git-unpack-objects: re-write to read from stdin

It gets a bit more complicated to unpack in a streaming environment, but
here it is.  The rewrite is actually a lot cleaner in other ways, it's
just a bit more subtle.

diff --git a/unpack-objects.c b/unpack-objects.c
index fbc899408e78c18b5cfeae00ad66927e3ef25053..0892d2b920cbf5b3456867aaaabe45f7599edcc0 100644 (file)
--- a/unpack-objects.c
+++ b/unpack-objects.c
@@ -4,278 +4,213 @@
 #include "pack.h"
 
 static int dry_run;
-static int nr_entries;
-static const char *base_name;
-static const char unpack_usage[] = "git-unpack-objects basename";
+static const char unpack_usage[] = "git-unpack-objects < pack-file";
 
-struct pack_entry {
-       unsigned int offset; /* network byte order */
-       unsigned char sha1[20];
-};
+/* We always read in 4kB chunks. */
+static unsigned char buffer[4096];
+static unsigned long offset, len, eof;
+static SHA_CTX ctx;
 
-static void *pack_base;
-static unsigned long pack_size;
-static void *index_base;
-static unsigned long index_size;
+/*
+ * Make sure at least "min" bytes are available in the buffer, and
+ * return the pointer to the buffer.
+ */
+static void * fill(int min)
+{
+       if (min <= len)
+               return buffer + offset;
+       if (eof)
+               die("unable to fill input");
+       if (min > sizeof(buffer))
+               die("cannot fill %d bytes", min);
+       if (offset) {
+               SHA1_Update(&ctx, buffer, offset);
+               memcpy(buffer, buffer + offset, len);
+               offset = 0;
+       }
+       do {
+               int ret = read(0, buffer + len, sizeof(buffer) - len);
+               if (ret <= 0) {
+                       if (!ret)
+                               die("early EOF");
+                       if (errno == EAGAIN || errno == EINTR)
+                               continue;
+                       die("read error on input: %s", strerror(errno));
+               }
+               len += ret;
+       } while (len < min);
+       return buffer;
+}
 
-static struct pack_entry **pack_list;
+static void use(int bytes)
+{
+       if (bytes > len)
+               die("used more bytes than were available");
+       len -= bytes;
+       offset += bytes;
+}
 
-static void *map_file(const char *suffix, unsigned long *sizep)
+static void *get_data(unsigned long size)
 {
-       static char pathname[PATH_MAX];
-       unsigned long len;
-       int fd;
-       struct stat st;
-       void *map;
-
-       len = snprintf(pathname, PATH_MAX, "%s.%s", base_name, suffix);
-       if (len >= PATH_MAX)
-               die("bad pack base-name");
-       fd = open(pathname, O_RDONLY);
-       if (fd < 0 || fstat(fd, &st))
-               die("unable to open '%s'", pathname);
-       len = st.st_size;
-       if (!len)
-               die("bad pack file '%s'", pathname);
-       map = mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0);
-       if (-1 == (int)(long)map)
-               die("unable to mmap '%s'", pathname);
-       close(fd);
-       *sizep = len;
-       return map;
+       z_stream stream;
+       void *buf = xmalloc(size);
+
+       if (!size)
+               return buf;
+       memset(&stream, 0, sizeof(stream));
+
+       stream.next_out = buf;
+       stream.avail_out = size;
+       stream.next_in = fill(1);
+       stream.avail_in = len;
+       inflateInit(&stream);
+
+       for (;;) {
+               int ret = inflate(&stream, 0);
+               use(len - stream.avail_in);
+               if (stream.total_out == size && ret == Z_STREAM_END)
+                       break;
+               if (ret != Z_OK)
+                       die("inflate returned %d\n", ret);
+               stream.next_in = fill(1);
+               stream.avail_in = len;
+       }
+       return buf;
 }
 
-static int sort_by_offset(const void *_a, const void *_b)
+struct delta_info {
+       unsigned char base_sha1[20];
+       unsigned long size;
+       void *delta;
+       struct delta_info *next;
+};
+
+static struct delta_info *delta_list;
+
+static void add_delta_to_list(unsigned char *base_sha1, void *delta, unsigned long size)
 {
-       struct pack_entry *a = *(struct pack_entry **)_a;
-       struct pack_entry *b = *(struct pack_entry **)_b;
-       unsigned int o1, o2;
+       struct delta_info *info = xmalloc(sizeof(*info));
 
-       o1 = ntohl(a->offset);
-       o2 = ntohl(b->offset);
-       return o1 < o2 ? -1 : 1;
+       memcpy(info->base_sha1, base_sha1, 20);
+       info->size = size;
+       info->delta = delta;
+       info->next = delta_list;
+       delta_list = info;
 }
 
-static int check_index(void)
+static void added_object(unsigned char *sha1, char *type, void *data, unsigned long size);
+
+static int resolve_delta(char *type,
+       void *base, unsigned long base_size, 
+       void *delta, unsigned long delta_size)
 {
-       unsigned int *array = index_base;
-       unsigned int nr;
-       int i;
+       void *result;
+       unsigned long result_size;
+       unsigned char sha1[20];
 
-       if (index_size < 4*256 + 20)
-               return error("index file too small");
-       nr = 0;
-       for (i = 0; i < 256; i++) {
-               unsigned int n = ntohl(array[i]);
-               if (n < nr)
-                       return error("non-monotonic index");
-               nr = n;
-       }
-       /*
-        * Total size:
-        *  - 256 index entries 4 bytes each
-        *  - 24-byte entries * nr (20-byte sha1 + 4-byte offset)
-        *  - 20-byte SHA1 of the packfile
-        *  - 20-byte SHA1 file checksum
-        */
-       if (index_size != 4*256 + nr * 24 + 20 + 20)
-               return error("wrong index file size");
-
-       nr_entries = nr;
-       pack_list = xmalloc(nr * sizeof(struct pack_entry *));
-       for (i = 0; i < nr; i++)
-               pack_list[i] = index_base + 4*256 + i*24;
-
-       qsort(pack_list, nr, sizeof(*pack_list), sort_by_offset);
-
-       printf("%d entries\n", nr);
+       result = patch_delta(base, base_size,
+                            delta, delta_size,
+                            &result_size);
+       if (!result)
+               die("failed to apply delta");
+       free(delta);
+
+       if (write_sha1_file(result, result_size, type, sha1) < 0)
+               die("failed to write object");
+       added_object(sha1, type, result, result_size);
+       free(result);
        return 0;
 }
 
-static int unpack_non_delta_entry(struct pack_entry *entry,
-                                 enum object_type kind,
-                                 unsigned char *data,
-                                 unsigned long size,
-                                 unsigned long left)
+static void added_object(unsigned char *sha1, char *type, void *data, unsigned long size)
 {
-       int st;
-       z_stream stream;
-       char *buffer;
+       struct delta_info **p = &delta_list;
+       struct delta_info *info;
+
+       while ((info = *p) != NULL) {
+               if (!memcmp(info->base_sha1, sha1, 20)) {
+                       *p = info->next;
+                       p = &delta_list;
+                       resolve_delta(type, data, size, info->delta, info->size);
+                       free(info);
+                       continue;
+               }
+               p = &info->next;
+       }
+}
+
+static int unpack_non_delta_entry(enum object_type kind, unsigned long size)
+{
+       void *buf = get_data(size);
        unsigned char sha1[20];
        char *type;
 
-       printf("%s %c %lu\n", sha1_to_hex(entry->sha1), ".CTBGD"[kind], size);
-       if (dry_run)
-               return 0;
-
-       buffer = xmalloc(size + 1);
-       buffer[size] = 0;
-       memset(&stream, 0, sizeof(stream));
-       stream.next_in = data;
-       stream.avail_in = left;
-       stream.next_out = buffer;
-       stream.avail_out = size;
-
-       inflateInit(&stream);
-       st = inflate(&stream, Z_FINISH);
-       inflateEnd(&stream);
-       if ((st != Z_STREAM_END) || stream.total_out != size)
-               goto err_finish;
        switch (kind) {
        case OBJ_COMMIT: type = "commit"; break;
        case OBJ_TREE:   type = "tree"; break;
        case OBJ_BLOB:   type = "blob"; break;
        case OBJ_TAG:    type = "tag"; break;
-       default: goto err_finish;
+       default: die("bad type %d", kind);
        }
-       if (write_sha1_file(buffer, size, type, sha1) < 0)
-               die("failed to write %s (%s)",
-                   sha1_to_hex(entry->sha1), type);
-       printf("%s %s\n", sha1_to_hex(sha1), type);
-       if (memcmp(sha1, entry->sha1, 20))
-               die("resulting %s have wrong SHA1", type);
-
- finish:
-       st = 0;
-       free(buffer);
-       return st;
- err_finish:
-       st = -1;
-       goto finish;
-}
-
-static int find_pack_entry(unsigned char *sha1, struct pack_entry **ent)
-{
-       int *level1_ofs = index_base;
-       int hi = ntohl(level1_ofs[*sha1]);
-       int lo = ((*sha1 == 0x0) ? 0 : ntohl(level1_ofs[*sha1 - 1]));
-       void *index = index_base + 4*256;
-
-       do {
-               int mi = (lo + hi) / 2;
-               int cmp = memcmp(index + 24 * mi + 4, sha1, 20);
-               if (!cmp) {
-                       *ent = index + 24 * mi;
-                       return 1;
-               }
-               if (cmp > 0)
-                       hi = mi;
-               else
-                       lo = mi+1;
-       } while (lo < hi);
+       if (write_sha1_file(buf, size, type, sha1) < 0)
+               die("failed to write object");
+       added_object(sha1, type, buf, size);
+       free(buf);
        return 0;
 }
 
-/* forward declaration for a mutually recursive function */
-static void unpack_entry(struct pack_entry *);
-
-static int unpack_delta_entry(struct pack_entry *entry,
-                             unsigned char *base_sha1,
-                             unsigned long delta_size,
-                             unsigned long left)
+static int unpack_delta_entry(unsigned long delta_size)
 {
-       void *data, *delta_data, *result, *base;
-       unsigned long data_size, result_size, base_size;
-       z_stream stream;
-       int st;
+       void *delta_data, *base;
+       unsigned long base_size;
        char type[20];
-       unsigned char sha1[20];
+       unsigned char base_sha1[20];
 
-       if (left < 20)
-               die("truncated pack file");
-       data = base_sha1 + 20;
-       data_size = left - 20;
-       printf("%s D %lu", sha1_to_hex(entry->sha1), delta_size);
-       printf(" %s\n", sha1_to_hex(base_sha1));
+       memcpy(base_sha1, fill(20), 20);
+       use(20);
 
-       if (dry_run)
-               return 0;
+       delta_data = get_data(delta_size);
 
-       /* pack+5 is the base sha1, unless we have it, we need to
-        * unpack it first.
-        */
        if (!has_sha1_file(base_sha1)) {
-               struct pack_entry *base;
-               if (!find_pack_entry(base_sha1, &base))
-                       die("cannot find delta-pack base object");
-               unpack_entry(base);
+               add_delta_to_list(base_sha1, delta_data, delta_size);
+               return 0;
        }
-       delta_data = xmalloc(delta_size);
-
-       memset(&stream, 0, sizeof(stream));
-
-       stream.next_in = data;
-       stream.avail_in = data_size;
-       stream.next_out = delta_data;
-       stream.avail_out = delta_size;
-
-       inflateInit(&stream);
-       st = inflate(&stream, Z_FINISH);
-       inflateEnd(&stream);
-       if ((st != Z_STREAM_END) || stream.total_out != delta_size)
-               die("delta data unpack failed");
-
        base = read_sha1_file(base_sha1, type, &base_size);
        if (!base)
                die("failed to read delta-pack base object %s", sha1_to_hex(base_sha1));
-       result = patch_delta(base, base_size,
-                            delta_data, delta_size,
-                            &result_size);
-       if (!result)
-               die("failed to apply delta");
-       free(delta_data);
-
-       if (write_sha1_file(result, result_size, type, sha1) < 0)
-               die("failed to write %s (%s)",
-                   sha1_to_hex(entry->sha1), type);
-       free(result);
-       printf("%s %s\n", sha1_to_hex(sha1), type);
-       if (memcmp(sha1, entry->sha1, 20))
-               die("resulting %s have wrong SHA1", type);
-       return 0;
+       return resolve_delta(type, base, base_size, delta_data, delta_size);
 }
 
-static void unpack_entry(struct pack_entry *entry)
+static void unpack_one(void)
 {
-       unsigned long offset, size, left;
        unsigned char *pack, c;
-       int type;
+       unsigned long size;
+       enum object_type type;
 
-       /* Have we done this one already due to deltas based on it? */
-       if (lookup_object(entry->sha1))
-               return;
-
-       offset = ntohl(entry->offset);
-       if (offset >= pack_size)
-               goto bad;
-
-       pack = pack_base + offset;
-       c = *pack++;
-       offset++;
+       pack = fill(1);
+       c = *pack;
+       use(1);
        type = (c >> 4) & 7;
        size = (c & 15);
        while (c & 0x80) {
-               if (offset >= pack_size)
-                       goto bad;
-               offset++;
+               pack = fill(1);
                c = *pack++;
+               use(1);
                size = (size << 7) + (c & 0x7f);
-               
        }
-       left = pack_size - offset;
        switch (type) {
        case OBJ_COMMIT:
        case OBJ_TREE:
        case OBJ_BLOB:
        case OBJ_TAG:
-               unpack_non_delta_entry(entry, type, pack, size, left);
+               unpack_non_delta_entry(type, size);
                return;
        case OBJ_DELTA:
-               unpack_delta_entry(entry, pack, size, left);
+               unpack_delta_entry(size);
                return;
+       default:
+               die("bad object type %d", type);
        }
-bad:
-       die("corrupted pack file");
 }
 
 /*
@@ -285,17 +220,28 @@ bad:
  */
 static void unpack_all(void)
 {
-       int i = nr_entries;
-
-       while (--i >= 0) {
-               struct pack_entry *entry = pack_list[i];
-               unpack_entry(entry);
-       }
+       int i;
+       struct pack_header *hdr = fill(sizeof(struct pack_header));
+       unsigned version = ntohl(hdr->hdr_version);
+       unsigned nr_objects = ntohl(hdr->hdr_entries);
+
+       if (ntohl(hdr->hdr_signature) != PACK_SIGNATURE)
+               die("bad pack file");
+       if (version != 1)
+               die("unable to handle pack file version %d", version);
+       fprintf(stderr, "Unpacking %d objects\n", nr_objects);
+
+       use(sizeof(struct pack_header));
+       for (i = 0; i < nr_objects; i++)
+               unpack_one();
+       if (delta_list)
+               die("unresolved deltas left after unpacking");
 }
 
 int main(int argc, char **argv)
 {
        int i;
+       unsigned char sha1[20];
 
        for (i = 1 ; i < argc; i++) {
                const char *arg = argv[i];
@@ -307,16 +253,32 @@ int main(int argc, char **argv)
                        }
                        usage(unpack_usage);
                }
-               if (base_name)
-                       usage(unpack_usage);
-               base_name = arg;
-       }
-       if (!base_name)
+
+               /* We don't take any non-flag arguments now.. Maybe some day */
                usage(unpack_usage);
-       index_base = map_file("idx", &index_size);
-       pack_base = map_file("pack", &pack_size);
-       if (check_index() < 0)
-               die("bad index file");
+       }
+       SHA1_Init(&ctx);
        unpack_all();
+       SHA1_Update(&ctx, buffer, offset);
+       SHA1_Final(sha1, &ctx);
+       if (memcmp(fill(20), sha1, 20))
+               die("final sha1 did not match");
+       use(20);
+
+       /* Write the last part of the buffer to stdout */
+       while (len) {
+               int ret = write(1, buffer + offset, len);
+               if (!ret)
+                       break;
+               if (ret < 0) {
+                       if (errno == EAGAIN || errno == EINTR)
+                               continue;
+                       break;
+               }
+               len -= ret;
+               offset += ret;
+       }
+
+       /* All done */
        return 0;
 }