lib/string_helpers.c

   1 /*
   2  * Helpers for formatting and printing strings
   3  *
   4  * Copyright 31 August 2008 James Bottomley
   5  */
   6 #include <linux/kernel.h>
   7 #include <linux/math64.h>
   8 #include <linux/module.h>
   9 #include <linux/string_helpers.h>
  10
  11 /**
  12  * string_get_size - get the size in the specified units
  13  * @size:       The size to be converted
  14  * @units:      units to use (powers of 1000 or 1024)
  15  * @buf:        buffer to format to
  16  * @len:        length of buffer
  17  *
  18  * This function returns a string formatted to 3 significant figures
  19  * giving the size in the required units.  Returns 0 on success or
  20  * error on failure.  @buf is always zero terminated.
  21  *
  22  */
  23 int string_get_size(u64 size, const enum string_size_units units,
  24                     char *buf, int len)
  25 {
  26         const char *units_10[] = { "B", "KB", "MB", "GB", "TB", "PB",
  27                                    "EB", "ZB", "YB", NULL};
  28         const char *units_2[] = {"B", "KiB", "MiB", "GiB", "TiB", "PiB",
  29                                  "EiB", "ZiB", "YiB", NULL };
  30         const char **units_str[] = {
  31                 [STRING_UNITS_10] =  units_10,
  32                 [STRING_UNITS_2] = units_2,
  33         };
  34         const int divisor[] = {
  35                 [STRING_UNITS_10] = 1000,
  36                 [STRING_UNITS_2] = 1024,
  37         };
  38         int i, j;
  39         u64 remainder = 0, sf_cap;
  40         char tmp[8];
  41
  42         tmp[0] = '\0';
  43
  44         for (i = 0; size > divisor[units] && units_str[units][i]; i++)
  45                 remainder = do_div(size, divisor[units]);
  46
  47         sf_cap = size;
  48         for (j = 0; sf_cap*10 < 1000; j++)
  49                 sf_cap *= 10;
  50
  51         if (j) {
  52                 remainder *= 1000;
  53                 do_div(remainder, divisor[units]);
  54                 snprintf(tmp, sizeof(tmp), ".%03lld",
  55                          (unsigned long long)remainder);
  56                 tmp[j+1] = '\0';
  57         }
  58
  59         snprintf(buf, len, "%lld%s%s", (unsigned long long)size,
  60                  tmp, units_str[units][i]);
  61
  62         return 0;
  63 }
  64 EXPORT_SYMBOL(string_get_size);