx,
-                                   uint32_t* const decoded_data) {
-  int n = dec->next_transform_;
-  assert(start_idx >= 0);
-  while (n-- > start_idx) {
-    VP8LTransform* const transform = &dec->transforms_[n];
-    VP8LInverseTransform(transform, 0, transform->ysize_,
-                         decoded_data, decoded_data);
-    ClearTransform(transform);
-  }
-  dec->next_transform_ = start_idx;
-}
-
 // For security reason, we need to remap the color map to span
 // the total possible bundled values, and not just the num_colors.
 static int ExpandColorMap(int num_colors, VP8LTransform* const transform) {
   int i;
   const int final_num_colors = 1 << (8 >> transform->bits_);
   uint32_t* const new_color_map =
       (uint32_t*)WebPSafeMalloc((uint64_t)final_num_colors,
                                 sizeof(*new_color_map));
   if (new_color_map == NULL) {
     return 0;
@@ skipping 134 matching lines @@
 static int DecodeImageStream(int xsize, int ysize,
                              int is_level0,
                              VP8LDecoder* const dec,
                              uint32_t** const decoded_data) {
   int ok = 1;
   int transform_xsize = xsize;
   int transform_ysize = ysize;
   VP8LBitReader* const br = &dec->br_;
   VP8LMetadata* const hdr = &dec->hdr_;
   uint32_t* data = NULL;
-  const int transform_start_idx = dec->next_transform_;
   int color_cache_bits = 0;
 
   // Read the transforms (may recurse).
   if (is_level0) {
     while (ok && VP8LReadBits(br, 1)) {
       ok = ReadTransform(&transform_xsize, &transform_ysize, dec);
     }
   }
 
   // Color cache
@@ skipping 39 matching lines @@
       dec->status_ = VP8_STATUS_OUT_OF_MEMORY;
       ok = 0;
       goto End;
     }
   }
 
   // Use the Huffman trees to decode the LZ77 encoded data.
   ok = DecodeImageData(dec, data, transform_xsize, transform_ysize, NULL);
   ok = ok && !br->error_;
 
-  // Apply transforms on the decoded data.
-  if (ok) ApplyInverseTransforms(dec, transform_start_idx, data);
-
  End:
 
   if (!ok) {
     free(data);
     ClearMetadata(hdr);
     // If not enough data (br.eos_) resulted in BIT_STREAM_ERROR, update the
     // status appropriately.
     if (dec->status_ == VP8_STATUS_BITSTREAM_ERROR && dec->br_.eos_) {
       dec->status_ = VP8_STATUS_SUSPENDED;
     }
@@ skipping 36 matching lines @@
 }
 
 //------------------------------------------------------------------------------
 // Special row-processing that only stores the alpha data.
 
 static void ExtractAlphaRows(VP8LDecoder* const dec, int row) {
   const int num_rows = row - dec->last_row_;
   const uint32_t* const in = dec->argb_ + dec->width_ * dec->last_row_;
 
   if (num_rows <= 0) return;  // Nothing to be done.
-  ApplyTransforms(dec, num_rows, in);
+  ApplyInverseTransforms(dec, num_rows, in);
 
   // Extract alpha (which is stored in the green plane).
   {
     const int width = dec->io_->width;      // the final width (!= dec->width_)
     const int cache_pixs = width * num_rows;
     uint8_t* const dst = (uint8_t*)dec->io_->opaque + width * dec->last_row_;
     const uint32_t* const src = dec->argb_cache_;
     int i;
     for (i = 0; i < cache_pixs; ++i) dst[i] = (src[i] >> 8) & 0xff;
   }
@@ skipping 109 matching lines @@
   VP8LClear(dec);
   assert(dec->status_ != VP8_STATUS_OK);
   return 0;
 }
 
 //------------------------------------------------------------------------------
 
 #if defined(__cplusplus) || defined(c_plusplus)
 }    // extern "C"
 #endif