strbuf.c

   1 #include "cache.h"
   2 #include "refs.h"
   3 #include "utf8.h"
   4
   5 int starts_with(const char *str, const char *prefix)
   6 {
   7         for (; ; str++, prefix++)
   8                 if (!*prefix)
   9                         return 1;
  10                 else if (*str != *prefix)
  11                         return 0;
  12 }
  13
  14 /*
  15  * Used as the default ->buf value, so that people can always assume
  16  * buf is non NULL and ->buf is NUL terminated even for a freshly
  17  * initialized strbuf.
  18  */
  19 char strbuf_slopbuf[1];
  20
  21 void strbuf_init(struct strbuf *sb, size_t hint)
  22 {
  23         sb->alloc = sb->len = 0;
  24         sb->buf = strbuf_slopbuf;
  25         if (hint)
  26                 strbuf_grow(sb, hint);
  27 }
  28
  29 void strbuf_release(struct strbuf *sb)
  30 {
  31         if (sb->alloc) {
  32                 free(sb->buf);
  33                 strbuf_init(sb, 0);
  34         }
  35 }
  36
  37 char *strbuf_detach(struct strbuf *sb, size_t *sz)
  38 {
  39         char *res;
  40         strbuf_grow(sb, 0);
  41         res = sb->buf;
  42         if (sz)
  43                 *sz = sb->len;
  44         strbuf_init(sb, 0);
  45         return res;
  46 }
  47
  48 void strbuf_attach(struct strbuf *sb, void *buf, size_t len, size_t alloc)
  49 {
  50         strbuf_release(sb);
  51         sb->buf   = buf;
  52         sb->len   = len;
  53         sb->alloc = alloc;
  54         strbuf_grow(sb, 0);
  55         sb->buf[sb->len] = '\0';
  56 }
  57
  58 void strbuf_grow(struct strbuf *sb, size_t extra)
  59 {
  60         int new_buf = !sb->alloc;
  61         if (unsigned_add_overflows(extra, 1) ||
  62             unsigned_add_overflows(sb->len, extra + 1))
  63                 die("you want to use way too much memory");
  64         if (new_buf)
  65                 sb->buf = NULL;
  66         ALLOC_GROW(sb->buf, sb->len + extra + 1, sb->alloc);
  67         if (new_buf)
  68                 sb->buf[0] = '\0';
  69 }
  70
  71 void strbuf_trim(struct strbuf *sb)
  72 {
  73         strbuf_rtrim(sb);
  74         strbuf_ltrim(sb);
  75 }
  76 void strbuf_rtrim(struct strbuf *sb)
  77 {
  78         while (sb->len > 0 && isspace((unsigned char)sb->buf[sb->len - 1]))
  79                 sb->len--;
  80         sb->buf[sb->len] = '\0';
  81 }
  82
  83 void strbuf_ltrim(struct strbuf *sb)
  84 {
  85         char *b = sb->buf;
  86         while (sb->len > 0 && isspace(*b)) {
  87                 b++;
  88                 sb->len--;
  89         }
  90         memmove(sb->buf, b, sb->len);
  91         sb->buf[sb->len] = '\0';
  92 }
  93
  94 int strbuf_reencode(struct strbuf *sb, const char *from, const char *to)
  95 {
  96         char *out;
  97         int len;
  98
  99         if (same_encoding(from, to))
 100                 return 0;
 101
 102         out = reencode_string_len(sb->buf, sb->len, to, from, &len);
 103         if (!out)
 104                 return -1;
 105
 106         strbuf_attach(sb, out, len, len);
 107         return 0;
 108 }
 109
 110 void strbuf_tolower(struct strbuf *sb)
 111 {
 112         char *p = sb->buf, *end = sb->buf + sb->len;
 113         for (; p < end; p++)
 114                 *p = tolower(*p);
 115 }
 116
 117 struct strbuf **strbuf_split_buf(const char *str, size_t slen,
 118                                  int terminator, int max)
 119 {
 120         struct strbuf **ret = NULL;
 121         size_t nr = 0, alloc = 0;
 122         struct strbuf *t;
 123
 124         while (slen) {
 125                 int len = slen;
 126                 if (max <= 0 || nr + 1 < max) {
 127                         const char *end = memchr(str, terminator, slen);
 128                         if (end)
 129                                 len = end - str + 1;
 130                 }
 131                 t = xmalloc(sizeof(struct strbuf));
 132                 strbuf_init(t, len);
 133                 strbuf_add(t, str, len);
 134                 ALLOC_GROW(ret, nr + 2, alloc);
 135                 ret[nr++] = t;
 136                 str += len;
 137                 slen -= len;
 138         }
 139         ALLOC_GROW(ret, nr + 1, alloc); /* In case string was empty */
 140         ret[nr] = NULL;
 141         return ret;
 142 }
 143
 144 void strbuf_list_free(struct strbuf **sbs)
 145 {
 146         struct strbuf **s = sbs;
 147
 148         while (*s) {
 149                 strbuf_release(*s);
 150                 free(*s++);
 151         }
 152         free(sbs);
 153 }
 154
 155 int strbuf_cmp(const struct strbuf *a, const struct strbuf *b)
 156 {
 157         int len = a->len < b->len ? a->len: b->len;
 158         int cmp = memcmp(a->buf, b->buf, len);
 159         if (cmp)
 160                 return cmp;
 161         return a->len < b->len ? -1: a->len != b->len;
 162 }
 163
 164 void strbuf_splice(struct strbuf *sb, size_t pos, size_t len,
 165                                    const void *data, size_t dlen)
 166 {
 167         if (unsigned_add_overflows(pos, len))
 168                 die("you want to use way too much memory");
 169         if (pos > sb->len)
 170                 die("`pos' is too far after the end of the buffer");
 171         if (pos + len > sb->len)
 172                 die("`pos + len' is too far after the end of the buffer");
 173
 174         if (dlen >= len)
 175                 strbuf_grow(sb, dlen - len);
 176         memmove(sb->buf + pos + dlen,
 177                         sb->buf + pos + len,
 178                         sb->len - pos - len);
 179         memcpy(sb->buf + pos, data, dlen);
 180         strbuf_setlen(sb, sb->len + dlen - len);
 181 }
 182
 183 void strbuf_insert(struct strbuf *sb, size_t pos, const void *data, size_t len)
 184 {
 185         strbuf_splice(sb, pos, 0, data, len);
 186 }
 187
 188 void strbuf_remove(struct strbuf *sb, size_t pos, size_t len)
 189 {
 190         strbuf_splice(sb, pos, len, NULL, 0);
 191 }
 192
 193 void strbuf_add(struct strbuf *sb, const void *data, size_t len)
 194 {
 195         strbuf_grow(sb, len);
 196         memcpy(sb->buf + sb->len, data, len);
 197         strbuf_setlen(sb, sb->len + len);
 198 }
 199
 200 void strbuf_adddup(struct strbuf *sb, size_t pos, size_t len)
 201 {
 202         strbuf_grow(sb, len);
 203         memcpy(sb->buf + sb->len, sb->buf + pos, len);
 204         strbuf_setlen(sb, sb->len + len);
 205 }
 206
 207 void strbuf_addchars(struct strbuf *sb, int c, size_t n)
 208 {
 209         strbuf_grow(sb, n);
 210         memset(sb->buf + sb->len, c, n);
 211         strbuf_setlen(sb, sb->len + n);
 212 }
 213
 214 void strbuf_addf(struct strbuf *sb, const char *fmt, ...)
 215 {
 216         va_list ap;
 217         va_start(ap, fmt);
 218         strbuf_vaddf(sb, fmt, ap);
 219         va_end(ap);
 220 }
 221
 222 static void add_lines(struct strbuf *out,
 223                         const char *prefix1,
 224                         const char *prefix2,
 225                         const char *buf, size_t size)
 226 {
 227         while (size) {
 228                 const char *prefix;
 229                 const char *next = memchr(buf, '\n', size);
 230                 next = next ? (next + 1) : (buf + size);
 231
 232                 prefix = ((prefix2 && (buf[0] == '\n' || buf[0] == '\t'))
 233                           ? prefix2 : prefix1);
 234                 strbuf_addstr(out, prefix);
 235                 strbuf_add(out, buf, next - buf);
 236                 size -= next - buf;
 237                 buf = next;
 238         }
 239         strbuf_complete_line(out);
 240 }
 241
 242 void strbuf_add_commented_lines(struct strbuf *out, const char *buf, size_t size)
 243 {
 244         static char prefix1[3];
 245         static char prefix2[2];
 246
 247         if (prefix1[0] != comment_line_char) {
 248                 xsnprintf(prefix1, sizeof(prefix1), "%c ", comment_line_char);
 249                 xsnprintf(prefix2, sizeof(prefix2), "%c", comment_line_char);
 250         }
 251         add_lines(out, prefix1, prefix2, buf, size);
 252 }
 253
 254 void strbuf_commented_addf(struct strbuf *sb, const char *fmt, ...)
 255 {
 256         va_list params;
 257         struct strbuf buf = STRBUF_INIT;
 258         int incomplete_line = sb->len && sb->buf[sb->len - 1] != '\n';
 259
 260         va_start(params, fmt);
 261         strbuf_vaddf(&buf, fmt, params);
 262         va_end(params);
 263
 264         strbuf_add_commented_lines(sb, buf.buf, buf.len);
 265         if (incomplete_line)
 266                 sb->buf[--sb->len] = '\0';
 267
 268         strbuf_release(&buf);
 269 }
 270
 271 void strbuf_vaddf(struct strbuf *sb, const char *fmt, va_list ap)
 272 {
 273         int len;
 274         va_list cp;
 275
 276         if (!strbuf_avail(sb))
 277                 strbuf_grow(sb, 64);
 278         va_copy(cp, ap);
 279         len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, cp);
 280         va_end(cp);
 281         if (len < 0)
 282                 die("BUG: your vsnprintf is broken (returned %d)", len);
 283         if (len > strbuf_avail(sb)) {
 284                 strbuf_grow(sb, len);
 285                 len = vsnprintf(sb->buf + sb->len, sb->alloc - sb->len, fmt, ap);
 286                 if (len > strbuf_avail(sb))
 287                         die("BUG: your vsnprintf is broken (insatiable)");
 288         }
 289         strbuf_setlen(sb, sb->len + len);
 290 }
 291
 292 void strbuf_expand(struct strbuf *sb, const char *format, expand_fn_t fn,
 293                    void *context)
 294 {
 295         for (;;) {
 296                 const char *percent;
 297                 size_t consumed;
 298
 299                 percent = strchrnul(format, '%');
 300                 strbuf_add(sb, format, percent - format);
 301                 if (!*percent)
 302                         break;
 303                 format = percent + 1;
 304
 305                 if (*format == '%') {
 306                         strbuf_addch(sb, '%');
 307                         format++;
 308                         continue;
 309                 }
 310
 311                 consumed = fn(sb, format, context);
 312                 if (consumed)
 313                         format += consumed;
 314                 else
 315                         strbuf_addch(sb, '%');
 316         }
 317 }
 318
 319 size_t strbuf_expand_dict_cb(struct strbuf *sb, const char *placeholder,
 320                 void *context)
 321 {
 322         struct strbuf_expand_dict_entry *e = context;
 323         size_t len;
 324
 325         for (; e->placeholder && (len = strlen(e->placeholder)); e++) {
 326                 if (!strncmp(placeholder, e->placeholder, len)) {
 327                         if (e->value)
 328                                 strbuf_addstr(sb, e->value);
 329                         return len;
 330                 }
 331         }
 332         return 0;
 333 }
 334
 335 void strbuf_addbuf_percentquote(struct strbuf *dst, const struct strbuf *src)
 336 {
 337         int i, len = src->len;
 338
 339         for (i = 0; i < len; i++) {
 340                 if (src->buf[i] == '%')
 341                         strbuf_addch(dst, '%');
 342                 strbuf_addch(dst, src->buf[i]);
 343         }
 344 }
 345
 346 size_t strbuf_fread(struct strbuf *sb, size_t size, FILE *f)
 347 {
 348         size_t res;
 349         size_t oldalloc = sb->alloc;
 350
 351         strbuf_grow(sb, size);
 352         res = fread(sb->buf + sb->len, 1, size, f);
 353         if (res > 0)
 354                 strbuf_setlen(sb, sb->len + res);
 355         else if (oldalloc == 0)
 356                 strbuf_release(sb);
 357         return res;
 358 }
 359
 360 ssize_t strbuf_read(struct strbuf *sb, int fd, size_t hint)
 361 {
 362         size_t oldlen = sb->len;
 363         size_t oldalloc = sb->alloc;
 364
 365         strbuf_grow(sb, hint ? hint : 8192);
 366         for (;;) {
 367                 ssize_t want = sb->alloc - sb->len - 1;
 368                 ssize_t got = read_in_full(fd, sb->buf + sb->len, want);
 369
 370                 if (got < 0) {
 371                         if (oldalloc == 0)
 372                                 strbuf_release(sb);
 373                         else
 374                                 strbuf_setlen(sb, oldlen);
 375                         return -1;
 376                 }
 377                 sb->len += got;
 378                 if (got < want)
 379                         break;
 380                 strbuf_grow(sb, 8192);
 381         }
 382
 383         sb->buf[sb->len] = '\0';
 384         return sb->len - oldlen;
 385 }
 386
 387 ssize_t strbuf_read_once(struct strbuf *sb, int fd, size_t hint)
 388 {
 389         ssize_t cnt;
 390
 391         strbuf_grow(sb, hint ? hint : 8192);
 392         cnt = xread_nonblock(fd, sb->buf + sb->len, sb->alloc - sb->len - 1);
 393         if (cnt > 0)
 394                 strbuf_setlen(sb, sb->len + cnt);
 395         return cnt;
 396 }
 397
 398 #define STRBUF_MAXLINK (2*PATH_MAX)
 399
 400 int strbuf_readlink(struct strbuf *sb, const char *path, size_t hint)
 401 {
 402         size_t oldalloc = sb->alloc;
 403
 404         if (hint < 32)
 405                 hint = 32;
 406
 407         while (hint < STRBUF_MAXLINK) {
 408                 int len;
 409
 410                 strbuf_grow(sb, hint);
 411                 len = readlink(path, sb->buf, hint);
 412                 if (len < 0) {
 413                         if (errno != ERANGE)
 414                                 break;
 415                 } else if (len < hint) {
 416                         strbuf_setlen(sb, len);
 417                         return 0;
 418                 }
 419
 420                 /* .. the buffer was too small - try again */
 421                 hint *= 2;
 422         }
 423         if (oldalloc == 0)
 424                 strbuf_release(sb);
 425         return -1;
 426 }
 427
 428 int strbuf_getcwd(struct strbuf *sb)
 429 {
 430         size_t oldalloc = sb->alloc;
 431         size_t guessed_len = 128;
 432
 433         for (;; guessed_len *= 2) {
 434                 strbuf_grow(sb, guessed_len);
 435                 if (getcwd(sb->buf, sb->alloc)) {
 436                         strbuf_setlen(sb, strlen(sb->buf));
 437                         return 0;
 438                 }
 439                 if (errno != ERANGE)
 440                         break;
 441         }
 442         if (oldalloc == 0)
 443                 strbuf_release(sb);
 444         else
 445                 strbuf_reset(sb);
 446         return -1;
 447 }
 448
 449 #ifdef HAVE_GETDELIM
 450 int strbuf_getwholeline(struct strbuf *sb, FILE *fp, int term)
 451 {
 452         ssize_t r;
 453
 454         if (feof(fp))
 455                 return EOF;
 456
 457         strbuf_reset(sb);
 458
 459         /* Translate slopbuf to NULL, as we cannot call realloc on it */
 460         if (!sb->alloc)
 461                 sb->buf = NULL;
 462         r = getdelim(&sb->buf, &sb->alloc, term, fp);
 463
 464         if (r > 0) {
 465                 sb->len = r;
 466                 return 0;
 467         }
 468         assert(r == -1);
 469
 470         /*
 471          * Normally we would have called xrealloc, which will try to free
 472          * memory and recover. But we have no way to tell getdelim() to do so.
 473          * Worse, we cannot try to recover ENOMEM ourselves, because we have
 474          * no idea how many bytes were read by getdelim.
 475          *
 476          * Dying here is reasonable. It mirrors what xrealloc would do on
 477          * catastrophic memory failure. We skip the opportunity to free pack
 478          * memory and retry, but that's unlikely to help for a malloc small
 479          * enough to hold a single line of input, anyway.
 480          */
 481         if (errno == ENOMEM)
 482                 die("Out of memory, getdelim failed");
 483
 484         /* Restore slopbuf that we moved out of the way before */
 485         if (!sb->buf)
 486                 strbuf_init(sb, 0);
 487         return EOF;
 488 }
 489 #else
 490 int strbuf_getwholeline(struct strbuf *sb, FILE *fp, int term)
 491 {
 492         int ch;
 493
 494         if (feof(fp))
 495                 return EOF;
 496
 497         strbuf_reset(sb);
 498         flockfile(fp);
 499         while ((ch = getc_unlocked(fp)) != EOF) {
 500                 if (!strbuf_avail(sb))
 501                         strbuf_grow(sb, 1);
 502                 sb->buf[sb->len++] = ch;
 503                 if (ch == term)
 504                         break;
 505         }
 506         funlockfile(fp);
 507         if (ch == EOF && sb->len == 0)
 508                 return EOF;
 509
 510         sb->buf[sb->len] = '\0';
 511         return 0;
 512 }
 513 #endif
 514
 515 int strbuf_getline(struct strbuf *sb, FILE *fp, int term)
 516 {
 517         if (strbuf_getwholeline(sb, fp, term))
 518                 return EOF;
 519         if (sb->buf[sb->len-1] == term)
 520                 strbuf_setlen(sb, sb->len-1);
 521         return 0;
 522 }
 523
 524 int strbuf_getwholeline_fd(struct strbuf *sb, int fd, int term)
 525 {
 526         strbuf_reset(sb);
 527
 528         while (1) {
 529                 char ch;
 530                 ssize_t len = xread(fd, &ch, 1);
 531                 if (len <= 0)
 532                         return EOF;
 533                 strbuf_addch(sb, ch);
 534                 if (ch == term)
 535                         break;
 536         }
 537         return 0;
 538 }
 539
 540 ssize_t strbuf_read_file(struct strbuf *sb, const char *path, size_t hint)
 541 {
 542         int fd;
 543         ssize_t len;
 544
 545         fd = open(path, O_RDONLY);
 546         if (fd < 0)
 547                 return -1;
 548         len = strbuf_read(sb, fd, hint);
 549         close(fd);
 550         if (len < 0)
 551                 return -1;
 552
 553         return len;
 554 }
 555
 556 void strbuf_add_lines(struct strbuf *out, const char *prefix,
 557                       const char *buf, size_t size)
 558 {
 559         add_lines(out, prefix, NULL, buf, size);
 560 }
 561
 562 void strbuf_addstr_xml_quoted(struct strbuf *buf, const char *s)
 563 {
 564         while (*s) {
 565                 size_t len = strcspn(s, "\"<>&");
 566                 strbuf_add(buf, s, len);
 567                 s += len;
 568                 switch (*s) {
 569                 case '"':
 570                         strbuf_addstr(buf, "&quot;");
 571                         break;
 572                 case '<':
 573                         strbuf_addstr(buf, "&lt;");
 574                         break;
 575                 case '>':
 576                         strbuf_addstr(buf, "&gt;");
 577                         break;
 578                 case '&':
 579                         strbuf_addstr(buf, "&amp;");
 580                         break;
 581                 case 0:
 582                         return;
 583                 }
 584                 s++;
 585         }
 586 }
 587
 588 static int is_rfc3986_reserved(char ch)
 589 {
 590         switch (ch) {
 591                 case '!': case '*': case '\'': case '(': case ')': case ';':
 592                 case ':': case '@': case '&': case '=': case '+': case '$':
 593                 case ',': case '/': case '?': case '#': case '[': case ']':
 594                         return 1;
 595         }
 596         return 0;
 597 }
 598
 599 static int is_rfc3986_unreserved(char ch)
 600 {
 601         return isalnum(ch) ||
 602                 ch == '-' || ch == '_' || ch == '.' || ch == '~';
 603 }
 604
 605 static void strbuf_add_urlencode(struct strbuf *sb, const char *s, size_t len,
 606                                  int reserved)
 607 {
 608         strbuf_grow(sb, len);
 609         while (len--) {
 610                 char ch = *s++;
 611                 if (is_rfc3986_unreserved(ch) ||
 612                     (!reserved && is_rfc3986_reserved(ch)))
 613                         strbuf_addch(sb, ch);
 614                 else
 615                         strbuf_addf(sb, "%%%02x", ch);
 616         }
 617 }
 618
 619 void strbuf_addstr_urlencode(struct strbuf *sb, const char *s,
 620                              int reserved)
 621 {
 622         strbuf_add_urlencode(sb, s, strlen(s), reserved);
 623 }
 624
 625 void strbuf_humanise_bytes(struct strbuf *buf, off_t bytes)
 626 {
 627         if (bytes > 1 << 30) {
 628                 strbuf_addf(buf, "%u.%2.2u GiB",
 629                             (int)(bytes >> 30),
 630                             (int)(bytes & ((1 << 30) - 1)) / 10737419);
 631         } else if (bytes > 1 << 20) {
 632                 int x = bytes + 5243;  /* for rounding */
 633                 strbuf_addf(buf, "%u.%2.2u MiB",
 634                             x >> 20, ((x & ((1 << 20) - 1)) * 100) >> 20);
 635         } else if (bytes > 1 << 10) {
 636                 int x = bytes + 5;  /* for rounding */
 637                 strbuf_addf(buf, "%u.%2.2u KiB",
 638                             x >> 10, ((x & ((1 << 10) - 1)) * 100) >> 10);
 639         } else {
 640                 strbuf_addf(buf, "%u bytes", (int)bytes);
 641         }
 642 }
 643
 644 void strbuf_add_absolute_path(struct strbuf *sb, const char *path)
 645 {
 646         if (!*path)
 647                 die("The empty string is not a valid path");
 648         if (!is_absolute_path(path)) {
 649                 struct stat cwd_stat, pwd_stat;
 650                 size_t orig_len = sb->len;
 651                 char *cwd = xgetcwd();
 652                 char *pwd = getenv("PWD");
 653                 if (pwd && strcmp(pwd, cwd) &&
 654                     !stat(cwd, &cwd_stat) &&
 655                     (cwd_stat.st_dev || cwd_stat.st_ino) &&
 656                     !stat(pwd, &pwd_stat) &&
 657                     pwd_stat.st_dev == cwd_stat.st_dev &&
 658                     pwd_stat.st_ino == cwd_stat.st_ino)
 659                         strbuf_addstr(sb, pwd);
 660                 else
 661                         strbuf_addstr(sb, cwd);
 662                 if (sb->len > orig_len && !is_dir_sep(sb->buf[sb->len - 1]))
 663                         strbuf_addch(sb, '/');
 664                 free(cwd);
 665         }
 666         strbuf_addstr(sb, path);
 667 }
 668
 669 int printf_ln(const char *fmt, ...)
 670 {
 671         int ret;
 672         va_list ap;
 673         va_start(ap, fmt);
 674         ret = vprintf(fmt, ap);
 675         va_end(ap);
 676         if (ret < 0 || putchar('\n') == EOF)
 677                 return -1;
 678         return ret + 1;
 679 }
 680
 681 int fprintf_ln(FILE *fp, const char *fmt, ...)
 682 {
 683         int ret;
 684         va_list ap;
 685         va_start(ap, fmt);
 686         ret = vfprintf(fp, fmt, ap);
 687         va_end(ap);
 688         if (ret < 0 || putc('\n', fp) == EOF)
 689                 return -1;
 690         return ret + 1;
 691 }
 692
 693 char *xstrdup_tolower(const char *string)
 694 {
 695         char *result;
 696         size_t len, i;
 697
 698         len = strlen(string);
 699         result = xmalloc(len + 1);
 700         for (i = 0; i < len; i++)
 701                 result[i] = tolower(string[i]);
 702         result[i] = '\0';
 703         return result;
 704 }
 705
 706 char *xstrvfmt(const char *fmt, va_list ap)
 707 {
 708         struct strbuf buf = STRBUF_INIT;
 709         strbuf_vaddf(&buf, fmt, ap);
 710         return strbuf_detach(&buf, NULL);
 711 }
 712
 713 char *xstrfmt(const char *fmt, ...)
 714 {
 715         va_list ap;
 716         char *ret;
 717
 718         va_start(ap, fmt);
 719         ret = xstrvfmt(fmt, ap);
 720         va_end(ap);
 721
 722         return ret;
 723 }
 724
 725 void strbuf_addftime(struct strbuf *sb, const char *fmt, const struct tm *tm)
 726 {
 727         size_t hint = 128;
 728         size_t len;
 729
 730         if (!*fmt)
 731                 return;
 732
 733         strbuf_grow(sb, hint);
 734         len = strftime(sb->buf + sb->len, sb->alloc - sb->len, fmt, tm);
 735
 736         if (!len) {
 737                 /*
 738                  * strftime reports "0" if it could not fit the result in the buffer.
 739                  * Unfortunately, it also reports "0" if the requested time string
 740                  * takes 0 bytes. So our strategy is to munge the format so that the
 741                  * output contains at least one character, and then drop the extra
 742                  * character before returning.
 743                  */
 744                 struct strbuf munged_fmt = STRBUF_INIT;
 745                 strbuf_addf(&munged_fmt, "%s ", fmt);
 746                 while (!len) {
 747                         hint *= 2;
 748                         strbuf_grow(sb, hint);
 749                         len = strftime(sb->buf + sb->len, sb->alloc - sb->len,
 750                                        munged_fmt.buf, tm);
 751                 }
 752                 strbuf_release(&munged_fmt);
 753                 len--; /* drop munged space */
 754         }
 755         strbuf_setlen(sb, sb->len + len);
 756 }
 757
 758 void strbuf_add_unique_abbrev(struct strbuf *sb, const unsigned char *sha1,
 759                               int abbrev_len)
 760 {
 761         int r;
 762         strbuf_grow(sb, GIT_SHA1_HEXSZ + 1);
 763         r = find_unique_abbrev_r(sb->buf + sb->len, sha1, abbrev_len);
 764         strbuf_setlen(sb, sb->len + r);
 765 }
 766
 767 /*
 768  * Returns the length of a line, without trailing spaces.
 769  *
 770  * If the line ends with newline, it will be removed too.
 771  */
 772 static size_t cleanup(char *line, size_t len)
 773 {
 774         while (len) {
 775                 unsigned char c = line[len - 1];
 776                 if (!isspace(c))
 777                         break;
 778                 len--;
 779         }
 780
 781         return len;
 782 }
 783
 784 /*
 785  * Remove empty lines from the beginning and end
 786  * and also trailing spaces from every line.
 787  *
 788  * Turn multiple consecutive empty lines between paragraphs
 789  * into just one empty line.
 790  *
 791  * If the input has only empty lines and spaces,
 792  * no output will be produced.
 793  *
 794  * If last line does not have a newline at the end, one is added.
 795  *
 796  * Enable skip_comments to skip every line starting with comment
 797  * character.
 798  */
 799 void strbuf_stripspace(struct strbuf *sb, int skip_comments)
 800 {
 801         int empties = 0;
 802         size_t i, j, len, newlen;
 803         char *eol;
 804
 805         /* We may have to add a newline. */
 806         strbuf_grow(sb, 1);
 807
 808         for (i = j = 0; i < sb->len; i += len, j += newlen) {
 809                 eol = memchr(sb->buf + i, '\n', sb->len - i);
 810                 len = eol ? eol - (sb->buf + i) + 1 : sb->len - i;
 811
 812                 if (skip_comments && len && sb->buf[i] == comment_line_char) {
 813                         newlen = 0;
 814                         continue;
 815                 }
 816                 newlen = cleanup(sb->buf + i, len);
 817
 818                 /* Not just an empty line? */
 819                 if (newlen) {
 820                         if (empties > 0 && j > 0)
 821                                 sb->buf[j++] = '\n';
 822                         empties = 0;
 823                         memmove(sb->buf + j, sb->buf + i, newlen);
 824                         sb->buf[newlen + j++] = '\n';
 825                 } else {
 826                         empties++;
 827                 }
 828         }
 829
 830         strbuf_setlen(sb, j);
 831 }