58 lines
2.9 KiB
C
58 lines
2.9 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/fmt/fmt.h"
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#include "libc/mem/mem.h"
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/**
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* Formats string w/ dynamic memory allocation.
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*
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* @param *strp is output-only and must be free'd, even on error; since
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* that's the behavior that'll make your code most portable
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* @return complete bytes written (excluding NUL) or -1 w/ errno
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* @see xasprintf() for a better API
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*/
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int(vasprintf)(char **strp, const char *fmt, va_list va) {
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/*
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* This implementation guarantees the smallest possible allocation,
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* using an optimistic approach w/o changing asymptotic complexity.
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*/
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size_t size = 32;
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if ((*strp = malloc(size))) {
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va_list va2;
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va_copy(va2, va);
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int wrote = (vsnprintf)(*strp, size, fmt, va);
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if (wrote == -1) return -1;
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if (wrote <= size - 1) {
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return wrote;
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} else {
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size = wrote + 1;
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char *buf2 = realloc(*strp, size);
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if (buf2) {
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*strp = buf2;
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wrote = (vsnprintf)(*strp, size, fmt, va2);
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assert(wrote == size - 1);
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return wrote;
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}
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}
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}
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return -1;
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}
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