88 lines
4.3 KiB
C
88 lines
4.3 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=8 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ This program is free software; you can redistribute it and/or modify │
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│ it under the terms of the GNU General Public License as published by │
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│ the Free Software Foundation; version 2 of the License. │
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│ │
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│ This program is distributed in the hope that it will be useful, but │
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│ WITHOUT ANY WARRANTY; without even the implied warranty of │
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│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
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│ General Public License for more details. │
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│ │
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│ You should have received a copy of the GNU General Public License │
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│ along with this program; if not, write to the Free Software │
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│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
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│ 02110-1301 USA │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/assert.h"
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#include "libc/bits/bits.h"
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#include "libc/bits/weaken.h"
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#include "libc/conv/conv.h"
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#include "libc/macros.h"
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#include "libc/mem/mem.h"
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#include "libc/runtime/runtime.h"
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#include "libc/str/str.h"
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#include "libc/sysv/errfuns.h"
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#define GUARANTEE_TERMINATOR 1
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#define INITIAL_CAPACITY (32 - GUARANTEE_TERMINATOR)
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/**
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* Grows array, The Cosmopolitan Way.
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*
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* This function may be called once an array has run out of space. If p
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* is NULL, a new array is allocated; otherwise, the array's made 1.5x
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* bigger. It has been written that this amortizes list appends down to
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* constant-time. Extended memory is zeroed. Growth is monotonic.
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*
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* If p points to to static memory or something on the stack, it'll be
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* converted to dynamic memory automatically. This can make algorithms
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* faster when the average case is a small amount of data. It also means
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* functions using this (and free_s()) won't have a hard-requirement on
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* malloc().
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*
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* Consider trying the higher-level append() and concat() APIs (defined
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* in libc/alg/arraylist.h) as an alternative to directly using grow().
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*
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* @param pp points to pointer holding memory address
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* @param capacity tracks maximum items that can be stored in p
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* can only be 0 if p is NULL (see reallocarray() for non-monotonic)
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* @param itemsize is the sizeof each item
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* @return true on success, or false w/ errno and *p is NOT free()'d
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* @error ENOMEM if realloc() not linked or mmap() failed
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* @note tiny programs might need to explicitly YOINK(realloc)
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* @see test/libc/runtime/grow_test.c
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*/
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bool __grow(void *pp, size_t *capacity, size_t itemsize, size_t extra) {
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void **p, *p1, *p2;
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size_t n1, n2; /* item counts */
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size_t t1, t2; /* byte counts */
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extra += GUARANTEE_TERMINATOR; /* p ⊃ p[𝑖]==0 */
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p = (void **)pp;
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assert(itemsize);
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assert((*p && *capacity) || (!*p && !*capacity));
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assert(!isheap(*p) || ((intptr_t)*p & 15) == 0);
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p1 = isheap(*p) ? *p : NULL;
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p2 = NULL;
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n1 = *capacity;
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n2 = (*p ? n1 + (n1 >> 1) : MAX(4, INITIAL_CAPACITY / itemsize)) + extra;
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if (!__builtin_mul_overflow(n1, itemsize, &t1) &&
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!__builtin_mul_overflow(n2, itemsize, &t2)) {
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if (weaken(realloc) && (p2 = weaken(realloc)(p1, ROUNDUP(t2, 32)))) {
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if (!p1 && *p) memcpy(p2, *p, t1);
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memset((char *)p2 + t1, 0, t2 - t1);
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*capacity = n2;
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*p = p2;
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return true;
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} else {
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enomem();
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}
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} else {
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eoverflow();
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}
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return false;
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}
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