cosmopolitan/libc/stdio/appendr.c
Justine Tunney d5910e2673
Fix bugs and make code tinier
- Fixed bug where stdio eof wasn't being sticky
- Fixed bug where fseeko() wasn't clearing eof state
- Removed assert() usage from libc favoring _unassert() / _npassert()
2022-10-09 23:21:34 -07:00

76 lines
3.2 KiB
C

/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ Copyright 2021 Justine Alexandra Roberts Tunney │
│ │
│ Permission to use, copy, modify, and/or distribute this software for │
│ any purpose with or without fee is hereby granted, provided that the │
│ above copyright notice and this permission notice appear in all copies. │
│ │
│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/assert.h"
#include "libc/dce.h"
#include "libc/intrin/bsr.h"
#include "libc/macros.internal.h"
#include "libc/mem/mem.h"
#include "libc/stdio/append.h"
#include "libc/str/str.h"
#define W sizeof(size_t)
/**
* Resets length of append buffer, e.g.
*
* char *b = 0;
* appends(&b, "hello");
* appendr(&b, 1);
* assert(!strcmp(b, "h"));
* appendr(&b, 0);
* assert(!strcmp(b, ""));
* free(b);
*
* If `i` is greater than the current length then the extra bytes are
* filled with NUL characters. If `i` is less than the current length
* then memory is released to the system.
*
* The resulting buffer is guaranteed to be NUL-terminated, i.e.
* `!b[appendz(b).i]` will be the case even if both params are 0.
*
* @return `i` or -1 if `ENOMEM`
* @see appendz(b).i to get buffer length
*/
ssize_t appendr(char **b, size_t i) {
char *p;
size_t n;
struct appendz z;
_unassert(b);
z = appendz((p = *b));
if (i != z.i || !p) {
n = ROUNDUP(i + 1, 8) + W;
if (n > z.n || _bsrl(n) < _bsrl(z.n)) {
if ((p = realloc(p, n))) {
z.n = malloc_usable_size(p);
_unassert(!(z.n & (W - 1)));
*b = p;
} else {
return -1;
}
}
if (i > z.i) {
bzero(p + z.i, i - z.i + 1);
} else {
p[i] = 0;
}
*(size_t *)(p + z.n - W) =
i | (!IsTiny() && W == 8 ? (size_t)APPEND_COOKIE << 48 : 0);
}
return i;
}