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/*
* SPDX-FileCopyrightText: 2022 - 2023, Alejandro Colomar <alx@kernel.org>
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#ifndef SHADOW_INCLUDE_LIB_STPEPRINTF_H_
#define SHADOW_INCLUDE_LIB_STPEPRINTF_H_
#include <config.h>
#if !defined(HAVE_STPEPRINTF)
#include <stdarg.h>
#include <stddef.h>
#include <stdio.h>
#include "defines.h"
format_attr(printf, 3, 4)
inline char *stpeprintf(char *dst, char *end, const char *restrict fmt, ...);
format_attr(printf, 3, 0)
inline char *vstpeprintf(char *dst, char *end, const char *restrict fmt,
va_list ap);
/*
* SYNOPSIS
* [[gnu::format(printf, 3, 4)]]
* char *_Nullable stpeprintf(char *_Nullable dst, char end[0],
* const char *restrict fmt, ...);
*
* [[gnu::format(printf, 3, 0)]]
* char *_Nullable vstpeprintf(char *_Nullable dst, char end[0],
* const char *restrict fmt, va_list ap);
*
*
* ARGUMENTS
* dst Destination buffer where to write a string.
*
* end Pointer to one after the last element of the buffer
* pointed to by `dst`. Usually, it should be calculated
* as `dst + NITEMS(dst)`.
*
* fmt Format string
*
* ...
* ap Variadic argument list
*
* DESCRIPTION
* These functions are very similar to [v]snprintf(3).
*
* The destination buffer is limited by a pointer to its end --one
* after its last element-- instead of a size. This allows
* chaining calls to it safely, unlike [v]snprintf(3), which is
* difficult to chain without invoking Undefined Behavior.
*
* RETURN VALUE
* dst + strlen(dst)
* • On success, these functions return a pointer to the
* terminating NUL byte.
*
* end
* • If this call truncated the resulting string.
* • If `dst == end` (a previous chained call to these
* functions truncated).
* NULL
* • If this function failed (see ERRORS).
* • If `dst == NULL` (a previous chained call to these
* functions failed).
*
* ERRORS
* These functions may fail for the same reasons as vsnprintf(3).
*/
inline char *
stpeprintf(char *dst, char *end, const char *restrict fmt, ...)
{
char *p;
va_list ap;
va_start(ap, fmt);
p = vstpeprintf(dst, end, fmt, ap);
va_end(ap);
return p;
}
inline char *
vstpeprintf(char *dst, char *end, const char *restrict fmt, va_list ap)
{
int len;
ptrdiff_t size;
if (dst == end)
return end;
if (dst == NULL)
return NULL;
size = end - dst;
len = vsnprintf(dst, size, fmt, ap);
if (len == -1)
return NULL;
if (len >= size)
return end;
return dst + len;
}
#endif // !HAVE_STPEPRINTF
#endif // include guard
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