source: MondoRescue/branches/2.2.5/mindi-busybox/libbb/human_readable.c

/* vi: set sw=4 ts=4: */
/*
 * June 30, 2001                 Manuel Novoa III
 *
 * All-integer version (hey, not everyone has floating point) of
 * make_human_readable_str, modified from similar code I had written
 * for busybox several months ago.
 *
 * Notes:
 *   1) I'm using an unsigned long long to hold the product size * block_size,
 *      as df (which calls this routine) could request a representation of a
 *      partition size in bytes > max of unsigned long.  If long longs aren't
 *      available, it would be possible to do what's needed using polynomial
 *      representations (say, powers of 1024) and manipulating coefficients.
 *      The base ten "bytes" output could be handled similarly.
 *
 *   2) This routine always outputs a decimal point and a tenths digit when
 *      display_unit != 0.  Hence, it isn't uncommon for the returned string
 *      to have a length of 5 or 6.
 *
 *      It might be nice to add a flag to indicate no decimal digits in
 *      that case.  This could be either an additional parameter, or a
 *      special value of display_unit.  Such a flag would also be nice for du.
 *
 *      Some code to omit the decimal point and tenths digit is sketched out
 *      and "#if 0"'d below.
 */

#include "libbb.h"

const char *make_human_readable_str(unsigned long long size,
    unsigned long block_size, unsigned long display_unit)
{
    /* The code will adjust for additional (appended) units */
    static const char zero_and_units[] ALIGN1 = { '0', 0, 'k', 'M', 'G', 'T' };
    static const char fmt[] ALIGN1 = "%llu";
    static const char fmt_tenths[] ALIGN1 = "%llu.%d%c";

    static char str[21] ALIGN1;  /* Sufficient for 64 bit unsigned integers */

    unsigned long long val;
    int frac;
    const char *u;
    const char *f;

    u = zero_and_units;
    f = fmt;
    frac = 0;

    val = size * block_size;
    if (val == 0) {
        return u;
    }

    if (display_unit) {
        val += display_unit/2;  /* Deal with rounding */
        val /= display_unit;    /* Don't combine with the line above!!! */
    } else {
        ++u;
        while ((val >= 1024)
         && (u < zero_and_units + sizeof(zero_and_units) - 1)
        ) {
            f = fmt_tenths;
            ++u;
            frac = (((int)(val % 1024)) * 10 + 1024/2) / 1024;
            val /= 1024;
        }
        if (frac >= 10) {       /* We need to round up here. */
            ++val;
            frac = 0;
        }
#if 0
        /* Sample code to omit decimal point and tenths digit. */
        if (/* no_tenths */ 1) {
            if (frac >= 5) {
                ++val;
            }
            f = "%llu%*c" /* fmt_no_tenths */;
            frac = 1;
        }
#endif
    }

    /* If f==fmt then 'frac' and 'u' are ignored. */
    snprintf(str, sizeof(str), f, val, frac, *u);

    return str;
}