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linux-next/lib/string_helpers.c
H. Peter Anvin a8659597bf [SCSI] lib: string_get_size(): don't hang on zero; no decimals on exact
We would hang forever when passing a zero to string_get_size().
Furthermore, string_get_size() would produce decimals on a value small
enough to be exact.  Finally, a few formatting issues are inconsistent
with standard SI style guidelines.

- If the value is less than the divisor, skip the entire rounding
  step.  This prints out all small values including zero as integers,
  without decimals.
- Add a space between the value and the symbol for the unit,
  consistent with standard SI practice.
- Lower case k in kB since we are talking about powers of 10.
- Finally, change "int" to "unsigned int" in one place to shut up a
  gcc warning when compiling the code out-of-kernel for testing.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
2008-10-23 11:42:20 -05:00

69 lines
1.7 KiB
C

/*
* Helpers for formatting and printing strings
*
* Copyright 31 August 2008 James Bottomley
*/
#include <linux/kernel.h>
#include <linux/math64.h>
#include <linux/module.h>
#include <linux/string_helpers.h>
/**
* string_get_size - get the size in the specified units
* @size: The size to be converted
* @units: units to use (powers of 1000 or 1024)
* @buf: buffer to format to
* @len: length of buffer
*
* This function returns a string formatted to 3 significant figures
* giving the size in the required units. Returns 0 on success or
* error on failure. @buf is always zero terminated.
*
*/
int string_get_size(u64 size, const enum string_size_units units,
char *buf, int len)
{
const char *units_10[] = { "B", "kB", "MB", "GB", "TB", "PB",
"EB", "ZB", "YB", NULL};
const char *units_2[] = {"B", "KiB", "MiB", "GiB", "TiB", "PiB",
"EiB", "ZiB", "YiB", NULL };
const char **units_str[] = {
[STRING_UNITS_10] = units_10,
[STRING_UNITS_2] = units_2,
};
const unsigned int divisor[] = {
[STRING_UNITS_10] = 1000,
[STRING_UNITS_2] = 1024,
};
int i, j;
u64 remainder = 0, sf_cap;
char tmp[8];
tmp[0] = '\0';
i = 0;
if (size >= divisor[units]) {
while (size >= divisor[units] && units_str[units][i]) {
remainder = do_div(size, divisor[units]);
i++;
}
sf_cap = size;
for (j = 0; sf_cap*10 < 1000; j++)
sf_cap *= 10;
if (j) {
remainder *= 1000;
do_div(remainder, divisor[units]);
snprintf(tmp, sizeof(tmp), ".%03lld",
(unsigned long long)remainder);
tmp[j+1] = '\0';
}
}
snprintf(buf, len, "%lld%s %s", (unsigned long long)size,
tmp, units_str[units][i]);
return 0;
}
EXPORT_SYMBOL(string_get_size);