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 #include "util/macros.h"
  32 #include "util/u_math.h"
  33
  34 /* Some versions of MinGW are missing _vscprintf's declaration, although they
  35  * still provide the symbol in the import library. */
  36 #ifdef __MINGW32__
  37 _CRTIMP int _vscprintf(const char *format, va_list argptr);
  38 #endif
  39
  40 #include "ralloc.h"
  41
  42 #ifndef va_copy
  43 #ifdef __va_copy
  44 #define va_copy(dest, src) __va_copy((dest), (src))
  45 #else
  46 #define va_copy(dest, src) (dest) = (src)
  47 #endif
  48 #endif
  49
  50 #define CANARY 0x5A1106
  51
  52 /* Align the header's size so that ralloc() allocations will return with the
  53  * same alignment as a libc malloc would have (8 on 32-bit GLIBC, 16 on
  54  * 64-bit), avoiding performance penalities on x86 and alignment faults on
  55  * ARM.
  56  */
  57 struct
  58 #ifdef _MSC_VER
  59 #if _WIN64
  60 __declspec(align(16))
  61 #else
  62  __declspec(align(8))
  63 #endif
  64 #elif defined(__LP64__)
  65  __attribute__((aligned(16)))
  66 #else
  67  __attribute__((aligned(8)))
  68 #endif
  69    ralloc_header
  70 {
  71 #ifndef NDEBUG
  72    /* A canary value used to determine whether a pointer is ralloc'd. */
  73    unsigned canary;
  74 #endif
  75
  76    struct ralloc_header *parent;
  77
  78    /* The first child (head of a linked list) */
  79    struct ralloc_header *child;
  80
  81    /* Linked list of siblings */
  82    struct ralloc_header *prev;
  83    struct ralloc_header *next;
  84
  85    void (*destructor)(void *);
  86 };
  87
  88 typedef struct ralloc_header ralloc_header;
  89
  90 static void unlink_block(ralloc_header *info);
  91 static void unsafe_free(ralloc_header *info);
  92
  93 static ralloc_header *
  94 get_header(const void *ptr)
  95 {
  96    ralloc_header *info = (ralloc_header *) (((char *) ptr) -
  97                                             sizeof(ralloc_header));
  98    assert(info->canary == CANARY);
  99    return info;
 100 }
 101
 102 #define PTR_FROM_HEADER(info) (((char *) info) + sizeof(ralloc_header))
 103
 104 static void
 105 add_child(ralloc_header *parent, ralloc_header *info)
 106 {
 107    if (parent != NULL) {
 108       info->parent = parent;
 109       info->next = parent->child;
 110       parent->child = info;
 111
 112       if (info->next != NULL)
 113          info->next->prev = info;
 114    }
 115 }
 116
 117 void *
 118 ralloc_context(const void *ctx)
 119 {
 120    return ralloc_size(ctx, 0);
 121 }
 122
 123 void *
 124 ralloc_size(const void *ctx, size_t size)
 125 {
 126    /* Some malloc allocation doesn't always align to 16 bytes even on 64 bits
 127     * system, from Android bionic/tests/malloc_test.cpp:
 128     *  - Allocations of a size that rounds up to a multiple of 16 bytes
 129     *    must have at least 16 byte alignment.
 130     *  - Allocations of a size that rounds up to a multiple of 8 bytes and
 131     *    not 16 bytes, are only required to have at least 8 byte alignment.
 132     */
 133    void *block = malloc(align64(size + sizeof(ralloc_header),
 134                                 alignof(ralloc_header)));
 135    ralloc_header *info;
 136    ralloc_header *parent;
 137
 138    if (unlikely(block == NULL))
 139       return NULL;
 140
 141    info = (ralloc_header *) block;
 142    /* measurements have shown that calloc is slower (because of
 143     * the multiplication overflow checking?), so clear things
 144     * manually
 145     */
 146    info->parent = NULL;
 147    info->child = NULL;
 148    info->prev = NULL;
 149    info->next = NULL;
 150    info->destructor = NULL;
 151
 152    parent = ctx != NULL ? get_header(ctx) : NULL;
 153
 154    add_child(parent, info);
 155
 156 #ifndef NDEBUG
 157    info->canary = CANARY;
 158 #endif
 159
 160    return PTR_FROM_HEADER(info);
 161 }
 162
 163 void *
 164 rzalloc_size(const void *ctx, size_t size)
 165 {
 166    void *ptr = ralloc_size(ctx, size);
 167
 168    if (likely(ptr))
 169       memset(ptr, 0, size);
 170
 171    return ptr;
 172 }
 173
 174 /* helper function - assumes ptr != NULL */
 175 static void *
 176 resize(void *ptr, size_t size)
 177 {
 178    ralloc_header *child, *old, *info;
 179
 180    old = get_header(ptr);
 181    info = realloc(old, align64(size + sizeof(ralloc_header),
 182                                alignof(ralloc_header)));
 183
 184    if (info == NULL)
 185       return NULL;
 186
 187    /* Update parent and sibling's links to the reallocated node. */
 188    if (info != old && info->parent != NULL) {
 189       if (info->parent->child == old)
 190          info->parent->child = info;
 191
 192       if (info->prev != NULL)
 193          info->prev->next = info;
 194
 195       if (info->next != NULL)
 196          info->next->prev = info;
 197    }
 198
 199    /* Update child->parent links for all children */
 200    for (child = info->child; child != NULL; child = child->next)
 201       child->parent = info;
 202
 203    return PTR_FROM_HEADER(info);
 204 }
 205
 206 void *
 207 reralloc_size(const void *ctx, void *ptr, size_t size)
 208 {
 209    if (unlikely(ptr == NULL))
 210       return ralloc_size(ctx, size);
 211
 212    assert(ralloc_parent(ptr) == ctx);
 213    return resize(ptr, size);
 214 }
 215
 216 void *
 217 rerzalloc_size(const void *ctx, void *ptr, size_t old_size, size_t new_size)
 218 {
 219    if (unlikely(ptr == NULL))
 220       return rzalloc_size(ctx, new_size);
 221
 222    assert(ralloc_parent(ptr) == ctx);
 223    ptr = resize(ptr, new_size);
 224
 225    if (new_size > old_size)
 226       memset((char *)ptr + old_size, 0, new_size - old_size);
 227
 228    return ptr;
 229 }
 230
 231 void *
 232 ralloc_array_size(const void *ctx, size_t size, unsigned count)
 233 {
 234    if (count > SIZE_MAX/size)
 235       return NULL;
 236
 237    return ralloc_size(ctx, size * count);
 238 }
 239
 240 void *
 241 rzalloc_array_size(const void *ctx, size_t size, unsigned count)
 242 {
 243    if (count > SIZE_MAX/size)
 244       return NULL;
 245
 246    return rzalloc_size(ctx, size * count);
 247 }
 248
 249 void *
 250 reralloc_array_size(const void *ctx, void *ptr, size_t size, unsigned count)
 251 {
 252    if (count > SIZE_MAX/size)
 253       return NULL;
 254
 255    return reralloc_size(ctx, ptr, size * count);
 256 }
 257
 258 void *
 259 rerzalloc_array_size(const void *ctx, void *ptr, size_t size,
 260                      unsigned old_count, unsigned new_count)
 261 {
 262    if (new_count > SIZE_MAX/size)
 263       return NULL;
 264
 265    return rerzalloc_size(ctx, ptr, size * old_count, size * new_count);
 266 }
 267
 268 void
 269 ralloc_free(void *ptr)
 270 {
 271    ralloc_header *info;
 272
 273    if (ptr == NULL)
 274       return;
 275
 276    info = get_header(ptr);
 277    unlink_block(info);
 278    unsafe_free(info);
 279 }
 280
 281 static void
 282 unlink_block(ralloc_header *info)
 283 {
 284    /* Unlink from parent & siblings */
 285    if (info->parent != NULL) {
 286       if (info->parent->child == info)
 287          info->parent->child = info->next;
 288
 289       if (info->prev != NULL)
 290          info->prev->next = info->next;
 291
 292       if (info->next != NULL)
 293          info->next->prev = info->prev;
 294    }
 295    info->parent = NULL;
 296    info->prev = NULL;
 297    info->next = NULL;
 298 }
 299
 300 static void
 301 unsafe_free(ralloc_header *info)
 302 {
 303    /* Recursively free any children...don't waste time unlinking them. */
 304    ralloc_header *temp;
 305    while (info->child != NULL) {
 306       temp = info->child;
 307       info->child = temp->next;
 308       unsafe_free(temp);
 309    }
 310
 311    /* Free the block itself.  Call the destructor first, if any. */
 312    if (info->destructor != NULL)
 313       info->destructor(PTR_FROM_HEADER(info));
 314
 315    free(info);
 316 }
 317
 318 void
 319 ralloc_steal(const void *new_ctx, void *ptr)
 320 {
 321    ralloc_header *info, *parent;
 322
 323    if (unlikely(ptr == NULL))
 324       return;
 325
 326    info = get_header(ptr);
 327    parent = new_ctx ? get_header(new_ctx) : NULL;
 328
 329    unlink_block(info);
 330
 331    add_child(parent, info);
 332 }
 333
 334 void
 335 ralloc_adopt(const void *new_ctx, void *old_ctx)
 336 {
 337    ralloc_header *new_info, *old_info, *child;
 338
 339    if (unlikely(old_ctx == NULL))
 340       return;
 341
 342    old_info = get_header(old_ctx);
 343    new_info = get_header(new_ctx);
 344
 345    /* If there are no children, bail. */
 346    if (unlikely(old_info->child == NULL))
 347       return;
 348
 349    /* Set all the children's parent to new_ctx; get a pointer to the last child. */
 350    for (child = old_info->child; child->next != NULL; child = child->next) {
 351       child->parent = new_info;
 352    }
 353    child->parent = new_info;
 354
 355    /* Connect the two lists together; parent them to new_ctx; make old_ctx empty. */
 356    child->next = new_info->child;
 357    if (child->next)
 358       child->next->prev = child;
 359    new_info->child = old_info->child;
 360    old_info->child = NULL;
 361 }
 362
 363 void *
 364 ralloc_parent(const void *ptr)
 365 {
 366    ralloc_header *info;
 367
 368    if (unlikely(ptr == NULL))
 369       return NULL;
 370
 371    info = get_header(ptr);
 372    return info->parent ? PTR_FROM_HEADER(info->parent) : NULL;
 373 }
 374
 375 void
 376 ralloc_set_destructor(const void *ptr, void(*destructor)(void *))
 377 {
 378    ralloc_header *info = get_header(ptr);
 379    info->destructor = destructor;
 380 }
 381
 382 char *
 383 ralloc_strdup(const void *ctx, const char *str)
 384 {
 385    size_t n;
 386    char *ptr;
 387
 388    if (unlikely(str == NULL))
 389       return NULL;
 390
 391    n = strlen(str);
 392    ptr = ralloc_array(ctx, char, n + 1);
 393    memcpy(ptr, str, n);
 394    ptr[n] = '\0';
 395    return ptr;
 396 }
 397
 398 char *
 399 ralloc_strndup(const void *ctx, const char *str, size_t max)
 400 {
 401    size_t n;
 402    char *ptr;
 403
 404    if (unlikely(str == NULL))
 405       return NULL;
 406
 407    n = strnlen(str, max);
 408    ptr = ralloc_array(ctx, char, n + 1);
 409    memcpy(ptr, str, n);
 410    ptr[n] = '\0';
 411    return ptr;
 412 }
 413
 414 /* helper routine for strcat/strncat - n is the exact amount to copy */
 415 static bool
 416 cat(char **dest, const char *str, size_t n)
 417 {
 418    char *both;
 419    size_t existing_length;
 420    assert(dest != NULL && *dest != NULL);
 421
 422    existing_length = strlen(*dest);
 423    both = resize(*dest, existing_length + n + 1);
 424    if (unlikely(both == NULL))
 425       return false;
 426
 427    memcpy(both + existing_length, str, n);
 428    both[existing_length + n] = '\0';
 429
 430    *dest = both;
 431    return true;
 432 }
 433
 434
 435 bool
 436 ralloc_strcat(char **dest, const char *str)
 437 {
 438    return cat(dest, str, strlen(str));
 439 }
 440
 441 bool
 442 ralloc_strncat(char **dest, const char *str, size_t n)
 443 {
 444    return cat(dest, str, strnlen(str, n));
 445 }
 446
 447 bool
 448 ralloc_str_append(char **dest, const char *str,
 449                   size_t existing_length, size_t str_size)
 450 {
 451    char *both;
 452    assert(dest != NULL && *dest != NULL);
 453
 454    both = resize(*dest, existing_length + str_size + 1);
 455    if (unlikely(both == NULL))
 456       return false;
 457
 458    memcpy(both + existing_length, str, str_size);
 459    both[existing_length + str_size] = '\0';
 460
 461    *dest = both;
 462
 463    return true;
 464 }
 465
 466 char *
 467 ralloc_asprintf(const void *ctx, const char *fmt, ...)
 468 {
 469    char *ptr;
 470    va_list args;
 471    va_start(args, fmt);
 472    ptr = ralloc_vasprintf(ctx, fmt, args);
 473    va_end(args);
 474    return ptr;
 475 }
 476
 477 /* Return the length of the string that would be generated by a printf-style
 478  * format and argument list, not including the \0 byte.
 479  */
 480 static size_t
 481 printf_length(const char *fmt, va_list untouched_args)
 482 {
 483    int size;
 484    char junk;
 485
 486    /* Make a copy of the va_list so the original caller can still use it */
 487    va_list args;
 488    va_copy(args, untouched_args);
 489
 490 #ifdef _WIN32
 491    /* We need to use _vcsprintf to calculate the size as vsnprintf returns -1
 492     * if the number of characters to write is greater than count.
 493     */
 494    size = _vscprintf(fmt, args);
 495    (void)junk;
 496 #else
 497    size = vsnprintf(&junk, 1, fmt, args);
 498 #endif
 499    assert(size >= 0);
 500
 501    va_end(args);
 502
 503    return size;
 504 }
 505
 506 char *
 507 ralloc_vasprintf(const void *ctx, const char *fmt, va_list args)
 508 {
 509    size_t size = printf_length(fmt, args) + 1;
 510
 511    char *ptr = ralloc_size(ctx, size);
 512    if (ptr != NULL)
 513       vsnprintf(ptr, size, fmt, args);
 514
 515    return ptr;
 516 }
 517
 518 bool
 519 ralloc_asprintf_append(char **str, const char *fmt, ...)
 520 {
 521    bool success;
 522    va_list args;
 523    va_start(args, fmt);
 524    success = ralloc_vasprintf_append(str, fmt, args);
 525    va_end(args);
 526    return success;
 527 }
 528
 529 bool
 530 ralloc_vasprintf_append(char **str, const char *fmt, va_list args)
 531 {
 532    size_t existing_length;
 533    assert(str != NULL);
 534    existing_length = *str ? strlen(*str) : 0;
 535    return ralloc_vasprintf_rewrite_tail(str, &existing_length, fmt, args);
 536 }
 537
 538 bool
 539 ralloc_asprintf_rewrite_tail(char **str, size_t *start, const char *fmt, ...)
 540 {
 541    bool success;
 542    va_list args;
 543    va_start(args, fmt);
 544    success = ralloc_vasprintf_rewrite_tail(str, start, fmt, args);
 545    va_end(args);
 546    return success;
 547 }
 548
 549 bool
 550 ralloc_vasprintf_rewrite_tail(char **str, size_t *start, const char *fmt,
 551                               va_list args)
 552 {
 553    size_t new_length;
 554    char *ptr;
 555
 556    assert(str != NULL);
 557
 558    if (unlikely(*str == NULL)) {
 559       // Assuming a NULL context is probably bad, but it's expected behavior.
 560       *str = ralloc_vasprintf(NULL, fmt, args);
 561       *start = strlen(*str);
 562       return true;
 563    }
 564
 565    new_length = printf_length(fmt, args);
 566
 567    ptr = resize(*str, *start + new_length + 1);
 568    if (unlikely(ptr == NULL))
 569       return false;
 570
 571    vsnprintf(ptr + *start, new_length + 1, fmt, args);
 572    *str = ptr;
 573    *start += new_length;
 574    return true;
 575 }
 576
 577 /***************************************************************************
 578  * Linear allocator for short-lived allocations.
 579  ***************************************************************************
 580  *
 581  * The allocator consists of a parent node (2K buffer), which requires
 582  * a ralloc parent, and child nodes (allocations). Child nodes can't be freed
 583  * directly, because the parent doesn't track them. You have to release
 584  * the parent node in order to release all its children.
 585  *
 586  * The allocator uses a fixed-sized buffer with a monotonically increasing
 587  * offset after each allocation. If the buffer is all used, another buffer
 588  * is allocated, sharing the same ralloc parent, so all buffers are at
 589  * the same level in the ralloc hierarchy.
 590  *
 591  * The linear parent node is always the first buffer and keeps track of all
 592  * other buffers.
 593  */
 594
 595 #define MIN_LINEAR_BUFSIZE 2048
 596 #define SUBALLOC_ALIGNMENT 8
 597 #define LMAGIC 0x87b9c7d3
 598
 599 struct
 600 #ifdef _MSC_VER
 601  __declspec(align(8))
 602 #elif defined(__LP64__)
 603  __attribute__((aligned(16)))
 604 #else
 605  __attribute__((aligned(8)))
 606 #endif
 607    linear_header {
 608 #ifndef NDEBUG
 609    unsigned magic;   /* for debugging */
 610 #endif
 611    unsigned offset;  /* points to the first unused byte in the buffer */
 612    unsigned size;    /* size of the buffer */
 613    void *ralloc_parent;          /* new buffers will use this */
 614    struct linear_header *next;   /* next buffer if we have more */
 615    struct linear_header *latest; /* the only buffer that has free space */
 616
 617    /* After this structure, the buffer begins.
 618     * Each suballocation consists of linear_size_chunk as its header followed
 619     * by the suballocation, so it goes:
 620     *
 621     * - linear_size_chunk
 622     * - allocated space
 623     * - linear_size_chunk
 624     * - allocated space
 625     * etc.
 626     *
 627     * linear_size_chunk is only needed by linear_realloc.
 628     */
 629 };
 630
 631 struct linear_size_chunk {
 632    unsigned size; /* for realloc */
 633    unsigned _padding;
 634 };
 635
 636 typedef struct linear_header linear_header;
 637 typedef struct linear_size_chunk linear_size_chunk;
 638
 639 #define LINEAR_PARENT_TO_HEADER(parent) \
 640    (linear_header*) \
 641    ((char*)(parent) - sizeof(linear_size_chunk) - sizeof(linear_header))
 642
 643 /* Allocate the linear buffer with its header. */
 644 static linear_header *
 645 create_linear_node(void *ralloc_ctx, unsigned min_size)
 646 {
 647    linear_header *node;
 648
 649    min_size += sizeof(linear_size_chunk);
 650
 651    if (likely(min_size < MIN_LINEAR_BUFSIZE))
 652       min_size = MIN_LINEAR_BUFSIZE;
 653
 654    node = ralloc_size(ralloc_ctx, sizeof(linear_header) + min_size);
 655    if (unlikely(!node))
 656       return NULL;
 657
 658 #ifndef NDEBUG
 659    node->magic = LMAGIC;
 660 #endif
 661    node->offset = 0;
 662    node->size = min_size;
 663    node->ralloc_parent = ralloc_ctx;
 664    node->next = NULL;
 665    node->latest = node;
 666    return node;
 667 }
 668
 669 void *
 670 linear_alloc_child(void *parent, unsigned size)
 671 {
 672    linear_header *first = LINEAR_PARENT_TO_HEADER(parent);
 673    linear_header *latest = first->latest;
 674    linear_header *new_node;
 675    linear_size_chunk *ptr;
 676    unsigned full_size;
 677
 678    assert(first->magic == LMAGIC);
 679    assert(!latest->next);
 680
 681    size = ALIGN_POT(size, SUBALLOC_ALIGNMENT);
 682    full_size = sizeof(linear_size_chunk) + size;
 683
 684    if (unlikely(latest->offset + full_size > latest->size)) {
 685       /* allocate a new node */
 686       new_node = create_linear_node(latest->ralloc_parent, size);
 687       if (unlikely(!new_node))
 688          return NULL;
 689
 690       first->latest = new_node;
 691       latest->latest = new_node;
 692       latest->next = new_node;
 693       latest = new_node;
 694    }
 695
 696    ptr = (linear_size_chunk *)((char*)&latest[1] + latest->offset);
 697    ptr->size = size;
 698    latest->offset += full_size;
 699
 700    assert((uintptr_t)&ptr[1] % SUBALLOC_ALIGNMENT == 0);
 701    return &ptr[1];
 702 }
 703
 704 void *
 705 linear_alloc_parent(void *ralloc_ctx, unsigned size)
 706 {
 707    linear_header *node;
 708
 709    if (unlikely(!ralloc_ctx))
 710       return NULL;
 711
 712    size = ALIGN_POT(size, SUBALLOC_ALIGNMENT);
 713
 714    node = create_linear_node(ralloc_ctx, size);
 715    if (unlikely(!node))
 716       return NULL;
 717
 718    return linear_alloc_child((char*)node +
 719                              sizeof(linear_header) +
 720                              sizeof(linear_size_chunk), size);
 721 }
 722
 723 void *
 724 linear_zalloc_child(void *parent, unsigned size)
 725 {
 726    void *ptr = linear_alloc_child(parent, size);
 727
 728    if (likely(ptr))
 729       memset(ptr, 0, size);
 730    return ptr;
 731 }
 732
 733 void *
 734 linear_zalloc_parent(void *parent, unsigned size)
 735 {
 736    void *ptr = linear_alloc_parent(parent, size);
 737
 738    if (likely(ptr))
 739       memset(ptr, 0, size);
 740    return ptr;
 741 }
 742
 743 void
 744 linear_free_parent(void *ptr)
 745 {
 746    linear_header *node;
 747
 748    if (unlikely(!ptr))
 749       return;
 750
 751    node = LINEAR_PARENT_TO_HEADER(ptr);
 752    assert(node->magic == LMAGIC);
 753
 754    while (node) {
 755       void *ptr = node;
 756
 757       node = node->next;
 758       ralloc_free(ptr);
 759    }
 760 }
 761
 762 void
 763 ralloc_steal_linear_parent(void *new_ralloc_ctx, void *ptr)
 764 {
 765    linear_header *node;
 766
 767    if (unlikely(!ptr))
 768       return;
 769
 770    node = LINEAR_PARENT_TO_HEADER(ptr);
 771    assert(node->magic == LMAGIC);
 772
 773    while (node) {
 774       ralloc_steal(new_ralloc_ctx, node);
 775       node->ralloc_parent = new_ralloc_ctx;
 776       node = node->next;
 777    }
 778 }
 779
 780 void *
 781 ralloc_parent_of_linear_parent(void *ptr)
 782 {
 783    linear_header *node = LINEAR_PARENT_TO_HEADER(ptr);
 784    assert(node->magic == LMAGIC);
 785    return node->ralloc_parent;
 786 }
 787
 788 void *
 789 linear_realloc(void *parent, void *old, unsigned new_size)
 790 {
 791    unsigned old_size = 0;
 792    ralloc_header *new_ptr;
 793
 794    new_ptr = linear_alloc_child(parent, new_size);
 795
 796    if (unlikely(!old))
 797       return new_ptr;
 798
 799    old_size = ((linear_size_chunk*)old)[-1].size;
 800
 801    if (likely(new_ptr && old_size))
 802       memcpy(new_ptr, old, MIN2(old_size, new_size));
 803
 804    return new_ptr;
 805 }
 806
 807 /* All code below is pretty much copied from ralloc and only the alloc
 808  * calls are different.
 809  */
 810
 811 char *
 812 linear_strdup(void *parent, const char *str)
 813 {
 814    unsigned n;
 815    char *ptr;
 816
 817    if (unlikely(!str))
 818       return NULL;
 819
 820    n = strlen(str);
 821    ptr = linear_alloc_child(parent, n + 1);
 822    if (unlikely(!ptr))
 823       return NULL;
 824
 825    memcpy(ptr, str, n);
 826    ptr[n] = '\0';
 827    return ptr;
 828 }
 829
 830 char *
 831 linear_asprintf(void *parent, const char *fmt, ...)
 832 {
 833    char *ptr;
 834    va_list args;
 835    va_start(args, fmt);
 836    ptr = linear_vasprintf(parent, fmt, args);
 837    va_end(args);
 838    return ptr;
 839 }
 840
 841 char *
 842 linear_vasprintf(void *parent, const char *fmt, va_list args)
 843 {
 844    unsigned size = printf_length(fmt, args) + 1;
 845
 846    char *ptr = linear_alloc_child(parent, size);
 847    if (ptr != NULL)
 848       vsnprintf(ptr, size, fmt, args);
 849
 850    return ptr;
 851 }
 852
 853 bool
 854 linear_asprintf_append(void *parent, char **str, const char *fmt, ...)
 855 {
 856    bool success;
 857    va_list args;
 858    va_start(args, fmt);
 859    success = linear_vasprintf_append(parent, str, fmt, args);
 860    va_end(args);
 861    return success;
 862 }
 863
 864 bool
 865 linear_vasprintf_append(void *parent, char **str, const char *fmt, va_list args)
 866 {
 867    size_t existing_length;
 868    assert(str != NULL);
 869    existing_length = *str ? strlen(*str) : 0;
 870    return linear_vasprintf_rewrite_tail(parent, str, &existing_length, fmt, args);
 871 }
 872
 873 bool
 874 linear_asprintf_rewrite_tail(void *parent, char **str, size_t *start,
 875                              const char *fmt, ...)
 876 {
 877    bool success;
 878    va_list args;
 879    va_start(args, fmt);
 880    success = linear_vasprintf_rewrite_tail(parent, str, start, fmt, args);
 881    va_end(args);
 882    return success;
 883 }
 884
 885 bool
 886 linear_vasprintf_rewrite_tail(void *parent, char **str, size_t *start,
 887                               const char *fmt, va_list args)
 888 {
 889    size_t new_length;
 890    char *ptr;
 891
 892    assert(str != NULL);
 893
 894    if (unlikely(*str == NULL)) {
 895       *str = linear_vasprintf(parent, fmt, args);
 896       *start = strlen(*str);
 897       return true;
 898    }
 899
 900    new_length = printf_length(fmt, args);
 901
 902    ptr = linear_realloc(parent, *str, *start + new_length + 1);
 903    if (unlikely(ptr == NULL))
 904       return false;
 905
 906    vsnprintf(ptr + *start, new_length + 1, fmt, args);
 907    *str = ptr;
 908    *start += new_length;
 909    return true;
 910 }
 911
 912 /* helper routine for strcat/strncat - n is the exact amount to copy */
 913 static bool
 914 linear_cat(void *parent, char **dest, const char *str, unsigned n)
 915 {
 916    char *both;
 917    unsigned existing_length;
 918    assert(dest != NULL && *dest != NULL);
 919
 920    existing_length = strlen(*dest);
 921    both = linear_realloc(parent, *dest, existing_length + n + 1);
 922    if (unlikely(both == NULL))
 923       return false;
 924
 925    memcpy(both + existing_length, str, n);
 926    both[existing_length + n] = '\0';
 927
 928    *dest = both;
 929    return true;
 930 }
 931
 932 bool
 933 linear_strcat(void *parent, char **dest, const char *str)
 934 {
 935    return linear_cat(parent, dest, str, strlen(str));
 936 }