text: // 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/
  //  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 "../utils/rescaler.h"
  #include "./decode_vp8.h"
  
  //------------------------------------------------------------------------------
  // WebPDecParams: Decoding output parameters. Transient internal object.
  
  typedef struct WebPDecParams WebPDecParams;
  typedef int (*OutputFunc)(const VP8Io* const io, WebPDecParams* const p);
  typedef int (*OutputRowFunc)(WebPDecParams* const p, int y_pos);
  
  struct WebPDecParams {
    WebPDecBuffer* output;             // output buffer.
    uint8_t* tmp_y, *tmp_u, *tmp_v;    // cache for the fancy upsampler
                                       // or used for tmp rescaling
  
    int last_y;                 // coordinate of the line that was last output
    const WebPDecoderOptions* options;  // if not NULL, use alt decoding features
    // rescalers
    WebPRescaler scaler_y, scaler_u, scaler_v, scaler_a;
    void* memory;                  // overall scratch memory for the output work.
  
    OutputFunc emit;               // output RGB or YUV samples
    OutputFunc emit_alpha;         // output alpha channel
    OutputRowFunc emit_alpha_row;  // output one line of rescaled alpha values
  };
  
  // Should be called first, before any use of the WebPDecParams object.
  void WebPResetDecParams(WebPDecParams* const params);
  
  //------------------------------------------------------------------------------
  // Header parsing helpers
  
  // Structure storing a description of the RIFF headers.
  typedef struct {
    const uint8_t* data;         // input buffer
    size_t data_size;            // input buffer size
    size_t offset;               // offset to main data chunk (VP8 or VP8L)
    const uint8_t* alpha_data;   // points to alpha chunk (if present)
    size_t alpha_data_size;      // alpha chunk size
    size_t compressed_size;      // VP8/VP8L compressed data size
    size_t riff_size;            // size of the riff payload (or 0 if absent)
    int is_lossless;             // true if a VP8L chunk is present
  } WebPHeaderStructure;
  
  // Skips over all valid chunks prior to the first VP8/VP8L frame header.
  // Returns VP8_STATUS_OK on success,
  //         VP8_STATUS_BITSTREAM_ERROR if an invalid header/chunk is found, and
  //         VP8_STATUS_NOT_ENOUGH_DATA if case of insufficient data.
  // In 'headers', compressed_size, offset, alpha_data, alpha_size and lossless
  // fields are updated appropriately upon success.
  VP8StatusCode WebPParseHeaders(WebPHeaderStructure* const headers);
  
  //------------------------------------------------------------------------------
  // Misc utils
  
  // Initializes VP8Io with custom setup, io and teardown functions. The default
  // hooks will use the supplied 'params' as io->opaque handle.
  void WebPInitCustomIo(WebPDecParams* const params, VP8Io* const io);
  
  // Setup crop_xxx fields, mb_w and mb_h in io. 'src_colorspace' refers
  // to the *compressed* format, not the output one.
  int WebPIoInitFromOptions(const WebPDecoderOptions* const options,
                            VP8Io* const io, WEBP_CSP_MODE src_colorspace);
  
  //------------------------------------------------------------------------------
  // Internal functions regarding WebPDecBuffer memory (in buffer.c).
  // Don't really need to be externally visible for now.
  
  // Prepare 'buffer' with the requested initial dimensions width/height.
  // If no external storage is supplied, initializes buffer by allocating output
  // memory and setting up the stride information. Validate the parameters. Return
  // an error code in case of problem (no memory, or invalid stride / size /
  // dimension / etc.). If *options is not NULL, also verify that the options'
  // parameters are valid and apply them to the width/height dimensions of the
  // output buffer. This takes cropping / scaling / rotation into account.
  VP8StatusCode WebPAllocateDecBuffer(int width, int height,
                                      const WebPDecoderOptions* const options,
                                      WebPDecBuffer* const buffer);
  
  // Copy 'src' into 'dst' buffer, making sure 'dst' is not marked as owner of the
  // memory (still held by 'src').
  void WebPCopyDecBuffer(const WebPDecBuffer* const src,
                         WebPDecBuffer* const dst);
  
  // Copy and transfer ownership from src to dst (beware of parameter order!)
  void WebPGrabDecBuffer(WebPDecBuffer* const src, WebPDecBuffer* const dst);
  
  
  
  //------------------------------------------------------------------------------
  
  #if defined(__cplusplus) || defined(c_plusplus)
  }    // extern "C"
  #endif
  
  #endif  /* WEBP_DEC_WEBPI_H_ */
  