[PATCH] delta read

This makes the core code aware of delta objects and undeltafy them as
needed.  The convention is to use read_sha1_file() to have
undeltafication done automatically (most users do that already so this
is transparent).

If the delta object itself has to be accessed then it must be done
through map_sha1_file() and unpack_sha1_file().

In that context mktag.c has been switched to read_sha1_file() as there
is no reason to do the full map+unpack manually.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

mktag.c

@@ -25,20 +25,14 @@
 static int verify_object(unsigned char *sha1, const char *expected_type)
 {
 	int ret = -1;
-	unsigned long mapsize;
-	void *map = map_sha1_file(sha1, &mapsize);
+	char type[100];
+	unsigned long size;
+	void *buffer = read_sha1_file(sha1, type, &size);
 
-	if (map) {
-		char type[100];
-		unsigned long size;
-		void *buffer = unpack_sha1_file(map, mapsize, type, &size);
-
-		if (buffer) {
-			if (!strcmp(type, expected_type))
-				ret = check_sha1_signature(sha1, buffer, size, type);
-			free(buffer);
-		}
-		munmap(map, mapsize);
+	if (buffer) {
+		if (!strcmp(type, expected_type))
+			ret = check_sha1_signature(sha1, buffer, size, type);
+		free(buffer);
 	}
 	return ret;
 }

sha1_file.c

@@ -9,6 +9,7 @@
 #include <stdarg.h>
 #include <limits.h>
 #include "cache.h"
+#include "delta.h"
 
 #ifndef O_NOATIME
 #if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
@@ -353,6 +354,19 @@ void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size
 	if (map) {
 		buf = unpack_sha1_file(map, mapsize, type, size);
 		munmap(map, mapsize);
+		if (buf && !strcmp(type, "delta")) {
+			void *ref = NULL, *delta = buf;
+			unsigned long ref_size, delta_size = *size;
+			buf = NULL;
+			if (delta_size > 20)
+				ref = read_sha1_file(delta, type, &ref_size);
+			if (ref)
+				buf = patch_delta(ref, ref_size,
+						  delta+20, delta_size-20, 
+						  size);
+			free(delta);
+			free(ref);
+		}
 		return buf;
 	}
 	return NULL;