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/*-*- 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 2020 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/calls/calls.h"
#include "libc/errno.h"
#include "libc/rand/lcg.internal.h"
#include "libc/rand/rand.h"
#include "libc/stdio/temp.h"
#include "libc/str/str.h"
#include "libc/sysv/consts/o.h"
#include "libc/sysv/errfuns.h"
#define RESEED 1024
#define ATTEMPTS 10
#define WILDCARD "XXXXXX"
int mkostempsmi(char *tpl, int slen, unsigned flags, uint64_t *rando, int mode,
int openit(const char *file, int flags, ...)) {
size_t len = strlen(tpl);
size_t wildlen = strlen(WILDCARD);
if (len < wildlen || slen > len - wildlen) {
return einval();
}
char *ss = tpl + len - wildlen - slen;
assert(memcmp(ss, WILDCARD, wildlen) == 0);
flags = (flags & ~(flags & O_ACCMODE)) | O_RDWR | O_CREAT | O_EXCL;
unsigned attempts = ATTEMPTS;
do {
char *p = ss;
uint32_t num = KnuthLinearCongruentialGenerator(rando) >> 32;
for (unsigned i = 0; i < wildlen; ++i) {
p[i] = "0123456789abcdefghijklmnopqrstuvwxyz"[num & 31];
num >>= 5;
}
int fd;
if ((fd = openit(tpl, flags, 0600)) != -1) return fd;
} while (--attempts && errno == EEXIST);
memcpy(ss, WILDCARD, wildlen);
return -1;
}
static uint64_t g_mkostemps_rand;
static uint64_t g_mkostemps_reseed;
/**
* Opens unique temporary file.
*
* The substring XXXXXX is replaced with a pseudorandom number that's
* seeded automatically and grants 30 bits of randomness to each value.
* Retries are made in the unlikely event of collisions.
*
* @param template is a pathname relative to current directory by default,
* that needs to have "XXXXXX" at the end of the string
* @param suffixlen may be nonzero to permit characters after the XXXXXX
* @param flags can have O_APPEND, O_CLOEXEC, etc.
* @param mode is conventionally 0600, for owner-only non-exec access
* @return exclusive open file descriptor for generated pathname,
* or -1 w/ errno
* @see kTmpPath
*/
nodiscard int mkostempsm(char *template, int suffixlen, unsigned flags,
int mode) {
if (g_mkostemps_reseed++ % RESEED == 0) g_mkostemps_rand = rand64();
return mkostempsmi(template, suffixlen, flags, &g_mkostemps_rand, mode, open);
}
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