From b9f7a4b5261b6d4e7bdbb5cc56d78d50ad1bd4a7 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Sat, 3 Apr 2010 14:48:36 +0100
Subject: [PATCH] script: Don't hash the entire image.

The reuse hit rate is very small, and most images are quickly
distinguished in the first few bytes... Though perhaps not for video as
in the swfdec-youtube case...
---
 util/cairo-script/cairo-script-operators.c | 35 +++++++++++++++-------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/util/cairo-script/cairo-script-operators.c b/util/cairo-script/cairo-script-operators.c
index 754a27e08..e583120f9 100644
--- a/util/cairo-script/cairo-script-operators.c
+++ b/util/cairo-script/cairo-script-operators.c
@@ -126,19 +126,17 @@ _csi_proxy_destroy (void *closure)
     cairo_script_interpreter_destroy (ctx);
 }
 
-static unsigned long
-_csi_blob_hash (const uint8_t *bytes, int len)
+static void
+_csi_blob_hash (csi_blob_t *blob, const uint32_t *data, int len)
 {
+    unsigned long hash = blob->hash;
     /* very simple! */
-    unsigned long hash = 5381;
-    unsigned long *data = (unsigned long *) bytes;
-    len /= sizeof (unsigned long);
     while (len--) {
 	unsigned long c = *data++;
 	hash *= 33;
 	hash ^= c;
     }
-    return hash;
+    blob->hash = hash;
 }
 
 static csi_boolean_t
@@ -152,10 +150,6 @@ _csi_blob_equal (const csi_list_t *link, void *data)
     if (A->len != B->len)
 	return FALSE;
 
-    if (A->hash == 0)
-	A->hash = _csi_blob_hash (A->bytes, A->len);
-    if (B->hash == 0)
-	B->hash = _csi_blob_hash (B->bytes, B->len);
     if (A->hash != B->hash)
 	return FALSE;
 
@@ -165,7 +159,7 @@ _csi_blob_equal (const csi_list_t *link, void *data)
 static void
 _csi_blob_init (csi_blob_t *blob, uint8_t *bytes, int len)
 {
-    blob->hash = 0;
+    blob->hash = 5381;
     blob->len = len;
     blob->bytes = bytes;
 }
@@ -1760,6 +1754,7 @@ _ft_create_for_source (csi_t *ctx,
     /* check for an existing FT_Face (kept alive by the font cache) */
     /* XXX index/flags */
     _csi_blob_init (&tmpl, (uint8_t *) source->string, source->len);
+    _csi_blob_hash (&tmpl, (uint32_t *) source->string, source->len / sizeof (uint32_t));
     link = _csi_list_find (ctx->_faces, _csi_blob_equal, &tmpl);
     if (link) {
 	if (--source->base.ref == 0)
@@ -1869,6 +1864,7 @@ _ft_create_for_pattern (csi_t *ctx,
     void *bytes;
 
     _csi_blob_init (&tmpl, (uint8_t *) string->string, string->len);
+    _csi_blob_hash (&tmpl, (uint32_t *) string->string, string->len / sizeof (uint32_t));
     link = _csi_list_find (ctx->_faces, _csi_blob_equal, &tmpl);
     if (link) {
 	if (--string->base.ref == 0)
@@ -3082,6 +3078,22 @@ _image_tag_done (void *closure)
     cairo_script_interpreter_destroy (ctx);
 }
 
+static void
+_image_hash (csi_blob_t *blob,
+	     cairo_surface_t *surface)
+{
+    uint32_t  value;
+
+    value = cairo_image_surface_get_width (surface);
+    _csi_blob_hash (blob, &value, 1);
+
+    value = cairo_image_surface_get_height (surface);
+    _csi_blob_hash (blob, &value, 1);
+
+    value = cairo_image_surface_get_format (surface);
+    _csi_blob_hash (blob, &value, 1);
+}
+
 static cairo_surface_t *
 _image_cached (csi_t *ctx, cairo_surface_t *surface)
 {
@@ -3097,6 +3109,7 @@ _image_cached (csi_t *ctx, cairo_surface_t *surface)
     stride = cairo_image_surface_get_stride (surface);
     height = cairo_image_surface_get_height (surface);
     _csi_blob_init (&tmpl, data, stride * height);
+    _image_hash (&tmpl, surface);
     link = _csi_list_find (ctx->_images, _csi_blob_equal, &tmpl);
     if (link) {
 	cairo_surface_destroy (surface);