mirror of
https://github.com/koverstreet/bcachefs-tools.git
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131 lines
3.3 KiB
C
131 lines
3.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Helpers for formatting and printing strings
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*
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* Copyright 31 August 2008 James Bottomley
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* Copyright (C) 2013, Intel Corporation
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*/
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#include <linux/bug.h>
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#include <linux/kernel.h>
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#include <linux/math64.h>
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#include <linux/export.h>
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#include <linux/ctype.h>
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#include <linux/device.h>
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#include <linux/errno.h>
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#include <linux/fs.h>
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#include <linux/limits.h>
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#include <linux/slab.h>
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#include <linux/string.h>
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#include <linux/string_helpers.h>
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/**
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* string_get_size - get the size in the specified units
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* @size: The size to be converted in blocks
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* @blk_size: Size of the block (use 1 for size in bytes)
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* @units: units to use (powers of 1000 or 1024)
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* @buf: buffer to format to
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* @len: length of buffer
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*
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* This function returns a string formatted to 3 significant figures
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* giving the size in the required units. @buf should have room for
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* at least 9 bytes and will always be zero terminated.
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*
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*/
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int string_get_size(u64 size, u64 blk_size, const enum string_size_units units,
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char *buf, int len)
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{
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static const char *const units_10[] = {
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"B", "kB", "MB", "GB", "TB", "PB", "EB", "ZB", "YB"
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};
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static const char *const units_2[] = {
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"B", "KiB", "MiB", "GiB", "TiB", "PiB", "EiB", "ZiB", "YiB"
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};
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static const char *const *const units_str[] = {
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[STRING_UNITS_10] = units_10,
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[STRING_UNITS_2] = units_2,
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};
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static const unsigned int divisor[] = {
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[STRING_UNITS_10] = 1000,
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[STRING_UNITS_2] = 1024,
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};
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static const unsigned int rounding[] = { 500, 50, 5 };
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int i = 0, j;
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u32 remainder = 0, sf_cap;
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char tmp[12];
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const char *unit;
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tmp[0] = '\0';
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if (blk_size == 0)
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size = 0;
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if (size == 0)
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goto out;
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/* This is Napier's algorithm. Reduce the original block size to
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*
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* coefficient * divisor[units]^i
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*
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* we do the reduction so both coefficients are just under 32 bits so
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* that multiplying them together won't overflow 64 bits and we keep
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* as much precision as possible in the numbers.
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*
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* Note: it's safe to throw away the remainders here because all the
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* precision is in the coefficients.
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*/
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while (blk_size >> 32) {
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do_div(blk_size, divisor[units]);
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i++;
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}
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while (size >> 32) {
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do_div(size, divisor[units]);
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i++;
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}
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/* now perform the actual multiplication keeping i as the sum of the
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* two logarithms */
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size *= blk_size;
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/* and logarithmically reduce it until it's just under the divisor */
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while (size >= divisor[units]) {
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remainder = do_div(size, divisor[units]);
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i++;
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}
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/* work out in j how many digits of precision we need from the
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* remainder */
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sf_cap = size;
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for (j = 0; sf_cap*10 < 1000; j++)
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sf_cap *= 10;
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if (units == STRING_UNITS_2) {
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/* express the remainder as a decimal. It's currently the
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* numerator of a fraction whose denominator is
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* divisor[units], which is 1 << 10 for STRING_UNITS_2 */
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remainder *= 1000;
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remainder >>= 10;
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}
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/* add a 5 to the digit below what will be printed to ensure
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* an arithmetical round up and carry it through to size */
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remainder += rounding[j];
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if (remainder >= 1000) {
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remainder -= 1000;
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size += 1;
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}
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if (j) {
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snprintf(tmp, sizeof(tmp), ".%03u", remainder);
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tmp[j+1] = '\0';
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}
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out:
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if (i >= ARRAY_SIZE(units_2))
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unit = "UNK";
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else
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unit = units_str[units][i];
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return snprintf(buf, len, "%u%s %s", (u32)size, tmp, unit);
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}
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EXPORT_SYMBOL(string_get_size);
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