sortix--sortix/libc/stdio/vsnprintf.cpp

/*******************************************************************************

    Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013, 2014.

    This file is part of the Sortix C Library.

    The Sortix C Library is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation, either version 3 of the License, or (at your
    option) any later version.

    The Sortix C Library is distributed in the hope that it will be useful, but
    WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
    License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with the Sortix C Library. If not, see <http://www.gnu.org/licenses/>.

    stdio/vsnprintf.cpp
    Prints a formatted string to a limited string.

*******************************************************************************/

#include <stdarg.h>
#include <stdio.h>
#include <string.h>

typedef struct vsnprintf_struct
{
	char* str;
	size_t size;
	size_t produced;
	size_t written;
} vsnprintf_t;

static size_t StringPrintCallback(void* user, const char* string,
                                  size_t stringlen)
{
	vsnprintf_t* info = (vsnprintf_t*) user;
	if ( info->produced < info->size )
	{
		size_t available = info->size - info->produced;
		size_t possible = (stringlen < available) ? stringlen : available;
		memcpy(info->str + info->produced, string, possible);
		info->written += possible;
	}
	info->produced += stringlen;
	return stringlen;
}

extern "C"
int vsnprintf(char* restrict str, size_t size, const char* restrict format,
              va_list list)
{
	vsnprintf_t info;
	info.str = str;
	info.size = size ? size-1 : 0;
	info.produced = 0;
	info.written = 0;
	int result = vcbprintf(&info, StringPrintCallback, format, list);
	if ( size )
		info.str[info.written] = '\0';
	return result;
}