--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/lib/cache.c	Sun Dec 27 22:01:17 2009 +0200
@@ -0,0 +1,55 @@
+#include "cache.h"
+
+static int pt_cache_new (struct pt_cache **cache_ptr)
+{
+    struct pt_cache *cache;
+
+    if ((cache = calloc(1, sizeof(*cache))) == NULL)
+        return -1;
+
+    // ok
+    *cache_ptr = cache;
+
+    return 0;
+}
+
+int pt_cache_open (struct pt_cache **cache_ptr, struct pt_image *img, int mode)
+{
+    struct pt_cache *cache;
+    
+    // alloc
+    if (pt_cache_new(&cache))
+        return -1;
+
+    
+}
+
+bool pt_cache_fresh (struct pt_cache *cache)
+{
+    // TODO: stat + mtime
+    return false;
+}
+
+/**
+ * Create a new cache file, open it, and write out the header.
+ */
+static int pt_cache_create (struct pt_cache *cache, struct pt_cache_header *header)
+{
+    
+}
+
+int pt_cache_update_png (struct pt_cache *cache, png_structp png, png_infop info)
+{
+    struct pt_cache_header header;
+
+    memset(&header, 0, sizeof(header));
+
+    // fill in basic info
+    header->width = png_get_image_width(png, info);
+    header->height = png_get_image_height(png, info);
+    header->bit_depth = png_get_bit_depth(png, info);
+    header->color_type = png_get_color_type(png, info);
+
+    // fill in other info
+    header->row_bytes = png_get_rowbytes(png, info);
+}