--- /dev/null
+#include "cache.h"
+#include "object.h"
+#include "delta.h"
+
+static const char pack_usage[] = "git-pack-objects [--window=N] base-name < object-list";
+
+enum object_type {
+ OBJ_NONE,
+ OBJ_COMMIT,
+ OBJ_TREE,
+ OBJ_BLOB,
+ OBJ_DELTA // NOTE! This is _not_ the same as a "delta" object in the filesystem
+};
+
+struct object_entry {
+ unsigned char sha1[20];
+ unsigned long size;
+ unsigned long offset;
+ unsigned int depth;
+ unsigned int flags;
+ enum object_type type;
+ unsigned long delta_size;
+ struct object_entry *delta;
+};
+
+static struct object_entry **sorted_by_sha, **sorted_by_type;
+static struct object_entry *objects = NULL;
+static int nr_objects = 0, nr_alloc = 0;
+static int delta_window = 10;
+static const char *base_name;
+
+struct myfile {
+ int fd;
+ unsigned long chars;
+ unsigned char buffer[8192];
+};
+
+static FILE *create_file(const char *suffix)
+{
+ static char filename[PATH_MAX];
+ unsigned len;
+
+ len = snprintf(filename, PATH_MAX, "%s.%s", base_name, suffix);
+ if (len >= PATH_MAX)
+ die("you wascally wabbit, you");
+ return fopen(filename, "w");
+}
+
+static unsigned long fwrite_compressed(void *in, unsigned long size, FILE *f)
+{
+ z_stream stream;
+ unsigned long maxsize;
+ void *out;
+
+ memset(&stream, 0, sizeof(stream));
+ deflateInit(&stream, Z_DEFAULT_COMPRESSION);
+ maxsize = deflateBound(&stream, size);
+ out = xmalloc(maxsize);
+
+ /* Compress it */
+ stream.next_in = in;
+ stream.avail_in = size;
+
+ stream.next_out = out;
+ stream.avail_out = maxsize;
+
+ while (deflate(&stream, Z_FINISH) == Z_OK)
+ /* nothing */;
+ deflateEnd(&stream);
+
+ size = stream.total_out;
+ fwrite(out, size, 1, f);
+ free(out);
+ return size;
+}
+
+static void *delta_against(void *buf, unsigned long size, struct object_entry *entry)
+{
+ unsigned long othersize, delta_size;
+ char type[10];
+ void *otherbuf = read_sha1_file(entry->delta->sha1, type, &othersize);
+ void *delta_buf;
+
+ if (!otherbuf)
+ die("unable to read %s", sha1_to_hex(entry->delta->sha1));
+ delta_buf = diff_delta(buf, size, otherbuf, othersize, &delta_size);
+ if (delta_size != entry->delta_size)
+ die("delta size changed");
+ free(buf);
+ free(otherbuf);
+ return delta_buf;
+}
+
+static unsigned long write_object(FILE *f, struct object_entry *entry)
+{
+ unsigned long size;
+ char type[10];
+ void *buf = read_sha1_file(entry->sha1, type, &size);
+ char header[21];
+ unsigned hdrlen, datalen;
+
+ if (!buf)
+ die("unable to read %s", sha1_to_hex(entry->sha1));
+ if (size != entry->size)
+ die("object %s size inconsistency (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
+
+ /*
+ * The object header is a byte of 'type' followed by four bytes of
+ * length, except for deltas that has the 20 bytes of delta sha
+ * instead.
+ */
+ header[0] = ".CTB"[entry->type];
+ datalen = htonl(size);
+ memcpy(header+1, &datalen, 4);
+ hdrlen = 5;
+ if (entry->delta) {
+ memcpy(header+1, entry->delta, 20);
+ buf = delta_against(buf, size, entry);
+ size = entry->delta_size;
+ hdrlen = 21;
+ }
+ fwrite(header, hdrlen, 1, f);
+ datalen = fwrite_compressed(buf, size, f);
+ free(buf);
+ return hdrlen + datalen;
+}
+
+static void write_pack_file(void)
+{
+ int i;
+ FILE *f = create_file("pack");
+ unsigned long offset = 0;
+ unsigned long mb;
+
+ for (i = 0; i < nr_objects; i++) {
+ struct object_entry *entry = objects + i;
+ entry->offset = offset;
+ offset += write_object(f, entry);
+ }
+ fclose(f);
+ mb = offset >> 20;
+ offset &= 0xfffff;
+}
+
+static void write_index_file(void)
+{
+ int i;
+ FILE *f = create_file("idx");
+ struct object_entry **list = sorted_by_sha;
+ struct object_entry **last = list + nr_objects;
+ unsigned int array[256];
+
+ /*
+ * Write the first-level table (the list is sorted,
+ * but we use a 256-entry lookup to be able to avoid
+ * having to do eight extra binary search iterations)
+ */
+ for (i = 0; i < 256; i++) {
+ struct object_entry **next = list;
+ while (next < last) {
+ struct object_entry *entry = *next;
+ if (entry->sha1[0] != i)
+ break;
+ next++;
+ }
+ array[i] = htonl(next - sorted_by_sha);
+ list = next;
+ }
+ fwrite(array, 256, sizeof(int), f);
+
+ /*
+ * Write the actual SHA1 entries..
+ */
+ list = sorted_by_sha;
+ for (i < 0; i < nr_objects; i++) {
+ struct object_entry *entry = *list++;
+ unsigned int offset = htonl(entry->offset);
+ fwrite(&offset, 4, 1, f);
+ fwrite(entry->sha1, 20, 1, f);
+ }
+ fclose(f);
+}
+
+static void add_object_entry(unsigned char *sha1)
+{
+ unsigned int idx = nr_objects;
+ struct object_entry *entry;
+
+ if (idx >= nr_alloc) {
+ unsigned int needed = (idx + 1024) * 3 / 2;
+ objects = xrealloc(objects, needed * sizeof(*entry));
+ nr_alloc = needed;
+ }
+ entry = objects + idx;
+ memset(entry, 0, sizeof(*entry));
+ memcpy(entry->sha1, sha1, 20);
+ nr_objects = idx+1;
+}
+
+static void check_object(struct object_entry *entry)
+{
+ char buffer[128];
+ char type[10];
+ unsigned long mapsize;
+ z_stream stream;
+ void *map;
+
+ map = map_sha1_file(entry->sha1, &mapsize);
+ if (!map)
+ die("unable to map %s", sha1_to_hex(entry->sha1));
+ if (unpack_sha1_header(&stream, map, mapsize, buffer, sizeof(buffer)) < 0)
+ die("unable to unpack %s header", sha1_to_hex(entry->sha1));
+ munmap(map, mapsize);
+ if (parse_sha1_header(buffer, type, &entry->size) < 0)
+ die("unable to parse %s header", sha1_to_hex(entry->sha1));
+ if (!strcmp(type, "commit")) {
+ entry->type = OBJ_COMMIT;
+ } else if (!strcmp(type, "tree")) {
+ entry->type = OBJ_TREE;
+ } else if (!strcmp(type, "blob")) {
+ entry->type = OBJ_BLOB;
+ } else
+ die("unable to pack object %s of type %s", sha1_to_hex(entry->sha1), type);
+}
+
+static void get_object_details(void)
+{
+ int i;
+ struct object_entry *entry = objects;
+
+ for (i = 0; i < nr_objects; i++)
+ check_object(entry++);
+}
+
+typedef int (*entry_sort_t)(const struct object_entry *, const struct object_entry *);
+
+static entry_sort_t current_sort;
+
+static int sort_comparator(const void *_a, const void *_b)
+{
+ struct object_entry *a = *(struct object_entry **)_a;
+ struct object_entry *b = *(struct object_entry **)_b;
+ return current_sort(a,b);
+}
+
+static struct object_entry **create_sorted_list(entry_sort_t sort)
+{
+ struct object_entry **list = xmalloc(nr_objects * sizeof(struct object_entry *));
+ int i;
+
+ for (i = 0; i < nr_objects; i++)
+ list[i] = objects + i;
+ current_sort = sort;
+ qsort(list, nr_objects, sizeof(struct object_entry *), sort_comparator);
+ return list;
+}
+
+static int sha1_sort(const struct object_entry *a, const struct object_entry *b)
+{
+ return memcmp(a->sha1, b->sha1, 20);
+}
+
+static int type_size_sort(const struct object_entry *a, const struct object_entry *b)
+{
+ if (a->type < b->type)
+ return -1;
+ if (a->type > b->type)
+ return 1;
+ if (a->size < b->size)
+ return -1;
+ if (a->size > b->size)
+ return 1;
+ return a < b ? -1 : (a > b);
+}
+
+struct unpacked {
+ struct object_entry *entry;
+ void *data;
+};
+
+/*
+ * We search for deltas in a list sorted by type and by size, and
+ * walk the "old" chain backwards in the list, so if the type
+ * has changed or the size difference is too big, there's no point
+ * in even continuing the walk, since the other old objects are
+ * going to be even smaller or of a different type. So return -1
+ * once we determine that there's no point even trying.
+ */
+static int try_delta(struct unpacked *cur, struct unpacked *old)
+{
+ struct object_entry *cur_entry = cur->entry;
+ struct object_entry *old_entry = old->entry;
+ unsigned long size, oldsize, delta_size;
+ void *delta_buf;
+
+ /* Don't bother doing diffs between different types */
+ if (cur_entry->type != old_entry->type)
+ return -1;
+
+ /* Size is guaranteed to be larger than or equal to oldsize */
+ size = cur_entry->size;
+ oldsize = old_entry->size;
+ if (size - oldsize > oldsize / 4)
+ return -1;
+
+ /*
+ * NOTE!
+ *
+ * We always delta from the bigger to the smaller, since that's
+ * more space-efficient (deletes don't have to say _what_ they
+ * delete).
+ */
+ delta_buf = diff_delta(cur->data, size, old->data, oldsize, &delta_size);
+ if (!delta_buf)
+ die("unable to create delta");
+ if (delta_size + 20 < size / 2) {
+ if (!cur_entry->delta || cur_entry->delta_size > delta_size) {
+ cur_entry->delta = old_entry;
+ cur_entry->delta_size = delta_size;
+ }
+ }
+ free(delta_buf);
+}
+
+static void find_deltas(struct object_entry **list, int window)
+{
+ unsigned int i;
+ unsigned int array_size = window * sizeof(struct unpacked);
+ struct unpacked *array = xmalloc(array_size);
+
+ memset(array, 0, array_size);
+ for (i = 0; i < nr_objects; i++) {
+ unsigned int idx = i % window;
+ struct object_entry *entry = list[i];
+ struct unpacked *n = array + idx;
+ unsigned long size;
+ char type[10];
+ int j;
+
+ free(n->data);
+ n->entry = entry;
+ n->data = read_sha1_file(entry->sha1, type, &size);
+ if (size != entry->size)
+ die("object %s inconsistent object length (%lu vs %lu)", sha1_to_hex(entry->sha1), size, entry->size);
+ for (j = 0; j < window; j++) {
+ unsigned int other_idx = idx - 1 - j;
+ struct unpacked *m;
+ if (other_idx < 0)
+ other_idx += window;
+ m = array + other_idx;
+ if (!m->entry)
+ break;
+ if (try_delta(n, m) < 0)
+ break;
+ }
+ }
+}
+
+int main(int argc, char **argv)
+{
+ char line[128];
+ int i;
+
+ for (i = 1; i < argc; i++) {
+ const char *arg = argv[i];
+
+ if (*arg == '-') {
+ if (!strncmp("--window=", arg, 9)) {
+ char *end;
+ delta_window = strtoul(arg+9, &end, 0);
+ if (!arg[9] || *end)
+ usage(pack_usage);
+ continue;
+ }
+ usage(pack_usage);
+ }
+ if (base_name)
+ usage(pack_usage);
+ base_name = arg;
+ }
+
+ if (!base_name)
+ usage(pack_usage);
+
+ while (fgets(line, sizeof(line), stdin) != NULL) {
+ unsigned char sha1[20];
+ if (get_sha1_hex(line, sha1))
+ die("expected sha1, got garbage");
+ add_object_entry(sha1);
+ }
+ get_object_details();
+
+ printf("Packing %d objects\n", nr_objects);
+
+ sorted_by_sha = create_sorted_list(sha1_sort);
+ sorted_by_type = create_sorted_list(type_size_sort);
+ if (delta_window)
+ find_deltas(sorted_by_type, delta_window);
+
+ write_pack_file();
+ write_index_file();
+ return 0;
+}
projects / git.git / commitdiff