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