src/util/ralloc.c

   1 /*
   2  * Copyright © 2010 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  21  * DEALINGS IN THE SOFTWARE.
  22  */
  23
  24 #include <assert.h>
  25 #include <stdlib.h>
  26 #include <stdarg.h>
  27 #include <stdio.h>
  28 #include <string.h>
  29 #include <stdint.h>
  30
  31 /* Some versions of MinGW are missing _vscprintf's declaration, although they
  32  * still provide the symbol in the import library. */
  33 #ifdef __MINGW32__
  34 _CRTIMP int _vscprintf(const char *format, va_list argptr);
  35 #endif
  36
  37 #include "ralloc.h"
  38
  39 #ifndef va_copy
  40 #ifdef __va_copy
  41 #define va_copy(dest, src) __va_copy((dest), (src))
  42 #else
  43 #define va_copy(dest, src) (dest) = (src)
  44 #endif
  45 #endif
  46
  47 #define CANARY 0x5A1106
  48
  49 /* Align the header's size so that ralloc() allocations will return with the
  50  * same alignment as a libc malloc would have (8 on 32-bit GLIBC, 16 on
  51  * 64-bit), avoiding performance penalities on x86 and alignment faults on
  52  * ARM.
  53  */
  54 struct
  55 #ifdef _MSC_VER
  56  __declspec(align(8))
  57 #elif defined(__LP64__)
  58  __attribute__((aligned(16)))
  59 #else
  60  __attribute__((aligned(8)))
  61 #endif
  62    ralloc_header
  63 {
  64 #ifdef DEBUG
  65    /* A canary value used to determine whether a pointer is ralloc'd. */
  66    unsigned canary;
  67 #endif
  68
  69    struct ralloc_header *parent;
  70
  71    /* The first child (head of a linked list) */
  72    struct ralloc_header *child;
  73
  74    /* Linked list of siblings */
  75    struct ralloc_header *prev;
  76    struct ralloc_header *next;
  77
  78    void (*destructor)(void *);
  79 };
  80
  81 typedef struct ralloc_header ralloc_header;
  82
  83 static void unlink_block(ralloc_header *info);
  84 static void unsafe_free(ralloc_header *info);
  85
  86 static ralloc_header *
  87 get_header(const void *ptr)
  88 {
  89    ralloc_header *info = (ralloc_header *) (((char *) ptr) -
  90                                             sizeof(ralloc_header));
  91 #ifdef DEBUG
  92    assert(info->canary == CANARY);
  93 #endif
  94    return info;
  95 }
  96
  97 #define PTR_FROM_HEADER(info) (((char *) info) + sizeof(ralloc_header))
  98
  99 static void
 100 add_child(ralloc_header *parent, ralloc_header *info)
 101 {
 102    if (parent != NULL) {
 103       info->parent = parent;
 104       info->next = parent->child;
 105       parent->child = info;
 106
 107       if (info->next != NULL)
 108          info->next->prev = info;
 109    }
 110 }
 111
 112 void *
 113 ralloc_context(const void *ctx)
 114 {
 115    return ralloc_size(ctx, 0);
 116 }
 117
 118 void *
 119 ralloc_size(const void *ctx, size_t size)
 120 {
 121    void *block = malloc(size + sizeof(ralloc_header));
 122    ralloc_header *info;
 123    ralloc_header *parent;
 124
 125    if (unlikely(block == NULL))
 126       return NULL;
 127
 128    info = (ralloc_header *) block;
 129    /* measurements have shown that calloc is slower (because of
 130     * the multiplication overflow checking?), so clear things
 131     * manually
 132     */
 133    info->parent = NULL;
 134    info->child = NULL;
 135    info->prev = NULL;
 136    info->next = NULL;
 137    info->destructor = NULL;
 138
 139    parent = ctx != NULL ? get_header(ctx) : NULL;
 140
 141    add_child(parent, info);
 142
 143 #ifdef DEBUG
 144    info->canary = CANARY;
 145 #endif
 146
 147    return PTR_FROM_HEADER(info);
 148 }
 149
 150 void *
 151 rzalloc_size(const void *ctx, size_t size)
 152 {
 153    void *ptr = ralloc_size(ctx, size);
 154
 155    if (likely(ptr))
 156       memset(ptr, 0, size);
 157
 158    return ptr;
 159 }
 160
 161 /* helper function - assumes ptr != NULL */
 162 static void *
 163 resize(void *ptr, size_t size)
 164 {
 165    ralloc_header *child, *old, *info;
 166
 167    old = get_header(ptr);
 168    info = realloc(old, size + sizeof(ralloc_header));
 169
 170    if (info == NULL)
 171       return NULL;
 172
 173    /* Update parent and sibling's links to the reallocated node. */
 174    if (info != old && info->parent != NULL) {
 175       if (info->parent->child == old)
 176          info->parent->child = info;
 177
 178       if (info->prev != NULL)
 179          info->prev->next = info;
 180
 181       if (info->next != NULL)
 182          info->next->prev = info;
 183    }
 184
 185    /* Update child->parent links for all children */
 186    for (child = info->child; child != NULL; child = child->next)
 187       child->parent = info;
 188
 189    return PTR_FROM_HEADER(info);
 190 }
 191
 192 void *
 193 reralloc_size(const void *ctx, void *ptr, size_t size)
 194 {
 195    if (unlikely(ptr == NULL))
 196       return ralloc_size(ctx, size);
 197
 198    assert(ralloc_parent(ptr) == ctx);
 199    return resize(ptr, size);
 200 }
 201
 202 void *
 203 ralloc_array_size(const void *ctx, size_t size, unsigned count)
 204 {
 205    if (count > SIZE_MAX/size)
 206       return NULL;
 207
 208    return ralloc_size(ctx, size * count);
 209 }
 210
 211 void *
 212 rzalloc_array_size(const void *ctx, size_t size, unsigned count)
 213 {
 214    if (count > SIZE_MAX/size)
 215       return NULL;
 216
 217    return rzalloc_size(ctx, size * count);
 218 }
 219
 220 void *
 221 reralloc_array_size(const void *ctx, void *ptr, size_t size, unsigned count)
 222 {
 223    if (count > SIZE_MAX/size)
 224       return NULL;
 225
 226    return reralloc_size(ctx, ptr, size * count);
 227 }
 228
 229 void
 230 ralloc_free(void *ptr)
 231 {
 232    ralloc_header *info;
 233
 234    if (ptr == NULL)
 235       return;
 236
 237    info = get_header(ptr);
 238    unlink_block(info);
 239    unsafe_free(info);
 240 }
 241
 242 static void
 243 unlink_block(ralloc_header *info)
 244 {
 245    /* Unlink from parent & siblings */
 246    if (info->parent != NULL) {
 247       if (info->parent->child == info)
 248          info->parent->child = info->next;
 249
 250       if (info->prev != NULL)
 251          info->prev->next = info->next;
 252
 253       if (info->next != NULL)
 254          info->next->prev = info->prev;
 255    }
 256    info->parent = NULL;
 257    info->prev = NULL;
 258    info->next = NULL;
 259 }
 260
 261 static void
 262 unsafe_free(ralloc_header *info)
 263 {
 264    /* Recursively free any children...don't waste time unlinking them. */
 265    ralloc_header *temp;
 266    while (info->child != NULL) {
 267       temp = info->child;
 268       info->child = temp->next;
 269       unsafe_free(temp);
 270    }
 271
 272    /* Free the block itself.  Call the destructor first, if any. */
 273    if (info->destructor != NULL)
 274       info->destructor(PTR_FROM_HEADER(info));
 275
 276    free(info);
 277 }
 278
 279 void
 280 ralloc_steal(const void *new_ctx, void *ptr)
 281 {
 282    ralloc_header *info, *parent;
 283
 284    if (unlikely(ptr == NULL))
 285       return;
 286
 287    info = get_header(ptr);
 288    parent = new_ctx ? get_header(new_ctx) : NULL;
 289
 290    unlink_block(info);
 291
 292    add_child(parent, info);
 293 }
 294
 295 void
 296 ralloc_adopt(const void *new_ctx, void *old_ctx)
 297 {
 298    ralloc_header *new_info, *old_info, *child;
 299
 300    if (unlikely(old_ctx == NULL))
 301       return;
 302
 303    old_info = get_header(old_ctx);
 304    new_info = get_header(new_ctx);
 305
 306    /* If there are no children, bail. */
 307    if (unlikely(old_info->child == NULL))
 308       return;
 309
 310    /* Set all the children's parent to new_ctx; get a pointer to the last child. */
 311    for (child = old_info->child; child->next != NULL; child = child->next) {
 312       child->parent = new_info;
 313    }
 314    child->parent = new_info;
 315
 316    /* Connect the two lists together; parent them to new_ctx; make old_ctx empty. */
 317    child->next = new_info->child;
 318    if (child->next)
 319       child->next->prev = child;
 320    new_info->child = old_info->child;
 321    old_info->child = NULL;
 322 }
 323
 324 void *
 325 ralloc_parent(const void *ptr)
 326 {
 327    ralloc_header *info;
 328
 329    if (unlikely(ptr == NULL))
 330       return NULL;
 331
 332    info = get_header(ptr);
 333    return info->parent ? PTR_FROM_HEADER(info->parent) : NULL;
 334 }
 335
 336 void
 337 ralloc_set_destructor(const void *ptr, void(*destructor)(void *))
 338 {
 339    ralloc_header *info = get_header(ptr);
 340    info->destructor = destructor;
 341 }
 342
 343 char *
 344 ralloc_strdup(const void *ctx, const char *str)
 345 {
 346    size_t n;
 347    char *ptr;
 348
 349    if (unlikely(str == NULL))
 350       return NULL;
 351
 352    n = strlen(str);
 353    ptr = ralloc_array(ctx, char, n + 1);
 354    memcpy(ptr, str, n);
 355    ptr[n] = '\0';
 356    return ptr;
 357 }
 358
 359 char *
 360 ralloc_strndup(const void *ctx, const char *str, size_t max)
 361 {
 362    size_t n;
 363    char *ptr;
 364
 365    if (unlikely(str == NULL))
 366       return NULL;
 367
 368    n = strnlen(str, max);
 369    ptr = ralloc_array(ctx, char, n + 1);
 370    memcpy(ptr, str, n);
 371    ptr[n] = '\0';
 372    return ptr;
 373 }
 374
 375 /* helper routine for strcat/strncat - n is the exact amount to copy */
 376 static bool
 377 cat(char **dest, const char *str, size_t n)
 378 {
 379    char *both;
 380    size_t existing_length;
 381    assert(dest != NULL && *dest != NULL);
 382
 383    existing_length = strlen(*dest);
 384    both = resize(*dest, existing_length + n + 1);
 385    if (unlikely(both == NULL))
 386       return false;
 387
 388    memcpy(both + existing_length, str, n);
 389    both[existing_length + n] = '\0';
 390
 391    *dest = both;
 392    return true;
 393 }
 394
 395
 396 bool
 397 ralloc_strcat(char **dest, const char *str)
 398 {
 399    return cat(dest, str, strlen(str));
 400 }
 401
 402 bool
 403 ralloc_strncat(char **dest, const char *str, size_t n)
 404 {
 405    return cat(dest, str, strnlen(str, n));
 406 }
 407
 408 bool
 409 ralloc_str_append(char **dest, const char *str,
 410                   size_t existing_length, size_t str_size)
 411 {
 412    char *both;
 413    assert(dest != NULL && *dest != NULL);
 414
 415    both = resize(*dest, existing_length + str_size + 1);
 416    if (unlikely(both == NULL))
 417       return false;
 418
 419    memcpy(both + existing_length, str, str_size);
 420    both[existing_length + str_size] = '\0';
 421
 422    *dest = both;
 423
 424    return true;
 425 }
 426
 427 char *
 428 ralloc_asprintf(const void *ctx, const char *fmt, ...)
 429 {
 430    char *ptr;
 431    va_list args;
 432    va_start(args, fmt);
 433    ptr = ralloc_vasprintf(ctx, fmt, args);
 434    va_end(args);
 435    return ptr;
 436 }
 437
 438 /* Return the length of the string that would be generated by a printf-style
 439  * format and argument list, not including the \0 byte.
 440  */
 441 static size_t
 442 printf_length(const char *fmt, va_list untouched_args)
 443 {
 444    int size;
 445    char junk;
 446
 447    /* Make a copy of the va_list so the original caller can still use it */
 448    va_list args;
 449    va_copy(args, untouched_args);
 450
 451 #ifdef _WIN32
 452    /* We need to use _vcsprintf to calculate the size as vsnprintf returns -1
 453     * if the number of characters to write is greater than count.
 454     */
 455    size = _vscprintf(fmt, args);
 456    (void)junk;
 457 #else
 458    size = vsnprintf(&junk, 1, fmt, args);
 459 #endif
 460    assert(size >= 0);
 461
 462    va_end(args);
 463
 464    return size;
 465 }
 466
 467 char *
 468 ralloc_vasprintf(const void *ctx, const char *fmt, va_list args)
 469 {
 470    size_t size = printf_length(fmt, args) + 1;
 471
 472    char *ptr = ralloc_size(ctx, size);
 473    if (ptr != NULL)
 474       vsnprintf(ptr, size, fmt, args);
 475
 476    return ptr;
 477 }
 478
 479 bool
 480 ralloc_asprintf_append(char **str, const char *fmt, ...)
 481 {
 482    bool success;
 483    va_list args;
 484    va_start(args, fmt);
 485    success = ralloc_vasprintf_append(str, fmt, args);
 486    va_end(args);
 487    return success;
 488 }
 489
 490 bool
 491 ralloc_vasprintf_append(char **str, const char *fmt, va_list args)
 492 {
 493    size_t existing_length;
 494    assert(str != NULL);
 495    existing_length = *str ? strlen(*str) : 0;
 496    return ralloc_vasprintf_rewrite_tail(str, &existing_length, fmt, args);
 497 }
 498
 499 bool
 500 ralloc_asprintf_rewrite_tail(char **str, size_t *start, const char *fmt, ...)
 501 {
 502    bool success;
 503    va_list args;
 504    va_start(args, fmt);
 505    success = ralloc_vasprintf_rewrite_tail(str, start, fmt, args);
 506    va_end(args);
 507    return success;
 508 }
 509
 510 bool
 511 ralloc_vasprintf_rewrite_tail(char **str, size_t *start, const char *fmt,
 512                               va_list args)
 513 {
 514    size_t new_length;
 515    char *ptr;
 516
 517    assert(str != NULL);
 518
 519    if (unlikely(*str == NULL)) {
 520       // Assuming a NULL context is probably bad, but it's expected behavior.
 521       *str = ralloc_vasprintf(NULL, fmt, args);
 522       *start = strlen(*str);
 523       return true;
 524    }
 525
 526    new_length = printf_length(fmt, args);
 527
 528    ptr = resize(*str, *start + new_length + 1);
 529    if (unlikely(ptr == NULL))
 530       return false;
 531
 532    vsnprintf(ptr + *start, new_length + 1, fmt, args);
 533    *str = ptr;
 534    *start += new_length;
 535    return true;
 536 }
 537
 538 /***************************************************************************
 539  * Linear allocator for short-lived allocations.
 540  ***************************************************************************
 541  *
 542  * The allocator consists of a parent node (2K buffer), which requires
 543  * a ralloc parent, and child nodes (allocations). Child nodes can't be freed
 544  * directly, because the parent doesn't track them. You have to release
 545  * the parent node in order to release all its children.
 546  *
 547  * The allocator uses a fixed-sized buffer with a monotonically increasing
 548  * offset after each allocation. If the buffer is all used, another buffer
 549  * is allocated, sharing the same ralloc parent, so all buffers are at
 550  * the same level in the ralloc hierarchy.
 551  *
 552  * The linear parent node is always the first buffer and keeps track of all
 553  * other buffers.
 554  */
 555
 556 #define MIN_LINEAR_BUFSIZE 2048
 557 #define SUBALLOC_ALIGNMENT sizeof(uintptr_t)
 558 #define LMAGIC 0x87b9c7d3
 559
 560 struct linear_header {
 561 #ifdef DEBUG
 562    unsigned magic;   /* for debugging */
 563 #endif
 564    unsigned offset;  /* points to the first unused byte in the buffer */
 565    unsigned size;    /* size of the buffer */
 566    void *ralloc_parent;          /* new buffers will use this */
 567    struct linear_header *next;   /* next buffer if we have more */
 568    struct linear_header *latest; /* the only buffer that has free space */
 569
 570    /* After this structure, the buffer begins.
 571     * Each suballocation consists of linear_size_chunk as its header followed
 572     * by the suballocation, so it goes:
 573     *
 574     * - linear_size_chunk
 575     * - allocated space
 576     * - linear_size_chunk
 577     * - allocated space
 578     * etc.
 579     *
 580     * linear_size_chunk is only needed by linear_realloc.
 581     */
 582 };
 583
 584 struct linear_size_chunk {
 585    unsigned size; /* for realloc */
 586    unsigned _padding;
 587 };
 588
 589 typedef struct linear_header linear_header;
 590 typedef struct linear_size_chunk linear_size_chunk;
 591
 592 #define LINEAR_PARENT_TO_HEADER(parent) \
 593    (linear_header*) \
 594    ((char*)(parent) - sizeof(linear_size_chunk) - sizeof(linear_header))
 595
 596 /* Allocate the linear buffer with its header. */
 597 static linear_header *
 598 create_linear_node(void *ralloc_ctx, unsigned min_size)
 599 {
 600    linear_header *node;
 601
 602    min_size += sizeof(linear_size_chunk);
 603
 604    if (likely(min_size < MIN_LINEAR_BUFSIZE))
 605       min_size = MIN_LINEAR_BUFSIZE;
 606
 607    node = ralloc_size(ralloc_ctx, sizeof(linear_header) + min_size);
 608    if (unlikely(!node))
 609       return NULL;
 610
 611 #ifdef DEBUG
 612    node->magic = LMAGIC;
 613 #endif
 614    node->offset = 0;
 615    node->size = min_size;
 616    node->ralloc_parent = ralloc_ctx;
 617    node->next = NULL;
 618    node->latest = node;
 619    return node;
 620 }
 621
 622 void *
 623 linear_alloc_child(void *parent, unsigned size)
 624 {
 625    linear_header *first = LINEAR_PARENT_TO_HEADER(parent);
 626    linear_header *latest = first->latest;
 627    linear_header *new_node;
 628    linear_size_chunk *ptr;
 629    unsigned full_size;
 630
 631 #ifdef DEBUG
 632    assert(first->magic == LMAGIC);
 633 #endif
 634    assert(!latest->next);
 635
 636    size = ALIGN_POT(size, SUBALLOC_ALIGNMENT);
 637    full_size = sizeof(linear_size_chunk) + size;
 638
 639    if (unlikely(latest->offset + full_size > latest->size)) {
 640       /* allocate a new node */
 641       new_node = create_linear_node(latest->ralloc_parent, size);
 642       if (unlikely(!new_node))
 643          return NULL;
 644
 645       first->latest = new_node;
 646       latest->latest = new_node;
 647       latest->next = new_node;
 648       latest = new_node;
 649    }
 650
 651    ptr = (linear_size_chunk *)((char*)&latest[1] + latest->offset);
 652    ptr->size = size;
 653    latest->offset += full_size;
 654    return &ptr[1];
 655 }
 656
 657 void *
 658 linear_alloc_parent(void *ralloc_ctx, unsigned size)
 659 {
 660    linear_header *node;
 661
 662    if (unlikely(!ralloc_ctx))
 663       return NULL;
 664
 665    size = ALIGN_POT(size, SUBALLOC_ALIGNMENT);
 666
 667    node = create_linear_node(ralloc_ctx, size);
 668    if (unlikely(!node))
 669       return NULL;
 670
 671    return linear_alloc_child((char*)node +
 672                              sizeof(linear_header) +
 673                              sizeof(linear_size_chunk), size);
 674 }
 675
 676 void *
 677 linear_zalloc_child(void *parent, unsigned size)
 678 {
 679    void *ptr = linear_alloc_child(parent, size);
 680
 681    if (likely(ptr))
 682       memset(ptr, 0, size);
 683    return ptr;
 684 }
 685
 686 void *
 687 linear_zalloc_parent(void *parent, unsigned size)
 688 {
 689    void *ptr = linear_alloc_parent(parent, size);
 690
 691    if (likely(ptr))
 692       memset(ptr, 0, size);
 693    return ptr;
 694 }
 695
 696 void
 697 linear_free_parent(void *ptr)
 698 {
 699    linear_header *node;
 700
 701    if (unlikely(!ptr))
 702       return;
 703
 704    node = LINEAR_PARENT_TO_HEADER(ptr);
 705 #ifdef DEBUG
 706    assert(node->magic == LMAGIC);
 707 #endif
 708
 709    while (node) {
 710       void *ptr = node;
 711
 712       node = node->next;
 713       ralloc_free(ptr);
 714    }
 715 }
 716
 717 void
 718 ralloc_steal_linear_parent(void *new_ralloc_ctx, void *ptr)
 719 {
 720    linear_header *node;
 721
 722    if (unlikely(!ptr))
 723       return;
 724
 725    node = LINEAR_PARENT_TO_HEADER(ptr);
 726 #ifdef DEBUG
 727    assert(node->magic == LMAGIC);
 728 #endif
 729
 730    while (node) {
 731       ralloc_steal(new_ralloc_ctx, node);
 732       node->ralloc_parent = new_ralloc_ctx;
 733       node = node->next;
 734    }
 735 }
 736
 737 void *
 738 ralloc_parent_of_linear_parent(void *ptr)
 739 {
 740    linear_header *node = LINEAR_PARENT_TO_HEADER(ptr);
 741 #ifdef DEBUG
 742    assert(node->magic == LMAGIC);
 743 #endif
 744    return node->ralloc_parent;
 745 }
 746
 747 void *
 748 linear_realloc(void *parent, void *old, unsigned new_size)
 749 {
 750    unsigned old_size = 0;
 751    ralloc_header *new_ptr;
 752
 753    new_ptr = linear_alloc_child(parent, new_size);
 754
 755    if (unlikely(!old))
 756       return new_ptr;
 757
 758    old_size = ((linear_size_chunk*)old)[-1].size;
 759
 760    if (likely(new_ptr && old_size))
 761       memcpy(new_ptr, old, MIN2(old_size, new_size));
 762
 763    return new_ptr;
 764 }
 765
 766 /* All code below is pretty much copied from ralloc and only the alloc
 767  * calls are different.
 768  */
 769
 770 char *
 771 linear_strdup(void *parent, const char *str)
 772 {
 773    unsigned n;
 774    char *ptr;
 775
 776    if (unlikely(!str))
 777       return NULL;
 778
 779    n = strlen(str);
 780    ptr = linear_alloc_child(parent, n + 1);
 781    if (unlikely(!ptr))
 782       return NULL;
 783
 784    memcpy(ptr, str, n);
 785    ptr[n] = '\0';
 786    return ptr;
 787 }
 788
 789 char *
 790 linear_asprintf(void *parent, const char *fmt, ...)
 791 {
 792    char *ptr;
 793    va_list args;
 794    va_start(args, fmt);
 795    ptr = linear_vasprintf(parent, fmt, args);
 796    va_end(args);
 797    return ptr;
 798 }
 799
 800 char *
 801 linear_vasprintf(void *parent, const char *fmt, va_list args)
 802 {
 803    unsigned size = printf_length(fmt, args) + 1;
 804
 805    char *ptr = linear_alloc_child(parent, size);
 806    if (ptr != NULL)
 807       vsnprintf(ptr, size, fmt, args);
 808
 809    return ptr;
 810 }
 811
 812 bool
 813 linear_asprintf_append(void *parent, char **str, const char *fmt, ...)
 814 {
 815    bool success;
 816    va_list args;
 817    va_start(args, fmt);
 818    success = linear_vasprintf_append(parent, str, fmt, args);
 819    va_end(args);
 820    return success;
 821 }
 822
 823 bool
 824 linear_vasprintf_append(void *parent, char **str, const char *fmt, va_list args)
 825 {
 826    size_t existing_length;
 827    assert(str != NULL);
 828    existing_length = *str ? strlen(*str) : 0;
 829    return linear_vasprintf_rewrite_tail(parent, str, &existing_length, fmt, args);
 830 }
 831
 832 bool
 833 linear_asprintf_rewrite_tail(void *parent, char **str, size_t *start,
 834                              const char *fmt, ...)
 835 {
 836    bool success;
 837    va_list args;
 838    va_start(args, fmt);
 839    success = linear_vasprintf_rewrite_tail(parent, str, start, fmt, args);
 840    va_end(args);
 841    return success;
 842 }
 843
 844 bool
 845 linear_vasprintf_rewrite_tail(void *parent, char **str, size_t *start,
 846                               const char *fmt, va_list args)
 847 {
 848    size_t new_length;
 849    char *ptr;
 850
 851    assert(str != NULL);
 852
 853    if (unlikely(*str == NULL)) {
 854       *str = linear_vasprintf(parent, fmt, args);
 855       *start = strlen(*str);
 856       return true;
 857    }
 858
 859    new_length = printf_length(fmt, args);
 860
 861    ptr = linear_realloc(parent, *str, *start + new_length + 1);
 862    if (unlikely(ptr == NULL))
 863       return false;
 864
 865    vsnprintf(ptr + *start, new_length + 1, fmt, args);
 866    *str = ptr;
 867    *start += new_length;
 868    return true;
 869 }
 870
 871 /* helper routine for strcat/strncat - n is the exact amount to copy */
 872 static bool
 873 linear_cat(void *parent, char **dest, const char *str, unsigned n)
 874 {
 875    char *both;
 876    unsigned existing_length;
 877    assert(dest != NULL && *dest != NULL);
 878
 879    existing_length = strlen(*dest);
 880    both = linear_realloc(parent, *dest, existing_length + n + 1);
 881    if (unlikely(both == NULL))
 882       return false;
 883
 884    memcpy(both + existing_length, str, n);
 885    both[existing_length + n] = '\0';
 886
 887    *dest = both;
 888    return true;
 889 }
 890
 891 bool
 892 linear_strcat(void *parent, char **dest, const char *str)
 893 {
 894    return linear_cat(parent, dest, str, strlen(str));
 895 }