mkdelta.con commit [PATCH] Fix tweak in similarity estimator. (cd1870e)
   1/*
   2 * Deltafication of a GIT database.
   3 *
   4 * (C) 2005 Nicolas Pitre <nico@cam.org>
   5 *
   6 * This code is free software; you can redistribute it and/or modify
   7 * it under the terms of the GNU General Public License version 2 as
   8 * published by the Free Software Foundation.
   9 */
  10
  11#include "cache.h"
  12#include "delta.h"
  13
  14static int replace_object(char *buf, unsigned long size, unsigned char *sha1)
  15{
  16        char tmpfile[PATH_MAX];
  17        int fd;
  18
  19        snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
  20        fd = mkstemp(tmpfile);
  21        if (fd < 0)
  22                return error("%s: %s\n", tmpfile, strerror(errno));
  23        if (write(fd, buf, size) != size) {
  24                perror("unable to write file");
  25                close(fd);
  26                unlink(tmpfile);
  27                return -1;
  28        }
  29        fchmod(fd, 0444);
  30        close(fd);
  31        if (rename(tmpfile, sha1_file_name(sha1))) {
  32                perror("unable to replace original object");
  33                unlink(tmpfile);
  34                return -1;
  35        }
  36        return 0;
  37}
  38
  39static void *create_object(char *buf, unsigned long len, char *hdr, int hdrlen,
  40                           unsigned long *retsize)
  41{
  42        char *compressed;
  43        unsigned long size;
  44        z_stream stream;
  45
  46        /* Set it up */
  47        memset(&stream, 0, sizeof(stream));
  48        deflateInit(&stream, Z_BEST_COMPRESSION);
  49        size = deflateBound(&stream, len+hdrlen);
  50        compressed = xmalloc(size);
  51
  52        /* Compress it */
  53        stream.next_out = compressed;
  54        stream.avail_out = size;
  55
  56        /* First header.. */
  57        stream.next_in = hdr;
  58        stream.avail_in = hdrlen;
  59        while (deflate(&stream, 0) == Z_OK)
  60                /* nothing */;
  61
  62        /* Then the data itself.. */
  63        stream.next_in = buf;
  64        stream.avail_in = len;
  65        while (deflate(&stream, Z_FINISH) == Z_OK)
  66                /* nothing */;
  67        deflateEnd(&stream);
  68        *retsize = stream.total_out;
  69        return compressed;
  70}
  71
  72static int restore_original_object(char *buf, unsigned long len,
  73                                   char *type, unsigned char *sha1)
  74{
  75        char hdr[50];
  76        int hdrlen, ret;
  77        void *compressed;
  78        unsigned long size;
  79
  80        hdrlen = sprintf(hdr, "%s %lu", type, len)+1;
  81        compressed = create_object(buf, len, hdr, hdrlen, &size);
  82        ret = replace_object(compressed, size, sha1);
  83        free(compressed);
  84        return ret;
  85}
  86
  87static void *create_delta_object(char *buf, unsigned long len,
  88                                 unsigned char *sha1_ref, unsigned long *size)
  89{
  90        char hdr[50];
  91        int hdrlen;
  92
  93        /* Generate the header + sha1 of reference for delta */
  94        hdrlen = sprintf(hdr, "delta %lu", len+20)+1;
  95        memcpy(hdr + hdrlen, sha1_ref, 20);
  96        hdrlen += 20;
  97
  98        return create_object(buf, len, hdr, hdrlen, size);
  99}
 100
 101static unsigned long get_object_size(unsigned char *sha1)
 102{
 103        struct stat st;
 104        if (stat(sha1_file_name(sha1), &st))
 105                die("%s: %s", sha1_to_hex(sha1), strerror(errno));
 106        return st.st_size;
 107}
 108
 109static void *get_buffer(unsigned char *sha1, char *type, unsigned long *size)
 110{
 111        unsigned long mapsize;
 112        void *map = map_sha1_file(sha1, &mapsize);
 113        if (map) {
 114                void *buffer = unpack_sha1_file(map, mapsize, type, size);
 115                munmap(map, mapsize);
 116                if (buffer)
 117                        return buffer;
 118        }
 119        error("unable to get object %s", sha1_to_hex(sha1));
 120        return NULL;
 121}
 122
 123static void *expand_delta(void *delta, unsigned long delta_size, char *type,
 124                          unsigned long *size, unsigned int *depth, char *head)
 125{
 126        void *buf = NULL;
 127        *depth++;
 128        if (delta_size < 20) {
 129                error("delta object is bad");
 130                free(delta);
 131        } else {
 132                unsigned long ref_size;
 133                void *ref = get_buffer(delta, type, &ref_size);
 134                if (ref && !strcmp(type, "delta"))
 135                        ref = expand_delta(ref, ref_size, type, &ref_size,
 136                                           depth, head);
 137                else
 138                        memcpy(head, delta, 20);
 139                if (ref)
 140                        buf = patch_delta(ref, ref_size, delta+20,
 141                                          delta_size-20, size);
 142                free(ref);
 143                free(delta);
 144        }
 145        return buf;
 146}
 147
 148static char *mkdelta_usage =
 149"mkdelta [ --max-depth=N ] <reference_sha1> <target_sha1> [ <next_sha1> ... ]";
 150
 151int main(int argc, char **argv)
 152{
 153        unsigned char sha1_ref[20], sha1_trg[20], head_ref[20], head_trg[20];
 154        char type_ref[20], type_trg[20];
 155        void *buf_ref, *buf_trg, *buf_delta;
 156        unsigned long size_ref, size_trg, size_orig, size_delta;
 157        unsigned int depth_ref, depth_trg, depth_max = -1;
 158        int i, verbose = 0;
 159
 160        for (i = 1; i < argc; i++) {
 161                if (!strcmp(argv[i], "-v")) {
 162                        verbose = 1;
 163                } else if (!strcmp(argv[i], "-d") && i+1 < argc) {
 164                        depth_max = atoi(argv[++i]);
 165                } else if (!strncmp(argv[i], "--max-depth=", 12)) {
 166                        depth_max = atoi(argv[i]+12);
 167                } else
 168                        break;
 169        }
 170
 171        if (i + (depth_max != 0) >= argc)
 172                usage(mkdelta_usage);
 173
 174        if (get_sha1(argv[i], sha1_ref))
 175                die("bad sha1 %s", argv[i]);
 176        depth_ref = 0;
 177        buf_ref = get_buffer(sha1_ref, type_ref, &size_ref);
 178        if (buf_ref && !strcmp(type_ref, "delta"))
 179                buf_ref = expand_delta(buf_ref, size_ref, type_ref,
 180                                       &size_ref, &depth_ref, head_ref);
 181        else
 182                memcpy(head_ref, sha1_ref, 20);
 183        if (!buf_ref)
 184                die("unable to obtain initial object %s", argv[i]);
 185
 186        if (depth_ref > depth_max) {
 187                if (restore_original_object(buf_ref, size_ref, type_ref, sha1_ref))
 188                        die("unable to restore %s", argv[i]);
 189                if (verbose)
 190                        printf("undelta %s (depth was %d)\n", argv[i], depth_ref);
 191                depth_ref = 0;
 192        }
 193
 194        /*
 195         * TODO: deltafication should be tried against any early object
 196         * in the object list and not only the previous object.
 197         */
 198
 199        while (++i < argc) {
 200                if (get_sha1(argv[i], sha1_trg))
 201                        die("bad sha1 %s", argv[i]);
 202                depth_trg = 0;
 203                buf_trg = get_buffer(sha1_trg, type_trg, &size_trg);
 204                if (buf_trg && !size_trg) {
 205                        if (verbose)
 206                                printf("skip    %s (object is empty)\n", argv[i]);
 207                        continue;
 208                }
 209                size_orig = size_trg;
 210                if (buf_trg && !strcmp(type_trg, "delta")) {
 211                        if (!memcmp(buf_trg, sha1_ref, 20)) {
 212                                /* delta already in place */
 213                                depth_ref++;
 214                                memcpy(sha1_ref, sha1_trg, 20);
 215                                buf_ref = patch_delta(buf_ref, size_ref,
 216                                                      buf_trg+20, size_trg-20,
 217                                                      &size_ref);
 218                                if (!buf_ref)
 219                                        die("unable to apply delta %s", argv[i]);
 220                                if (depth_ref > depth_max) {
 221                                        if (restore_original_object(buf_ref, size_ref,
 222                                                                    type_ref, sha1_ref))
 223                                                die("unable to restore %s", argv[i]);
 224                                        if (verbose)
 225                                                printf("undelta %s (depth was %d)\n", argv[i], depth_ref);
 226                                        depth_ref = 0;
 227                                        continue;
 228                                }
 229                                if (verbose)
 230                                        printf("skip    %s (delta already in place)\n", argv[i]);
 231                                continue;
 232                        }
 233                        buf_trg = expand_delta(buf_trg, size_trg, type_trg,
 234                                               &size_trg, &depth_trg, head_trg);
 235                } else
 236                        memcpy(head_trg, sha1_trg, 20);
 237                if (!buf_trg)
 238                        die("unable to read target object %s", argv[i]);
 239
 240                if (depth_trg > depth_max) {
 241                        if (restore_original_object(buf_trg, size_trg, type_trg, sha1_trg))
 242                                die("unable to restore %s", argv[i]);
 243                        if (verbose)
 244                                printf("undelta %s (depth was %d)\n", argv[i], depth_trg);
 245                        depth_trg = 0;
 246                        size_orig = size_trg;
 247                }
 248
 249                if (depth_max == 0)
 250                        goto skip;
 251
 252                if (strcmp(type_ref, type_trg))
 253                        die("type mismatch for object %s", argv[i]);
 254
 255                if (!size_ref) {
 256                        if (verbose)
 257                                printf("skip    %s (initial object is empty)\n", argv[i]);
 258                        goto skip;
 259                }
 260                
 261                if (depth_ref + 1 > depth_max) {
 262                        if (verbose)
 263                                printf("skip    %s (exceeding max link depth)\n", argv[i]);
 264                        goto skip;
 265                }
 266
 267                if (!memcmp(head_ref, sha1_trg, 20)) {
 268                        if (verbose)
 269                                printf("skip    %s (would create a loop)\n", argv[i]);
 270                        goto skip;
 271                }
 272
 273                buf_delta = diff_delta(buf_ref, size_ref, buf_trg, size_trg, &size_delta);
 274                if (!buf_delta)
 275                        die("out of memory");
 276
 277                /* no need to even try to compress if original
 278                   uncompressed is already smaller */
 279                if (size_delta+20 < size_orig) {
 280                        void *buf_obj;
 281                        unsigned long size_obj;
 282                        buf_obj = create_delta_object(buf_delta, size_delta,
 283                                                      sha1_ref, &size_obj);
 284                        free(buf_delta);
 285                        size_orig = get_object_size(sha1_trg);
 286                        if (size_obj >= size_orig) {
 287                                free(buf_obj);
 288                                if (verbose)
 289                                        printf("skip    %s (original is smaller)\n", argv[i]);
 290                                goto skip;
 291                        }
 292                        if (replace_object(buf_obj, size_obj, sha1_trg))
 293                                die("unable to write delta for %s", argv[i]);
 294                        free(buf_obj);
 295                        depth_ref++;
 296                        if (verbose)
 297                                printf("delta   %s (size=%ld.%02ld%%, depth=%d)\n",
 298                                       argv[i], size_obj*100 / size_orig,
 299                                       (size_obj*10000 / size_orig)%100,
 300                                       depth_ref);
 301                } else {
 302                        free(buf_delta);
 303                        if (verbose)
 304                                printf("skip    %s (original is smaller)\n", argv[i]);
 305                        skip:
 306                        depth_ref = depth_trg;
 307                        memcpy(head_ref, head_trg, 20);
 308                }
 309
 310                free(buf_ref);
 311                buf_ref = buf_trg;
 312                size_ref = size_trg;
 313                memcpy(sha1_ref, sha1_trg, 20);
 314        }
 315
 316        return 0;
 317}