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/export.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         static const char *units_10[] = { "B", "kB", "MB", "GB", "TB", "PB",
  27                                    "EB", "ZB", "YB", NULL};
  28         static const char *units_2[] = {"B", "KiB", "MiB", "GiB", "TiB", "PiB",
  29                                  "EiB", "ZiB", "YiB", NULL };
  30         static const char **units_str[] = {
  31                 [STRING_UNITS_10] =  units_10,
  32                 [STRING_UNITS_2] = units_2,
  33         };
  34         static const unsigned 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         i = 0;
  44         if (size >= divisor[units]) {
  45                 while (size >= divisor[units] && units_str[units][i]) {
  46                         remainder = do_div(size, divisor[units]);
  47                         i++;
  48                 }
  49
  50                 sf_cap = size;
  51                 for (j = 0; sf_cap*10 < 1000; j++)
  52                         sf_cap *= 10;
  53
  54                 if (j) {
  55                         remainder *= 1000;
  56                         do_div(remainder, divisor[units]);
  57                         snprintf(tmp, sizeof(tmp), ".%03lld",
  58                                  (unsigned long long)remainder);
  59                         tmp[j+1] = '\0';
  60                 }
  61         }
  62
  63         snprintf(buf, len, "%lld%s %s", (unsigned long long)size,
  64                  tmp, units_str[units][i]);
  65
  66         return 0;
  67 }
  68 EXPORT_SYMBOL(string_get_size);