mirror of
https://github.com/jart/cosmopolitan.git
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64 lines
3 KiB
C
64 lines
3 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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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/dce.h"
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#include "libc/fmt/fmt.h"
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#include "libc/limits.h"
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#include "libc/macros.internal.h"
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#include "libc/runtime/runtime.h"
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#include "libc/str/str.h"
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struct SprintfStr {
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char *p;
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size_t i;
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size_t n;
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};
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static int vsnprintfputchar(const char *s, struct SprintfStr *t, size_t n) {
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if (n) {
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if (n == 1 && t->i < t->n) {
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t->p[t->i] = s[0];
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} else if (t->i + n <= t->n) {
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memcpy(t->p + t->i, s, n);
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} else if (t->i < t->n) {
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memcpy(t->p + t->i, s, t->n - t->i);
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}
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t->i += n;
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}
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return 0;
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}
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/**
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* Formats string to buffer w/ preexisting vararg state.
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*
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* @param buf stores output and a NUL-terminator is always written,
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* provided buf!=NULL && size!=0
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* @param size is byte capacity buf
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* @return number of bytes written, excluding the NUL terminator; or,
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* if the output buffer wasn't passed, or was too short, then the
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* number of characters that *would* have been written is returned
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* @see __fmt() and printf() for detailed documentation
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* @asyncsignalsafe
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* @vforksafe
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*/
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int(vsnprintf)(char *buf, size_t size, const char *fmt, va_list va) {
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struct SprintfStr str = {buf, 0, size};
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__fmt(vsnprintfputchar, &str, fmt, va);
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if (str.n) str.p[MIN(str.i, str.n - 1)] = '\0';
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return str.i;
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}
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