1 files changed, 69 insertions, 0 deletions
diff --git a/third_party/libwebp/dec/alpha.c b/third_party/libwebp/dec/alpha.c
new file mode 100644
index 0000000..3052ced
--- /dev/null
+++ b/third_party/libwebp/dec/alpha.c
@@ -0,0 +1,69 @@
+// Copyright 2011 Google Inc.
+//
+// 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/
+// -----------------------------------------------------------------------------
+//
+// Alpha-plane decompression.
+//
+// Author: Skal (pascal.massimino@gmail.com)
+
+#include <stdlib.h>
+#include "vp8i.h"
+
+#ifdef WEBP_EXPERIMENTAL_FEATURES
+
+#include "zlib.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+//------------------------------------------------------------------------------
+
+const uint8_t* VP8DecompressAlphaRows(VP8Decoder* const dec,
+                                      int row, int num_rows) {
+  uint8_t* output = dec->alpha_plane_;
+  const int stride = dec->pic_hdr_.width_;
+  if (row < 0 || row + num_rows > dec->pic_hdr_.height_) {
+    return NULL;    // sanity check
+  }
+  if (row == 0) {
+    // TODO(skal): for now, we just decompress everything during the first call.
+    // Later, we'll decode progressively, but we need to store the
+    // z_stream state.
+    const uint8_t* data = dec->alpha_data_;
+    size_t data_size = dec->alpha_data_size_;
+    const size_t output_size = stride * dec->pic_hdr_.height_;
+    int ret = Z_OK;
+    z_stream strm;
+
+    memset(&strm, 0, sizeof(strm));
+    if (inflateInit(&strm) != Z_OK) {
+      return 0;
+    }
+    strm.avail_in = data_size;
+    strm.next_in = (unsigned char*)data;
+    do {
+      strm.avail_out = output_size;
+      strm.next_out = output;
+      ret = inflate(&strm, Z_NO_FLUSH);
+      if (ret == Z_NEED_DICT || ret == Z_DATA_ERROR || ret == Z_MEM_ERROR) {
+        break;
+      }
+    } while (strm.avail_out == 0);
+
+    inflateEnd(&strm);
+    if (ret != Z_STREAM_END) {
+      return NULL;    // error
+    }
+  }
+  return output + row * stride;
+}
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}    // extern "C"
+#endif
+
+#endif    // WEBP_EXPERIMENTAL_FEATURES