methods/rred.cc

   1 // Copyright (c) 2014 Anthony Towns
   2 //
   3 // This program is free software; you can redistribute it and/or modify
   4 // it under the terms of the GNU General Public License as published by
   5 // the Free Software Foundation; either version 2 of the License, or
   6 // (at your option) any later version.
   7
   8 #include <config.h>
   9
  10 #include <apt-pkg/init.h>
  11 #include <apt-pkg/fileutl.h>
  12 #include <apt-pkg/error.h>
  13 #include <apt-pkg/acquire-method.h>
  14 #include <apt-pkg/strutl.h>
  15 #include <apt-pkg/hashes.h>
  16 #include <apt-pkg/configuration.h>
  17 #include "aptmethod.h"
  18
  19 #include <stddef.h>
  20 #include <iostream>
  21 #include <string>
  22 #include <list>
  23 #include <vector>
  24
  25 #include <assert.h>
  26 #include <errno.h>
  27 #include <stdio.h>
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #include <sys/stat.h>
  31 #include <sys/time.h>
  32
  33 #include <apti18n.h>
  34
  35 #define BLOCK_SIZE (512*1024)
  36
  37 class MemBlock {
  38    char *start;
  39    size_t size;
  40    char *free;
  41    MemBlock *next;
  42
  43    explicit MemBlock(size_t size) : size(size), next(NULL)
  44    {
  45       free = start = new char[size];
  46    }
  47
  48    size_t avail(void) { return size - (free - start); }
  49
  50    public:
  51
  52    MemBlock(void) {
  53       free = start = new char[BLOCK_SIZE];
  54       size = BLOCK_SIZE;
  55       next = NULL;
  56    }
  57
  58    ~MemBlock() {
  59       delete [] start;
  60       delete next;
  61    }
  62
  63    void clear(void) {
  64       free = start;
  65       if (next)
  66          next->clear();
  67    }
  68
  69    char *add_easy(char *src, size_t len, char *last)
  70    {
  71       if (last) {
  72          for (MemBlock *k = this; k; k = k->next) {
  73             if (k->free == last) {
  74                if (len <= k->avail()) {
  75                   char *n = k->add(src, len);
  76                   assert(last == n);
  77                   if (last == n)
  78                      return NULL;
  79                   return n;
  80                } else {
  81                   break;
  82                }
  83             } else if (last >= start && last < free) {
  84                break;
  85             }
  86          }
  87       }
  88       return add(src, len);
  89    }
  90
  91    char *add(char *src, size_t len) {
  92       if (len > avail()) {
  93          if (!next) {
  94             if (len > BLOCK_SIZE)  {
  95                next = new MemBlock(len);
  96             } else {
  97                next = new MemBlock;
  98             }
  99          }
 100          return next->add(src, len);
 101       }
 102       char *dst = free;
 103       free += len;
 104       memcpy(dst, src, len);
 105       return dst;
 106    }
 107 };
 108
 109 struct Change {
 110    /* Ordering:
 111     *
 112     *   1. write out <offset> lines unchanged
 113     *   2. skip <del_cnt> lines from source
 114     *   3. write out <add_cnt> lines (<add>/<add_len>)
 115     */
 116    size_t offset;
 117    size_t del_cnt;
 118    size_t add_cnt; /* lines */
 119    size_t add_len; /* bytes */
 120    char *add;
 121
 122    explicit Change(size_t off)
 123    {
 124       offset = off;
 125       del_cnt = add_cnt = add_len = 0;
 126       add = NULL;
 127    }
 128
 129    /* actually, don't write <lines> lines from <add> */
 130    void skip_lines(size_t lines)
 131    {
 132       while (lines > 0) {
 133          char *s = (char*) memchr(add, '\n', add_len);
 134          assert(s != NULL);
 135          s++;
 136          add_len -= (s - add);
 137          add_cnt--;
 138          lines--;
 139          if (add_len == 0) {
 140             add = NULL;
 141             assert(add_cnt == 0);
 142             assert(lines == 0);
 143          } else {
 144             add = s;
 145             assert(add_cnt > 0);
 146          }
 147       }
 148    }
 149 };
 150
 151 class FileChanges {
 152    std::list<struct Change> changes;
 153    std::list<struct Change>::iterator where;
 154    size_t pos; // line number is as far left of iterator as possible
 155
 156    bool pos_is_okay(void) const
 157    {
 158 #ifdef POSDEBUG
 159       size_t cpos = 0;
 160       std::list<struct Change>::const_iterator x;
 161       for (x = changes.begin(); x != where; ++x) {
 162          assert(x != changes.end());
 163          cpos += x->offset + x->add_cnt;
 164       }
 165       return cpos == pos;
 166 #else
 167       return true;
 168 #endif
 169    }
 170
 171    public:
 172    FileChanges() {
 173       where = changes.end();
 174       pos = 0;
 175    }
 176
 177    std::list<struct Change>::iterator begin(void) { return changes.begin(); }
 178    std::list<struct Change>::iterator end(void) { return changes.end(); }
 179
 180    std::list<struct Change>::reverse_iterator rbegin(void) { return changes.rbegin(); }
 181    std::list<struct Change>::reverse_iterator rend(void) { return changes.rend(); }
 182
 183    void add_change(Change c) {
 184       assert(pos_is_okay());
 185       go_to_change_for(c.offset);
 186       assert(pos + where->offset == c.offset);
 187       if (c.del_cnt > 0)
 188          delete_lines(c.del_cnt);
 189       assert(pos + where->offset == c.offset);
 190       if (c.add_len > 0) {
 191          assert(pos_is_okay());
 192          if (where->add_len > 0)
 193             new_change();
 194          assert(where->add_len == 0 && where->add_cnt == 0);
 195
 196          where->add_len = c.add_len;
 197          where->add_cnt = c.add_cnt;
 198          where->add = c.add;
 199       }
 200       assert(pos_is_okay());
 201       merge();
 202       assert(pos_is_okay());
 203    }
 204
 205    private:
 206    void merge(void)
 207    {
 208       while (where->offset == 0 && where != changes.begin()) {
 209          left();
 210       }
 211       std::list<struct Change>::iterator next = where;
 212       ++next;
 213
 214       while (next != changes.end() && next->offset == 0) {
 215          where->del_cnt += next->del_cnt;
 216          next->del_cnt = 0;
 217          if (next->add == NULL) {
 218             next = changes.erase(next);
 219          } else if (where->add == NULL) {
 220             where->add = next->add;
 221             where->add_len = next->add_len;
 222             where->add_cnt = next->add_cnt;
 223             next = changes.erase(next);
 224          } else {
 225             ++next;
 226          }
 227       }
 228    }
 229
 230    void go_to_change_for(size_t line)
 231    {
 232       while(where != changes.end()) {
 233          if (line < pos) {
 234             left();
 235             continue;
 236          }
 237          if (pos + where->offset + where->add_cnt <= line) {
 238             right();
 239             continue;
 240          }
 241          // line is somewhere in this slot
 242          if (line < pos + where->offset) {
 243             break;
 244          } else if (line == pos + where->offset) {
 245             return;
 246          } else {
 247             split(line - pos);
 248             right();
 249             return;
 250          }
 251       }
 252       /* it goes before this patch */
 253       insert(line-pos);
 254    }
 255
 256    void new_change(void) { insert(where->offset); }
 257
 258    void insert(size_t offset)
 259    {
 260       assert(pos_is_okay());
 261       assert(where == changes.end() || offset <= where->offset);
 262       if (where != changes.end())
 263          where->offset -= offset;
 264       changes.insert(where, Change(offset));
 265       --where;
 266       assert(pos_is_okay());
 267    }
 268
 269    void split(size_t offset)
 270    {
 271       assert(pos_is_okay());
 272
 273       assert(where->offset < offset);
 274       assert(offset < where->offset + where->add_cnt);
 275
 276       size_t keep_lines = offset - where->offset;
 277
 278       Change before(*where);
 279
 280       where->del_cnt = 0;
 281       where->offset = 0;
 282       where->skip_lines(keep_lines);
 283
 284       before.add_cnt = keep_lines;
 285       before.add_len -= where->add_len;
 286
 287       changes.insert(where, before);
 288       --where;
 289       assert(pos_is_okay());
 290    }
 291
 292    void delete_lines(size_t cnt)
 293    {
 294       std::list<struct Change>::iterator x = where;
 295       assert(pos_is_okay());
 296       while (cnt > 0)
 297       {
 298          size_t del;
 299          del = x->add_cnt;
 300          if (del > cnt)
 301             del = cnt;
 302          x->skip_lines(del);
 303          cnt -= del;
 304
 305          ++x;
 306          if (x == changes.end()) {
 307             del = cnt;
 308          } else {
 309             del = x->offset;
 310             if (del > cnt)
 311                del = cnt;
 312             x->offset -= del;
 313          }
 314          where->del_cnt += del;
 315          cnt -= del;
 316       }
 317       assert(pos_is_okay());
 318    }
 319
 320    void left(void) {
 321       assert(pos_is_okay());
 322       --where;
 323       pos -= where->offset + where->add_cnt;
 324       assert(pos_is_okay());
 325    }
 326
 327    void right(void) {
 328       assert(pos_is_okay());
 329       pos += where->offset + where->add_cnt;
 330       ++where;
 331       assert(pos_is_okay());
 332    }
 333 };
 334
 335 class Patch {
 336    FileChanges filechanges;
 337    MemBlock add_text;
 338
 339    static bool retry_fwrite(char *b, size_t l, FileFd &f, Hashes *hash)
 340    {
 341       if (f.Write(b, l) == false)
 342          return false;
 343       if (hash)
 344          hash->Add((unsigned char*)b, l);
 345       return true;
 346    }
 347
 348    static void dump_rest(FileFd &o, FileFd &i, Hashes *hash)
 349    {
 350       char buffer[BLOCK_SIZE];
 351       unsigned long long l = 0;
 352       while (i.Read(buffer, sizeof(buffer), &l)) {
 353          if (l ==0  || !retry_fwrite(buffer, l, o, hash))
 354             break;
 355       }
 356    }
 357
 358    static void dump_lines(FileFd &o, FileFd &i, size_t n, Hashes *hash)
 359    {
 360       char buffer[BLOCK_SIZE];
 361       while (n > 0) {
 362          if (i.ReadLine(buffer, sizeof(buffer)) == NULL)
 363             buffer[0] = '\0';
 364          size_t const l = strlen(buffer);
 365          if (l == 0 || buffer[l-1] == '\n')
 366             n--;
 367          retry_fwrite(buffer, l, o, hash);
 368       }
 369    }
 370
 371    static void skip_lines(FileFd &i, int n)
 372    {
 373       char buffer[BLOCK_SIZE];
 374       while (n > 0) {
 375          if (i.ReadLine(buffer, sizeof(buffer)) == NULL)
 376             buffer[0] = '\0';
 377          size_t const l = strlen(buffer);
 378          if (l == 0 || buffer[l-1] == '\n')
 379             n--;
 380       }
 381    }
 382
 383    static void dump_mem(FileFd &o, char *p, size_t s, Hashes *hash) {
 384       retry_fwrite(p, s, o, hash);
 385    }
 386
 387    public:
 388
 389    bool read_diff(FileFd &f, Hashes * const h)
 390    {
 391       char buffer[BLOCK_SIZE];
 392       bool cmdwanted = true;
 393
 394       Change ch(std::numeric_limits<size_t>::max());
 395       if (f.ReadLine(buffer, sizeof(buffer)) == NULL)
 396          return _error->Error("Reading first line of patchfile %s failed", f.Name().c_str());
 397       do {
 398          if (h != NULL)
 399             h->Add(buffer);
 400          if (cmdwanted) {
 401             char *m, *c;
 402             size_t s, e;
 403             errno = 0;
 404             s = strtoul(buffer, &m, 10);
 405             if (unlikely(m == buffer || s == std::numeric_limits<unsigned long>::max() || errno != 0))
 406                return _error->Error("Parsing patchfile %s failed: Expected an effected line start", f.Name().c_str());
 407             else if (*m == ',') {
 408                ++m;
 409                e = strtol(m, &c, 10);
 410                if (unlikely(m == c || e == std::numeric_limits<unsigned long>::max() || errno != 0))
 411                   return _error->Error("Parsing patchfile %s failed: Expected an effected line end", f.Name().c_str());
 412                if (unlikely(e < s))
 413                   return _error->Error("Parsing patchfile %s failed: Effected lines end %lu is before start %lu", f.Name().c_str(), e, s);
 414             } else {
 415                e = s;
 416                c = m;
 417             }
 418             if (s > ch.offset)
 419                return _error->Error("Parsing patchfile %s failed: Effected line is after previous effected line", f.Name().c_str());
 420             switch(*c) {
 421                case 'a':
 422                   cmdwanted = false;
 423                   ch.add = NULL;
 424                   ch.add_cnt = 0;
 425                   ch.add_len = 0;
 426                   ch.offset = s;
 427                   ch.del_cnt = 0;
 428                   break;
 429                case 'c':
 430                   if (unlikely(s == 0))
 431                      return _error->Error("Parsing patchfile %s failed: Change command can't effect line zero", f.Name().c_str());
 432                   cmdwanted = false;
 433                   ch.add = NULL;
 434                   ch.add_cnt = 0;
 435                   ch.add_len = 0;
 436                   ch.offset = s - 1;
 437                   ch.del_cnt = e - s + 1;
 438                   break;
 439                case 'd':
 440                   if (unlikely(s == 0))
 441                      return _error->Error("Parsing patchfile %s failed: Delete command can't effect line zero", f.Name().c_str());
 442                   ch.offset = s - 1;
 443                   ch.del_cnt = e - s + 1;
 444                   ch.add = NULL;
 445                   ch.add_cnt = 0;
 446                   ch.add_len = 0;
 447                   filechanges.add_change(ch);
 448                   break;
 449                default:
 450                   return _error->Error("Parsing patchfile %s failed: Unknown command", f.Name().c_str());
 451             }
 452          } else { /* !cmdwanted */
 453             if (strcmp(buffer, ".\n") == 0) {
 454                cmdwanted = true;
 455                filechanges.add_change(ch);
 456             } else {
 457                char *last = NULL;
 458                char *add;
 459                size_t l;
 460                if (ch.add)
 461                   last = ch.add + ch.add_len;
 462                l = strlen(buffer);
 463                add = add_text.add_easy(buffer, l, last);
 464                if (!add) {
 465                   ch.add_len += l;
 466                   ch.add_cnt++;
 467                } else {
 468                   if (ch.add) {
 469                      filechanges.add_change(ch);
 470                      ch.del_cnt = 0;
 471                   }
 472                   ch.offset += ch.add_cnt;
 473                   ch.add = add;
 474                   ch.add_len = l;
 475                   ch.add_cnt = 1;
 476                }
 477             }
 478          }
 479       } while(f.ReadLine(buffer, sizeof(buffer)));
 480       return true;
 481    }
 482
 483    void write_diff(FileFd &f)
 484    {
 485       unsigned long long line = 0;
 486       std::list<struct Change>::reverse_iterator ch;
 487       for (ch = filechanges.rbegin(); ch != filechanges.rend(); ++ch) {
 488          line += ch->offset + ch->del_cnt;
 489       }
 490
 491       for (ch = filechanges.rbegin(); ch != filechanges.rend(); ++ch) {
 492          std::list<struct Change>::reverse_iterator mg_i, mg_e = ch;
 493          while (ch->del_cnt == 0 && ch->offset == 0)
 494          {
 495             ++ch;
 496             if (unlikely(ch == filechanges.rend()))
 497                return;
 498          }
 499          line -= ch->del_cnt;
 500          std::string buf;
 501          if (ch->add_cnt > 0) {
 502             if (ch->del_cnt == 0) {
 503                strprintf(buf, "%llua\n", line);
 504             } else if (ch->del_cnt == 1) {
 505                strprintf(buf, "%lluc\n", line+1);
 506             } else {
 507                strprintf(buf, "%llu,%lluc\n", line+1, line+ch->del_cnt);
 508             }
 509             f.Write(buf.c_str(), buf.length());
 510
 511             mg_i = ch;
 512             do {
 513                dump_mem(f, mg_i->add, mg_i->add_len, NULL);
 514             } while (mg_i-- != mg_e);
 515
 516             buf = ".\n";
 517             f.Write(buf.c_str(), buf.length());
 518          } else if (ch->del_cnt == 1) {
 519             strprintf(buf, "%llud\n", line+1);
 520             f.Write(buf.c_str(), buf.length());
 521          } else if (ch->del_cnt > 1) {
 522             strprintf(buf, "%llu,%llud\n", line+1, line+ch->del_cnt);
 523             f.Write(buf.c_str(), buf.length());
 524          }
 525          line -= ch->offset;
 526       }
 527    }
 528
 529    void apply_against_file(FileFd &out, FileFd &in, Hashes *hash = NULL)
 530    {
 531       std::list<struct Change>::iterator ch;
 532       for (ch = filechanges.begin(); ch != filechanges.end(); ++ch) {
 533          dump_lines(out, in, ch->offset, hash);
 534          skip_lines(in, ch->del_cnt);
 535          dump_mem(out, ch->add, ch->add_len, hash);
 536       }
 537       dump_rest(out, in, hash);
 538       out.Flush();
 539    }
 540 };
 541
 542 class RredMethod : public aptMethod {
 543    private:
 544       bool Debug;
 545
 546       struct PDiffFile {
 547          std::string FileName;
 548          HashStringList ExpectedHashes;
 549          PDiffFile(std::string const &FileName, HashStringList const &ExpectedHashes) :
 550             FileName(FileName), ExpectedHashes(ExpectedHashes) {}
 551       };
 552
 553       HashStringList ReadExpectedHashesForPatch(unsigned int const patch, std::string const &Message)
 554       {
 555          HashStringList ExpectedHashes;
 556          for (char const * const * type = HashString::SupportedHashes(); *type != NULL; ++type)
 557          {
 558             std::string tagname;
 559             strprintf(tagname, "Patch-%d-%s-Hash", patch, *type);
 560             std::string const hashsum = LookupTag(Message, tagname.c_str());
 561             if (hashsum.empty() == false)
 562                ExpectedHashes.push_back(HashString(*type, hashsum));
 563          }
 564          return ExpectedHashes;
 565       }
 566
 567    protected:
 568       virtual bool URIAcquire(std::string const &Message, FetchItem *Itm) APT_OVERRIDE {
 569          Debug = _config->FindB("Debug::pkgAcquire::RRed", false);
 570          URI Get = Itm->Uri;
 571          std::string Path = Get.Host + Get.Path; // rred:/path - no host
 572
 573          FetchResult Res;
 574          Res.Filename = Itm->DestFile;
 575          if (Itm->Uri.empty())
 576          {
 577             Path = Itm->DestFile;
 578             Itm->DestFile.append(".result");
 579          } else
 580             URIStart(Res);
 581
 582          std::vector<PDiffFile> patchfiles;
 583          Patch patch;
 584
 585          if (FileExists(Path + ".ed") == true)
 586          {
 587             HashStringList const ExpectedHashes = ReadExpectedHashesForPatch(0, Message);
 588             std::string const FileName = Path + ".ed";
 589             if (ExpectedHashes.usable() == false)
 590                return _error->Error("No hashes found for uncompressed patch: %s", FileName.c_str());
 591             patchfiles.push_back(PDiffFile(FileName, ExpectedHashes));
 592          }
 593          else
 594          {
 595             _error->PushToStack();
 596             std::vector<std::string> patches = GetListOfFilesInDir(flNotFile(Path), "gz", true, false);
 597             _error->RevertToStack();
 598
 599             std::string const baseName = Path + ".ed.";
 600             unsigned int seen_patches = 0;
 601             for (std::vector<std::string>::const_iterator p = patches.begin();
 602                   p != patches.end(); ++p)
 603             {
 604                if (p->compare(0, baseName.length(), baseName) == 0)
 605                {
 606                   HashStringList const ExpectedHashes = ReadExpectedHashesForPatch(seen_patches, Message);
 607                   if (ExpectedHashes.usable() == false)
 608                      return _error->Error("No hashes found for uncompressed patch %d: %s", seen_patches, p->c_str());
 609                   patchfiles.push_back(PDiffFile(*p, ExpectedHashes));
 610                   ++seen_patches;
 611                }
 612             }
 613          }
 614
 615          std::string patch_name;
 616          for (std::vector<PDiffFile>::iterator I = patchfiles.begin();
 617                I != patchfiles.end();
 618                ++I)
 619          {
 620             patch_name = I->FileName;
 621             if (Debug == true)
 622                std::clog << "Patching " << Path << " with " << patch_name
 623                   << std::endl;
 624
 625             FileFd p;
 626             Hashes patch_hash(I->ExpectedHashes);
 627             // all patches are compressed, even if the name doesn't reflect it
 628             if (p.Open(patch_name, FileFd::ReadOnly, FileFd::Gzip) == false ||
 629                   patch.read_diff(p, &patch_hash) == false)
 630             {
 631                _error->DumpErrors(std::cerr, GlobalError::DEBUG, false);
 632                return false;
 633             }
 634             p.Close();
 635             HashStringList const hsl = patch_hash.GetHashStringList();
 636             if (hsl != I->ExpectedHashes)
 637                return _error->Error("Hash Sum mismatch for uncompressed patch %s", patch_name.c_str());
 638          }
 639
 640          if (Debug == true)
 641             std::clog << "Applying patches against " << Path
 642                << " and writing results to " << Itm->DestFile
 643                << std::endl;
 644
 645          FileFd inp, out;
 646          if (inp.Open(Path, FileFd::ReadOnly, FileFd::Extension) == false)
 647          {
 648             std::cerr << "FAILED to open inp " << Path << std::endl;
 649             return _error->Error("Failed to open inp %s", Path.c_str());
 650          }
 651          if (out.Open(Itm->DestFile, FileFd::WriteOnly | FileFd::Create | FileFd::BufferedWrite, FileFd::Extension) == false)
 652          {
 653             std::cerr << "FAILED to open out " << Itm->DestFile << std::endl;
 654             return _error->Error("Failed to open out %s", Itm->DestFile.c_str());
 655          }
 656
 657          Hashes hash(Itm->ExpectedHashes);
 658          patch.apply_against_file(out, inp, &hash);
 659
 660          out.Close();
 661          inp.Close();
 662
 663          if (_error->PendingError() == true) {
 664             std::cerr << "FAILED to read or write files" << std::endl;
 665             return false;
 666          }
 667
 668          if (Debug == true) {
 669             std::clog << "rred: finished file patching of " << Path  << "." << std::endl;
 670          }
 671
 672          struct stat bufbase, bufpatch;
 673          if (stat(Path.c_str(), &bufbase) != 0 ||
 674                stat(patch_name.c_str(), &bufpatch) != 0)
 675             return _error->Errno("stat", _("Failed to stat %s"), Path.c_str());
 676
 677          struct timeval times[2];
 678          times[0].tv_sec = bufbase.st_atime;
 679          times[1].tv_sec = bufpatch.st_mtime;
 680          times[0].tv_usec = times[1].tv_usec = 0;
 681          if (utimes(Itm->DestFile.c_str(), times) != 0)
 682             return _error->Errno("utimes",_("Failed to set modification time"));
 683
 684          if (stat(Itm->DestFile.c_str(), &bufbase) != 0)
 685             return _error->Errno("stat", _("Failed to stat %s"), Itm->DestFile.c_str());
 686
 687          Res.LastModified = bufbase.st_mtime;
 688          Res.Size = bufbase.st_size;
 689          Res.TakeHashes(hash);
 690          URIDone(Res);
 691
 692          return true;
 693       }
 694
 695    public:
 696       RredMethod() : aptMethod("rred", "2.0", SendConfig), Debug(false) {}
 697 };
 698
 699 int main(int argc, char **argv)
 700 {
 701    int i;
 702    bool just_diff = true;
 703    bool test = false;
 704    Patch patch;
 705
 706    if (argc <= 1) {
 707       RredMethod Mth;
 708       return Mth.Run();
 709    }
 710
 711    // Usage: rred -t input output diff ...
 712    if (argc > 1 && strcmp(argv[1], "-t") == 0) {
 713       // Read config files so we see compressors.
 714       pkgInitConfig(*_config);
 715       just_diff = false;
 716       test = true;
 717       i = 4;
 718    } else if (argc > 1 && strcmp(argv[1], "-f") == 0) {
 719       just_diff = false;
 720       i = 2;
 721    } else {
 722       i = 1;
 723    }
 724
 725    for (; i < argc; i++) {
 726       FileFd p;
 727       if (p.Open(argv[i], FileFd::ReadOnly) == false) {
 728          _error->DumpErrors(std::cerr);
 729          exit(1);
 730       }
 731       if (patch.read_diff(p, NULL) == false)
 732       {
 733          _error->DumpErrors(std::cerr);
 734          exit(2);
 735       }
 736    }
 737
 738    if (test) {
 739       FileFd out, inp;
 740       std::cerr << "Patching " << argv[2] << " into " << argv[3] << "\n";
 741       inp.Open(argv[2], FileFd::ReadOnly,FileFd::Extension);
 742       out.Open(argv[3], FileFd::WriteOnly | FileFd::Create | FileFd::BufferedWrite, FileFd::Extension);
 743       patch.apply_against_file(out, inp);
 744       out.Close();
 745    } else if (just_diff) {
 746       FileFd out;
 747       out.OpenDescriptor(STDOUT_FILENO, FileFd::WriteOnly | FileFd::Create);
 748       patch.write_diff(out);
 749       out.Close();
 750    } else {
 751       FileFd out, inp;
 752       out.OpenDescriptor(STDOUT_FILENO, FileFd::WriteOnly | FileFd::Create | FileFd::BufferedWrite);
 753       inp.OpenDescriptor(STDIN_FILENO, FileFd::ReadOnly);
 754       patch.apply_against_file(out, inp);
 755       out.Close();
 756    }
 757    return 0;
 758 }