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/*
 * Copyright (C) 2006 Josef Cejka
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <print.h>
#include <printf/printf_core.h>
#include <memstr.h>

struct vsnprintf_data {
    size_t size; /* total space for string */
    size_t len; /* count of currently used characters */
    char *string; /* destination string */
};

int vsnprintf_write(const char *str, size_t count, struct vsnprintf_data *data);

/** Write string to given buffer.
 * Write at most data->size characters including trailing zero. According to C99 has snprintf to return number
 * of characters that would have been written if enough space had been available. Hence the return value is not
 * number of really printed characters but size of input string. Number of really used characters 
 * is stored in data->len.
 * @param str source string to print
 * @param count size of source string
 * @param data structure with destination string, counter of used space and total string size.
 * @return number of characters to print (not characters really printed!)
 */
int vsnprintf_write(const char *str, size_t count, struct vsnprintf_data *data)
{
    size_t i,j;
    i = data->size - data->len;
    j = count;

    if (i > 0) {
        if (i <= j) { 
            if (i == 1) {
                /* We have only one free byte left in buffer => write there trailing zero */
                data->string[data->size - 1] = 0;
                data->len = data->size;
            } else {
                /* We have not enought space for whole string with the trailing zero => print only a part of string */
                memcpy((void *)(data->string + data->len), (void *)str, i - 1);
                data->string[data->size - 1] = 0;
                data->len = data->size;
            }
        } else {
            /* Buffer is big enought to print whole string */
            memcpy((void *)(data->string + data->len), (void *)str, j);
            data->len += j;
            /* Put trailing zero at end, but not count it into data->len so it could be rewritten next time */
            data->string[data->len] = 0;
        }
    }
    
    return count;   
}

int vsnprintf(char *str, size_t size, const char *fmt, va_list ap)
{
    struct vsnprintf_data data = {size, 0, str};
    struct printf_spec ps = {(int(*)(void *, size_t, void *))vsnprintf_write, &data};

    /* Print 0 at end of string - fix the case that nothing will be printed */
    if (size > 0)
        str[0] = 0;
    
    /* vsnprintf_write ensures that str will be terminated by zero. */
    return printf_core(fmt, &ps, ap);
}