libwebp: update snapshot to v0.2.0-rc1

third_party/libwebp/dec/idec.c

Index: third_party/libwebp/dec/idec.c
diff --git a/third_party/libwebp/dec/idec.c b/third_party/libwebp/dec/idec.c
index 3c773dd361a402943eb17933a7d6b9fcf0f03a2a..7df790ced86aa8940df4ab7994fdf1fa39760838 100644
--- a/third_party/libwebp/dec/idec.c
+++ b/third_party/libwebp/dec/idec.c
@@ -1,4 +1,4 @@
-// Copyright 2011 Google Inc.
+// Copyright 2011 Google Inc. All Rights Reserved.
 //
 // This code is licensed under the same terms as WebM:
 //  Software License Agreement:  http://www.webmproject.org/license/software/
@@ -13,13 +13,16 @@
 #include <string.h>
 #include <stdlib.h>
 
-#include "webpi.h"
-#include "vp8i.h"
+#include "./webpi.h"
+#include "./vp8i.h"
+#include "../utils/utils.h"
 
 #if defined(__cplusplus) || defined(c_plusplus)
 extern "C" {
 #endif
 
+// In append mode, buffer allocations increase as multiples of this value.
+// Needs to be a power of 2.
 #define CHUNK_SIZE 4096
 #define MAX_MB_SIZE 4096
 
@@ -33,6 +36,8 @@ typedef enum {
   STATE_VP8_FRAME_HEADER,  // For VP8 Frame header (within VP8 chunk).
   STATE_VP8_PARTS0,
   STATE_VP8_DATA,
+  STATE_VP8L_HEADER,
+  STATE_VP8L_DATA,
   STATE_DONE,
   STATE_ERROR
 } DecState;
@@ -47,8 +52,8 @@ typedef enum {
 // storage for partition #0 and partial data (in a rolling fashion)
 typedef struct {
   MemBufferMode mode_;  // Operation mode
-  uint32_t start_;      // start location of the data to be decoded
-  uint32_t end_;        // end location
+  size_t start_;        // start location of the data to be decoded
+  size_t end_;          // end location
   size_t buf_size_;     // size of the allocated buffer
   uint8_t* buf_;        // We don't own this buffer in case WebPIUpdate()
 
@@ -59,12 +64,13 @@ typedef struct {
 struct WebPIDecoder {
   DecState state_;         // current decoding state
   WebPDecParams params_;   // Params to store output info
-  VP8Decoder* dec_;
+  int is_lossless_;        // for down-casting 'dec_'.
+  void* dec_;              // either a VP8Decoder or a VP8LDecoder instance
   VP8Io io_;
 
   MemBuffer mem_;          // input memory buffer.
   WebPDecBuffer output_;   // output buffer (when no external one is supplied)
-  uint32_t vp8_size_;      // VP8 size extracted from VP8 Header.
+  size_t chunk_size_;      // Compressed VP8/VP8L size extracted from Header.
 };
 
 // MB context to restore in case VP8DecodeMB() fails
@@ -80,104 +86,105 @@ typedef struct {
 //------------------------------------------------------------------------------
 // MemBuffer: incoming data handling
 
-#define REMAP(PTR, OLD_BASE, NEW_BASE) (PTR) = (NEW_BASE) + ((PTR) - OLD_BASE)
+static void RemapBitReader(VP8BitReader* const br, ptrdiff_t offset) {
+  if (br->buf_ != NULL) {
+    br->buf_ += offset;
+    br->buf_end_ += offset;
+  }
+}
 
-static inline size_t MemDataSize(const MemBuffer* mem) {
+static WEBP_INLINE size_t MemDataSize(const MemBuffer* mem) {
   return (mem->end_ - mem->start_);
 }
 
+static void DoRemap(WebPIDecoder* const idec, ptrdiff_t offset) {
+  MemBuffer* const mem = &idec->mem_;
+  const uint8_t* const new_base = mem->buf_ + mem->start_;
+  // note: for VP8, setting up idec->io_ is only really needed at the beginning
+  // of the decoding, till partition #0 is complete.
+  idec->io_.data = new_base;
+  idec->io_.data_size = MemDataSize(mem);
+
+  if (idec->dec_ != NULL) {
+    if (!idec->is_lossless_) {
+      VP8Decoder* const dec = (VP8Decoder*)idec->dec_;
+      const int last_part = dec->num_parts_ - 1;
+      if (offset != 0) {
+        int p;
+        for (p = 0; p <= last_part; ++p) {
+          RemapBitReader(dec->parts_ + p, offset);
+        }
+        // Remap partition #0 data pointer to new offset, but only in MAP
+        // mode (in APPEND mode, partition #0 is copied into a fixed memory).
+        if (mem->mode_ == MEM_MODE_MAP) {
+          RemapBitReader(&dec->br_, offset);
+        }
+      }
+      assert(last_part >= 0);
+      dec->parts_[last_part].buf_end_ = mem->buf_ + mem->end_;
+    } else {    // Resize lossless bitreader
+      VP8LDecoder* const dec = (VP8LDecoder*)idec->dec_;
+      VP8LBitReaderSetBuffer(&dec->br_, new_base, MemDataSize(mem));
+    }
+  }
+}
+
 // Appends data to the end of MemBuffer->buf_. It expands the allocated memory
 // size if required and also updates VP8BitReader's if new memory is allocated.
 static int AppendToMemBuffer(WebPIDecoder* const idec,
                              const uint8_t* const data, size_t data_size) {
   MemBuffer* const mem = &idec->mem_;
-  VP8Decoder* const dec = idec->dec_;
-  const int last_part = dec->num_parts_ - 1;
+  const uint8_t* const old_base = mem->buf_ + mem->start_;
   assert(mem->mode_ == MEM_MODE_APPEND);
+  if (data_size > MAX_CHUNK_PAYLOAD) {
+    // security safeguard: trying to allocate more than what the format
+    // allows for a chunk should be considered a smoke smell.
+    return 0;
+  }
 
   if (mem->end_ + data_size > mem->buf_size_) {  // Need some free memory
-    int p;
-    uint8_t* new_buf = NULL;
-    const int num_chunks = (MemDataSize(mem) + data_size + CHUNK_SIZE - 1)
-        / CHUNK_SIZE;
-    const size_t new_size = num_chunks * CHUNK_SIZE;
-    const uint8_t* const base = mem->buf_ + mem->start_;
-
-    new_buf = (uint8_t*)malloc(new_size);
-    if (!new_buf) return 0;
-    memcpy(new_buf, base, MemDataSize(mem));
-
-    // adjust VP8BitReader pointers
-    for (p = 0; p <= last_part; ++p) {
-      if (dec->parts_[p].buf_) {
-        REMAP(dec->parts_[p].buf_, base, new_buf);
-        REMAP(dec->parts_[p].buf_end_, base, new_buf);
-      }
-    }
-
-    // adjust memory pointers
+    const size_t current_size = MemDataSize(mem);
+    const uint64_t new_size = (uint64_t)current_size + data_size;
+    const uint64_t extra_size = (new_size + CHUNK_SIZE - 1) & ~(CHUNK_SIZE - 1);
+    uint8_t* const new_buf =
+        (uint8_t*)WebPSafeMalloc(extra_size, sizeof(*new_buf));
+    if (new_buf == NULL) return 0;
+    memcpy(new_buf, old_base, current_size);
     free(mem->buf_);
     mem->buf_ = new_buf;
-    mem->buf_size_ = new_size;
-
-    mem->end_ = MemDataSize(mem);
+    mem->buf_size_ = (size_t)extra_size;
     mem->start_ = 0;
+    mem->end_ = current_size;
   }
 
   memcpy(mem->buf_ + mem->end_, data, data_size);
   mem->end_ += data_size;
   assert(mem->end_ <= mem->buf_size_);
-  assert(last_part >= 0);
-  dec->parts_[last_part].buf_end_ = mem->buf_ + mem->end_;
 
-  // note: setting up idec->io_ is only really needed at the beginning
-  // of the decoding, till partition #0 is complete.
-  idec->io_.data = mem->buf_ + mem->start_;
-  idec->io_.data_size = MemDataSize(mem);
+  DoRemap(idec, mem->buf_ + mem->start_ - old_base);
   return 1;
 }
 
 static int RemapMemBuffer(WebPIDecoder* const idec,
                           const uint8_t* const data, size_t data_size) {
-  int p;
   MemBuffer* const mem = &idec->mem_;
-  VP8Decoder* const dec = idec->dec_;
-  const int last_part = dec->num_parts_ - 1;
-  const uint8_t* base = mem->buf_;
-
+  const uint8_t* const old_base = mem->buf_ + mem->start_;
   assert(mem->mode_ == MEM_MODE_MAP);
-  if (data_size < mem->buf_size_) {
-    return 0;  // we cannot remap to a shorter buffer!
-  }
-
-  for (p = 0; p <= last_part; ++p) {
-    if (dec->parts_[p].buf_) {
-      REMAP(dec->parts_[p].buf_, base, data);
-      REMAP(dec->parts_[p].buf_end_, base, data);
-    }
-  }
-  assert(last_part >= 0);
-  dec->parts_[last_part].buf_end_ = data + data_size;
 
-  // Remap partition #0 data pointer to new offset.
-  if (dec->br_.buf_) {
-    REMAP(dec->br_.buf_, base, data);
-    REMAP(dec->br_.buf_end_, base, data);
-  }
+  if (data_size < mem->buf_size_) return 0;  // can't remap to a shorter buffer!
 
   mem->buf_ = (uint8_t*)data;
   mem->end_ = mem->buf_size_ = data_size;
 
-  idec->io_.data = data;
-  idec->io_.data_size = data_size;
+  DoRemap(idec, mem->buf_ + mem->start_ - old_base);
   return 1;
 }
 
 static void InitMemBuffer(MemBuffer* const mem) {
   mem->mode_       = MEM_MODE_NONE;
-  mem->buf_        = 0;
+  mem->buf_        = NULL;
   mem->buf_size_   = 0;
-  mem->part0_buf_  = 0;
+  mem->part0_buf_  = NULL;
   mem->part0_size_ = 0;
 }
 
@@ -199,8 +206,6 @@ static int CheckMemBufferMode(MemBuffer* const mem, MemBufferMode expected) {
   return 1;
 }
 
-#undef REMAP
-
 //------------------------------------------------------------------------------
 // Macroblock-decoding contexts
 
@@ -246,66 +251,96 @@ static VP8StatusCode IDecError(WebPIDecoder* const idec, VP8StatusCode error) {
 }
 
 static void ChangeState(WebPIDecoder* const idec, DecState new_state,
-                        uint32_t consumed_bytes) {
+                        size_t consumed_bytes) {
+  MemBuffer* const mem = &idec->mem_;
   idec->state_ = new_state;
-  idec->mem_.start_ += consumed_bytes;
-  assert(idec->mem_.start_ <= idec->mem_.end_);
+  mem->start_ += consumed_bytes;
+  assert(mem->start_ <= mem->end_);
+  idec->io_.data = mem->buf_ + mem->start_;
+  idec->io_.data_size = MemDataSize(mem);
 }
 
 // Headers
 static VP8StatusCode DecodeWebPHeaders(WebPIDecoder* const idec) {
-  const uint8_t* data = idec->mem_.buf_ + idec->mem_.start_;
-  uint32_t curr_size = MemDataSize(&idec->mem_);
-  uint32_t vp8_size;
-  uint32_t bytes_skipped;
+  MemBuffer* const mem = &idec->mem_;
+  const uint8_t* data = mem->buf_ + mem->start_;
+  size_t curr_size = MemDataSize(mem);
   VP8StatusCode status;
+  WebPHeaderStructure headers;
 
-  status = WebPParseHeaders(&data, &curr_size, &vp8_size, &bytes_skipped);
+  headers.data = data;
+  headers.data_size = curr_size;
+  status = WebPParseHeaders(&headers);
   if (status == VP8_STATUS_NOT_ENOUGH_DATA) {
     return VP8_STATUS_SUSPENDED;  // We haven't found a VP8 chunk yet.
-  } else if (status == VP8_STATUS_OK) {
-    idec->vp8_size_ = vp8_size;
-    ChangeState(idec, STATE_VP8_FRAME_HEADER, bytes_skipped);
-    return VP8_STATUS_OK;  // We have skipped all pre-VP8 chunks.
-  } else {
+  } else if (status != VP8_STATUS_OK) {
     return IDecError(idec, status);
   }
+
+  idec->chunk_size_ = headers.compressed_size;
+  idec->is_lossless_ = headers.is_lossless;
+  if (!idec->is_lossless_) {
+    VP8Decoder* const dec = VP8New();
+    if (dec == NULL) {
+      return VP8_STATUS_OUT_OF_MEMORY;
+    }
+    idec->dec_ = dec;
+#ifdef WEBP_USE_THREAD
+    dec->use_threads_ = (idec->params_.options != NULL) &&
+                        (idec->params_.options->use_threads > 0);
+#else
+    dec->use_threads_ = 0;
+#endif
+    dec->alpha_data_ = headers.alpha_data;
+    dec->alpha_data_size_ = headers.alpha_data_size;
+    ChangeState(idec, STATE_VP8_FRAME_HEADER, headers.offset);
+  } else {
+    VP8LDecoder* const dec = VP8LNew();
+    if (dec == NULL) {
+      return VP8_STATUS_OUT_OF_MEMORY;
+    }
+    idec->dec_ = dec;
+    ChangeState(idec, STATE_VP8L_HEADER, headers.offset);
+  }
+  return VP8_STATUS_OK;
 }
 
 static VP8StatusCode DecodeVP8FrameHeader(WebPIDecoder* const idec) {
   const uint8_t* data = idec->mem_.buf_ + idec->mem_.start_;
-  const uint32_t curr_size = MemDataSize(&idec->mem_);
+  const size_t curr_size = MemDataSize(&idec->mem_);
   uint32_t bits;
 
   if (curr_size < VP8_FRAME_HEADER_SIZE) {
     // Not enough data bytes to extract VP8 Frame Header.
     return VP8_STATUS_SUSPENDED;
   }
-  if (!VP8GetInfo(data, curr_size, idec->vp8_size_, NULL, NULL, NULL)) {
+  if (!VP8GetInfo(data, curr_size, idec->chunk_size_, NULL, NULL)) {
     return IDecError(idec, VP8_STATUS_BITSTREAM_ERROR);
   }
 
   bits = data[0] | (data[1] << 8) | (data[2] << 16);
   idec->mem_.part0_size_ = (bits >> 5) + VP8_FRAME_HEADER_SIZE;
 
-  idec->io_.data_size = curr_size;
   idec->io_.data = data;
+  idec->io_.data_size = curr_size;
   idec->state_ = STATE_VP8_PARTS0;
   return VP8_STATUS_OK;
 }
 
 // Partition #0
-static int CopyParts0Data(WebPIDecoder* idec) {
-  VP8BitReader* const br = &idec->dec_->br_;
+static int CopyParts0Data(WebPIDecoder* const idec) {
+  VP8Decoder* const dec = (VP8Decoder*)idec->dec_;
+  VP8BitReader* const br = &dec->br_;
   const size_t psize = br->buf_end_ - br->buf_;
   MemBuffer* const mem = &idec->mem_;
-  assert(!mem->part0_buf_);
+  assert(!idec->is_lossless_);
+  assert(mem->part0_buf_ == NULL);
   assert(psize > 0);
-  assert(psize <= mem->part0_size_);
+  assert(psize <= mem->part0_size_);  // Format limit: no need for runtime check
   if (mem->mode_ == MEM_MODE_APPEND) {
     // We copy and grab ownership of the partition #0 data.
     uint8_t* const part0_buf = (uint8_t*)malloc(psize);
-    if (!part0_buf) {
+    if (part0_buf == NULL) {
       return 0;
     }
     memcpy(part0_buf, br->buf_, psize);
@@ -320,7 +355,7 @@ static int CopyParts0Data(WebPIDecoder* idec) {
 }
 
 static VP8StatusCode DecodePartition0(WebPIDecoder* const idec) {
-  VP8Decoder* const dec = idec->dec_;
+  VP8Decoder* const dec = (VP8Decoder*)idec->dec_;
   VP8Io* const io = &idec->io_;
   const WebPDecParams* const params = &idec->params_;
   WebPDecBuffer* const output = params->output;
@@ -368,13 +403,11 @@ static VP8StatusCode DecodePartition0(WebPIDecoder* const idec) {
 
 // Remaining partitions
 static VP8StatusCode DecodeRemaining(WebPIDecoder* const idec) {
-  VP8BitReader* br;
-  VP8Decoder* const dec = idec->dec_;
+  VP8Decoder* const dec = (VP8Decoder*)idec->dec_;
   VP8Io* const io = &idec->io_;
 
   assert(dec->ready_);
 
-  br = &dec->br_;
   for (; dec->mb_y_ < dec->mb_h_; ++dec->mb_y_) {
     VP8BitReader* token_br = &dec->parts_[dec->mb_y_ & (dec->num_parts_ - 1)];
     if (dec->mb_x_ == 0) {
@@ -417,13 +450,69 @@ static VP8StatusCode DecodeRemaining(WebPIDecoder* const idec) {
   return VP8_STATUS_OK;
 }
 
+static int ErrorStatusLossless(WebPIDecoder* const idec, VP8StatusCode status) {
+  if (status == VP8_STATUS_SUSPENDED || status == VP8_STATUS_NOT_ENOUGH_DATA) {
+    return VP8_STATUS_SUSPENDED;
+  }
+  return IDecError(idec, status);
+}
+
+static VP8StatusCode DecodeVP8LHeader(WebPIDecoder* const idec) {
+  VP8Io* const io = &idec->io_;
+  VP8LDecoder* const dec = (VP8LDecoder*)idec->dec_;
+  const WebPDecParams* const params = &idec->params_;
+  WebPDecBuffer* const output = params->output;
+  size_t curr_size = MemDataSize(&idec->mem_);
+  assert(idec->is_lossless_);
+
+  // Wait until there's enough data for decoding header.
+  if (curr_size < (idec->chunk_size_ >> 3)) {
+    return VP8_STATUS_SUSPENDED;
+  }
+  if (!VP8LDecodeHeader(dec, io)) {
+    return ErrorStatusLossless(idec, dec->status_);
+  }
+  // Allocate/verify output buffer now.
+  dec->status_ = WebPAllocateDecBuffer(io->width, io->height, params->options,
+                                       output);
+  if (dec->status_ != VP8_STATUS_OK) {
+    return IDecError(idec, dec->status_);
+  }
+
+  idec->state_ = STATE_VP8L_DATA;
+  return VP8_STATUS_OK;
+}
+
+static VP8StatusCode DecodeVP8LData(WebPIDecoder* const idec) {
+  VP8LDecoder* const dec = (VP8LDecoder*)idec->dec_;
+  const size_t curr_size = MemDataSize(&idec->mem_);
+  assert(idec->is_lossless_);
+
+  // At present Lossless decoder can't decode image incrementally. So wait till
+  // all the image data is aggregated before image can be decoded.
+  if (curr_size < idec->chunk_size_) {
+    return VP8_STATUS_SUSPENDED;
+  }
+
+  if (!VP8LDecodeImage(dec)) {
+    return ErrorStatusLossless(idec, dec->status_);
+  }
+
+  idec->state_ = STATE_DONE;
+
+  return VP8_STATUS_OK;
+}
+
   // Main decoding loop
 static VP8StatusCode IDecode(WebPIDecoder* idec) {
   VP8StatusCode status = VP8_STATUS_SUSPENDED;
-  assert(idec->dec_);
 
   if (idec->state_ == STATE_PRE_VP8) {
     status = DecodeWebPHeaders(idec);
+  } else {
+    if (idec->dec_ == NULL) {
+      return VP8_STATUS_SUSPENDED;    // can't continue if we have no decoder.
+    }
   }
   if (idec->state_ == STATE_VP8_FRAME_HEADER) {
     status = DecodeVP8FrameHeader(idec);
@@ -434,25 +523,26 @@ static VP8StatusCode IDecode(WebPIDecoder* idec) {
   if (idec->state_ == STATE_VP8_DATA) {
     status = DecodeRemaining(idec);
   }
+  if (idec->state_ == STATE_VP8L_HEADER) {
+    status = DecodeVP8LHeader(idec);
+  }
+  if (idec->state_ == STATE_VP8L_DATA) {
+    status = DecodeVP8LData(idec);
+  }
   return status;
 }
 
 //------------------------------------------------------------------------------
 // Public functions
 
-WebPIDecoder* WebPINewDecoder(WebPDecBuffer* const output_buffer) {
-  WebPIDecoder* idec = (WebPIDecoder*)calloc(1, sizeof(WebPIDecoder));
+WebPIDecoder* WebPINewDecoder(WebPDecBuffer* output_buffer) {
+  WebPIDecoder* idec = (WebPIDecoder*)calloc(1, sizeof(*idec));
   if (idec == NULL) {
     return NULL;
   }
 
-  idec->dec_ = VP8New();
-  if (idec->dec_ == NULL) {
-    free(idec);
-    return NULL;
-  }
-
   idec->state_ = STATE_PRE_VP8;
+  idec->chunk_size_ = 0;
 
   InitMemBuffer(&idec->mem_);
   WebPInitDecBuffer(&idec->output_);
@@ -462,19 +552,11 @@ WebPIDecoder* WebPINewDecoder(WebPDecBuffer* const output_buffer) {
   idec->params_.output = output_buffer ? output_buffer : &idec->output_;
   WebPInitCustomIo(&idec->params_, &idec->io_);  // Plug the I/O functions.
 
-#ifdef WEBP_USE_THREAD
-  idec->dec_->use_threads_ = idec->params_.options &&
-                             (idec->params_.options->use_threads > 0);
-#else
-  idec->dec_->use_threads_ = 0;
-#endif
-  idec->vp8_size_ = 0;
-
   return idec;
 }
 
-WebPIDecoder* WebPIDecode(const uint8_t* data, uint32_t data_size,
-                          WebPDecoderConfig* const config) {
+WebPIDecoder* WebPIDecode(const uint8_t* data, size_t data_size,
+                          WebPDecoderConfig* config) {
   WebPIDecoder* idec;
 
   // Parse the bitstream's features, if requested:
@@ -485,7 +567,7 @@ WebPIDecoder* WebPIDecode(const uint8_t* data, uint32_t data_size,
   }
   // Create an instance of the incremental decoder
   idec = WebPINewDecoder(config ? &config->output : NULL);
-  if (!idec) {
+  if (idec == NULL) {
     return NULL;
   }
   // Finish initialization
@@ -495,9 +577,15 @@ WebPIDecoder* WebPIDecode(const uint8_t* data, uint32_t data_size,
   return idec;
 }
 
-void WebPIDelete(WebPIDecoder* const idec) {
-  if (!idec) return;
-  VP8Delete(idec->dec_);
+void WebPIDelete(WebPIDecoder* idec) {
+  if (idec == NULL) return;
+  if (idec->dec_ != NULL) {
+    if (!idec->is_lossless_) {
+      VP8Delete(idec->dec_);
+    } else {
+      VP8LDelete(idec->dec_);
+    }
+  }
   ClearMemBuffer(&idec->mem_);
   WebPFreeDecBuffer(&idec->output_);
   free(idec);
@@ -506,19 +594,12 @@ void WebPIDelete(WebPIDecoder* const idec) {
 //------------------------------------------------------------------------------
 // Wrapper toward WebPINewDecoder
 
-WebPIDecoder* WebPINew(WEBP_CSP_MODE mode) {
-  WebPIDecoder* const idec = WebPINewDecoder(NULL);
-  if (!idec) return NULL;
-  idec->output_.colorspace = mode;
-  return idec;
-}
-
 WebPIDecoder* WebPINewRGB(WEBP_CSP_MODE mode, uint8_t* output_buffer,
-                          int output_buffer_size, int output_stride) {
+                          size_t output_buffer_size, int output_stride) {
   WebPIDecoder* idec;
   if (mode >= MODE_YUV) return NULL;
   idec = WebPINewDecoder(NULL);
-  if (!idec) return NULL;
+  if (idec == NULL) return NULL;
   idec->output_.colorspace = mode;
   idec->output_.is_external_memory = 1;
   idec->output_.u.RGBA.rgba = output_buffer;
@@ -527,12 +608,13 @@ WebPIDecoder* WebPINewRGB(WEBP_CSP_MODE mode, uint8_t* output_buffer,
   return idec;
 }
 
-WebPIDecoder* WebPINewYUV(uint8_t* luma, int luma_size, int luma_stride,
-                          uint8_t* u, int u_size, int u_stride,
-                          uint8_t* v, int v_size, int v_stride) {
+WebPIDecoder* WebPINewYUVA(uint8_t* luma, size_t luma_size, int luma_stride,
+                           uint8_t* u, size_t u_size, int u_stride,
+                           uint8_t* v, size_t v_size, int v_stride,
+                           uint8_t* a, size_t a_size, int a_stride) {
   WebPIDecoder* const idec = WebPINewDecoder(NULL);
-  if (!idec) return NULL;
-  idec->output_.colorspace = MODE_YUV;
+  if (idec == NULL) return NULL;
+  idec->output_.colorspace = (a == NULL) ? MODE_YUV : MODE_YUVA;
   idec->output_.is_external_memory = 1;
   idec->output_.u.YUVA.y = luma;
   idec->output_.u.YUVA.y_stride = luma_stride;
@@ -543,16 +625,25 @@ WebPIDecoder* WebPINewYUV(uint8_t* luma, int luma_size, int luma_stride,
   idec->output_.u.YUVA.v = v;
   idec->output_.u.YUVA.v_stride = v_stride;
   idec->output_.u.YUVA.v_size = v_size;
+  idec->output_.u.YUVA.a = a;
+  idec->output_.u.YUVA.a_stride = a_stride;
+  idec->output_.u.YUVA.a_size = a_size;
   return idec;
 }
 
+WebPIDecoder* WebPINewYUV(uint8_t* luma, size_t luma_size, int luma_stride,
+                          uint8_t* u, size_t u_size, int u_stride,
+                          uint8_t* v, size_t v_size, int v_stride) {
+  return WebPINewYUVA(luma, luma_size, luma_stride,
+                      u, u_size, u_stride,
+                      v, v_size, v_stride,
+                      NULL, 0, 0);
+}
+
 //------------------------------------------------------------------------------
 
 static VP8StatusCode IDecCheckStatus(const WebPIDecoder* const idec) {
   assert(idec);
-  if (idec->dec_ == NULL) {
-    return VP8_STATUS_USER_ABORT;
-  }
   if (idec->state_ == STATE_ERROR) {
     return VP8_STATUS_BITSTREAM_ERROR;
   }
@@ -562,8 +653,8 @@ static VP8StatusCode IDecCheckStatus(const WebPIDecoder* const idec) {
   return VP8_STATUS_SUSPENDED;
 }
 
-VP8StatusCode WebPIAppend(WebPIDecoder* const idec, const uint8_t* data,
-                          uint32_t data_size) {
+VP8StatusCode WebPIAppend(WebPIDecoder* idec,
+                          const uint8_t* data, size_t data_size) {
   VP8StatusCode status;
   if (idec == NULL || data == NULL) {
     return VP8_STATUS_INVALID_PARAM;
@@ -583,8 +674,8 @@ VP8StatusCode WebPIAppend(WebPIDecoder* const idec, const uint8_t* data,
   return IDecode(idec);
 }
 
-VP8StatusCode WebPIUpdate(WebPIDecoder* const idec, const uint8_t* data,
-                          uint32_t data_size) {
+VP8StatusCode WebPIUpdate(WebPIDecoder* idec,
+                          const uint8_t* data, size_t data_size) {
   VP8StatusCode status;
   if (idec == NULL || data == NULL) {
     return VP8_STATUS_INVALID_PARAM;
@@ -607,61 +698,67 @@ VP8StatusCode WebPIUpdate(WebPIDecoder* const idec, const uint8_t* data,
 //------------------------------------------------------------------------------
 
 static const WebPDecBuffer* GetOutputBuffer(const WebPIDecoder* const idec) {
-  if (!idec || !idec->dec_ || idec->state_ <= STATE_VP8_PARTS0) {
+  if (idec == NULL || idec->dec_ == NULL) {
+    return NULL;
+  }
+  if (idec->state_ <= STATE_VP8_PARTS0) {
     return NULL;
   }
   return idec->params_.output;
 }
 
-const WebPDecBuffer* WebPIDecodedArea(const WebPIDecoder* const idec,
-                                      int* const left, int* const top,
-                                      int* const width, int* const height) {
+const WebPDecBuffer* WebPIDecodedArea(const WebPIDecoder* idec,
+                                      int* left, int* top,
+                                      int* width, int* height) {
   const WebPDecBuffer* const src = GetOutputBuffer(idec);
-  if (left) *left = 0;
-  if (top) *top = 0;
+  if (left != NULL) *left = 0;
+  if (top != NULL) *top = 0;
   // TODO(skal): later include handling of rotations.
   if (src) {
-    if (width) *width = src->width;
-    if (height) *height = idec->params_.last_y;
+    if (width != NULL) *width = src->width;
+    if (height != NULL) *height = idec->params_.last_y;
   } else {
-    if (width) *width = 0;
-    if (height) *height = 0;
+    if (width != NULL) *width = 0;
+    if (height != NULL) *height = 0;
   }
   return src;
 }
 
-uint8_t* WebPIDecGetRGB(const WebPIDecoder* const idec, int* last_y,
+uint8_t* WebPIDecGetRGB(const WebPIDecoder* idec, int* last_y,
                         int* width, int* height, int* stride) {
   const WebPDecBuffer* const src = GetOutputBuffer(idec);
-  if (!src) return NULL;
+  if (src == NULL) return NULL;
   if (src->colorspace >= MODE_YUV) {
     return NULL;
   }
 
-  if (last_y) *last_y = idec->params_.last_y;
-  if (width) *width = src->width;
-  if (height) *height = src->height;
-  if (stride) *stride = src->u.RGBA.stride;
+  if (last_y != NULL) *last_y = idec->params_.last_y;
+  if (width != NULL) *width = src->width;
+  if (height != NULL) *height = src->height;
+  if (stride != NULL) *stride = src->u.RGBA.stride;
 
   return src->u.RGBA.rgba;
 }
 
-uint8_t* WebPIDecGetYUV(const WebPIDecoder* const idec, int* last_y,
-                        uint8_t** u, uint8_t** v,
-                        int* width, int* height, int *stride, int* uv_stride) {
+uint8_t* WebPIDecGetYUVA(const WebPIDecoder* idec, int* last_y,
+                         uint8_t** u, uint8_t** v, uint8_t** a,
+                         int* width, int* height,
+                         int* stride, int* uv_stride, int* a_stride) {
   const WebPDecBuffer* const src = GetOutputBuffer(idec);
-  if (!src) return NULL;
+  if (src == NULL) return NULL;
   if (src->colorspace < MODE_YUV) {
     return NULL;
   }
 
-  if (last_y) *last_y = idec->params_.last_y;
-  if (u) *u = src->u.YUVA.u;
-  if (v) *v = src->u.YUVA.v;
-  if (width) *width = src->width;
-  if (height) *height = src->height;
-  if (stride) *stride = src->u.YUVA.y_stride;
-  if (uv_stride) *uv_stride = src->u.YUVA.u_stride;
+  if (last_y != NULL) *last_y = idec->params_.last_y;
+  if (u != NULL) *u = src->u.YUVA.u;
+  if (v != NULL) *v = src->u.YUVA.v;
+  if (a != NULL) *a = src->u.YUVA.a;
+  if (width != NULL) *width = src->width;
+  if (height != NULL) *height = src->height;
+  if (stride != NULL) *stride = src->u.YUVA.y_stride;
+  if (uv_stride != NULL) *uv_stride = src->u.YUVA.u_stride;
+  if (a_stride != NULL) *a_stride = src->u.YUVA.a_stride;
 
   return src->u.YUVA.y;
 }
@@ -671,7 +768,7 @@ int WebPISetIOHooks(WebPIDecoder* const idec,
                     VP8IoSetupHook setup,
                     VP8IoTeardownHook teardown,
                     void* user_data) {
-  if (!idec || !idec->dec_ || idec->state_ > STATE_PRE_VP8) {
+  if (idec == NULL || idec->state_ > STATE_PRE_VP8) {
     return 0;
   }