Use the embedded profile-id if it is available, else fallback to the file MD5

This should speed up startup as we can use the pre-cooked value rather than
using g_compute_checksum_for_data on every profile.

This speeds up startup by more than 70% if all the system profiles are fixed.

2 files changed, 50 insertions, 8 deletions

diff --git a/doc/device-and-profile-naming-spec.txt b/doc/device-and-profile-naming-spec.txt
index d43d67b..8ec13e0 100644
--- a/doc/device-and-profile-naming-spec.txt
+++ b/doc/device-and-profile-naming-spec.txt
@@ -129,10 +129,18 @@ and spaces and does not have to be escaped.
 A profile ID is the same for binary identical profiles, even if
 duplicated on the filesystem.
 
-In line with other ICC reccomendations, the complete MD5 file checksum
-is used for the profile ID, e.g.
+In line with other ICC reccomendations, the embedded profile ID (bytes
+84 to 99) is used, after converting it to a hexadecimal encoding.
 
-Format:		icc-{%checksum}
+Format:		icc-{%embedded-profile-id}
+Example:	icc-3c219b18958837493b586581f8c2a2a4
+
+The ICC do not mandate the embedded profile-id and only recommend it,
+and as such few profiles in the wild use a real value.
+If the embedded profile ID is not set, the complete MD5 file checksum
+should be used instead, e.g.
+
+Format:		icc-{%file-checksum}
 Example:	icc-bd847723f676e2b846daaf6759330624
 
 If a physical profile does not exist (for instance, for embedded printer
diff --git a/src/cd-profile.c b/src/cd-profile.c
index 2b480e4..405b185 100644
--- a/src/cd-profile.c
+++ b/src/cd-profile.c
@@ -635,6 +635,36 @@ out:
 }
 
 /**
+ * cd_profile_get_precooked_md5:
+ **/
+static gchar *
+cd_profile_get_precooked_md5 (cmsHPROFILE lcms_profile)
+{
+	cmsUInt8Number profile_id[16];
+	gboolean md5_precooked = FALSE;
+	guint i;
+	gchar *md5 = NULL;
+
+	/* check to see if we have a pre-cooked MD5 */
+	cmsGetHeaderProfileID (lcms_profile, profile_id);
+	for (i=0; i<16; i++) {
+		if (profile_id[i] != 0) {
+			md5_precooked = TRUE;
+			break;
+		}
+	}
+	if (!md5_precooked)
+		goto out;
+
+	/* convert to a hex string */
+	md5 = g_new0 (gchar, 32 + 1);
+	for (i=0; i<16; i++)
+		g_snprintf (md5 + i*2, 3, "%x", profile_id[i]);
+out:
+	return md5;
+}
+
+/**
  * cd_profile_set_filename:
  **/
 gboolean
@@ -771,11 +801,15 @@ cd_profile_set_filename (CdProfile *profile, const gchar *filename, GError **err
 			     g_strdup (fake_md5));
 	}
 
-	/* generate and set checksum */
-	profile->priv->checksum =
-		g_compute_checksum_for_data (G_CHECKSUM_MD5,
-					     (const guchar *) data,
-					    len);
+	/* use a pre-cooked MD5 if available, else fall back to
+	 * calculating it ourselves */
+	profile->priv->checksum = cd_profile_get_precooked_md5 (lcms_profile);
+	if (profile->priv->checksum == NULL) {
+		profile->priv->checksum =
+			g_compute_checksum_for_data (G_CHECKSUM_MD5,
+						     (const guchar *) data,
+						     len);
+	}
 
 	/* success */
 	g_free (profile->priv->filename);