Extract some useful functions around decoding buffer WebPDecParams.

This is to prepare for incremental decoding.

Change-Id: Ibb1ac6c1f2d10e096c4fbcf0c06bce77b30ca457

src/dec/webpi.h

@@ -0,0 +1,59 @@
+// 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/
+// -----------------------------------------------------------------------------
+//
+// Internal header: WebP decoding parameters and custom IO on buffer
+//
+// Author: somnath@google.com (Somnath Banerjee)
+
+#ifndef WEBP_DEC_WEBPI_H
+#define WEBP_DEC_WEBPI_H
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+#include "webp/decode_vp8.h"
+
+typedef enum { MODE_RGB = 0, MODE_RGBA = 1,
+               MODE_BGR = 2, MODE_BGRA = 3,
+               MODE_YUV = 4 } WEBP_CSP_MODE;
+
+  // Decoding output parameters.
+typedef struct {
+  uint8_t* output;      // rgb(a) or luma
+  uint8_t *u, *v;
+  uint8_t *top_y, *top_u, *top_v;
+  int stride;           // rgb(a) stride or luma stride
+  int u_stride;
+  int v_stride;
+  WEBP_CSP_MODE mode;
+} WebPDecParams;
+
+// If a RIFF container is detected, validate it and skip over it. Returns
+// VP8 bit-stream size if RIFF header is valid else returns 0
+uint32_t WebPCheckRIFFHeader(const uint8_t** data_ptr,
+                             uint32_t *data_size_ptr);
+
+// Initializes VP8Io with custom setup, io and teardown functions
+void WebPInitCustomIo(VP8Io* const io);
+
+// Initializes params_out by allocating output buffer and setting the
+// stride information. It also outputs width and height information of
+// the WebP image. Returns 1 if succeeds.
+int WebPInitDecParams(const uint8_t* data, uint32_t data_size, int* width,
+                      int* height, WebPDecParams* const params_out);
+
+// Verifies various size configurations (e.g stride >= width, specified
+// output size <= stride * height etc.). Returns 0 if checks fail.
+int WebPCheckDecParams(const VP8Io* io, const WebPDecParams* params,
+                       int output_size, int output_u_size, int output_v_size);
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}    // extern "C"
+#endif
+
+#endif  // WEBP_DEC_WEBPI_H