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#include "xsnprintf.h"
#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include "debug.h"
/*
* ISO C doesn't require vsnprintf(3) to set errno on failure, but
* POSIX does:
*
* "If an output error was encountered, these functions shall return
* a negative value and set errno to indicate the error."
*
* The mandated errors of interest are:
*
* - EILSEQ: A wide-character code does not correspond to a valid character
* - EOVERFLOW: The value of n is greater than INT_MAX
* - EOVERFLOW: The value to be returned is greater than INT_MAX
*
* ISO C11 states:
*
* "The vsnprintf function returns the number of characters that would
* have been written had n been sufficiently large, not counting the
* terminating null character, or a negative value if an encoding error
* occurred. Thus, the null-terminated output has been completely
* written if and only if the returned value is nonnegative and less
* than n."
*
* See also:
*
* - ISO C11 ยง7.21.6.12p3
* - https://pubs.opengroup.org/onlinepubs/9699919799/functions/vsnprintf.html
* - https://pubs.opengroup.org/onlinepubs/9699919799/functions/snprintf.html
*/
size_t
xvsnprintf(char *restrict buf, size_t n, const char *restrict format, va_list ap)
{
int len = vsnprintf(buf, n, format, ap);
if (unlikely(len < 0 || len >= (int)n)) {
FATAL_ERROR(__func__, (len < 0) ? errno : ENOBUFS);
}
return (size_t)len;
}
size_t
xsnprintf(char *restrict buf, size_t n, const char *restrict format, ...)
{
va_list ap;
va_start(ap, format);
size_t len = xvsnprintf(buf, n, format, ap);
va_end(ap);
return len;
}
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