http-walker.c

   1 #include "cache.h"
   2 #include "commit.h"
   3 #include "pack.h"
   4 #include "walker.h"
   5 #include "http.h"
   6
   7 #define PREV_BUF_SIZE 4096
   8 #define RANGE_HEADER_SIZE 30
   9
  10 struct alt_base
  11 {
  12         char *base;
  13         int got_indices;
  14         struct packed_git *packs;
  15         struct alt_base *next;
  16 };
  17
  18 enum object_request_state {
  19         WAITING,
  20         ABORTED,
  21         ACTIVE,
  22         COMPLETE,
  23 };
  24
  25 struct object_request
  26 {
  27         struct walker *walker;
  28         unsigned char sha1[20];
  29         struct alt_base *repo;
  30         char *url;
  31         char filename[PATH_MAX];
  32         char tmpfile[PATH_MAX];
  33         int local;
  34         enum object_request_state state;
  35         CURLcode curl_result;
  36         char errorstr[CURL_ERROR_SIZE];
  37         long http_code;
  38         unsigned char real_sha1[20];
  39         git_SHA_CTX c;
  40         z_stream stream;
  41         int zret;
  42         int rename;
  43         struct active_request_slot *slot;
  44         struct object_request *next;
  45 };
  46
  47 struct alternates_request {
  48         struct walker *walker;
  49         const char *base;
  50         char *url;
  51         struct strbuf *buffer;
  52         struct active_request_slot *slot;
  53         int http_specific;
  54 };
  55
  56 struct walker_data {
  57         const char *url;
  58         int got_alternates;
  59         struct alt_base *alt;
  60         struct curl_slist *no_pragma_header;
  61 };
  62
  63 static struct object_request *object_queue_head;
  64
  65 static size_t fwrite_sha1_file(void *ptr, size_t eltsize, size_t nmemb,
  66                                void *data)
  67 {
  68         unsigned char expn[4096];
  69         size_t size = eltsize * nmemb;
  70         int posn = 0;
  71         struct object_request *obj_req = (struct object_request *)data;
  72         do {
  73                 ssize_t retval = xwrite(obj_req->local,
  74                                         (char *) ptr + posn, size - posn);
  75                 if (retval < 0)
  76                         return posn;
  77                 posn += retval;
  78         } while (posn < size);
  79
  80         obj_req->stream.avail_in = size;
  81         obj_req->stream.next_in = ptr;
  82         do {
  83                 obj_req->stream.next_out = expn;
  84                 obj_req->stream.avail_out = sizeof(expn);
  85                 obj_req->zret = git_inflate(&obj_req->stream, Z_SYNC_FLUSH);
  86                 git_SHA1_Update(&obj_req->c, expn,
  87                                 sizeof(expn) - obj_req->stream.avail_out);
  88         } while (obj_req->stream.avail_in && obj_req->zret == Z_OK);
  89         data_received++;
  90         return size;
  91 }
  92
  93 static void fetch_alternates(struct walker *walker, const char *base);
  94
  95 static void process_object_response(void *callback_data);
  96
  97 static void start_object_request(struct walker *walker,
  98                                  struct object_request *obj_req)
  99 {
 100         char *hex = sha1_to_hex(obj_req->sha1);
 101         char prevfile[PATH_MAX];
 102         char *url;
 103         char *posn;
 104         int prevlocal;
 105         unsigned char prev_buf[PREV_BUF_SIZE];
 106         ssize_t prev_read = 0;
 107         long prev_posn = 0;
 108         char range[RANGE_HEADER_SIZE];
 109         struct curl_slist *range_header = NULL;
 110         struct active_request_slot *slot;
 111         struct walker_data *data = walker->data;
 112
 113         snprintf(prevfile, sizeof(prevfile), "%s.prev", obj_req->filename);
 114         unlink_or_warn(prevfile);
 115         rename(obj_req->tmpfile, prevfile);
 116         unlink_or_warn(obj_req->tmpfile);
 117
 118         if (obj_req->local != -1)
 119                 error("fd leakage in start: %d", obj_req->local);
 120         obj_req->local = open(obj_req->tmpfile,
 121                               O_WRONLY | O_CREAT | O_EXCL, 0666);
 122         /*
 123          * This could have failed due to the "lazy directory creation";
 124          * try to mkdir the last path component.
 125          */
 126         if (obj_req->local < 0 && errno == ENOENT) {
 127                 char *dir = strrchr(obj_req->tmpfile, '/');
 128                 if (dir) {
 129                         *dir = 0;
 130                         mkdir(obj_req->tmpfile, 0777);
 131                         *dir = '/';
 132                 }
 133                 obj_req->local = open(obj_req->tmpfile,
 134                                       O_WRONLY | O_CREAT | O_EXCL, 0666);
 135         }
 136
 137         if (obj_req->local < 0) {
 138                 obj_req->state = ABORTED;
 139                 error("Couldn't create temporary file %s for %s: %s",
 140                       obj_req->tmpfile, obj_req->filename, strerror(errno));
 141                 return;
 142         }
 143
 144         memset(&obj_req->stream, 0, sizeof(obj_req->stream));
 145
 146         git_inflate_init(&obj_req->stream);
 147
 148         git_SHA1_Init(&obj_req->c);
 149
 150         url = xmalloc(strlen(obj_req->repo->base) + 51);
 151         obj_req->url = xmalloc(strlen(obj_req->repo->base) + 51);
 152         strcpy(url, obj_req->repo->base);
 153         posn = url + strlen(obj_req->repo->base);
 154         strcpy(posn, "/objects/");
 155         posn += 9;
 156         memcpy(posn, hex, 2);
 157         posn += 2;
 158         *(posn++) = '/';
 159         strcpy(posn, hex + 2);
 160         strcpy(obj_req->url, url);
 161
 162         /*
 163          * If a previous temp file is present, process what was already
 164          * fetched.
 165          */
 166         prevlocal = open(prevfile, O_RDONLY);
 167         if (prevlocal != -1) {
 168                 do {
 169                         prev_read = xread(prevlocal, prev_buf, PREV_BUF_SIZE);
 170                         if (prev_read>0) {
 171                                 if (fwrite_sha1_file(prev_buf,
 172                                                      1,
 173                                                      prev_read,
 174                                                      obj_req) == prev_read)
 175                                         prev_posn += prev_read;
 176                                 else
 177                                         prev_read = -1;
 178                         }
 179                 } while (prev_read > 0);
 180                 close(prevlocal);
 181         }
 182         unlink_or_warn(prevfile);
 183
 184         /*
 185          * Reset inflate/SHA1 if there was an error reading the previous temp
 186          * file; also rewind to the beginning of the local file.
 187          */
 188         if (prev_read == -1) {
 189                 memset(&obj_req->stream, 0, sizeof(obj_req->stream));
 190                 git_inflate_init(&obj_req->stream);
 191                 git_SHA1_Init(&obj_req->c);
 192                 if (prev_posn>0) {
 193                         prev_posn = 0;
 194                         lseek(obj_req->local, 0, SEEK_SET);
 195                         ftruncate(obj_req->local, 0);
 196                 }
 197         }
 198
 199         slot = get_active_slot();
 200         slot->callback_func = process_object_response;
 201         slot->callback_data = obj_req;
 202         obj_req->slot = slot;
 203
 204         curl_easy_setopt(slot->curl, CURLOPT_FILE, obj_req);
 205         curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_sha1_file);
 206         curl_easy_setopt(slot->curl, CURLOPT_ERRORBUFFER, obj_req->errorstr);
 207         curl_easy_setopt(slot->curl, CURLOPT_URL, url);
 208         curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, data->no_pragma_header);
 209
 210         /*
 211          * If we have successfully processed data from a previous fetch
 212          * attempt, only fetch the data we don't already have.
 213          */
 214         if (prev_posn>0) {
 215                 if (walker->get_verbosely)
 216                         fprintf(stderr,
 217                                 "Resuming fetch of object %s at byte %ld\n",
 218                                 hex, prev_posn);
 219                 sprintf(range, "Range: bytes=%ld-", prev_posn);
 220                 range_header = curl_slist_append(range_header, range);
 221                 curl_easy_setopt(slot->curl,
 222                                  CURLOPT_HTTPHEADER, range_header);
 223         }
 224
 225         /* Try to get the request started, abort the request on error */
 226         obj_req->state = ACTIVE;
 227         if (!start_active_slot(slot)) {
 228                 obj_req->state = ABORTED;
 229                 obj_req->slot = NULL;
 230                 close(obj_req->local);
 231                 obj_req->local = -1;
 232                 free(obj_req->url);
 233                 return;
 234         }
 235 }
 236
 237 static void finish_object_request(struct object_request *obj_req)
 238 {
 239         struct stat st;
 240
 241         close(obj_req->local);
 242         obj_req->local = -1;
 243
 244         if (obj_req->http_code == 416) {
 245                 fprintf(stderr, "Warning: requested range invalid; we may already have all the data.\n");
 246         } else if (obj_req->curl_result != CURLE_OK) {
 247                 if (stat(obj_req->tmpfile, &st) == 0)
 248                         if (st.st_size == 0)
 249                                 unlink_or_warn(obj_req->tmpfile);
 250                 return;
 251         }
 252
 253         git_inflate_end(&obj_req->stream);
 254         git_SHA1_Final(obj_req->real_sha1, &obj_req->c);
 255         if (obj_req->zret != Z_STREAM_END) {
 256                 unlink_or_warn(obj_req->tmpfile);
 257                 return;
 258         }
 259         if (hashcmp(obj_req->sha1, obj_req->real_sha1)) {
 260                 unlink_or_warn(obj_req->tmpfile);
 261                 return;
 262         }
 263         obj_req->rename =
 264                 move_temp_to_file(obj_req->tmpfile, obj_req->filename);
 265
 266         if (obj_req->rename == 0)
 267                 walker_say(obj_req->walker, "got %s\n", sha1_to_hex(obj_req->sha1));
 268 }
 269
 270 static void process_object_response(void *callback_data)
 271 {
 272         struct object_request *obj_req =
 273                 (struct object_request *)callback_data;
 274         struct walker *walker = obj_req->walker;
 275         struct walker_data *data = walker->data;
 276         struct alt_base *alt = data->alt;
 277
 278         obj_req->curl_result = obj_req->slot->curl_result;
 279         obj_req->http_code = obj_req->slot->http_code;
 280         obj_req->slot = NULL;
 281         obj_req->state = COMPLETE;
 282
 283         /* Use alternates if necessary */
 284         if (missing_target(obj_req)) {
 285                 fetch_alternates(walker, alt->base);
 286                 if (obj_req->repo->next != NULL) {
 287                         obj_req->repo =
 288                                 obj_req->repo->next;
 289                         close(obj_req->local);
 290                         obj_req->local = -1;
 291                         start_object_request(walker, obj_req);
 292                         return;
 293                 }
 294         }
 295
 296         finish_object_request(obj_req);
 297 }
 298
 299 static void release_object_request(struct object_request *obj_req)
 300 {
 301         struct object_request *entry = object_queue_head;
 302
 303         if (obj_req->local != -1)
 304                 error("fd leakage in release: %d", obj_req->local);
 305         if (obj_req == object_queue_head) {
 306                 object_queue_head = obj_req->next;
 307         } else {
 308                 while (entry->next != NULL && entry->next != obj_req)
 309                         entry = entry->next;
 310                 if (entry->next == obj_req)
 311                         entry->next = entry->next->next;
 312         }
 313
 314         free(obj_req->url);
 315         free(obj_req);
 316 }
 317
 318 #ifdef USE_CURL_MULTI
 319 static int fill_active_slot(struct walker *walker)
 320 {
 321         struct object_request *obj_req;
 322
 323         for (obj_req = object_queue_head; obj_req; obj_req = obj_req->next) {
 324                 if (obj_req->state == WAITING) {
 325                         if (has_sha1_file(obj_req->sha1))
 326                                 obj_req->state = COMPLETE;
 327                         else {
 328                                 start_object_request(walker, obj_req);
 329                                 return 1;
 330                         }
 331                 }
 332         }
 333         return 0;
 334 }
 335 #endif
 336
 337 static void prefetch(struct walker *walker, unsigned char *sha1)
 338 {
 339         struct object_request *newreq;
 340         struct object_request *tail;
 341         struct walker_data *data = walker->data;
 342         char *filename = sha1_file_name(sha1);
 343
 344         newreq = xmalloc(sizeof(*newreq));
 345         newreq->walker = walker;
 346         hashcpy(newreq->sha1, sha1);
 347         newreq->repo = data->alt;
 348         newreq->url = NULL;
 349         newreq->local = -1;
 350         newreq->state = WAITING;
 351         snprintf(newreq->filename, sizeof(newreq->filename), "%s", filename);
 352         snprintf(newreq->tmpfile, sizeof(newreq->tmpfile),
 353                  "%s.temp", filename);
 354         newreq->slot = NULL;
 355         newreq->next = NULL;
 356
 357         if (object_queue_head == NULL) {
 358                 object_queue_head = newreq;
 359         } else {
 360                 tail = object_queue_head;
 361                 while (tail->next != NULL)
 362                         tail = tail->next;
 363                 tail->next = newreq;
 364         }
 365
 366 #ifdef USE_CURL_MULTI
 367         fill_active_slots();
 368         step_active_slots();
 369 #endif
 370 }
 371
 372 static int fetch_index(struct walker *walker, struct alt_base *repo, unsigned char *sha1)
 373 {
 374         char *hex = sha1_to_hex(sha1);
 375         char *filename;
 376         char *url;
 377         char tmpfile[PATH_MAX];
 378         long prev_posn = 0;
 379         char range[RANGE_HEADER_SIZE];
 380         struct curl_slist *range_header = NULL;
 381         struct walker_data *data = walker->data;
 382
 383         FILE *indexfile;
 384         struct active_request_slot *slot;
 385         struct slot_results results;
 386
 387         if (has_pack_index(sha1))
 388                 return 0;
 389
 390         if (walker->get_verbosely)
 391                 fprintf(stderr, "Getting index for pack %s\n", hex);
 392
 393         url = xmalloc(strlen(repo->base) + 64);
 394         sprintf(url, "%s/objects/pack/pack-%s.idx", repo->base, hex);
 395
 396         filename = sha1_pack_index_name(sha1);
 397         snprintf(tmpfile, sizeof(tmpfile), "%s.temp", filename);
 398         indexfile = fopen(tmpfile, "a");
 399         if (!indexfile)
 400                 return error("Unable to open local file %s for pack index",
 401                              tmpfile);
 402
 403         slot = get_active_slot();
 404         slot->results = &results;
 405         curl_easy_setopt(slot->curl, CURLOPT_FILE, indexfile);
 406         curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
 407         curl_easy_setopt(slot->curl, CURLOPT_URL, url);
 408         curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, data->no_pragma_header);
 409         slot->local = indexfile;
 410
 411         /*
 412          * If there is data present from a previous transfer attempt,
 413          * resume where it left off
 414          */
 415         prev_posn = ftell(indexfile);
 416         if (prev_posn>0) {
 417                 if (walker->get_verbosely)
 418                         fprintf(stderr,
 419                                 "Resuming fetch of index for pack %s at byte %ld\n",
 420                                 hex, prev_posn);
 421                 sprintf(range, "Range: bytes=%ld-", prev_posn);
 422                 range_header = curl_slist_append(range_header, range);
 423                 curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, range_header);
 424         }
 425
 426         if (start_active_slot(slot)) {
 427                 run_active_slot(slot);
 428                 if (results.curl_result != CURLE_OK) {
 429                         fclose(indexfile);
 430                         slot->local = NULL;
 431                         return error("Unable to get pack index %s\n%s", url,
 432                                      curl_errorstr);
 433                 }
 434         } else {
 435                 fclose(indexfile);
 436                 slot->local = NULL;
 437                 return error("Unable to start request");
 438         }
 439
 440         fclose(indexfile);
 441         slot->local = NULL;
 442
 443         return move_temp_to_file(tmpfile, filename);
 444 }
 445
 446 static int setup_index(struct walker *walker, struct alt_base *repo, unsigned char *sha1)
 447 {
 448         struct packed_git *new_pack;
 449         if (has_pack_file(sha1))
 450                 return 0; /* don't list this as something we can get */
 451
 452         if (fetch_index(walker, repo, sha1))
 453                 return -1;
 454
 455         new_pack = parse_pack_index(sha1);
 456         if (!new_pack)
 457                 return -1; /* parse_pack_index() already issued error message */
 458         new_pack->next = repo->packs;
 459         repo->packs = new_pack;
 460         return 0;
 461 }
 462
 463 static void process_alternates_response(void *callback_data)
 464 {
 465         struct alternates_request *alt_req =
 466                 (struct alternates_request *)callback_data;
 467         struct walker *walker = alt_req->walker;
 468         struct walker_data *cdata = walker->data;
 469         struct active_request_slot *slot = alt_req->slot;
 470         struct alt_base *tail = cdata->alt;
 471         const char *base = alt_req->base;
 472         static const char null_byte = '\0';
 473         char *data;
 474         int i = 0;
 475
 476         if (alt_req->http_specific) {
 477                 if (slot->curl_result != CURLE_OK ||
 478                     !alt_req->buffer->len) {
 479
 480                         /* Try reusing the slot to get non-http alternates */
 481                         alt_req->http_specific = 0;
 482                         sprintf(alt_req->url, "%s/objects/info/alternates",
 483                                 base);
 484                         curl_easy_setopt(slot->curl, CURLOPT_URL,
 485                                          alt_req->url);
 486                         active_requests++;
 487                         slot->in_use = 1;
 488                         if (slot->finished != NULL)
 489                                 (*slot->finished) = 0;
 490                         if (!start_active_slot(slot)) {
 491                                 cdata->got_alternates = -1;
 492                                 slot->in_use = 0;
 493                                 if (slot->finished != NULL)
 494                                         (*slot->finished) = 1;
 495                         }
 496                         return;
 497                 }
 498         } else if (slot->curl_result != CURLE_OK) {
 499                 if (!missing_target(slot)) {
 500                         cdata->got_alternates = -1;
 501                         return;
 502                 }
 503         }
 504
 505         fwrite_buffer(&null_byte, 1, 1, alt_req->buffer);
 506         alt_req->buffer->len--;
 507         data = alt_req->buffer->buf;
 508
 509         while (i < alt_req->buffer->len) {
 510                 int posn = i;
 511                 while (posn < alt_req->buffer->len && data[posn] != '\n')
 512                         posn++;
 513                 if (data[posn] == '\n') {
 514                         int okay = 0;
 515                         int serverlen = 0;
 516                         struct alt_base *newalt;
 517                         char *target = NULL;
 518                         if (data[i] == '/') {
 519                                 /*
 520                                  * This counts
 521                                  * http://git.host/pub/scm/linux.git/
 522                                  * -----------here^
 523                                  * so memcpy(dst, base, serverlen) will
 524                                  * copy up to "...git.host".
 525                                  */
 526                                 const char *colon_ss = strstr(base,"://");
 527                                 if (colon_ss) {
 528                                         serverlen = (strchr(colon_ss + 3, '/')
 529                                                      - base);
 530                                         okay = 1;
 531                                 }
 532                         } else if (!memcmp(data + i, "../", 3)) {
 533                                 /*
 534                                  * Relative URL; chop the corresponding
 535                                  * number of subpath from base (and ../
 536                                  * from data), and concatenate the result.
 537                                  *
 538                                  * The code first drops ../ from data, and
 539                                  * then drops one ../ from data and one path
 540                                  * from base.  IOW, one extra ../ is dropped
 541                                  * from data than path is dropped from base.
 542                                  *
 543                                  * This is not wrong.  The alternate in
 544                                  *     http://git.host/pub/scm/linux.git/
 545                                  * to borrow from
 546                                  *     http://git.host/pub/scm/linus.git/
 547                                  * is ../../linus.git/objects/.  You need
 548                                  * two ../../ to borrow from your direct
 549                                  * neighbour.
 550                                  */
 551                                 i += 3;
 552                                 serverlen = strlen(base);
 553                                 while (i + 2 < posn &&
 554                                        !memcmp(data + i, "../", 3)) {
 555                                         do {
 556                                                 serverlen--;
 557                                         } while (serverlen &&
 558                                                  base[serverlen - 1] != '/');
 559                                         i += 3;
 560                                 }
 561                                 /* If the server got removed, give up. */
 562                                 okay = strchr(base, ':') - base + 3 <
 563                                        serverlen;
 564                         } else if (alt_req->http_specific) {
 565                                 char *colon = strchr(data + i, ':');
 566                                 char *slash = strchr(data + i, '/');
 567                                 if (colon && slash && colon < data + posn &&
 568                                     slash < data + posn && colon < slash) {
 569                                         okay = 1;
 570                                 }
 571                         }
 572                         /* skip "objects\n" at end */
 573                         if (okay) {
 574                                 target = xmalloc(serverlen + posn - i - 6);
 575                                 memcpy(target, base, serverlen);
 576                                 memcpy(target + serverlen, data + i,
 577                                        posn - i - 7);
 578                                 target[serverlen + posn - i - 7] = 0;
 579                                 if (walker->get_verbosely)
 580                                         fprintf(stderr,
 581                                                 "Also look at %s\n", target);
 582                                 newalt = xmalloc(sizeof(*newalt));
 583                                 newalt->next = NULL;
 584                                 newalt->base = target;
 585                                 newalt->got_indices = 0;
 586                                 newalt->packs = NULL;
 587
 588                                 while (tail->next != NULL)
 589                                         tail = tail->next;
 590                                 tail->next = newalt;
 591                         }
 592                 }
 593                 i = posn + 1;
 594         }
 595
 596         cdata->got_alternates = 1;
 597 }
 598
 599 static void fetch_alternates(struct walker *walker, const char *base)
 600 {
 601         struct strbuf buffer = STRBUF_INIT;
 602         char *url;
 603         struct active_request_slot *slot;
 604         struct alternates_request alt_req;
 605         struct walker_data *cdata = walker->data;
 606
 607         /*
 608          * If another request has already started fetching alternates,
 609          * wait for them to arrive and return to processing this request's
 610          * curl message
 611          */
 612 #ifdef USE_CURL_MULTI
 613         while (cdata->got_alternates == 0) {
 614                 step_active_slots();
 615         }
 616 #endif
 617
 618         /* Nothing to do if they've already been fetched */
 619         if (cdata->got_alternates == 1)
 620                 return;
 621
 622         /* Start the fetch */
 623         cdata->got_alternates = 0;
 624
 625         if (walker->get_verbosely)
 626                 fprintf(stderr, "Getting alternates list for %s\n", base);
 627
 628         url = xmalloc(strlen(base) + 31);
 629         sprintf(url, "%s/objects/info/http-alternates", base);
 630
 631         /*
 632          * Use a callback to process the result, since another request
 633          * may fail and need to have alternates loaded before continuing
 634          */
 635         slot = get_active_slot();
 636         slot->callback_func = process_alternates_response;
 637         alt_req.walker = walker;
 638         slot->callback_data = &alt_req;
 639
 640         curl_easy_setopt(slot->curl, CURLOPT_FILE, &buffer);
 641         curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
 642         curl_easy_setopt(slot->curl, CURLOPT_URL, url);
 643
 644         alt_req.base = base;
 645         alt_req.url = url;
 646         alt_req.buffer = &buffer;
 647         alt_req.http_specific = 1;
 648         alt_req.slot = slot;
 649
 650         if (start_active_slot(slot))
 651                 run_active_slot(slot);
 652         else
 653                 cdata->got_alternates = -1;
 654
 655         strbuf_release(&buffer);
 656         free(url);
 657 }
 658
 659 static int fetch_indices(struct walker *walker, struct alt_base *repo)
 660 {
 661         unsigned char sha1[20];
 662         char *url;
 663         struct strbuf buffer = STRBUF_INIT;
 664         char *data;
 665         int i = 0;
 666         int ret = 0;
 667
 668         struct active_request_slot *slot;
 669         struct slot_results results;
 670
 671         if (repo->got_indices)
 672                 return 0;
 673
 674         if (walker->get_verbosely)
 675                 fprintf(stderr, "Getting pack list for %s\n", repo->base);
 676
 677         url = xmalloc(strlen(repo->base) + 21);
 678         sprintf(url, "%s/objects/info/packs", repo->base);
 679
 680         slot = get_active_slot();
 681         slot->results = &results;
 682         curl_easy_setopt(slot->curl, CURLOPT_FILE, &buffer);
 683         curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
 684         curl_easy_setopt(slot->curl, CURLOPT_URL, url);
 685         curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, NULL);
 686         if (start_active_slot(slot)) {
 687                 run_active_slot(slot);
 688                 if (results.curl_result != CURLE_OK) {
 689                         if (missing_target(&results)) {
 690                                 repo->got_indices = 1;
 691                                 goto cleanup;
 692                         } else {
 693                                 repo->got_indices = 0;
 694                                 ret = error("%s", curl_errorstr);
 695                                 goto cleanup;
 696                         }
 697                 }
 698         } else {
 699                 repo->got_indices = 0;
 700                 ret = error("Unable to start request");
 701                 goto cleanup;
 702         }
 703
 704         data = buffer.buf;
 705         while (i < buffer.len) {
 706                 switch (data[i]) {
 707                 case 'P':
 708                         i++;
 709                         if (i + 52 <= buffer.len &&
 710                             !prefixcmp(data + i, " pack-") &&
 711                             !prefixcmp(data + i + 46, ".pack\n")) {
 712                                 get_sha1_hex(data + i + 6, sha1);
 713                                 setup_index(walker, repo, sha1);
 714                                 i += 51;
 715                                 break;
 716                         }
 717                 default:
 718                         while (i < buffer.len && data[i] != '\n')
 719                                 i++;
 720                 }
 721                 i++;
 722         }
 723
 724         repo->got_indices = 1;
 725 cleanup:
 726         strbuf_release(&buffer);
 727         free(url);
 728         return ret;
 729 }
 730
 731 static int fetch_pack(struct walker *walker, struct alt_base *repo, unsigned char *sha1)
 732 {
 733         char *url;
 734         struct packed_git *target;
 735         struct packed_git **lst;
 736         FILE *packfile;
 737         char *filename;
 738         char tmpfile[PATH_MAX];
 739         int ret;
 740         long prev_posn = 0;
 741         char range[RANGE_HEADER_SIZE];
 742         struct curl_slist *range_header = NULL;
 743         struct walker_data *data = walker->data;
 744
 745         struct active_request_slot *slot;
 746         struct slot_results results;
 747
 748         if (fetch_indices(walker, repo))
 749                 return -1;
 750         target = find_sha1_pack(sha1, repo->packs);
 751         if (!target)
 752                 return -1;
 753
 754         if (walker->get_verbosely) {
 755                 fprintf(stderr, "Getting pack %s\n",
 756                         sha1_to_hex(target->sha1));
 757                 fprintf(stderr, " which contains %s\n",
 758                         sha1_to_hex(sha1));
 759         }
 760
 761         url = xmalloc(strlen(repo->base) + 65);
 762         sprintf(url, "%s/objects/pack/pack-%s.pack",
 763                 repo->base, sha1_to_hex(target->sha1));
 764
 765         filename = sha1_pack_name(target->sha1);
 766         snprintf(tmpfile, sizeof(tmpfile), "%s.temp", filename);
 767         packfile = fopen(tmpfile, "a");
 768         if (!packfile)
 769                 return error("Unable to open local file %s for pack",
 770                              tmpfile);
 771
 772         slot = get_active_slot();
 773         slot->results = &results;
 774         curl_easy_setopt(slot->curl, CURLOPT_FILE, packfile);
 775         curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
 776         curl_easy_setopt(slot->curl, CURLOPT_URL, url);
 777         curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, data->no_pragma_header);
 778         slot->local = packfile;
 779
 780         /*
 781          * If there is data present from a previous transfer attempt,
 782          * resume where it left off
 783          */
 784         prev_posn = ftell(packfile);
 785         if (prev_posn>0) {
 786                 if (walker->get_verbosely)
 787                         fprintf(stderr,
 788                                 "Resuming fetch of pack %s at byte %ld\n",
 789                                 sha1_to_hex(target->sha1), prev_posn);
 790                 sprintf(range, "Range: bytes=%ld-", prev_posn);
 791                 range_header = curl_slist_append(range_header, range);
 792                 curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, range_header);
 793         }
 794
 795         if (start_active_slot(slot)) {
 796                 run_active_slot(slot);
 797                 if (results.curl_result != CURLE_OK) {
 798                         fclose(packfile);
 799                         slot->local = NULL;
 800                         return error("Unable to get pack file %s\n%s", url,
 801                                      curl_errorstr);
 802                 }
 803         } else {
 804                 fclose(packfile);
 805                 slot->local = NULL;
 806                 return error("Unable to start request");
 807         }
 808
 809         target->pack_size = ftell(packfile);
 810         fclose(packfile);
 811         slot->local = NULL;
 812
 813         ret = move_temp_to_file(tmpfile, filename);
 814         if (ret)
 815                 return ret;
 816
 817         lst = &repo->packs;
 818         while (*lst != target)
 819                 lst = &((*lst)->next);
 820         *lst = (*lst)->next;
 821
 822         if (verify_pack(target))
 823                 return -1;
 824         install_packed_git(target);
 825
 826         return 0;
 827 }
 828
 829 static void abort_object_request(struct object_request *obj_req)
 830 {
 831         if (obj_req->local >= 0) {
 832                 close(obj_req->local);
 833                 obj_req->local = -1;
 834         }
 835         unlink_or_warn(obj_req->tmpfile);
 836         if (obj_req->slot) {
 837                 release_active_slot(obj_req->slot);
 838                 obj_req->slot = NULL;
 839         }
 840         release_object_request(obj_req);
 841 }
 842
 843 static int fetch_object(struct walker *walker, struct alt_base *repo, unsigned char *sha1)
 844 {
 845         char *hex = sha1_to_hex(sha1);
 846         int ret = 0;
 847         struct object_request *obj_req = object_queue_head;
 848
 849         while (obj_req != NULL && hashcmp(obj_req->sha1, sha1))
 850                 obj_req = obj_req->next;
 851         if (obj_req == NULL)
 852                 return error("Couldn't find request for %s in the queue", hex);
 853
 854         if (has_sha1_file(obj_req->sha1)) {
 855                 abort_object_request(obj_req);
 856                 return 0;
 857         }
 858
 859 #ifdef USE_CURL_MULTI
 860         while (obj_req->state == WAITING)
 861                 step_active_slots();
 862 #else
 863         start_object_request(walker, obj_req);
 864 #endif
 865
 866         while (obj_req->state == ACTIVE)
 867                 run_active_slot(obj_req->slot);
 868
 869         if (obj_req->local != -1) {
 870                 close(obj_req->local);
 871                 obj_req->local = -1;
 872         }
 873
 874         if (obj_req->state == ABORTED) {
 875                 ret = error("Request for %s aborted", hex);
 876         } else if (obj_req->curl_result != CURLE_OK &&
 877                    obj_req->http_code != 416) {
 878                 if (missing_target(obj_req))
 879                         ret = -1; /* Be silent, it is probably in a pack. */
 880                 else
 881                         ret = error("%s (curl_result = %d, http_code = %ld, sha1 = %s)",
 882                                     obj_req->errorstr, obj_req->curl_result,
 883                                     obj_req->http_code, hex);
 884         } else if (obj_req->zret != Z_STREAM_END) {
 885                 walker->corrupt_object_found++;
 886                 ret = error("File %s (%s) corrupt", hex, obj_req->url);
 887         } else if (hashcmp(obj_req->sha1, obj_req->real_sha1)) {
 888                 ret = error("File %s has bad hash", hex);
 889         } else if (obj_req->rename < 0) {
 890                 ret = error("unable to write sha1 filename %s",
 891                             obj_req->filename);
 892         }
 893
 894         release_object_request(obj_req);
 895         return ret;
 896 }
 897
 898 static int fetch(struct walker *walker, unsigned char *sha1)
 899 {
 900         struct walker_data *data = walker->data;
 901         struct alt_base *altbase = data->alt;
 902
 903         if (!fetch_object(walker, altbase, sha1))
 904                 return 0;
 905         while (altbase) {
 906                 if (!fetch_pack(walker, altbase, sha1))
 907                         return 0;
 908                 fetch_alternates(walker, data->alt->base);
 909                 altbase = altbase->next;
 910         }
 911         return error("Unable to find %s under %s", sha1_to_hex(sha1),
 912                      data->alt->base);
 913 }
 914
 915 static int fetch_ref(struct walker *walker, struct ref *ref)
 916 {
 917         struct walker_data *data = walker->data;
 918         return http_fetch_ref(data->alt->base, ref);
 919 }
 920
 921 static void cleanup(struct walker *walker)
 922 {
 923         struct walker_data *data = walker->data;
 924         http_cleanup();
 925
 926         curl_slist_free_all(data->no_pragma_header);
 927 }
 928
 929 struct walker *get_http_walker(const char *url, struct remote *remote)
 930 {
 931         char *s;
 932         struct walker_data *data = xmalloc(sizeof(struct walker_data));
 933         struct walker *walker = xmalloc(sizeof(struct walker));
 934
 935         http_init(remote);
 936
 937         data->no_pragma_header = curl_slist_append(NULL, "Pragma:");
 938
 939         data->alt = xmalloc(sizeof(*data->alt));
 940         data->alt->base = xmalloc(strlen(url) + 1);
 941         strcpy(data->alt->base, url);
 942         for (s = data->alt->base + strlen(data->alt->base) - 1; *s == '/'; --s)
 943                 *s = 0;
 944
 945         data->alt->got_indices = 0;
 946         data->alt->packs = NULL;
 947         data->alt->next = NULL;
 948         data->got_alternates = -1;
 949
 950         walker->corrupt_object_found = 0;
 951         walker->fetch = fetch;
 952         walker->fetch_ref = fetch_ref;
 953         walker->prefetch = prefetch;
 954         walker->cleanup = cleanup;
 955         walker->data = data;
 956
 957 #ifdef USE_CURL_MULTI
 958         add_fill_function(walker, (int (*)(void *)) fill_active_slot);
 959 #endif
 960
 961         return walker;
 962 }