apply.c

   1 /*
   2  * apply.c
   3  *
   4  * Copyright (C) Linus Torvalds, 2005
   5  *
   6  * This applies patches on top of some (arbitrary) version of the SCM.
   7  *
   8  * NOTE! It does all its work in the index file, and only cares about
   9  * the files in the working directory if you tell it to "merge" the
  10  * patch apply.
  11  *
  12  * Even when merging it always takes the source from the index, and
  13  * uses the working tree as a "branch" for a 3-way merge.
  14  */
  15 #include <ctype.h>
  16
  17 #include "cache.h"
  18
  19 // We default to the merge behaviour, since that's what most people would
  20 // expect
  21 static int merge_patch = 1;
  22 static const char apply_usage[] = "git-apply <patch>";
  23
  24 /*
  25  * Various "current state", notably line numbers and what
  26  * file (and how) we're patching right now.. The "is_xxxx"
  27  * things are flags, where -1 means "don't know yet".
  28  */
  29 static int linenr = 1;
  30 static int old_mode, new_mode;
  31 static char *old_name, *new_name, *def_name;
  32 static int is_rename, is_copy, is_new, is_delete;
  33
  34 #define CHUNKSIZE (8192)
  35 #define SLOP (16)
  36
  37 static void *read_patch_file(int fd, unsigned long *sizep)
  38 {
  39         unsigned long size = 0, alloc = CHUNKSIZE;
  40         void *buffer = xmalloc(alloc);
  41
  42         for (;;) {
  43                 int nr = alloc - size;
  44                 if (nr < 1024) {
  45                         alloc += CHUNKSIZE;
  46                         buffer = xrealloc(buffer, alloc);
  47                         nr = alloc - size;
  48                 }
  49                 nr = read(fd, buffer + size, nr);
  50                 if (!nr)
  51                         break;
  52                 if (nr < 0) {
  53                         if (errno == EAGAIN)
  54                                 continue;
  55                         die("git-apply: read returned %s", strerror(errno));
  56                 }
  57                 size += nr;
  58         }
  59         *sizep = size;
  60
  61         /*
  62          * Make sure that we have some slop in the buffer
  63          * so that we can do speculative "memcmp" etc, and
  64          * see to it that it is NUL-filled.
  65          */
  66         if (alloc < size + SLOP)
  67                 buffer = xrealloc(buffer, size + SLOP);
  68         memset(buffer + size, 0, SLOP);
  69         return buffer;
  70 }
  71
  72 static unsigned long linelen(char *buffer, unsigned long size)
  73 {
  74         unsigned long len = 0;
  75         while (size--) {
  76                 len++;
  77                 if (*buffer++ == '\n')
  78                         break;
  79         }
  80         return len;
  81 }
  82
  83 static int is_dev_null(const char *str)
  84 {
  85         return !memcmp("/dev/null", str, 9) && isspace(str[9]);
  86 }
  87
  88 static char * find_name(const char *line, char *def, int p_value)
  89 {
  90         int len;
  91         const char *start = line;
  92         char *name;
  93
  94         for (;;) {
  95                 char c = *line;
  96                 if (isspace(c))
  97                         break;
  98                 line++;
  99                 if (c == '/' && !--p_value)
 100                         start = line;
 101         }
 102         if (!start)
 103                 return def;
 104         len = line - start;
 105         if (!len)
 106                 return def;
 107
 108         /*
 109          * Generally we prefer the shorter name, especially
 110          * if the other one is just a variation of that with
 111          * something else tacked on to the end (ie "file.orig"
 112          * or "file~").
 113          */
 114         if (def) {
 115                 int deflen = strlen(def);
 116                 if (deflen < len && !strncmp(start, def, deflen))
 117                         return def;
 118         }
 119
 120         name = xmalloc(len + 1);
 121         memcpy(name, start, len);
 122         name[len] = 0;
 123         free(def);
 124         return name;
 125 }
 126
 127 /*
 128  * Get the name etc info from the --/+++ lines of a traditional patch header
 129  *
 130  * NOTE! This hardcodes "-p1" behaviour in filename detection.
 131  */
 132 static int parse_traditional_patch(const char *first, const char *second)
 133 {
 134         int p_value = 1;
 135         char *name;
 136
 137         first += 4;     // skip "--- "
 138         second += 4;    // skip "+++ "
 139         if (is_dev_null(first)) {
 140                 is_new = 1;
 141                 name = find_name(second, def_name, p_value);
 142         } else if (is_dev_null(second)) {
 143                 is_delete = 1;
 144                 name = find_name(first, def_name, p_value);
 145         } else {
 146                 name = find_name(first, def_name, p_value);
 147                 name = find_name(second, name, p_value);
 148         }
 149         if (!name)
 150                 die("unable to find filename in patch at line %d", linenr);
 151         old_name = name;
 152         new_name = name;
 153 }
 154
 155 static int gitdiff_hdrend(const char *line)
 156 {
 157         return -1;
 158 }
 159
 160 static int gitdiff_oldname(const char *line)
 161 {
 162         if (!old_name)
 163                 old_name = find_name(line, NULL, 1);
 164         return 0;
 165 }
 166
 167 static int gitdiff_newname(const char *line)
 168 {
 169         if (!new_name)
 170                 new_name = find_name(line, NULL, 1);
 171         return 0;
 172 }
 173
 174 static int gitdiff_oldmode(const char *line)
 175 {
 176         old_mode = strtoul(line, NULL, 8);
 177         return 0;
 178 }
 179
 180 static int gitdiff_newmode(const char *line)
 181 {
 182         new_mode = strtoul(line, NULL, 8);
 183         return 0;
 184 }
 185
 186 static int gitdiff_delete(const char *line)
 187 {
 188         is_delete = 1;
 189         return gitdiff_oldmode(line);
 190 }
 191
 192 static int gitdiff_newfile(const char *line)
 193 {
 194         is_new = 1;
 195         return gitdiff_newmode(line);
 196 }
 197
 198 static int gitdiff_copysrc(const char *line)
 199 {
 200         is_copy = 1;
 201         old_name = find_name(line, NULL, 0);
 202         return 0;
 203 }
 204
 205 static int gitdiff_copydst(const char *line)
 206 {
 207         is_copy = 1;
 208         new_name = find_name(line, NULL, 0);
 209         return 0;
 210 }
 211
 212 static int gitdiff_renamesrc(const char *line)
 213 {
 214         is_rename = 1;
 215         old_name = find_name(line, NULL, 0);
 216         return 0;
 217 }
 218
 219 static int gitdiff_renamedst(const char *line)
 220 {
 221         is_rename = 1;
 222         new_name = find_name(line, NULL, 0);
 223         return 0;
 224 }
 225
 226 static int gitdiff_similarity(const char *line)
 227 {
 228         return 0;
 229 }
 230
 231 /* Verify that we recognize the lines following a git header */
 232 static int parse_git_header(char *line, int len, unsigned int size)
 233 {
 234         unsigned long offset;
 235
 236         /* A git diff has explicit new/delete information, so we don't guess */
 237         is_new = 0;
 238         is_delete = 0;
 239
 240         line += len;
 241         size -= len;
 242         linenr++;
 243         for (offset = len ; size > 0 ; offset += len, size -= len, line += len, linenr++) {
 244                 static const struct opentry {
 245                         const char *str;
 246                         int (*fn)(const char *);
 247                 } optable[] = {
 248                         { "@@ -", gitdiff_hdrend },
 249                         { "--- ", gitdiff_oldname },
 250                         { "+++ ", gitdiff_newname },
 251                         { "old mode ", gitdiff_oldmode },
 252                         { "new mode ", gitdiff_newmode },
 253                         { "deleted file mode ", gitdiff_delete },
 254                         { "new file mode ", gitdiff_newfile },
 255                         { "copy from ", gitdiff_copysrc },
 256                         { "copy to ", gitdiff_copydst },
 257                         { "rename from ", gitdiff_renamesrc },
 258                         { "rename to ", gitdiff_renamedst },
 259                         { "similarity index ", gitdiff_similarity },
 260                 };
 261                 int i;
 262
 263                 len = linelen(line, size);
 264                 if (!len || line[len-1] != '\n')
 265                         break;
 266                 for (i = 0; i < sizeof(optable) / sizeof(optable[0]); i++) {
 267                         const struct opentry *p = optable + i;
 268                         int oplen = strlen(p->str);
 269                         if (len < oplen || memcmp(p->str, line, oplen))
 270                                 continue;
 271                         if (p->fn(line + oplen) < 0)
 272                                 return offset;
 273                 }
 274         }
 275
 276         return offset;
 277 }
 278
 279 static int parse_num(const char *line, int len, int offset, const char *expect, unsigned long *p)
 280 {
 281         char *ptr;
 282         int digits, ex;
 283
 284         if (offset < 0 || offset >= len)
 285                 return -1;
 286         line += offset;
 287         len -= offset;
 288
 289         if (!isdigit(*line))
 290                 return -1;
 291         *p = strtoul(line, &ptr, 10);
 292
 293         digits = ptr - line;
 294
 295         offset += digits;
 296         line += digits;
 297         len -= digits;
 298
 299         ex = strlen(expect);
 300         if (ex > len)
 301                 return -1;
 302         if (memcmp(line, expect, ex))
 303                 return -1;
 304
 305         return offset + ex;
 306 }
 307
 308 /*
 309  * Parse a unified diff fragment header of the
 310  * form "@@ -a,b +c,d @@"
 311  */
 312 static int parse_fragment_header(char *line, int len, unsigned long *pos)
 313 {
 314         int offset;
 315
 316         if (!len || line[len-1] != '\n')
 317                 return -1;
 318
 319         /* Figure out the number of lines in a fragment */
 320         offset = parse_num(line, len, 4, ",", pos);
 321         offset = parse_num(line, len, offset, " +", pos+1);
 322         offset = parse_num(line, len, offset, ",", pos+2);
 323         offset = parse_num(line, len, offset, " @@", pos+3);
 324
 325         return offset;
 326 }
 327
 328 static int find_header(char *line, unsigned long size, int *hdrsize)
 329 {
 330         unsigned long offset, len;
 331
 332         is_rename = is_copy = 0;
 333         is_new = is_delete = -1;
 334         old_mode = new_mode = 0;
 335         def_name = old_name = new_name = NULL;
 336         for (offset = 0; size > 0; offset += len, size -= len, line += len, linenr++) {
 337                 unsigned long nextlen;
 338
 339                 len = linelen(line, size);
 340                 if (!len)
 341                         break;
 342
 343                 /* Testing this early allows us to take a few shortcuts.. */
 344                 if (len < 6)
 345                         continue;
 346
 347                 /*
 348                  * Make sure we don't find any unconnected patch fragmants.
 349                  * That's a sign that we didn't find a header, and that a
 350                  * patch has become corrupted/broken up.
 351                  */
 352                 if (!memcmp("@@ -", line, 4)) {
 353                         unsigned long pos[4];
 354                         if (parse_fragment_header(line, len, pos) < 0)
 355                                 continue;
 356                         error("patch fragment without header at line %d: %.*s", linenr, len-1, line);
 357                 }
 358
 359                 if (size < len + 6)
 360                         break;
 361
 362                 /*
 363                  * Git patch? It might not have a real patch, just a rename
 364                  * or mode change, so we handle that specially
 365                  */
 366                 if (!memcmp("diff --git ", line, 11)) {
 367                         int git_hdr_len = parse_git_header(line, len, size);
 368                         if (git_hdr_len < 0)
 369                                 continue;
 370
 371                         *hdrsize = git_hdr_len;
 372                         return offset;
 373                 }
 374
 375                 /** --- followed by +++ ? */
 376                 if (memcmp("--- ", line,  4) || memcmp("+++ ", line + len, 4))
 377                         continue;
 378
 379                 /*
 380                  * We only accept unified patches, so we want it to
 381                  * at least have "@@ -a,b +c,d @@\n", which is 14 chars
 382                  * minimum
 383                  */
 384                 nextlen = linelen(line + len, size - len);
 385                 if (size < nextlen + 14 || memcmp("@@ -", line + len + nextlen, 4))
 386                         continue;
 387
 388                 /* Ok, we'll consider it a patch */
 389                 parse_traditional_patch(line, line+len);
 390                 *hdrsize = len + nextlen;
 391                 linenr += 2;
 392                 return offset;
 393         }
 394         return -1;
 395 }
 396
 397 /*
 398  * Parse a unified diff. Note that this really needs
 399  * to parse each fragment separately, since the only
 400  * way to know the difference between a "---" that is
 401  * part of a patch, and a "---" that starts the next
 402  * patch is to look at the line counts..
 403  */
 404 static int apply_fragment(char *line, unsigned long size)
 405 {
 406         int len = linelen(line, size), offset;
 407         unsigned long pos[4], oldlines, newlines;
 408
 409         offset = parse_fragment_header(line, len, pos);
 410         if (offset < 0)
 411                 return -1;
 412         oldlines = pos[1];
 413         newlines = pos[3];
 414
 415         if (is_new < 0 && (pos[0] || oldlines))
 416                 is_new = 0;
 417         if (is_delete < 0 && (pos[1] || newlines))
 418                 is_delete = 0;
 419
 420         /* Parse the thing.. */
 421         line += len;
 422         size -= len;
 423         linenr++;
 424         for (offset = len; size > 0; offset += len, size -= len, line += len, linenr++) {
 425                 if (!oldlines && !newlines)
 426                         break;
 427                 len = linelen(line, size);
 428                 if (!len || line[len-1] != '\n')
 429                         return -1;
 430                 switch (*line) {
 431                 default:
 432                         return -1;
 433                 case ' ':
 434                         oldlines--;
 435                         newlines--;
 436                         break;
 437                 case '-':
 438                         oldlines--;
 439                         break;
 440                 case '+':
 441                         newlines--;
 442                         break;
 443                 }
 444         }
 445         return offset;
 446 }
 447
 448 static int apply_single_patch(char *line, unsigned long size)
 449 {
 450         unsigned long offset = 0;
 451
 452         while (size > 4 && !memcmp(line, "@@ -", 4)) {
 453                 int len = apply_fragment(line, size);
 454                 if (len <= 0)
 455                         die("corrupt patch at line %d", linenr);
 456
 457 printf("applying fragment:\n%.*s\n\n", len, line);
 458
 459                 offset += len;
 460                 line += len;
 461                 size -= len;
 462         }
 463         return offset;
 464 }
 465
 466 static int apply_chunk(char *buffer, unsigned long size)
 467 {
 468         int hdrsize, patchsize;
 469         int offset = find_header(buffer, size, &hdrsize);
 470         char *header, *patch;
 471
 472         if (offset < 0)
 473                 return offset;
 474         header = buffer + offset;
 475
 476 printf("Found header:\n%.*s\n\n", hdrsize, header);
 477 printf("Rename: %d\n", is_rename);
 478 printf("Copy:   %d\n", is_copy);
 479 printf("New:    %d\n", is_new);
 480 printf("Delete: %d\n", is_delete);
 481 printf("Mode:   %o->%o\n", old_mode, new_mode);
 482 printf("Name:   '%s'->'%s'\n", old_name, new_name);
 483
 484         patch = header + hdrsize;
 485         patchsize = apply_single_patch(patch, size - offset - hdrsize);
 486
 487         return offset + hdrsize + patchsize;
 488 }
 489
 490 static int apply_patch(int fd)
 491 {
 492         unsigned long offset, size;
 493         char *buffer = read_patch_file(fd, &size);
 494
 495         if (!buffer)
 496                 return -1;
 497         offset = 0;
 498         while (size > 0) {
 499                 int nr = apply_chunk(buffer + offset, size);
 500                 if (nr < 0)
 501                         break;
 502                 offset += nr;
 503                 size -= nr;
 504         }
 505         free(buffer);
 506         return 0;
 507 }
 508
 509 int main(int argc, char **argv)
 510 {
 511         int i;
 512         int read_stdin = 1;
 513
 514         if (read_cache() < 0)
 515                 die("unable to read index file");
 516
 517         for (i = 1; i < argc; i++) {
 518                 const char *arg = argv[i];
 519                 int fd;
 520
 521                 if (!strcmp(arg, "-")) {
 522                         apply_patch(0);
 523                         read_stdin = 0;
 524                         continue;
 525                 }
 526                 if (!strcmp(arg, "--no-merge")) {
 527                         merge_patch = 0;
 528                         continue;
 529                 }
 530                 fd = open(arg, O_RDONLY);
 531                 if (fd < 0)
 532                         usage(apply_usage);
 533                 read_stdin = 0;
 534                 apply_patch(fd);
 535                 close(fd);
 536         }
 537         if (read_stdin)
 538                 apply_patch(0);
 539         return 0;
 540 }