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Justine Tunney 2020-06-15 07:18:57 -07:00
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libc/mem/realloc.S Normal file
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/*-*- mode:asm; indent-tabs-mode:t; tab-width:8; coding:utf-8 -*-│
│vi: set et ft=asm ts=8 tw=8 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2020 Justine Alexandra Roberts Tunney │
│ │
│ This program is free software; you can redistribute it and/or modify │
│ it under the terms of the GNU General Public License as published by │
│ the Free Software Foundation; version 2 of the License. │
│ │
│ This program is distributed in the hope that it will be useful, but │
│ WITHOUT ANY WARRANTY; without even the implied warranty of │
│ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU │
│ General Public License for more details. │
│ │
│ You should have received a copy of the GNU General Public License │
│ along with this program; if not, write to the Free Software │
│ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA │
│ 02110-1301 USA │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/macros.h"
#include "libc/notice.inc"
.yoink __FILE__
/ Allocates / resizes / frees memory, e.g.
/
/ Returns a pointer to a chunk of size n that contains the same data as
/ does chunk p up to the minimum of (n, p's size) bytes, or null if no
/ space is available.
/
/ If p is NULL, realloc is equivalent to malloc.
/ If p is not NULL and n is 0, realloc is equivalent to free.
/
/ The returned pointer may or may not be the same as p. The algorithm
/ prefers extending p in most cases when possible, otherwise it employs
/ the equivalent of a malloc-copy-free sequence.
/
/ Please note that p is NOT free()'d should realloc() fail, thus:
/
/ if ((p2 = realloc(p, n2))) {
/ p = p2;
/ ...
/ } else {
/ ...
/ }
/
/ if n is for fewer bytes than already held by p, the newly unused
/ space is lopped off and freed if possible.
/
/ The old unix realloc convention of allowing the last-free'd chunk to
/ be used as an argument to realloc is not supported.
/
/ @param rdi (p) is address of current allocation or NULL
/ @param rsi (n) is number of bytes needed
/ @return rax is result, or NULL w/ errno w/o free(p)
/ @note realloc(p=0, n=0) → malloc(32)
/ @note realloc(p≠0, n=0) → free(p)
/ @see dlrealloc()
realloc:jmp *hook$realloc(%rip)
.endfn realloc,globl