uspace/libc/generic/io/vsnprintf.c

   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 int vsnprintf_write(const char *str, size_t count, struct vsnprintf_data *data);
  47
  48 /** Write string to given buffer.
  49  * Write at most data->size characters including trailing zero. According to C99 has snprintf to return number
  50  * of characters that would have been written if enough space had been available. Hence the return value is not
  51  * number of really printed characters but size of input string. Number of really used characters
  52  * is stored in data->len.
  53  * @param str source string to print
  54  * @param count size of source string
  55  * @param data structure with destination string, counter of used space and total string size.
  56  * @return number of characters to print (not characters really printed!)
  57  */
  58 int vsnprintf_write(const char *str, size_t count, struct vsnprintf_data *data)
  59 {
  60         size_t i;
  61         i = data->size - data->len;
  62
  63         if (i == 0) {
  64                 return count;
  65         }
  66
  67         if (i == 1) {
  68                 /* We have only one free byte left in buffer => write there trailing zero */
  69                 data->string[data->size - 1] = 0;
  70                 data->len = data->size;
  71                 return count;
  72         }
  73
  74         if (i <= count) {
  75                 /* We have not enought space for whole string with the trailing zero => print only a part of string */
  76                         memcpy((void *)(data->string + data->len), (void *)str, i - 1);
  77                         data->string[data->size - 1] = 0;
  78                         data->len = data->size;
  79                         return count;
  80         }
  81
  82         /* Buffer is big enought to print whole string */
  83         memcpy((void *)(data->string + data->len), (void *)str, count);
  84         data->len += count;
  85         /* Put trailing zero at end, but not count it into data->len so it could be rewritten next time */
  86         data->string[data->len] = 0;
  87
  88         return count;
  89 }
  90
  91 /** Print formatted to the given buffer with limited size.
  92  * @param str   buffer
  93  * @param size  buffer size
  94  * @param fmt   format string
  95  * \see For more details about format string see printf_core.
  96  */
  97 int vsnprintf(char *str, size_t size, const char *fmt, va_list ap)
  98 {
  99         struct vsnprintf_data data = {size, 0, str};
 100         struct printf_spec ps = {(int(*)(void *, size_t, void *))vsnprintf_write, &data};
 101
 102         /* Print 0 at end of string - fix the case that nothing will be printed */
 103         if (size > 0)
 104                 str[0] = 0;
 105
 106         /* vsnprintf_write ensures that str will be terminated by zero. */
 107         return printf_core(fmt, &ps, ap);
 108 }
 109
 110 /** @}
 111  */