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  1. /*
  2.  * Copyright (c) 2006 Josef Cejka
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup libc
  30.  * @{
  31.  */
  32. /** @file
  33.  */
  34.  
  35. #include <stdarg.h>
  36. #include <stdio.h>
  37. #include <string.h>
  38. #include <io/printf_core.h>
  39.  
  40. struct vsnprintf_data {
  41.     size_t size;    /* total space for string */
  42.     size_t len; /* count of currently used characters */
  43.     char *string;   /* destination string */
  44. };
  45.  
  46. /** Write string to given buffer.
  47.  * Write at most data->size characters including trailing zero. According to C99
  48.  * has snprintf to return number of characters that would have been written if
  49.  * enough space had been available. Hence the return value is not number of
  50.  * really printed characters but size of input string. Number of really used
  51.  * characters is stored in data->len.
  52.  *
  53.  * @param str       Source string to print.
  54.  * @param count     Size of the source string.
  55.  * @param data      Structure with destination string, counter of used space
  56.  *          and total string size.
  57.  * @return      Number of characters to print (not characters really
  58.  *          printed!)
  59.  */
  60. static int
  61. vsnprintf_write(const char *str, size_t count, struct vsnprintf_data *data)
  62. {
  63.     size_t i;
  64.     i = data->size - data->len;
  65.  
  66.     if (i == 0) {
  67.         return count;
  68.     }
  69.    
  70.     if (i == 1) {
  71.         /*
  72.          * We have only one free byte left in buffer => write there
  73.          * trailing zero.
  74.          */
  75.         data->string[data->size - 1] = 0;
  76.         data->len = data->size;
  77.         return count;
  78.     }
  79.    
  80.     if (i <= count) {
  81.         /*
  82.          * We have not enought space for whole string with the trailing
  83.          * zero => print only a part of string.
  84.          */
  85.         memcpy((void *)(data->string + data->len), (void *)str, i - 1);
  86.         data->string[data->size - 1] = 0;
  87.         data->len = data->size;
  88.         return count;
  89.     }
  90.    
  91.     /* Buffer is big enought to print whole string */
  92.     memcpy((void *)(data->string + data->len), (void *)str, count);
  93.     data->len += count;
  94.     /*
  95.      * Put trailing zero at end, but not count it into data->len so it could
  96.      * be rewritten next time.
  97.      */
  98.     data->string[data->len] = 0;
  99.  
  100.     return count;  
  101. }
  102.  
  103. /** Print formatted to the given buffer with limited size.
  104.  * @param str       Buffer.
  105.  * @param size      Bffer size.
  106.  * @param fmt       Format string.
  107.  * \see For more details about format string see printf_core.
  108.  */
  109. int vsnprintf(char *str, size_t size, const char *fmt, va_list ap)
  110. {
  111.     struct vsnprintf_data data = {size, 0, str};
  112.     struct printf_spec ps = {
  113.         (int(*)(void *, size_t, void *)) vsnprintf_write,
  114.         &data
  115.     };
  116.  
  117.     /*
  118.      * Print 0 at end of string - fix the case that nothing will be printed.
  119.      */
  120.     if (size > 0)
  121.         str[0] = 0;
  122.    
  123.     /* vsnprintf_write ensures that str will be terminated by zero. */
  124.     return printf_core(fmt, &ps, ap);
  125. }
  126.  
  127. /** @}
  128.  */
  129.