libwebp: update to 0.5.0

third_party/libwebp/dec/vp8l.c

 // Copyright 2012 Google Inc. All Rights Reserved.
 //
 // Use of this source code is governed by a BSD-style license
 // that can be found in the COPYING file in the root of the source
 // tree. An additional intellectual property rights grant can be found
 // in the file PATENTS. All contributing project authors may
 // be found in the AUTHORS file in the root of the source tree.
 // -----------------------------------------------------------------------------
 //
 // main entry for the decoder
 //
 // Authors: Vikas Arora (vikaas.arora@gmail.com)
 //          Jyrki Alakuijala (jyrki@google.com)
 
 #include <stdlib.h>
 
 #include "./alphai.h"
 #include "./vp8li.h"
 #include "../dsp/dsp.h"
 #include "../dsp/lossless.h"
 #include "../dsp/yuv.h"
+#include "../utils/endian_inl.h"
 #include "../utils/huffman.h"
 #include "../utils/utils.h"
 
 #define NUM_ARGB_CACHE_ROWS          16
 
 static const int kCodeLengthLiterals = 16;
 static const int kCodeLengthRepeatCode = 16;
 static const int kCodeLengthExtraBits[3] = { 2, 3, 7 };
 static const int kCodeLengthRepeatOffsets[3] = { 3, 3, 11 };
 
@@ skipping 11 matching lines @@
   ALPHA = 3,
   DIST  = 4
 } HuffIndex;
 
 static const uint16_t kAlphabetSize[HUFFMAN_CODES_PER_META_CODE] = {
   NUM_LITERAL_CODES + NUM_LENGTH_CODES,
   NUM_LITERAL_CODES, NUM_LITERAL_CODES, NUM_LITERAL_CODES,
   NUM_DISTANCE_CODES
 };
 
+static const uint8_t kLiteralMap[HUFFMAN_CODES_PER_META_CODE] = {
+  0, 1, 1, 1, 0
+};
 
 #define NUM_CODE_LENGTH_CODES       19
 static const uint8_t kCodeLengthCodeOrder[NUM_CODE_LENGTH_CODES] = {
   17, 18, 0, 1, 2, 3, 4, 5, 16, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
 };
 
 #define CODE_TO_PLANE_CODES        120
 static const uint8_t kCodeToPlane[CODE_TO_PLANE_CODES] = {
   0x18, 0x07, 0x17, 0x19, 0x28, 0x06, 0x27, 0x29, 0x16, 0x1a,
   0x26, 0x2a, 0x38, 0x05, 0x37, 0x39, 0x15, 0x1b, 0x36, 0x3a,
   0x25, 0x2b, 0x48, 0x04, 0x47, 0x49, 0x14, 0x1c, 0x35, 0x3b,
   0x46, 0x4a, 0x24, 0x2c, 0x58, 0x45, 0x4b, 0x34, 0x3c, 0x03,
   0x57, 0x59, 0x13, 0x1d, 0x56, 0x5a, 0x23, 0x2d, 0x44, 0x4c,
   0x55, 0x5b, 0x33, 0x3d, 0x68, 0x02, 0x67, 0x69, 0x12, 0x1e,
   0x66, 0x6a, 0x22, 0x2e, 0x54, 0x5c, 0x43, 0x4d, 0x65, 0x6b,
   0x32, 0x3e, 0x78, 0x01, 0x77, 0x79, 0x53, 0x5d, 0x11, 0x1f,
   0x64, 0x6c, 0x42, 0x4e, 0x76, 0x7a, 0x21, 0x2f, 0x75, 0x7b,
   0x31, 0x3f, 0x63, 0x6d, 0x52, 0x5e, 0x00, 0x74, 0x7c, 0x41,
   0x4f, 0x10, 0x20, 0x62, 0x6e, 0x30, 0x73, 0x7d, 0x51, 0x5f,
   0x40, 0x72, 0x7e, 0x61, 0x6f, 0x50, 0x71, 0x7f, 0x60, 0x70
 };
 
+// Memory needed for lookup tables of one Huffman tree group. Red, blue, alpha
+// and distance alphabets are constant (256 for red, blue and alpha, 40 for
+// distance) and lookup table sizes for them in worst case are 630 and 410
+// respectively. Size of green alphabet depends on color cache size and is equal
+// to 256 (green component values) + 24 (length prefix values)
+// + color_cache_size (between 0 and 2048).
+// All values computed for 8-bit first level lookup with Mark Adler's tool:
+// http://www.hdfgroup.org/ftp/lib-external/zlib/zlib-1.2.5/examples/enough.c
+#define FIXED_TABLE_SIZE (630 * 3 + 410)
+static const int kTableSize[12] = {
+  FIXED_TABLE_SIZE + 654,
+  FIXED_TABLE_SIZE + 656,
+  FIXED_TABLE_SIZE + 658,
+  FIXED_TABLE_SIZE + 662,
+  FIXED_TABLE_SIZE + 670,
+  FIXED_TABLE_SIZE + 686,
+  FIXED_TABLE_SIZE + 718,
+  FIXED_TABLE_SIZE + 782,
+  FIXED_TABLE_SIZE + 912,
+  FIXED_TABLE_SIZE + 1168,
+  FIXED_TABLE_SIZE + 1680,
+  FIXED_TABLE_SIZE + 2704
+};
+
 static int DecodeImageStream(int xsize, int ysize,
                              int is_level0,
                              VP8LDecoder* const dec,
                              uint32_t** const decoded_data);
 
 //------------------------------------------------------------------------------
 
 int VP8LCheckSignature(const uint8_t* const data, size_t size) {
   return (size >= VP8L_FRAME_HEADER_SIZE &&
           data[0] == VP8L_MAGIC_BYTE &&
           (data[4] >> 5) == 0);  // version
 }
 
 static int ReadImageInfo(VP8LBitReader* const br,
                          int* const width, int* const height,
                          int* const has_alpha) {
   if (VP8LReadBits(br, 8) != VP8L_MAGIC_BYTE) return 0;
   *width = VP8LReadBits(br, VP8L_IMAGE_SIZE_BITS) + 1;
   *height = VP8LReadBits(br, VP8L_IMAGE_SIZE_BITS) + 1;
   *has_alpha = VP8LReadBits(br, 1);
   if (VP8LReadBits(br, VP8L_VERSION_BITS) != 0) return 0;
-  return 1;
+  return !br->eos_;
 }
 
 int VP8LGetInfo(const uint8_t* data, size_t data_size,
                 int* const width, int* const height, int* const has_alpha) {
   if (data == NULL || data_size < VP8L_FRAME_HEADER_SIZE) {
     return 0;         // not enough data
   } else if (!VP8LCheckSignature(data, data_size)) {
     return 0;         // bad signature
   } else {
     int w, h, a;
@@ skipping 37 matching lines @@
     const int xoffset = 8 - (dist_code & 0xf);
     const int dist = yoffset * xsize + xoffset;
     return (dist >= 1) ? dist : 1;  // dist<1 can happen if xsize is very small
   }
 }
 
 //------------------------------------------------------------------------------
 // Decodes the next Huffman code from bit-stream.
 // FillBitWindow(br) needs to be called at minimum every second call
 // to ReadSymbol, in order to pre-fetch enough bits.
-static WEBP_INLINE int ReadSymbol(const HuffmanTree* tree,
+static WEBP_INLINE int ReadSymbol(const HuffmanCode* table,
                                   VP8LBitReader* const br) {
-  const HuffmanTreeNode* node = tree->root_;
-  uint32_t bits = VP8LPrefetchBits(br);
-  int bitpos = br->bit_pos_;
-  // Check if we find the bit combination from the Huffman lookup table.
-  const int lut_ix = bits & (HUFF_LUT - 1);
-  const int lut_bits = tree->lut_bits_[lut_ix];
-  if (lut_bits <= HUFF_LUT_BITS) {
-    VP8LSetBitPos(br, bitpos + lut_bits);
-    return tree->lut_symbol_[lut_ix];
+  int nbits;
+  uint32_t val = VP8LPrefetchBits(br);
+  table += val & HUFFMAN_TABLE_MASK;
+  nbits = table->bits - HUFFMAN_TABLE_BITS;
+  if (nbits > 0) {
+    VP8LSetBitPos(br, br->bit_pos_ + HUFFMAN_TABLE_BITS);
+    val = VP8LPrefetchBits(br);
+    table += table->value;
+    table += val & ((1 << nbits) - 1);
   }
-  node += tree->lut_jump_[lut_ix];
-  bitpos += HUFF_LUT_BITS;
-  bits >>= HUFF_LUT_BITS;
+  VP8LSetBitPos(br, br->bit_pos_ + table->bits);
+  return table->value;
+}
 
-  // Decode the value from a binary tree.
-  assert(node != NULL);
-  do {
-    node = HuffmanTreeNextNode(node, bits & 1);
-    bits >>= 1;
-    ++bitpos;
-  } while (HuffmanTreeNodeIsNotLeaf(node));
-  VP8LSetBitPos(br, bitpos);
-  return node->symbol_;
+// Reads packed symbol depending on GREEN channel
+#define BITS_SPECIAL_MARKER 0x100  // something large enough (and a bit-mask)
+#define PACKED_NON_LITERAL_CODE 0  // must be < NUM_LITERAL_CODES
+static WEBP_INLINE int ReadPackedSymbols(const HTreeGroup* group,
+                                         VP8LBitReader* const br,
+                                         uint32_t* const dst) {
+  const uint32_t val = VP8LPrefetchBits(br) & (HUFFMAN_PACKED_TABLE_SIZE - 1);
+  const HuffmanCode32 code = group->packed_table[val];
+  assert(group->use_packed_table);
+  if (code.bits < BITS_SPECIAL_MARKER) {
+    VP8LSetBitPos(br, br->bit_pos_ + code.bits);
+    *dst = code.value;
+    return PACKED_NON_LITERAL_CODE;
+  } else {
+    VP8LSetBitPos(br, br->bit_pos_ + code.bits - BITS_SPECIAL_MARKER);
+    assert(code.value >= NUM_LITERAL_CODES);
+    return code.value;
+  }
+}
+
+static int AccumulateHCode(HuffmanCode hcode, int shift,
+                           HuffmanCode32* const huff) {
+  huff->bits += hcode.bits;
+  huff->value |= (uint32_t)hcode.value << shift;
+  assert(huff->bits <= HUFFMAN_TABLE_BITS);
+  return hcode.bits;
+}
+
+static void BuildPackedTable(HTreeGroup* const htree_group) {
+  uint32_t code;
+  for (code = 0; code < HUFFMAN_PACKED_TABLE_SIZE; ++code) {
+    uint32_t bits = code;
+    HuffmanCode32* const huff = &htree_group->packed_table[bits];
+    HuffmanCode hcode = htree_group->htrees[GREEN][bits];
+    if (hcode.value >= NUM_LITERAL_CODES) {
+      huff->bits = hcode.bits + BITS_SPECIAL_MARKER;
+      huff->value = hcode.value;
+    } else {
+      huff->bits = 0;
+      huff->value = 0;
+      bits >>= AccumulateHCode(hcode, 8, huff);
+      bits >>= AccumulateHCode(htree_group->htrees[RED][bits], 16, huff);
+      bits >>= AccumulateHCode(htree_group->htrees[BLUE][bits], 0, huff);
+      bits >>= AccumulateHCode(htree_group->htrees[ALPHA][bits], 24, huff);
+      (void)bits;
+    }
+  }
 }
 
 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;
-  int huff_codes[NUM_CODE_LENGTH_CODES] = { 0 };
+  HuffmanCode table[1 << LENGTHS_TABLE_BITS];
 
-  if (!VP8LHuffmanTreeBuildImplicit(&tree, code_length_code_lengths,
-                                    huff_codes, NUM_CODE_LENGTH_CODES)) {
-    dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
-    return 0;
+  if (!VP8LBuildHuffmanTable(table, LENGTHS_TABLE_BITS,
+                             code_length_code_lengths,
+                             NUM_CODE_LENGTH_CODES)) {
+    goto End;
   }
 
   if (VP8LReadBits(br, 1)) {    // use length
     const int length_nbits = 2 + 2 * VP8LReadBits(br, 3);
     max_symbol = 2 + VP8LReadBits(br, length_nbits);
     if (max_symbol > num_symbols) {
-      dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
       goto End;
     }
   } else {
     max_symbol = num_symbols;
   }
 
   symbol = 0;
   while (symbol < num_symbols) {
+    const HuffmanCode* p;
     int code_len;
     if (max_symbol-- == 0) break;
     VP8LFillBitWindow(br);
-    code_len = ReadSymbol(&tree, br);
+    p = &table[VP8LPrefetchBits(br) & LENGTHS_TABLE_MASK];
+    VP8LSetBitPos(br, br->bit_pos_ + p->bits);
+    code_len = p->value;
     if (code_len < kCodeLengthLiterals) {
       code_lengths[symbol++] = code_len;
       if (code_len != 0) prev_code_len = code_len;
     } else {
       const int use_prev = (code_len == kCodeLengthRepeatCode);
       const int slot = code_len - kCodeLengthLiterals;
       const int extra_bits = kCodeLengthExtraBits[slot];
       const int repeat_offset = kCodeLengthRepeatOffsets[slot];
       int repeat = VP8LReadBits(br, extra_bits) + repeat_offset;
       if (symbol + repeat > num_symbols) {
-        dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
         goto End;
       } else {
         const int length = use_prev ? prev_code_len : 0;
         while (repeat-- > 0) code_lengths[symbol++] = length;
       }
     }
   }
   ok = 1;
 
  End:
-  VP8LHuffmanTreeFree(&tree);
   if (!ok) dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
   return ok;
 }
 
 // 'code_lengths' is pre-allocated temporary buffer, used for creating Huffman
 // tree.
 static int ReadHuffmanCode(int alphabet_size, VP8LDecoder* const dec,
-                           int* const code_lengths, int* const huff_codes,
-                           HuffmanTree* const tree) {
+                           int* const code_lengths, HuffmanCode* const table) {
   int ok = 0;
+  int size = 0;
   VP8LBitReader* const br = &dec->br_;
   const int simple_code = VP8LReadBits(br, 1);
 
+  memset(code_lengths, 0, alphabet_size * sizeof(*code_lengths));
+
   if (simple_code) {  // Read symbols, codes & code lengths directly.
-    int symbols[2];
-    int codes[2];
     const int num_symbols = VP8LReadBits(br, 1) + 1;
     const int first_symbol_len_code = VP8LReadBits(br, 1);
     // The first code is either 1 bit or 8 bit code.
-    symbols[0] = VP8LReadBits(br, (first_symbol_len_code == 0) ? 1 : 8);
-    codes[0] = 0;
-    code_lengths[0] = num_symbols - 1;
+    int symbol = VP8LReadBits(br, (first_symbol_len_code == 0) ? 1 : 8);
+    code_lengths[symbol] = 1;
     // The second code (if present), is always 8 bit long.
     if (num_symbols == 2) {
-      symbols[1] = VP8LReadBits(br, 8);
-      codes[1] = 1;
-      code_lengths[1] = num_symbols - 1;
+      symbol = VP8LReadBits(br, 8);
+      code_lengths[symbol] = 1;
     }
-    ok = VP8LHuffmanTreeBuildExplicit(tree, code_lengths, codes, symbols,
-                                      alphabet_size, num_symbols);
+    ok = 1;
   } else {  // Decode Huffman-coded code lengths.
     int i;
     int code_length_code_lengths[NUM_CODE_LENGTH_CODES] = { 0 };
     const int num_codes = VP8LReadBits(br, 4) + 4;
     if (num_codes > NUM_CODE_LENGTH_CODES) {
       dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
       return 0;
     }
 
-    memset(code_lengths, 0, alphabet_size * sizeof(*code_lengths));
-
     for (i = 0; i < num_codes; ++i) {
       code_length_code_lengths[kCodeLengthCodeOrder[i]] = VP8LReadBits(br, 3);
     }
     ok = ReadHuffmanCodeLengths(dec, code_length_code_lengths, alphabet_size,
                                 code_lengths);
-    ok = ok && VP8LHuffmanTreeBuildImplicit(tree, code_lengths, huff_codes,
-                                            alphabet_size);
   }
-  ok = ok && !br->error_;
-  if (!ok) {
+
+  ok = ok && !br->eos_;
+  if (ok) {
+    size = VP8LBuildHuffmanTable(table, HUFFMAN_TABLE_BITS,
+                                 code_lengths, alphabet_size);
+  }
+  if (!ok || size == 0) {
     dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
     return 0;
   }
-  return 1;
+  return size;
 }
 
 static int ReadHuffmanCodes(VP8LDecoder* const dec, int xsize, int ysize,
                             int color_cache_bits, int allow_recursion) {
   int i, j;
   VP8LBitReader* const br = &dec->br_;
   VP8LMetadata* const hdr = &dec->hdr_;
   uint32_t* huffman_image = NULL;
   HTreeGroup* htree_groups = NULL;
+  HuffmanCode* huffman_tables = NULL;
+  HuffmanCode* next = NULL;
   int num_htree_groups = 1;
   int max_alphabet_size = 0;
   int* code_lengths = NULL;
-  int* huff_codes = NULL;
+  const int table_size = kTableSize[color_cache_bits];
 
   if (allow_recursion && VP8LReadBits(br, 1)) {
     // use meta Huffman codes.
     const int huffman_precision = VP8LReadBits(br, 3) + 2;
     const int huffman_xsize = VP8LSubSampleSize(xsize, huffman_precision);
     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 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;
+  if (br->eos_) goto Error;
 
   // Find maximum alphabet size for the htree group.
   for (j = 0; j < HUFFMAN_CODES_PER_META_CODE; ++j) {
     int alphabet_size = kAlphabetSize[j];
     if (j == 0 && color_cache_bits > 0) {
       alphabet_size += 1 << color_cache_bits;
     }
     if (max_alphabet_size < alphabet_size) {
       max_alphabet_size = alphabet_size;
     }
   }
 
+  huffman_tables = (HuffmanCode*)WebPSafeMalloc(num_htree_groups * table_size,
+                                                sizeof(*huffman_tables));
   htree_groups = VP8LHtreeGroupsNew(num_htree_groups);
-  code_lengths =
-      (int*)WebPSafeCalloc((uint64_t)max_alphabet_size, sizeof(*code_lengths));
-  huff_codes =
-      (int*)WebPSafeMalloc((uint64_t)max_alphabet_size, sizeof(*huff_codes));
+  code_lengths = (int*)WebPSafeCalloc((uint64_t)max_alphabet_size,
+                                      sizeof(*code_lengths));
 
-  if (htree_groups == NULL || code_lengths == NULL || huff_codes == NULL) {
+  if (htree_groups == NULL || code_lengths == NULL || huffman_tables == NULL) {
     dec->status_ = VP8_STATUS_OUT_OF_MEMORY;
     goto Error;
   }
 
+  next = huffman_tables;
   for (i = 0; i < num_htree_groups; ++i) {
-    HuffmanTree* const htrees = htree_groups[i].htrees_;
+    HTreeGroup* const htree_group = &htree_groups[i];
+    HuffmanCode** const htrees = htree_group->htrees;
+    int size;
+    int total_size = 0;
+    int is_trivial_literal = 1;
+    int max_bits = 0;
     for (j = 0; j < HUFFMAN_CODES_PER_META_CODE; ++j) {
       int alphabet_size = kAlphabetSize[j];
-      HuffmanTree* const htree = htrees + j;
+      htrees[j] = next;
       if (j == 0 && color_cache_bits > 0) {
         alphabet_size += 1 << color_cache_bits;
       }
-      if (!ReadHuffmanCode(alphabet_size, dec, code_lengths, huff_codes,
-                           htree)) {
+      size = ReadHuffmanCode(alphabet_size, dec, code_lengths, next);
+      if (size == 0) {
         goto Error;
       }
+      if (is_trivial_literal && kLiteralMap[j] == 1) {
+        is_trivial_literal = (next->bits == 0);
+      }
+      total_size += next->bits;
+      next += size;
+      if (j <= ALPHA) {
+        int local_max_bits = code_lengths[0];
+        int k;
+        for (k = 1; k < alphabet_size; ++k) {
+          if (code_lengths[k] > local_max_bits) {
+            local_max_bits = code_lengths[k];
+          }
+        }
+        max_bits += local_max_bits;
+      }
     }
+    htree_group->is_trivial_literal = is_trivial_literal;
+    htree_group->is_trivial_code = 0;
+    if (is_trivial_literal) {
+      const int red = htrees[RED][0].value;
+      const int blue = htrees[BLUE][0].value;
+      const int alpha = htrees[ALPHA][0].value;
+      htree_group->literal_arb =
+          ((uint32_t)alpha << 24) | (red << 16) | blue;
+      if (total_size == 0 && htrees[GREEN][0].value < NUM_LITERAL_CODES) {
+        htree_group->is_trivial_code = 1;
+        htree_group->literal_arb |= htrees[GREEN][0].value << 8;
+      }
+    }
+    htree_group->use_packed_table = !htree_group->is_trivial_code &&
+                                    (max_bits < HUFFMAN_PACKED_BITS);
+    if (htree_group->use_packed_table) BuildPackedTable(htree_group);
   }
-  WebPSafeFree(huff_codes);
   WebPSafeFree(code_lengths);
 
   // All OK. Finalize pointers and return.
   hdr->huffman_image_ = huffman_image;
   hdr->num_htree_groups_ = num_htree_groups;
   hdr->htree_groups_ = htree_groups;
+  hdr->huffman_tables_ = huffman_tables;
   return 1;
 
  Error:
-  WebPSafeFree(huff_codes);
   WebPSafeFree(code_lengths);
   WebPSafeFree(huffman_image);
-  VP8LHtreeGroupsFree(htree_groups, num_htree_groups);
+  WebPSafeFree(huffman_tables);
+  VP8LHtreeGroupsFree(htree_groups);
   return 0;
 }
 
 //------------------------------------------------------------------------------
 // Scaling.
 
 static int AllocateAndInitRescaler(VP8LDecoder* const dec, VP8Io* const io) {
   const int num_channels = 4;
   const int in_width = io->mb_w;
   const int out_width = io->scaled_width;
@@ skipping 77 matching lines @@
     VP8LConvertFromBGRA((const uint32_t*)row_in, mb_w, colorspace, row_out);
     row_in += in_stride;
     row_out += out_stride;
   }
   return mb_h;  // Num rows out == num rows in.
 }
 
 //------------------------------------------------------------------------------
 // Export to YUVA
 
-// TODO(skal): should be in yuv.c
 static void ConvertToYUVA(const uint32_t* const src, int width, int y_pos,
                           const WebPDecBuffer* const output) {
   const WebPYUVABuffer* const buf = &output->u.YUVA;
+
   // first, the luma plane
-  {
-    int i;
-    uint8_t* const y = buf->y + y_pos * buf->y_stride;
-    for (i = 0; i < width; ++i) {
-      const uint32_t p = src[i];
-      y[i] = VP8RGBToY((p >> 16) & 0xff, (p >> 8) & 0xff, (p >> 0) & 0xff,
-                       YUV_HALF);
-    }
-  }
+  WebPConvertARGBToY(src, buf->y + y_pos * buf->y_stride, width);
 
   // then U/V planes
   {
     uint8_t* const u = buf->u + (y_pos >> 1) * buf->u_stride;
     uint8_t* const v = buf->v + (y_pos >> 1) * buf->v_stride;
-    const int uv_width = width >> 1;
-    int i;
-    for (i = 0; i < uv_width; ++i) {
-      const uint32_t v0 = src[2 * i + 0];
-      const uint32_t v1 = src[2 * i + 1];
-      // VP8RGBToU/V expects four accumulated pixels. Hence we need to
-      // scale r/g/b value by a factor 2. We just shift v0/v1 one bit less.
-      const int r = ((v0 >> 15) & 0x1fe) + ((v1 >> 15) & 0x1fe);
-      const int g = ((v0 >>  7) & 0x1fe) + ((v1 >>  7) & 0x1fe);
-      const int b = ((v0 <<  1) & 0x1fe) + ((v1 <<  1) & 0x1fe);
-      if (!(y_pos & 1)) {  // even lines: store values
-        u[i] = VP8RGBToU(r, g, b, YUV_HALF << 2);
-        v[i] = VP8RGBToV(r, g, b, YUV_HALF << 2);
-      } else {             // odd lines: average with previous values
-        const int tmp_u = VP8RGBToU(r, g, b, YUV_HALF << 2);
-        const int tmp_v = VP8RGBToV(r, g, b, YUV_HALF << 2);
-        // Approximated average-of-four. But it's an acceptable diff.
-        u[i] = (u[i] + tmp_u + 1) >> 1;
-        v[i] = (v[i] + tmp_v + 1) >> 1;
-      }
-    }
-    if (width & 1) {       // last pixel
-      const uint32_t v0 = src[2 * i + 0];
-      const int r = (v0 >> 14) & 0x3fc;
-      const int g = (v0 >>  6) & 0x3fc;
-      const int b = (v0 <<  2) & 0x3fc;
-      if (!(y_pos & 1)) {  // even lines
-        u[i] = VP8RGBToU(r, g, b, YUV_HALF << 2);
-        v[i] = VP8RGBToV(r, g, b, YUV_HALF << 2);
-      } else {             // odd lines (note: we could just skip this)
-        const int tmp_u = VP8RGBToU(r, g, b, YUV_HALF << 2);
-        const int tmp_v = VP8RGBToV(r, g, b, YUV_HALF << 2);
-        u[i] = (u[i] + tmp_u + 1) >> 1;
-        v[i] = (v[i] + tmp_v + 1) >> 1;
-      }
-    }
+    // even lines: store values
+    // odd lines: average with previous values
+    WebPConvertARGBToUV(src, u, v, width, !(y_pos & 1));
   }
   // Lastly, store alpha if needed.
   if (buf->a != NULL) {
-    int i;
     uint8_t* const a = buf->a + y_pos * buf->a_stride;
-    for (i = 0; i < width; ++i) a[i] = (src[i] >> 24);
+#if defined(WORDS_BIGENDIAN)
+    WebPExtractAlpha((uint8_t*)src + 0, 0, width, 1, a, 0);
+#else
+    WebPExtractAlpha((uint8_t*)src + 3, 0, width, 1, a, 0);
+#endif
   }
 }
 
 static int ExportYUVA(const VP8LDecoder* const dec, int y_pos) {
   WebPRescaler* const rescaler = dec->rescaler;
   uint32_t* const src = (uint32_t*)rescaler->dst;
   const int dst_width = rescaler->dst_width;
   int num_lines_out = 0;
   while (WebPRescalerHasPendingOutput(rescaler)) {
     WebPRescalerExportRow(rescaler);
@@ skipping 128 matching lines @@
 
   // Emit output.
   {
     VP8Io* const io = dec->io_;
     uint8_t* rows_data = (uint8_t*)dec->argb_cache_;
     const int in_stride = io->width * sizeof(uint32_t);  // in unit of RGBA
     if (!SetCropWindow(io, dec->last_row_, row, &rows_data, in_stride)) {
       // Nothing to output (this time).
     } else {
       const WebPDecBuffer* const output = dec->output_;
-      if (output->colorspace < MODE_YUV) {  // convert to RGBA
+      if (WebPIsRGBMode(output->colorspace)) {  // convert to RGBA
         const WebPRGBABuffer* const buf = &output->u.RGBA;
         uint8_t* const rgba = buf->rgba + dec->last_out_row_ * buf->stride;
         const int num_rows_out = io->use_scaling ?
             EmitRescaledRowsRGBA(dec, rows_data, in_stride, io->mb_h,
                                  rgba, buf->stride) :
             EmitRows(output->colorspace, rows_data, in_stride,
                      io->mb_w, io->mb_h, rgba, buf->stride);
         // Update 'last_out_row_'.
         dec->last_out_row_ += num_rows_out;
       } else {                              // convert to YUVA
@@ skipping 11 matching lines @@
 }
 
 // Row-processing for the special case when alpha data contains only one
 // transform (color indexing), and trivial non-green literals.
 static int Is8bOptimizable(const VP8LMetadata* const hdr) {
   int i;
   if (hdr->color_cache_size_ > 0) return 0;
   // When the Huffman tree contains only one symbol, we can skip the
   // call to ReadSymbol() for red/blue/alpha channels.
   for (i = 0; i < hdr->num_htree_groups_; ++i) {
-    const HuffmanTree* const htrees = hdr->htree_groups_[i].htrees_;
-    if (htrees[RED].num_nodes_ > 1) return 0;
-    if (htrees[BLUE].num_nodes_ > 1) return 0;
-    if (htrees[ALPHA].num_nodes_ > 1) return 0;
+    HuffmanCode** const htrees = hdr->htree_groups_[i].htrees;
+    if (htrees[RED][0].bits > 0) return 0;
+    if (htrees[BLUE][0].bits > 0) return 0;
+    if (htrees[ALPHA][0].bits > 0) return 0;
   }
   return 1;
 }
 
 static void ExtractPalettedAlphaRows(VP8LDecoder* const dec, int row) {
   const int num_rows = row - dec->last_row_;
   const uint8_t* const in =
       (uint8_t*)dec->pixels_ + dec->width_ * dec->last_row_;
   if (num_rows > 0) {
     ApplyInverseTransformsAlpha(dec, num_rows, in);
   }
   dec->last_row_ = dec->last_out_row_ = row;
 }
 
+//------------------------------------------------------------------------------
+// Helper functions for fast pattern copy (8b and 32b)
+
+// cyclic rotation of pattern word
+static WEBP_INLINE uint32_t Rotate8b(uint32_t V) {
+#if defined(WORDS_BIGENDIAN)
+  return ((V & 0xff000000u) >> 24) | (V << 8);
+#else
+  return ((V & 0xffu) << 24) | (V >> 8);
+#endif
+}
+
+// copy 1, 2 or 4-bytes pattern
+static WEBP_INLINE void CopySmallPattern8b(const uint8_t* src, uint8_t* dst,
+                                           int length, uint32_t pattern) {
+  int i;
+  // align 'dst' to 4-bytes boundary. Adjust the pattern along the way.
+  while ((uintptr_t)dst & 3) {
+    *dst++ = *src++;
+    pattern = Rotate8b(pattern);
+    --length;
+  }
+  // Copy the pattern 4 bytes at a time.
+  for (i = 0; i < (length >> 2); ++i) {
+    ((uint32_t*)dst)[i] = pattern;
+  }
+  // Finish with left-overs. 'pattern' is still correctly positioned,
+  // so no Rotate8b() call is needed.
+  for (i <<= 2; i < length; ++i) {
+    dst[i] = src[i];
+  }
+}
+
+static WEBP_INLINE void CopyBlock8b(uint8_t* const dst, int dist, int length) {
+  const uint8_t* src = dst - dist;
+  if (length >= 8) {
+    uint32_t pattern = 0;
+    switch (dist) {
+      case 1:
+        pattern = src[0];
+#if defined(__arm__) || defined(_M_ARM)   // arm doesn't like multiply that much
+        pattern |= pattern << 8;
+        pattern |= pattern << 16;
+#elif defined(WEBP_USE_MIPS_DSP_R2)
+        __asm__ volatile ("replv.qb %0, %0" : "+r"(pattern));
+#else
+        pattern = 0x01010101u * pattern;
+#endif
+        break;
+      case 2:
+        memcpy(&pattern, src, sizeof(uint16_t));
+#if defined(__arm__) || defined(_M_ARM)
+        pattern |= pattern << 16;
+#elif defined(WEBP_USE_MIPS_DSP_R2)
+        __asm__ volatile ("replv.ph %0, %0" : "+r"(pattern));
+#else
+        pattern = 0x00010001u * pattern;
+#endif
+        break;
+      case 4:
+        memcpy(&pattern, src, sizeof(uint32_t));
+        break;
+      default:
+        goto Copy;
+        break;
+    }
+    CopySmallPattern8b(src, dst, length, pattern);
+    return;
+  }
+ Copy:
+  if (dist >= length) {  // no overlap -> use memcpy()
+    memcpy(dst, src, length * sizeof(*dst));
+  } else {
+    int i;
+    for (i = 0; i < length; ++i) dst[i] = src[i];
+  }
+}
+
+// copy pattern of 1 or 2 uint32_t's
+static WEBP_INLINE void CopySmallPattern32b(const uint32_t* src,
+                                            uint32_t* dst,
+                                            int length, uint64_t pattern) {
+  int i;
+  if ((uintptr_t)dst & 4) {           // Align 'dst' to 8-bytes boundary.
+    *dst++ = *src++;
+    pattern = (pattern >> 32) | (pattern << 32);
+    --length;
+  }
+  assert(0 == ((uintptr_t)dst & 7));
+  for (i = 0; i < (length >> 1); ++i) {
+    ((uint64_t*)dst)[i] = pattern;    // Copy the pattern 8 bytes at a time.
+  }
+  if (length & 1) {                   // Finish with left-over.
+    dst[i << 1] = src[i << 1];
+  }
+}
+
+static WEBP_INLINE void CopyBlock32b(uint32_t* const dst,
+                                     int dist, int length) {
+  const uint32_t* const src = dst - dist;
+  if (dist <= 2 && length >= 4 && ((uintptr_t)dst & 3) == 0) {
+    uint64_t pattern;
+    if (dist == 1) {
+      pattern = (uint64_t)src[0];
+      pattern |= pattern << 32;
+    } else {
+      memcpy(&pattern, src, sizeof(pattern));
+    }
+    CopySmallPattern32b(src, dst, length, pattern);
+  } else if (dist >= length) {  // no overlap
+    memcpy(dst, src, length * sizeof(*dst));
+  } else {
+    int i;
+    for (i = 0; i < length; ++i) dst[i] = src[i];
+  }
+}
+
+//------------------------------------------------------------------------------
+
 static int DecodeAlphaData(VP8LDecoder* const dec, uint8_t* const data,
                            int width, int height, int last_row) {
   int ok = 1;
   int row = dec->last_pixel_ / width;
   int col = dec->last_pixel_ % width;
   VP8LBitReader* const br = &dec->br_;
   VP8LMetadata* const hdr = &dec->hdr_;
   const HTreeGroup* htree_group = GetHtreeGroupForPos(hdr, col, row);
   int pos = dec->last_pixel_;         // current position
   const int end = width * height;     // End of data
   const int last = width * last_row;  // Last pixel to decode
   const int len_code_limit = NUM_LITERAL_CODES + NUM_LENGTH_CODES;
   const int mask = hdr->huffman_mask_;
   assert(htree_group != NULL);
   assert(pos < end);
   assert(last_row <= height);
   assert(Is8bOptimizable(hdr));
 
   while (!br->eos_ && pos < last) {
     int code;
     // Only update when changing tile.
     if ((col & mask) == 0) {
       htree_group = GetHtreeGroupForPos(hdr, col, row);
     }
     VP8LFillBitWindow(br);
-    code = ReadSymbol(&htree_group->htrees_[GREEN], br);
+    code = ReadSymbol(htree_group->htrees[GREEN], br);
     if (code < NUM_LITERAL_CODES) {  // Literal
       data[pos] = code;
       ++pos;
       ++col;
       if (col >= width) {
         col = 0;
         ++row;
         if (row % NUM_ARGB_CACHE_ROWS == 0) {
           ExtractPalettedAlphaRows(dec, row);
         }
       }
     } else if (code < len_code_limit) {  // Backward reference
       int dist_code, dist;
       const int length_sym = code - NUM_LITERAL_CODES;
       const int length = GetCopyLength(length_sym, br);
-      const int dist_symbol = ReadSymbol(&htree_group->htrees_[DIST], br);
+      const int dist_symbol = ReadSymbol(htree_group->htrees[DIST], br);
       VP8LFillBitWindow(br);
       dist_code = GetCopyDistance(dist_symbol, br);
       dist = PlaneCodeToDistance(width, dist_code);
       if (pos >= dist && end - pos >= length) {
-        int i;
-        for (i = 0; i < length; ++i) data[pos + i] = data[pos + i - dist];
+        CopyBlock8b(data + pos, dist, length);
       } else {
         ok = 0;
         goto End;
       }
       pos += length;
       col += length;
       while (col >= width) {
         col -= width;
         ++row;
         if (row % NUM_ARGB_CACHE_ROWS == 0) {
           ExtractPalettedAlphaRows(dec, row);
         }
       }
       if (pos < last && (col & mask)) {
         htree_group = GetHtreeGroupForPos(hdr, col, row);
       }
     } else {  // Not reached
       ok = 0;
       goto End;
     }
     assert(br->eos_ == VP8LIsEndOfStream(br));
-    ok = !br->error_;
-    if (!ok) goto End;
   }
   // Process the remaining rows corresponding to last row-block.
   ExtractPalettedAlphaRows(dec, row);
 
  End:
-  if (br->error_ || !ok || (br->eos_ && pos < end)) {
+  if (!ok || (br->eos_ && pos < end)) {
     ok = 0;
     dec->status_ = br->eos_ ? VP8_STATUS_SUSPENDED
                             : VP8_STATUS_BITSTREAM_ERROR;
   } else {
-    dec->last_pixel_ = (int)pos;
-    if (pos == end) dec->state_ = READ_DATA;
+    dec->last_pixel_ = pos;
   }
   return ok;
 }
 
+static void SaveState(VP8LDecoder* const dec, int last_pixel) {
+  assert(dec->incremental_);
+  dec->saved_br_ = dec->br_;
+  dec->saved_last_pixel_ = last_pixel;
+  if (dec->hdr_.color_cache_size_ > 0) {
+    VP8LColorCacheCopy(&dec->hdr_.color_cache_, &dec->hdr_.saved_color_cache_);
+  }
+}
+
+static void RestoreState(VP8LDecoder* const dec) {
+  assert(dec->br_.eos_);
+  dec->status_ = VP8_STATUS_SUSPENDED;
+  dec->br_ = dec->saved_br_;
+  dec->last_pixel_ = dec->saved_last_pixel_;
+  if (dec->hdr_.color_cache_size_ > 0) {
+    VP8LColorCacheCopy(&dec->hdr_.saved_color_cache_, &dec->hdr_.color_cache_);
+  }
+}
+
+#define SYNC_EVERY_N_ROWS 8  // minimum number of rows between check-points
 static int DecodeImageData(VP8LDecoder* const dec, uint32_t* const data,
                            int width, int height, int last_row,
                            ProcessRowsFunc process_func) {
-  int ok = 1;
   int row = dec->last_pixel_ / width;
   int col = dec->last_pixel_ % width;
   VP8LBitReader* const br = &dec->br_;
   VP8LMetadata* const hdr = &dec->hdr_;
   HTreeGroup* htree_group = GetHtreeGroupForPos(hdr, col, row);
   uint32_t* src = data + dec->last_pixel_;
   uint32_t* last_cached = src;
   uint32_t* const src_end = data + width * height;     // End of data
   uint32_t* const src_last = data + width * last_row;  // Last pixel to decode
   const int len_code_limit = NUM_LITERAL_CODES + NUM_LENGTH_CODES;
   const int color_cache_limit = len_code_limit + hdr->color_cache_size_;
+  int next_sync_row = dec->incremental_ ? row : 1 << 24;
   VP8LColorCache* const color_cache =
       (hdr->color_cache_size_ > 0) ? &hdr->color_cache_ : NULL;
   const int mask = hdr->huffman_mask_;
   assert(htree_group != NULL);
   assert(src < src_end);
   assert(src_last <= src_end);
 
-  while (!br->eos_ && src < src_last) {
+  while (src < src_last) {
     int code;
+    if (row >= next_sync_row) {
+      SaveState(dec, (int)(src - data));
+      next_sync_row = row + SYNC_EVERY_N_ROWS;
+    }
     // Only update when changing tile. Note we could use this test:
     // if "((((prev_col ^ col) | prev_row ^ row)) > mask)" -> tile changed
     // but that's actually slower and needs storing the previous col/row.
-    if ((col & mask) == 0) {
-      htree_group = GetHtreeGroupForPos(hdr, col, row);
+    if ((col & mask) == 0) htree_group = GetHtreeGroupForPos(hdr, col, row);
+    if (htree_group->is_trivial_code) {
+      *src = htree_group->literal_arb;
+      goto AdvanceByOne;
     }
     VP8LFillBitWindow(br);
-    code = ReadSymbol(&htree_group->htrees_[GREEN], br);
+    if (htree_group->use_packed_table) {
+      code = ReadPackedSymbols(htree_group, br, src);
+      if (code == PACKED_NON_LITERAL_CODE) goto AdvanceByOne;
+    } else {
+      code = ReadSymbol(htree_group->htrees[GREEN], br);
+    }
+    if (br->eos_) break;  // early out
     if (code < NUM_LITERAL_CODES) {  // Literal
-      int red, green, blue, alpha;
-      red = ReadSymbol(&htree_group->htrees_[RED], br);
-      green = code;
-      VP8LFillBitWindow(br);
-      blue = ReadSymbol(&htree_group->htrees_[BLUE], br);
-      alpha = ReadSymbol(&htree_group->htrees_[ALPHA], br);
-      *src = ((uint32_t)alpha << 24) | (red << 16) | (green << 8) | blue;
+      if (htree_group->is_trivial_literal) {
+        *src = htree_group->literal_arb | (code << 8);
+      } else {
+        int red, blue, alpha;
+        red = ReadSymbol(htree_group->htrees[RED], br);
+        VP8LFillBitWindow(br);
+        blue = ReadSymbol(htree_group->htrees[BLUE], br);
+        alpha = ReadSymbol(htree_group->htrees[ALPHA], br);
+        if (br->eos_) break;
+        *src = ((uint32_t)alpha << 24) | (red << 16) | (code << 8) | blue;
+      }
     AdvanceByOne:
       ++src;
       ++col;
       if (col >= width) {
         col = 0;
         ++row;
         if ((row % NUM_ARGB_CACHE_ROWS == 0) && (process_func != NULL)) {
           process_func(dec, row);
         }
         if (color_cache != NULL) {
           while (last_cached < src) {
             VP8LColorCacheInsert(color_cache, *last_cached++);
           }
         }
       }
     } else if (code < len_code_limit) {  // Backward reference
       int dist_code, dist;
       const int length_sym = code - NUM_LITERAL_CODES;
       const int length = GetCopyLength(length_sym, br);
-      const int dist_symbol = ReadSymbol(&htree_group->htrees_[DIST], br);
+      const int dist_symbol = ReadSymbol(htree_group->htrees[DIST], br);
       VP8LFillBitWindow(br);
       dist_code = GetCopyDistance(dist_symbol, br);
       dist = PlaneCodeToDistance(width, dist_code);
+      if (br->eos_) break;
       if (src - data < (ptrdiff_t)dist || src_end - src < (ptrdiff_t)length) {
-        ok = 0;
-        goto End;
+        goto Error;
       } else {
-        int i;
-        for (i = 0; i < length; ++i) src[i] = src[i - dist];
-        src += length;
+        CopyBlock32b(src, dist, length);
       }
+      src += length;
       col += length;
       while (col >= width) {
         col -= width;
         ++row;
         if ((row % NUM_ARGB_CACHE_ROWS == 0) && (process_func != NULL)) {
           process_func(dec, row);
         }
       }
-      if (src < src_end) {
-        if (col & mask) htree_group = GetHtreeGroupForPos(hdr, col, row);
-        if (color_cache != NULL) {
-          while (last_cached < src) {
-            VP8LColorCacheInsert(color_cache, *last_cached++);
-          }
+      // Because of the check done above (before 'src' was incremented by
+      // 'length'), the following holds true.
+      assert(src <= src_end);
+      if (col & mask) htree_group = GetHtreeGroupForPos(hdr, col, row);
+      if (color_cache != NULL) {
+        while (last_cached < src) {
+          VP8LColorCacheInsert(color_cache, *last_cached++);
         }
       }
     } else if (code < color_cache_limit) {  // Color cache
       const int key = code - len_code_limit;
       assert(color_cache != NULL);
       while (last_cached < src) {
         VP8LColorCacheInsert(color_cache, *last_cached++);
       }
       *src = VP8LColorCacheLookup(color_cache, key);
       goto AdvanceByOne;
     } else {  // Not reached
-      ok = 0;
-      goto End;
+      goto Error;
     }
     assert(br->eos_ == VP8LIsEndOfStream(br));
-    ok = !br->error_;
-    if (!ok) goto End;
   }
-  // Process the remaining rows corresponding to last row-block.
-  if (process_func != NULL) process_func(dec, row);
 
- End:
-  if (br->error_ || !ok || (br->eos_ && src < src_end)) {
-    ok = 0;
-    dec->status_ = br->eos_ ? VP8_STATUS_SUSPENDED
-                            : VP8_STATUS_BITSTREAM_ERROR;
+  if (dec->incremental_ && br->eos_ && src < src_end) {
+    RestoreState(dec);
+  } else if (!br->eos_) {
+    // Process the remaining rows corresponding to last row-block.
+    if (process_func != NULL) {
+      process_func(dec, row);
+    }
+    dec->status_ = VP8_STATUS_OK;
+    dec->last_pixel_ = (int)(src - data);  // end-of-scan marker
   } else {
-    dec->last_pixel_ = (int)(src - data);
-    if (src == src_end) dec->state_ = READ_DATA;
+    // if not incremental, and we are past the end of buffer (eos_=1), then this
+    // is a real bitstream error.
+    goto Error;
   }
-  return ok;
+  return 1;
+
+ Error:
+  dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
+  return 0;
 }
 
 // -----------------------------------------------------------------------------
 // VP8LTransform
 
 static void ClearTransform(VP8LTransform* const transform) {
   WebPSafeFree(transform->data_);
   transform->data_ = NULL;
 }
 
@@ skipping 73 matching lines @@
       break;
   }
 
   return ok;
 }
 
 // -----------------------------------------------------------------------------
 // VP8LMetadata
 
 static void InitMetadata(VP8LMetadata* const hdr) {
-  assert(hdr);
+  assert(hdr != NULL);
   memset(hdr, 0, sizeof(*hdr));
 }
 
 static void ClearMetadata(VP8LMetadata* const hdr) {
-  assert(hdr);
+  assert(hdr != NULL);
 
   WebPSafeFree(hdr->huffman_image_);
-  VP8LHtreeGroupsFree(hdr->htree_groups_, hdr->num_htree_groups_);
+  WebPSafeFree(hdr->huffman_tables_);
+  VP8LHtreeGroupsFree(hdr->htree_groups_);
   VP8LColorCacheClear(&hdr->color_cache_);
+  VP8LColorCacheClear(&hdr->saved_color_cache_);
   InitMetadata(hdr);
 }
 
 // -----------------------------------------------------------------------------
 // VP8LDecoder
 
 VP8LDecoder* VP8LNew(void) {
   VP8LDecoder* const dec = (VP8LDecoder*)WebPSafeCalloc(1ULL, sizeof(*dec));
   if (dec == NULL) return NULL;
   dec->status_ = VP8_STATUS_OK;
-  dec->action_ = READ_DIM;
   dec->state_ = READ_DIM;
 
   VP8LDspInit();  // Init critical function pointers.
 
   return dec;
 }
 
 void VP8LClear(VP8LDecoder* const dec) {
   int i;
   if (dec == NULL) return;
@@ skipping 91 matching lines @@
     if (data == NULL) {
       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,
                        transform_ysize, NULL);
-  ok = ok && !br->error_;
+  ok = ok && !br->eos_;
 
  End:
-
   if (!ok) {
     WebPSafeFree(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;
-    }
   } else {
     if (decoded_data != NULL) {
       *decoded_data = data;
     } else {
       // We allocate image data in this function only for transforms. At level 0
       // (that is: not the transforms), we shouldn't have allocated anything.
       assert(data == NULL);
       assert(is_level0);
     }
     dec->last_pixel_ = 0;  // Reset for future DECODE_DATA_FUNC() calls.
@@ skipping 76 matching lines @@
 
   VP8InitIo(io);
   WebPInitCustomIo(NULL, io);  // Just a sanity Init. io won't be used.
   io->opaque = output;
   io->width = alph_dec->width_;
   io->height = alph_dec->height_;
 
   dec->status_ = VP8_STATUS_OK;
   VP8LInitBitReader(&dec->br_, data, data_size);
 
-  dec->action_ = READ_HDR;
   if (!DecodeImageStream(alph_dec->width_, alph_dec->height_, 1, dec, NULL)) {
     goto Err;
   }
 
   // Special case: if alpha data uses only the color indexing transform and
   // doesn't use color cache (a frequent case), we will use DecodeAlphaData()
   // method that only needs allocation of 1 byte per pixel (alpha channel).
   if (dec->next_transform_ == 1 &&
       dec->transforms_[0].type_ == COLOR_INDEXING_TRANSFORM &&
       Is8bOptimizable(&dec->hdr_)) {
     alph_dec->use_8b_decode = 1;
     ok = AllocateInternalBuffers8b(dec);
   } else {
     // Allocate internal buffers (note that dec->width_ may have changed here).
     alph_dec->use_8b_decode = 0;
     ok = AllocateInternalBuffers32b(dec, alph_dec->width_);
   }
 
   if (!ok) goto Err;
 
-  dec->action_ = READ_DATA;
   return 1;
 
  Err:
   VP8LDelete(alph_dec->vp8l_dec_);
   alph_dec->vp8l_dec_ = NULL;
   return 0;
 }
 
 int VP8LDecodeAlphaImageStream(ALPHDecoder* const alph_dec, int last_row) {
   VP8LDecoder* const dec = alph_dec->vp8l_dec_;
   assert(dec != NULL);
-  assert(dec->action_ == READ_DATA);
   assert(last_row <= dec->height_);
 
   if (dec->last_pixel_ == dec->width_ * dec->height_) {
     return 1;  // done
   }
 
   // Decode (with special row processing).
   return alph_dec->use_8b_decode ?
       DecodeAlphaData(dec, (uint8_t*)dec->pixels_, dec->width_, dec->height_,
                       last_row) :
@@ skipping 16 matching lines @@
   dec->status_ = VP8_STATUS_OK;
   VP8LInitBitReader(&dec->br_, io->data, io->data_size);
   if (!ReadImageInfo(&dec->br_, &width, &height, &has_alpha)) {
     dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
     goto Error;
   }
   dec->state_ = READ_DIM;
   io->width = width;
   io->height = height;
 
-  dec->action_ = READ_HDR;
   if (!DecodeImageStream(width, height, 1, dec, NULL)) goto Error;
   return 1;
 
  Error:
   VP8LClear(dec);
   assert(dec->status_ != VP8_STATUS_OK);
   return 0;
 }
 
 int VP8LDecodeImage(VP8LDecoder* const dec) {
   VP8Io* io = NULL;
   WebPDecParams* params = NULL;
 
   // Sanity checks.
   if (dec == NULL) return 0;
 
-  dec->status_ = VP8_STATUS_BITSTREAM_ERROR;
+  assert(dec->hdr_.huffman_tables_ != NULL);
   assert(dec->hdr_.htree_groups_ != NULL);
   assert(dec->hdr_.num_htree_groups_ > 0);
 
   io = dec->io_;
   assert(io != NULL);
   params = (WebPDecParams*)io->opaque;
   assert(params != NULL);
-  dec->output_ = params->output;
-  assert(dec->output_ != NULL);
 
   // Initialization.
-  if (!WebPIoInitFromOptions(params->options, io, MODE_BGRA)) {
-    dec->status_ = VP8_STATUS_INVALID_PARAM;
-    goto Err;
-  }
+  if (dec->state_ != READ_DATA) {
+    dec->output_ = params->output;
+    assert(dec->output_ != NULL);
 
-  if (!AllocateInternalBuffers32b(dec, io->width)) goto Err;
+    if (!WebPIoInitFromOptions(params->options, io, MODE_BGRA)) {
+      dec->status_ = VP8_STATUS_INVALID_PARAM;
+      goto Err;
+    }
 
-  if (io->use_scaling && !AllocateAndInitRescaler(dec, io)) goto Err;
+    if (!AllocateInternalBuffers32b(dec, io->width)) goto Err;
 
-  if (io->use_scaling || WebPIsPremultipliedMode(dec->output_->colorspace)) {
-    // need the alpha-multiply functions for premultiplied output or rescaling
-    WebPInitAlphaProcessing();
+    if (io->use_scaling && !AllocateAndInitRescaler(dec, io)) goto Err;
+
+    if (io->use_scaling || WebPIsPremultipliedMode(dec->output_->colorspace)) {
+      // need the alpha-multiply functions for premultiplied output or rescaling
+      WebPInitAlphaProcessing();
+    }
+    if (!WebPIsRGBMode(dec->output_->colorspace)) {
+      WebPInitConvertARGBToYUV();
+      if (dec->output_->u.YUVA.a != NULL) WebPInitAlphaProcessing();
+    }
+    if (dec->incremental_) {
+      if (dec->hdr_.color_cache_size_ > 0 &&
+          dec->hdr_.saved_color_cache_.colors_ == NULL) {
+        if (!VP8LColorCacheInit(&dec->hdr_.saved_color_cache_,
+                                dec->hdr_.color_cache_.hash_bits_)) {
+          dec->status_ = VP8_STATUS_OUT_OF_MEMORY;
+          goto Err;
+        }
+      }
+    }
+    dec->state_ = READ_DATA;
   }
 
   // Decode.
-  dec->action_ = READ_DATA;
   if (!DecodeImageData(dec, dec->pixels_, dec->width_, dec->height_,
                        dec->height_, ProcessRows)) {
     goto Err;
   }
 
-  // Cleanup.
   params->last_y = dec->last_out_row_;
-  VP8LClear(dec);
   return 1;
 
  Err:
   VP8LClear(dec);
   assert(dec->status_ != VP8_STATUS_OK);
   return 0;
 }
 
 //------------------------------------------------------------------------------