83 lines
4.0 KiB
C
83 lines
4.0 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=2 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/calls/calls.h"
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#include "libc/errno.h"
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#include "libc/rand/lcg.h"
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#include "libc/rand/rand.h"
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#include "libc/stdio/temp.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/o.h"
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#include "libc/sysv/errfuns.h"
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#define RESEED 1024
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#define ATTEMPTS 10
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#define WILDCARD "XXXXXX"
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int mkostempsmi(char *tpl, int slen, unsigned flags, uint64_t *rando, int mode,
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int openit(const char *file, int flags, ...)) {
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size_t len = strlen(tpl);
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size_t wildlen = strlen(WILDCARD);
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if (len < wildlen || slen > len - wildlen) {
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return einval();
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}
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char *ss = tpl + len - wildlen - slen;
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assert(memcmp(ss, WILDCARD, wildlen) == 0);
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flags = (flags & ~(flags & O_ACCMODE)) | O_RDWR | O_CREAT | O_EXCL;
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unsigned attempts = ATTEMPTS;
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do {
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char *p = ss;
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uint32_t num = KnuthLinearCongruentialGenerator(rando) >> 32;
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for (unsigned i = 0; i < wildlen; ++i) {
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p[i] = "0123456789abcdefghijklmnopqrstuvwxyz"[num & 31];
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num >>= 5;
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}
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int fd;
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if ((fd = openit(tpl, flags, 0600)) != -1) return fd;
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} while (--attempts && errno == EEXIST);
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memcpy(ss, WILDCARD, wildlen);
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return -1;
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}
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static uint64_t g_mkostemps_rand;
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static uint64_t g_mkostemps_reseed;
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/**
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* Opens unique temporary file.
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*
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* The substring XXXXXX is replaced with a pseudorandom number that's
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* seeded automatically and grants 30 bits of randomness to each value.
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* Retries are made in the unlikely event of collisions.
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*
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* @param template is a pathname relative to current directory by default,
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* that needs to have "XXXXXX" at the end of the string
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* @param suffixlen may be nonzero to permit characters after the XXXXXX
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* @param flags can have O_APPEND, O_CLOEXEC, etc.
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* @param mode is conventionally 0600, for owner-only non-exec access
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* @return exclusive open file descriptor for generated pathname,
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* or -1 w/ errno
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* @see kTmpPath
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*/
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nodiscard int mkostempsm(char *template, int suffixlen, unsigned flags,
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int mode) {
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if (g_mkostemps_reseed++ % RESEED == 0) g_mkostemps_rand = rand64();
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return mkostempsmi(template, suffixlen, flags, &g_mkostemps_rand, mode, open);
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}
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