76 lines
2.1 KiB
C
76 lines
2.1 KiB
C
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/*
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* xsbprintf.c - string buffer formatting helpers
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*
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* Written by Juergen Perlinger (perlinger@ntp.org) for the NTP project.
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* The contents of 'html/copyright.html' apply.
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*/
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#include <config.h>
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#include <sys/types.h>
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#include "ntp_stdlib.h"
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/* eXtended Varlist String Buffer printf
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*
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* Formats via 'vsnprintf' into a string buffer, with some semantic
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* specialties:
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*
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* - The start of the buffer pointer is updated according to the number
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* of characters written.
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* - If the buffer is insufficient to format the number of charactes,
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* the partial result will be be discarded, and zero is returned to
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* indicate nothing was written to the buffer.
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* - On successful formatting, the return code is the return value of
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* the inner call to 'vsnprintf()'.
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* - If there is any error, the state of the buffer will not be
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* changed. (Bytes in the buffer might be smashed, but the buffer
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* position does not change, and the NUL marker stays in place at the
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* current buffer position.)
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* - If '(*ppbuf - pend) <= 0' (or ppbuf is NULL), fail with EINVAL.
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*/
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int
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xvsbprintf(
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char **ppbuf, /* pointer to buffer pointer (I/O) */
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char * const pend, /* buffer end (I) */
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char const *pfmt, /* printf-like format string */
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va_list va /* formatting args for above */
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)
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{
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char *pbuf = (ppbuf) ? *ppbuf : NULL;
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int rc = -1;
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if (pbuf && (pend - pbuf > 0)) {
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size_t blen = (size_t)(pend - pbuf);
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rc = vsnprintf(pbuf, blen, pfmt, va);
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if (rc > 0) {
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if ((size_t)rc >= blen)
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rc = 0;
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pbuf += rc;
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}
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*pbuf = '\0'; /* fear of bad vsnprintf */
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*ppbuf = pbuf;
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} else {
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errno = EINVAL;
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}
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return rc;
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}
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/* variadic wrapper around the buffer string formatter */
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int
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xsbprintf(
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char **ppbuf, /* pointer to buffer pointer (I/O) */
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char * const pend, /* buffer end (I) */
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char const *pfmt, /* printf-like format string */
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... /* formatting args for above */
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)
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{
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va_list va;
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int rc;
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va_start(va, pfmt);
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rc = xvsbprintf(ppbuf, pend, pfmt, va);
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va_end(va);
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return rc;
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}
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/* that's all folks! */
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