[PATCH] Update git-clone documentation
[git.git] / sha1_file.c
index 8d189d4..895c1fa 100644 (file)
@@ -20,6 +20,8 @@
 #endif
 #endif
 
+const unsigned char null_sha1[20] = { 0, };
+
 static unsigned int sha1_file_open_flag = O_NOATIME;
 
 static unsigned hexval(char c)
@@ -50,26 +52,33 @@ static char *git_dir, *git_object_dir, *git_index_file, *git_refs_dir,
        *git_graft_file;
 static void setup_git_env(void)
 {
-       git_dir = gitenv(GIT_DIR_ENVIRONMENT);
+       git_dir = getenv(GIT_DIR_ENVIRONMENT);
        if (!git_dir)
                git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
-       git_object_dir = gitenv(DB_ENVIRONMENT);
+       git_object_dir = getenv(DB_ENVIRONMENT);
        if (!git_object_dir) {
                git_object_dir = xmalloc(strlen(git_dir) + 9);
                sprintf(git_object_dir, "%s/objects", git_dir);
        }
        git_refs_dir = xmalloc(strlen(git_dir) + 6);
        sprintf(git_refs_dir, "%s/refs", git_dir);
-       git_index_file = gitenv(INDEX_ENVIRONMENT);
+       git_index_file = getenv(INDEX_ENVIRONMENT);
        if (!git_index_file) {
                git_index_file = xmalloc(strlen(git_dir) + 7);
                sprintf(git_index_file, "%s/index", git_dir);
        }
-       git_graft_file = gitenv(GRAFT_ENVIRONMENT);
+       git_graft_file = getenv(GRAFT_ENVIRONMENT);
        if (!git_graft_file)
                git_graft_file = strdup(git_path("info/grafts"));
 }
 
+char *get_git_dir(void)
+{
+       if (!git_dir)
+               setup_git_env();
+       return git_dir;
+}
+
 char *get_object_directory(void)
 {
        if (!git_object_dir)
@@ -222,84 +231,123 @@ char *sha1_pack_index_name(const unsigned char *sha1)
        return base;
 }
 
-struct alternate_object_database *alt_odb;
+struct alternate_object_database *alt_odb_list;
+static struct alternate_object_database **alt_odb_tail;
 
 /*
  * Prepare alternate object database registry.
- * alt_odb points at an array of struct alternate_object_database.
- * This array is terminated with an element that has both its base
- * and name set to NULL.  alt_odb[n] comes from n'th non-empty
- * element from colon separated ALTERNATE_DB_ENVIRONMENT environment
- * variable, and its base points at a statically allocated buffer
- * that contains "/the/directory/corresponding/to/.git/objects/...",
- * while its name points just after the slash at the end of
- * ".git/objects/" in the example above, and has enough space to hold
- * 40-byte hex SHA1, an extra slash for the first level indirection,
- * and the terminating NUL.
- * This function allocates the alt_odb array and all the strings
- * pointed by base fields of the array elements with one xmalloc();
- * the string pool immediately follows the array.
+ *
+ * The variable alt_odb_list points at the list of struct
+ * alternate_object_database.  The elements on this list come from
+ * non-empty elements from colon separated ALTERNATE_DB_ENVIRONMENT
+ * environment variable, and $GIT_OBJECT_DIRECTORY/info/alternates,
+ * whose contents is exactly in the same format as that environment
+ * variable.  Its base points at a statically allocated buffer that
+ * contains "/the/directory/corresponding/to/.git/objects/...", while
+ * its name points just after the slash at the end of ".git/objects/"
+ * in the example above, and has enough space to hold 40-byte hex
+ * SHA1, an extra slash for the first level indirection, and the
+ * terminating NUL.
  */
-void prepare_alt_odb(void)
+static void link_alt_odb_entries(const char *alt, const char *ep, int sep,
+                                const char *relative_base)
 {
-       int pass, totlen, i;
        const char *cp, *last;
-       char *op = NULL;
-       const char *alt = gitenv(ALTERNATE_DB_ENVIRONMENT) ? : "";
+       struct alternate_object_database *ent;
+       int base_len = -1;
+
+       last = alt;
+       while (last < ep) {
+               cp = last;
+               if (cp < ep && *cp == '#') {
+                       while (cp < ep && *cp != sep)
+                               cp++;
+                       last = cp + 1;
+                       continue;
+               }
+               for ( ; cp < ep && *cp != sep; cp++)
+                       ;
+               if (last != cp) {
+                       /* 43 = 40-byte + 2 '/' + terminating NUL */
+                       int pfxlen = cp - last;
+                       int entlen = pfxlen + 43;
+
+                       if (*last != '/' && relative_base) {
+                               /* Relative alt-odb */
+                               if (base_len < 0)
+                                       base_len = strlen(relative_base) + 1;
+                               entlen += base_len;
+                               pfxlen += base_len;
+                       }
+                       ent = xmalloc(sizeof(*ent) + entlen);
+                       *alt_odb_tail = ent;
+                       alt_odb_tail = &(ent->next);
+                       ent->next = NULL;
+                       if (*last != '/' && relative_base) {
+                               memcpy(ent->base, relative_base, base_len - 1);
+                               ent->base[base_len - 1] = '/';
+                               memcpy(ent->base + base_len,
+                                      last, cp - last);
+                       }
+                       else
+                               memcpy(ent->base, last, pfxlen);
+                       ent->name = ent->base + pfxlen + 1;
+                       ent->base[pfxlen] = ent->base[pfxlen + 3] = '/';
+                       ent->base[entlen-1] = 0;
+               }
+               while (cp < ep && *cp == sep)
+                       cp++;
+               last = cp;
+       }
+}
+
+void prepare_alt_odb(void)
+{
+       char path[PATH_MAX];
+       char *map;
+       int fd;
+       struct stat st;
+       char *alt;
+
+       alt = getenv(ALTERNATE_DB_ENVIRONMENT);
+       if (!alt) alt = "";
 
-       if (alt_odb)
+       if (alt_odb_tail)
+               return;
+       alt_odb_tail = &alt_odb_list;
+       link_alt_odb_entries(alt, alt + strlen(alt), ':', NULL);
+
+       sprintf(path, "%s/info/alternates", get_object_directory());
+       fd = open(path, O_RDONLY);
+       if (fd < 0)
+               return;
+       if (fstat(fd, &st) || (st.st_size == 0)) {
+               close(fd);
                return;
-       /* The first pass counts how large an area to allocate to
-        * hold the entire alt_odb structure, including array of
-        * structs and path buffers for them.  The second pass fills
-        * the structure and prepares the path buffers for use by
-        * fill_sha1_path().
-        */
-       for (totlen = pass = 0; pass < 2; pass++) {
-               last = alt;
-               i = 0;
-               do {
-                       cp = strchr(last, ':') ? : last + strlen(last);
-                       if (last != cp) {
-                               /* 43 = 40-byte + 2 '/' + terminating NUL */
-                               int pfxlen = cp - last;
-                               int entlen = pfxlen + 43;
-                               if (pass == 0)
-                                       totlen += entlen;
-                               else {
-                                       alt_odb[i].base = op;
-                                       alt_odb[i].name = op + pfxlen + 1;
-                                       memcpy(op, last, pfxlen);
-                                       op[pfxlen] = op[pfxlen + 3] = '/';
-                                       op[entlen-1] = 0;
-                                       op += entlen;
-                               }
-                               i++;
-                       }
-                       while (*cp && *cp == ':')
-                               cp++;
-                       last = cp;
-               } while (*cp);
-               if (pass)
-                       break;
-               alt_odb = xmalloc(sizeof(*alt_odb) * (i + 1) + totlen);
-               alt_odb[i].base = alt_odb[i].name = NULL;
-               op = (char*)(&alt_odb[i+1]);
        }
+       map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
+       close(fd);
+       if (map == MAP_FAILED)
+               return;
+
+       link_alt_odb_entries(map, map + st.st_size, '\n',
+                            get_object_directory());
+       munmap(map, st.st_size);
 }
 
 static char *find_sha1_file(const unsigned char *sha1, struct stat *st)
 {
-       int i;
        char *name = sha1_file_name(sha1);
+       struct alternate_object_database *alt;
 
        if (!stat(name, st))
                return name;
        prepare_alt_odb();
-       for (i = 0; (name = alt_odb[i].name) != NULL; i++) {
+       for (alt = alt_odb_list; alt; alt = alt->next) {
+               name = alt->name;
                fill_sha1_path(name, sha1);
-               if (!stat(alt_odb[i].base, st))
-                       return alt_odb[i].base;
+               if (!stat(alt->base, st))
+                       return alt->base;
        }
        return NULL;
 }
@@ -460,12 +508,18 @@ struct packed_git *add_packed_git(char *path, int path_len)
 
 struct packed_git *parse_pack_index(unsigned char *sha1)
 {
+       char *path = sha1_pack_index_name(sha1);
+       return parse_pack_index_file(sha1, path);
+}
+
+struct packed_git *parse_pack_index_file(const unsigned char *sha1, char *idx_path)
+{
        struct packed_git *p;
        unsigned long idx_size;
        void *idx_map;
-       char *path = sha1_pack_index_name(sha1);
+       char *path;
 
-       if (check_packed_git_idx(path, &idx_size, &idx_map))
+       if (check_packed_git_idx(idx_path, &idx_size, &idx_map))
                return NULL;
 
        path = sha1_pack_name(sha1);
@@ -522,18 +576,18 @@ static void prepare_packed_git_one(char *objdir)
 
 void prepare_packed_git(void)
 {
-       int i;
        static int run_once = 0;
+       struct alternate_object_database *alt;
 
-       if (run_once++)
+       if (run_once)
                return;
-
        prepare_packed_git_one(get_object_directory());
        prepare_alt_odb();
-       for (i = 0; alt_odb[i].base != NULL; i++) {
-               alt_odb[i].name[0] = 0;
-               prepare_packed_git_one(alt_odb[i].base);
+       for (alt = alt_odb_list; alt; alt = alt->next) {
+               alt->name[0] = 0;
+               prepare_packed_git_one(alt->base);
        }
+       run_once = 1;
 }
 
 int check_sha1_signature(const unsigned char *sha1, void *map, unsigned long size, const char *type)
@@ -819,7 +873,8 @@ void packed_object_info_detail(struct pack_entry *e,
                strcpy(type, "tag");
                break;
        default:
-               die("corrupted pack file");
+               die("corrupted pack file %s containing object of kind %d",
+                   p->pack_name, kind);
        }
        *store_size = 0; /* notyet */
 }
@@ -858,7 +913,8 @@ static int packed_object_info(struct pack_entry *entry,
                strcpy(type, "tag");
                break;
        default:
-               die("corrupted pack file");
+               die("corrupted pack file %s containing object of kind %d",
+                   p->pack_name, kind);
        }
        if (sizep)
                *sizep = size;
@@ -958,7 +1014,7 @@ static void *unpack_entry(struct pack_entry *entry,
        retval = unpack_entry_gently(entry, type, sizep);
        unuse_packed_git(p);
        if (!retval)
-               die("corrupted pack file");
+               die("corrupted pack file %s", p->pack_name);
        return retval;
 }