[PATCH] assorted delta code cleanup

This is a wrap-up patch including all the cleanups I've done to the
delta code and its usage.  The most important change is the
factorization of the delta header handling code.

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

diff --git a/count-delta.c b/count-delta.c
index 8901034..7559ff6 100644 (file)
--- a/count-delta.c
+++ b/count-delta.c
@@ -6,23 +6,9 @@
 #include <stdlib.h>
 #include <string.h>
 #include <limits.h>
+#include "delta.h"
 #include "count-delta.h"
 
-static unsigned long get_hdr_size(const unsigned char **datap)
-{
-       const unsigned char *data = *datap;
-       unsigned char cmd = *data++;
-       unsigned long size = cmd & ~0x80;
-       int i = 7;
-       while (cmd & 0x80) {
-               cmd = *data++;
-               size |= (cmd & ~0x80) << i;
-               i += 7;
-       }
-       *datap = data;
-       return size;
-}
-
 /*
  * NOTE.  We do not _interpret_ delta fully.  As an approximation, we
  * just count the number of bytes that are copied from the source, and
@@ -44,15 +30,14 @@ int count_delta(void *delta_buf, unsigned long delta_size,
        unsigned char cmd;
        unsigned long src_size, dst_size, out;
 
-       /* the smallest delta size possible is 4 bytes */
-       if (delta_size < 4)
+       if (delta_size < DELTA_SIZE_MIN)
                return -1;
 
        data = delta_buf;
        top = delta_buf + delta_size;
 
-       src_size = get_hdr_size(&data);
-       dst_size = get_hdr_size(&data);
+       src_size = get_delta_hdr_size(&data);
+       dst_size = get_delta_hdr_size(&data);
 
        added_literal = copied_from_source = out = 0;
        while (data < top) {

diff --git a/delta.h b/delta.h
index bc3a220..31d1820 100644 (file)
--- a/delta.h
+++ b/delta.h
@@ -9,4 +9,26 @@ extern void *patch_delta(void *src_buf, unsigned long src_size,
                         void *delta_buf, unsigned long delta_size,
                         unsigned long *dst_size);
 
+/* the smallest possible delta size is 4 bytes */
+#define DELTA_SIZE_MIN 4
+
+/*
+ * This must be called twice on the delta data buffer, first to get the
+ * expected reference buffer size, and again to get the result buffer size.
+ */
+static inline unsigned long get_delta_hdr_size(const unsigned char **datap)
+{
+       const unsigned char *data = *datap;
+       unsigned char cmd = *data++;
+       unsigned long size = cmd & ~0x80;
+       int i = 7;
+       while (cmd & 0x80) {
+               cmd = *data++;
+               size |= (cmd & ~0x80) << i;
+               i += 7;
+       }
+       *datap = data;
+       return size;
+}
+
 #endif

diff --git a/diff-delta.c b/diff-delta.c
index 67f6081..b2ae7b5 100644 (file)
--- a/diff-delta.c
+++ b/diff-delta.c
@@ -306,12 +306,13 @@ void *diff_delta(void *from_buf, unsigned long from_size,
                        *orig = i;
                }
 
-               /* next time around the largest possible output is 1 + 4 + 3 */
                if (max_size && outpos > max_size) {
                        free(out);
                        delta_cleanup(&bdf);
                        return NULL;
                }
+
+               /* next time around the largest possible output is 1 + 4 + 3 */
                if (outpos > outsize - 8) {
                        void *tmp = out;
                        outsize = outsize * 3 / 2;

diff --git a/pack-objects.c b/pack-objects.c
index fc969e3..d95f45e 100644 (file)
--- a/pack-objects.c
+++ b/pack-objects.c
@@ -34,7 +34,7 @@ static void *delta_against(void *buf, unsigned long size, struct object_entry *e
        if (!otherbuf)
                die("unable to read %s", sha1_to_hex(entry->delta->sha1));
         delta_buf = diff_delta(otherbuf, othersize,
-                              buf, size, &delta_size, ~0UL);
+                              buf, size, &delta_size, 0);
         if (!delta_buf || delta_size != entry->delta_size)
                die("delta size changed");
         free(buf);

diff --git a/patch-delta.c b/patch-delta.c
index b68dd13..26281ea 100644 (file)
--- a/patch-delta.c
+++ b/patch-delta.c
@@ -20,36 +20,20 @@ void *patch_delta(void *src_buf, unsigned long src_size,
        const unsigned char *data, *top;
        unsigned char *dst_buf, *out, cmd;
        unsigned long size;
-       int i;
 
-       /* the smallest delta size possible is 4 bytes */
-       if (delta_size < 4)
+       if (delta_size < DELTA_SIZE_MIN)
                return NULL;
 
        data = delta_buf;
        top = delta_buf + delta_size;
 
        /* make sure the orig file size matches what we expect */
-       cmd = *data++;
-       size = cmd & ~0x80;
-       i = 7;
-       while (cmd & 0x80) {
-               cmd = *data++;
-               size |= (cmd & ~0x80) << i;
-               i += 7;
-       }
+       size = get_delta_hdr_size(&data);
        if (size != src_size)
                return NULL;
 
        /* now the result size */
-       cmd = *data++;
-       size = cmd & ~0x80;
-       i = 7;
-       while (cmd & 0x80) {
-               cmd = *data++;
-               size |= (cmd & ~0x80) << i;
-               i += 7;
-       }
+       size = get_delta_hdr_size(&data);
        dst_buf = malloc(size);
        if (!dst_buf)
                return NULL;

diff --git a/sha1_file.c b/sha1_file.c
index f6cf180..737ecb4 100644 (file)
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -592,22 +592,6 @@ void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned l
        return unpack_sha1_rest(&stream, hdr, *size);
 }
 
-static unsigned long parse_delta_size(unsigned char **p)
-{
-       unsigned char c;
-       unsigned long size = 0;
-       unsigned shift = 0;
-       unsigned char *data = *p;
-
-       do {
-               c = *data++;
-               size += (c & 0x7f) << shift;
-               shift += 7;
-       } while (c & 0x80);
-       *p = data;
-       return size;
-}
-
 static int packed_delta_info(unsigned char *base_sha1,
                             unsigned long delta_size,
                             unsigned long left,
@@ -645,11 +629,12 @@ static int packed_delta_info(unsigned char *base_sha1,
         * the result size.  Verify the base size while we are at it.
         */
        data = delta_head;
-       verify_base_size = parse_delta_size(&data);
-       result_size = parse_delta_size(&data);
+       verify_base_size = get_delta_hdr_size(&data);
        if (verify_base_size != base_size)
                die("delta base size mismatch");
 
+       /* Read the result size */
+       result_size = get_delta_hdr_size(&data);
        *sizep = result_size;
        return 0;
 }