[PATCH] SHA1 naive collision checking

[git.git] / fsck-cache.c

diff --git a/fsck-cache.c b/fsck-cache.c
index a01513e..bb5cf19 100644 (file)
--- a/fsck-cache.c
+++ b/fsck-cache.c
@@ -3,38 +3,145 @@
 #include <sys/types.h>
 #include <dirent.h>
 
+struct needs {
+       unsigned char parent[20];
+       unsigned char needs[20];
+       char tag[10];
+};
+
+struct seen {
+       unsigned char sha1[20];
+       char tag[10];
+       unsigned needed;
+};
+
+static struct needs *needs;
+static struct seen *seen;
+
+static int nr_seen, alloc_seen, nr_needs, alloc_needs;
+
 /*
- * These two functions should build up a graph in memory about
+ * These two functions build up a graph in memory about
  * what objects we've referenced, and found, and types..
- *
- * Right now we don't do that kind of reachability checking. Yet.
  */
-static void mark_needs_sha1(unsigned char *parent, const char * type, unsigned char *child)
+static int compare_seen(const void *s1, const void *s2)
+{
+       return memcmp(s1, s2, 20);
+}
+
+static int lookup_seen(unsigned char *sha1, char *tag)
+{
+       int first = 0, last = nr_seen;
+
+       while (last > first) {
+               int next = (last + first) / 2;
+               struct seen *s = seen + next;
+               int cmp = memcmp(sha1, s->sha1, 20);
+
+               if (cmp < 0) {
+                       last = next;
+                       continue;
+               }
+               if (cmp > 0) {
+                       first = next+1;
+                       continue;
+               }
+               if (strcmp(tag, s->tag))
+                       break;
+               s->needed++;
+               return 1;
+       }
+       return 0;
+}
+
+static void check_connectivity(void)
+{
+       int i;
+
+       /* Sort the "seen" tags for quicker lookup */
+       qsort(seen, nr_seen, sizeof(struct seen), compare_seen);
+
+       /* Look up all the requirements, warn about missing objects.. */
+       for (i = 0; i < nr_needs; i++) {
+               struct needs *n = needs + i;
+               char hex[60];
+
+               if (lookup_seen(n->needs, n->tag))
+                       continue;
+               strcpy(hex, sha1_to_hex(n->parent));
+               printf("missing %s: %s referenced by %s\n", n->tag, sha1_to_hex(n->needs), hex);
+       }
+
+       /* Tell the user about things not referenced.. */
+       for (i = 0; i < nr_seen; i++) {
+               struct seen *s = seen + i;
+
+               if (s->needed)
+                       continue;
+               printf("unreferenced %s: %s\n", s->tag, sha1_to_hex(s->sha1));
+       }
+}
+
+static void mark_needs_sha1(unsigned char *parent, const char * tag, unsigned char *child)
 {
+       struct needs *n;
+
+       if (nr_needs == alloc_needs) {
+               alloc_needs = alloc_nr(alloc_needs);
+               needs = realloc(needs, alloc_needs*sizeof(struct needs));
+       }
+       n = needs + nr_needs;
+       nr_needs++;
+       memcpy(n->parent, parent, 20);
+       memcpy(n->needs, child, 20);
+       strncpy(n->tag, tag, sizeof(n->tag));
 }
 
 static int mark_sha1_seen(unsigned char *sha1, char *tag)
 {
+       struct seen *s;
+
+       if (nr_seen == alloc_seen) {
+               alloc_seen = alloc_nr(alloc_seen);
+               seen = realloc(seen, alloc_seen*sizeof(struct seen));
+       }
+       s = seen + nr_seen;
+       memset(s, 0, sizeof(*s));
+       nr_seen++;
+       memcpy(s->sha1, sha1, 20);
+       strncpy(s->tag, tag, sizeof(s->tag));
+       
        return 0;
 }
 
 static int fsck_tree(unsigned char *sha1, void *data, unsigned long size)
 {
+       int warn_old_tree = 1;
+
        while (size) {
                int len = 1+strlen(data);
                unsigned char *file_sha1 = data + len;
                char *path = strchr(data, ' ');
-               if (size < len + 20 || !path)
+               unsigned int mode;
+               if (size < len + 20 || !path || sscanf(data, "%o", &mode) != 1)
                        return -1;
+
+               /* Warn about trees that don't do the recursive thing.. */
+               if (warn_old_tree && strchr(path, '/')) {
+                       fprintf(stderr, "warning: fsck-cache: tree %s has full pathnames in it\n", sha1_to_hex(sha1));
+                       warn_old_tree = 0;
+               }
+
                data += len + 20;
                size -= len + 20;
-               mark_needs_sha1(sha1, "blob", file_sha1);
+               mark_needs_sha1(sha1, S_ISDIR(mode) ? "tree" : "blob", file_sha1);
        }
        return 0;
 }
 
 static int fsck_commit(unsigned char *sha1, void *data, unsigned long size)
 {
+       int parents;
        unsigned char tree_sha1[20];
        unsigned char parent_sha1[20];
 
@@ -44,12 +151,16 @@ static int fsck_commit(unsigned char *sha1, void *data, unsigned long size)
                return -1;
        mark_needs_sha1(sha1, "tree", tree_sha1);
        data += 5 + 40 + 1;     /* "tree " + <hex sha1> + '\n' */
+       parents = 0;
        while (!memcmp(data, "parent ", 7)) {
                if (get_sha1_hex(data + 7, parent_sha1) < 0)
                        return -1;
                mark_needs_sha1(sha1, "commit", parent_sha1);
                data += 7 + 40 + 1;     /* "parent " + <hex sha1> + '\n' */
+               parents++;
        }
+       if (!parents)
+               printf("root: %s\n", sha1_to_hex(sha1));
        return 0;
 }
 
@@ -135,5 +246,6 @@ int main(int argc, char **argv)
                sprintf(dir, "%s/%02x", sha1_dir, i);
                fsck_dir(i, dir);
        }
+       check_connectivity();
        return 0;
 }