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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. #include <print.h>
  30. #include <printf/printf_core.h>
  31. #include <memstr.h>
  32.  
  33. struct vsnprintf_data {
  34.     size_t size; /* total space for string */
  35.     size_t len; /* count of currently used characters */
  36.     char *string; /* destination string */
  37. };
  38.  
  39. int vsnprintf_write(const char *str, size_t count, struct vsnprintf_data *data);
  40.  
  41. /** Write string to given buffer.
  42.  * Write at most data->size characters including trailing zero. According to C99, snprintf() has to return number
  43.  * of characters that would have been written if enough space had been available. Hence the return value is not
  44.  * number of really printed characters but size of the input string. Number of really used characters
  45.  * is stored in data->len.
  46.  * @param str source string to print
  47.  * @param count size of source string
  48.  * @param data structure with destination string, counter of used space and total string size.
  49.  * @return number of characters to print (not characters really printed!)
  50.  */
  51. int vsnprintf_write(const char *str, size_t count, struct vsnprintf_data *data)
  52. {
  53.     size_t i;
  54.     i = data->size - data->len;
  55.  
  56.     if ((count == 0) || (i == 0)) {
  57.         return 0;
  58.     }
  59.    
  60.     if (i == 1) {
  61.         /* We have only one free byte left in buffer => write there trailing zero */
  62.         data->string[data->size - 1] = 0;
  63.         data->len = data->size;
  64.         return 1;
  65.     }
  66.    
  67.     if (i <= count) {
  68.         /* We have not enought space for whole string with the trailing zero => print only a part of string */
  69.             memcpy((void *)(data->string + data->len), (void *)str, i - 1);
  70.             data->string[data->size - 1] = 0;
  71.             data->len = data->size;
  72.             return i;
  73.     }
  74.    
  75.     /* Buffer is big enought to print whole string */
  76.     memcpy((void *)(data->string + data->len), (void *)str, count);
  77.     data->len += count;
  78.     /* Put trailing zero at end, but not count it into data->len so it could be rewritten next time */
  79.     data->string[data->len] = 0;
  80.  
  81.     return count;  
  82. }
  83.  
  84. int vsnprintf(char *str, size_t size, const char *fmt, va_list ap)
  85. {
  86.     struct vsnprintf_data data = {size, 0, str};
  87.     struct printf_spec ps = {(int(*)(void *, size_t, void *))vsnprintf_write, &data};
  88.  
  89.     /* Print 0 at end of string - fix the case that nothing will be printed */
  90.     if (size > 0)
  91.         str[0] = 0;
  92.    
  93.     /* vsnprintf_write ensures that str will be terminated by zero. */
  94.     return printf_core(fmt, &ps, ap);
  95. }
  96.