xdiff: generate "anti-diffs" aka what is common to two files

diff --git a/commit.c b/commit.c
index 946615d2ad5c364fe63b201aa9a9574737804c38..e51ffa1c6cf5948c0e6c6d0b905fc868f4464ccf 100644 (file)
--- a/commit.c
+++ b/commit.c
@@ -236,6 +236,7 @@ static struct commit_graft *lookup_commit_graft(const unsigned char *sha1)
 
 int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
 {
+       char *tail = buffer;
        char *bufptr = buffer;
        unsigned char parent[20];
        struct commit_list **pptr;
@@ -245,9 +246,10 @@ int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
        if (item->object.parsed)
                return 0;
        item->object.parsed = 1;
-       if (memcmp(bufptr, "tree ", 5))
+       tail += size;
+       if (tail <= bufptr + 5 || memcmp(bufptr, "tree ", 5))
                return error("bogus commit object %s", sha1_to_hex(item->object.sha1));
-       if (get_sha1_hex(bufptr + 5, parent) < 0)
+       if (tail <= bufptr + 45 || get_sha1_hex(bufptr + 5, parent) < 0)
                return error("bad tree pointer in commit %s",
                             sha1_to_hex(item->object.sha1));
        item->tree = lookup_tree(parent);
@@ -257,10 +259,12 @@ int parse_commit_buffer(struct commit *item, void *buffer, unsigned long size)
        pptr = &item->parents;
 
        graft = lookup_commit_graft(item->object.sha1);
-       while (!memcmp(bufptr, "parent ", 7)) {
+       while (bufptr + 48 < tail && !memcmp(bufptr, "parent ", 7)) {
                struct commit *new_parent;
 
-               if (get_sha1_hex(bufptr + 7, parent) || bufptr[47] != '\n')
+               if (tail <= bufptr + 48 ||
+                   get_sha1_hex(bufptr + 7, parent) ||
+                   bufptr[47] != '\n')
                        return error("bad parents in commit %s", sha1_to_hex(item->object.sha1));
                bufptr += 48;
                if (graft)
@@ -543,7 +547,7 @@ static int add_merge_info(enum cmit_fmt fmt, char *buf, const struct commit *com
                const char *hex = abbrev
                        ? find_unique_abbrev(p->object.sha1, abbrev)
                        : sha1_to_hex(p->object.sha1);
-               char *dots = (abbrev && strlen(hex) != 40) ? "..." : "";
+               const char *dots = (abbrev && strlen(hex) != 40) ? "..." : "";
                parent = parent->next;
 
                offset += sprintf(buf + offset, " %s%s", hex, dots);