/* Library to make sure that each image is read only once.

   This means stdin and named pipes would work without surprises,
   at the cost of more memory.                                    */

#ifndef PNG_CACHE_H_
#define PNG_CACHE_H_

#include<png.h>

/* Linked list of cached files.

   Linked list means updates require quadratic time, but we expect
   the list to only contain a few files because they came from argv. */
typedef struct image_cache
{
   /* Input file name, not owned by this struct. */
   const char *filename;

   /* Image handle. */
   png_image image;

   /* Pixel data, owned by this struct. */
   png_bytep pixels;

   /* Pointer to next image. */
   struct image_cache *next;
} ImageCache;

/* Add image to cache.

   Returns pointer to image data on success, or NULL on error. */
ImageCache *LoadImage(const char *filename, ImageCache **cache);

/* Release memory. */
void FreeImageCache(ImageCache **cache);

#endif  /* PNG_CACHE_H_ */