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synced 2024-08-26 19:19:18 +00:00
![Junio C Hamano](/assets/img/avatar_default.png)
This changes the generation of hash packfiles have in their names, from "hash of object names as fed to us" to "hash of object names in the resulting pack, in the order they appear in the index file". The new "git-index-pack" command is taught to output the computed hash value to its standard output. With this, we can store downloaded pack in a temporary file without knowing its final name, run git-index-pack to generate idx for it while finding out its final name, and then rename the pack and idx to their final names. Signed-off-by: Junio C Hamano <junkio@cox.net>
463 lines
12 KiB
C
463 lines
12 KiB
C
#include "cache.h"
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#include "delta.h"
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#include "pack.h"
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#include "csum-file.h"
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static const char index_pack_usage[] =
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"git-index-pack [-o index-file] pack-file";
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struct object_entry
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{
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unsigned long offset;
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enum object_type type;
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enum object_type real_type;
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unsigned char sha1[20];
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};
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struct delta_entry
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{
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struct object_entry *obj;
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unsigned char base_sha1[20];
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};
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static const char *pack_name;
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static unsigned char *pack_base;
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static unsigned long pack_size;
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static struct object_entry *objects;
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static struct delta_entry *deltas;
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static int nr_objects;
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static int nr_deltas;
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static void open_pack_file(void)
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{
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int fd;
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struct stat st;
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fd = open(pack_name, O_RDONLY);
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if (fd < 0)
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die("cannot open packfile '%s': %s", pack_name,
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strerror(errno));
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if (fstat(fd, &st)) {
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int err = errno;
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close(fd);
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die("cannot fstat packfile '%s': %s", pack_name,
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strerror(err));
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}
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pack_size = st.st_size;
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pack_base = mmap(NULL, pack_size, PROT_READ, MAP_PRIVATE, fd, 0);
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if (pack_base == MAP_FAILED) {
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int err = errno;
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close(fd);
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die("cannot mmap packfile '%s': %s", pack_name,
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strerror(err));
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}
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close(fd);
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}
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static void parse_pack_header(void)
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{
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const struct pack_header *hdr;
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unsigned char sha1[20];
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SHA_CTX ctx;
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/* Ensure there are enough bytes for the header and final SHA1 */
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if (pack_size < sizeof(struct pack_header) + 20)
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die("packfile '%s' is too small", pack_name);
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/* Header consistency check */
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hdr = (void *)pack_base;
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if (hdr->hdr_signature != htonl(PACK_SIGNATURE))
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die("packfile '%s' signature mismatch", pack_name);
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if (hdr->hdr_version != htonl(PACK_VERSION))
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die("packfile '%s' version %d different from ours %d",
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pack_name, ntohl(hdr->hdr_version), PACK_VERSION);
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nr_objects = ntohl(hdr->hdr_entries);
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/* Check packfile integrity */
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SHA1_Init(&ctx);
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SHA1_Update(&ctx, pack_base, pack_size - 20);
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SHA1_Final(sha1, &ctx);
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if (memcmp(sha1, pack_base + pack_size - 20, 20))
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die("packfile '%s' SHA1 mismatch", pack_name);
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}
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static void bad_object(unsigned long offset, const char *format,
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...) NORETURN __attribute__((format (printf, 2, 3)));
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static void bad_object(unsigned long offset, const char *format, ...)
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{
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va_list params;
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char buf[1024];
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va_start(params, format);
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vsnprintf(buf, sizeof(buf), format, params);
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va_end(params);
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die("packfile '%s': bad object at offset %lu: %s",
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pack_name, offset, buf);
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}
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static void *unpack_entry_data(unsigned long offset,
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unsigned long *current_pos, unsigned long size)
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{
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unsigned long pack_limit = pack_size - 20;
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unsigned long pos = *current_pos;
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z_stream stream;
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void *buf = xmalloc(size);
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memset(&stream, 0, sizeof(stream));
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stream.next_out = buf;
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stream.avail_out = size;
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stream.next_in = pack_base + pos;
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stream.avail_in = pack_limit - pos;
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inflateInit(&stream);
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for (;;) {
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int ret = inflate(&stream, 0);
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if (ret == Z_STREAM_END)
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break;
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if (ret != Z_OK)
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bad_object(offset, "inflate returned %d", ret);
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}
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inflateEnd(&stream);
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if (stream.total_out != size)
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bad_object(offset, "size mismatch (expected %lu, got %lu)",
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size, stream.total_out);
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*current_pos = pack_limit - stream.avail_in;
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return buf;
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}
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static void *unpack_raw_entry(unsigned long offset,
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enum object_type *obj_type,
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unsigned long *obj_size,
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unsigned char *delta_base,
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unsigned long *next_obj_offset)
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{
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unsigned long pack_limit = pack_size - 20;
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unsigned long pos = offset;
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unsigned char c;
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unsigned long size;
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unsigned shift;
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enum object_type type;
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void *data;
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c = pack_base[pos++];
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type = (c >> 4) & 7;
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size = (c & 15);
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shift = 4;
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while (c & 0x80) {
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if (pos >= pack_limit)
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bad_object(offset, "object extends past end of pack");
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c = pack_base[pos++];
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size += (c & 0x7fUL) << shift;
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shift += 7;
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}
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switch (type) {
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case OBJ_DELTA:
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if (pos + 20 >= pack_limit)
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bad_object(offset, "object extends past end of pack");
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memcpy(delta_base, pack_base + pos, 20);
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pos += 20;
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/* fallthru */
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case OBJ_COMMIT:
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case OBJ_TREE:
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case OBJ_BLOB:
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case OBJ_TAG:
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data = unpack_entry_data(offset, &pos, size);
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break;
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default:
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bad_object(offset, "bad object type %d", type);
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}
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*obj_type = type;
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*obj_size = size;
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*next_obj_offset = pos;
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return data;
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}
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static int find_delta(const unsigned char *base_sha1)
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{
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int first = 0, last = nr_deltas;
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while (first < last) {
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int next = (first + last) / 2;
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struct delta_entry *delta = &deltas[next];
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int cmp;
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cmp = memcmp(base_sha1, delta->base_sha1, 20);
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if (!cmp)
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return next;
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if (cmp < 0) {
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last = next;
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continue;
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}
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first = next+1;
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}
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return -first-1;
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}
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static int find_deltas_based_on_sha1(const unsigned char *base_sha1,
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int *first_index, int *last_index)
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{
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int first = find_delta(base_sha1);
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int last = first;
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int end = nr_deltas - 1;
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if (first < 0)
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return -1;
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while (first > 0 && !memcmp(deltas[first-1].base_sha1, base_sha1, 20))
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--first;
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while (last < end && !memcmp(deltas[last+1].base_sha1, base_sha1, 20))
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++last;
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*first_index = first;
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*last_index = last;
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return 0;
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}
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static void sha1_object(const void *data, unsigned long size,
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enum object_type type, unsigned char *sha1)
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{
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SHA_CTX ctx;
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char header[50];
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int header_size;
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const char *type_str;
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switch (type) {
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case OBJ_COMMIT: type_str = "commit"; break;
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case OBJ_TREE: type_str = "tree"; break;
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case OBJ_BLOB: type_str = "blob"; break;
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case OBJ_TAG: type_str = "tag"; break;
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default:
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die("bad type %d", type);
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}
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header_size = sprintf(header, "%s %lu", type_str, size) + 1;
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SHA1_Init(&ctx);
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SHA1_Update(&ctx, header, header_size);
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SHA1_Update(&ctx, data, size);
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SHA1_Final(sha1, &ctx);
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}
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static void resolve_delta(struct delta_entry *delta, void *base_data,
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unsigned long base_size, enum object_type type)
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{
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struct object_entry *obj = delta->obj;
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void *delta_data;
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unsigned long delta_size;
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void *result;
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unsigned long result_size;
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enum object_type delta_type;
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unsigned char base_sha1[20];
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unsigned long next_obj_offset;
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int j, first, last;
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obj->real_type = type;
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delta_data = unpack_raw_entry(obj->offset, &delta_type,
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&delta_size, base_sha1,
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&next_obj_offset);
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result = patch_delta(base_data, base_size, delta_data, delta_size,
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&result_size);
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free(delta_data);
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if (!result)
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bad_object(obj->offset, "failed to apply delta");
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sha1_object(result, result_size, type, obj->sha1);
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if (!find_deltas_based_on_sha1(obj->sha1, &first, &last)) {
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for (j = first; j <= last; j++)
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resolve_delta(&deltas[j], result, result_size, type);
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}
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free(result);
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}
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static int compare_delta_entry(const void *a, const void *b)
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{
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const struct delta_entry *delta_a = a;
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const struct delta_entry *delta_b = b;
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return memcmp(delta_a->base_sha1, delta_b->base_sha1, 20);
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}
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static void parse_pack_objects(void)
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{
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int i;
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unsigned long offset = sizeof(struct pack_header);
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unsigned char base_sha1[20];
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void *data;
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unsigned long data_size;
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/*
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* First pass:
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* - find locations of all objects;
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* - calculate SHA1 of all non-delta objects;
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* - remember base SHA1 for all deltas.
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*/
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for (i = 0; i < nr_objects; i++) {
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struct object_entry *obj = &objects[i];
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obj->offset = offset;
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data = unpack_raw_entry(offset, &obj->type, &data_size,
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base_sha1, &offset);
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obj->real_type = obj->type;
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if (obj->type == OBJ_DELTA) {
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struct delta_entry *delta = &deltas[nr_deltas++];
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delta->obj = obj;
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memcpy(delta->base_sha1, base_sha1, 20);
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} else
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sha1_object(data, data_size, obj->type, obj->sha1);
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free(data);
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}
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if (offset != pack_size - 20)
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die("packfile '%s' has junk at the end", pack_name);
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/* Sort deltas by base SHA1 for fast searching */
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qsort(deltas, nr_deltas, sizeof(struct delta_entry),
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compare_delta_entry);
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/*
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* Second pass:
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* - for all non-delta objects, look if it is used as a base for
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* deltas;
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* - if used as a base, uncompress the object and apply all deltas,
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* recursively checking if the resulting object is used as a base
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* for some more deltas.
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*/
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for (i = 0; i < nr_objects; i++) {
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struct object_entry *obj = &objects[i];
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int j, first, last;
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if (obj->type == OBJ_DELTA)
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continue;
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if (find_deltas_based_on_sha1(obj->sha1, &first, &last))
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continue;
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data = unpack_raw_entry(obj->offset, &obj->type, &data_size,
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base_sha1, &offset);
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for (j = first; j <= last; j++)
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resolve_delta(&deltas[j], data, data_size, obj->type);
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free(data);
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}
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/* Check for unresolved deltas */
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for (i = 0; i < nr_deltas; i++) {
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if (deltas[i].obj->real_type == OBJ_DELTA)
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die("packfile '%s' has unresolved deltas", pack_name);
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}
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}
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static int sha1_compare(const void *_a, const void *_b)
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{
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struct object_entry *a = *(struct object_entry **)_a;
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struct object_entry *b = *(struct object_entry **)_b;
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return memcmp(a->sha1, b->sha1, 20);
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}
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static void write_index_file(const char *index_name, unsigned char *sha1)
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{
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struct sha1file *f;
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struct object_entry **sorted_by_sha =
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xcalloc(nr_objects, sizeof(struct object_entry *));
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struct object_entry **list = sorted_by_sha;
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struct object_entry **last = sorted_by_sha + nr_objects;
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unsigned int array[256];
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int i;
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SHA_CTX ctx;
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for (i = 0; i < nr_objects; ++i)
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sorted_by_sha[i] = &objects[i];
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qsort(sorted_by_sha, nr_objects, sizeof(sorted_by_sha[0]),
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sha1_compare);
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unlink(index_name);
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f = sha1create("%s", index_name);
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/*
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* Write the first-level table (the list is sorted,
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* but we use a 256-entry lookup to be able to avoid
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* having to do eight extra binary search iterations).
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*/
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for (i = 0; i < 256; i++) {
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struct object_entry **next = list;
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while (next < last) {
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struct object_entry *obj = *next;
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if (obj->sha1[0] != i)
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break;
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next++;
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}
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array[i] = htonl(next - sorted_by_sha);
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list = next;
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}
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sha1write(f, array, 256 * sizeof(int));
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/* recompute the SHA1 hash of sorted object names.
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* currently pack-objects does not do this, but that
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* can be fixed.
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*/
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SHA1_Init(&ctx);
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/*
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* Write the actual SHA1 entries..
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*/
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list = sorted_by_sha;
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for (i = 0; i < nr_objects; i++) {
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struct object_entry *obj = *list++;
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unsigned int offset = htonl(obj->offset);
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sha1write(f, &offset, 4);
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sha1write(f, obj->sha1, 20);
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SHA1_Update(&ctx, obj->sha1, 20);
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}
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sha1write(f, pack_base + pack_size - 20, 20);
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sha1close(f, NULL, 1);
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free(sorted_by_sha);
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SHA1_Final(sha1, &ctx);
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}
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int main(int argc, char **argv)
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{
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int i;
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char *index_name = NULL;
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char *index_name_buf = NULL;
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unsigned char sha1[20];
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for (i = 1; i < argc; i++) {
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const char *arg = argv[i];
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if (*arg == '-') {
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if (!strcmp(arg, "-o")) {
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if (index_name || (i+1) >= argc)
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usage(index_pack_usage);
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index_name = argv[++i];
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} else
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usage(index_pack_usage);
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continue;
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}
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if (pack_name)
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usage(index_pack_usage);
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pack_name = arg;
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}
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if (!pack_name)
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usage(index_pack_usage);
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if (!index_name) {
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int len = strlen(pack_name);
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if (len < 5 || strcmp(pack_name + len - 5, ".pack"))
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die("packfile name '%s' does not end with '.pack'",
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pack_name);
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index_name_buf = xmalloc(len - 1);
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memcpy(index_name_buf, pack_name, len - 5);
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strcpy(index_name_buf + len - 5, ".idx");
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index_name = index_name_buf;
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}
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open_pack_file();
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parse_pack_header();
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objects = xcalloc(nr_objects, sizeof(struct object_entry));
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deltas = xcalloc(nr_objects, sizeof(struct delta_entry));
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parse_pack_objects();
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free(deltas);
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write_index_file(index_name, sha1);
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free(objects);
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free(index_name_buf);
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printf("%s\n", sha1_to_hex(sha1));
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return 0;
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}
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