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    Subject[PATCH] Add human-readable units modifier to vsnprintf()
    On Tue, May 22, 2012 at 08:36:30PM -0700, Joe Perches wrote:
    > On Tue, 2012-05-22 at 23:12 -0400, Kent Overstreet wrote:
    > > On Tue, May 22, 2012 at 02:17:06PM -0700, Tejun Heo wrote:
    > []
    > > > > +ssize_t hprint(char *buf, int64_t v)
    > > > > +{
    > > > > + static const char units[] = "?kMGTPEZY";
    > > > > + char dec[3] = "";
    > > > > + int u, t = 0;
    > > > > +
    > > > > + for (u = 0; v >= 1024 || v <= -1024; u++) {
    > > > > + t = v & ~(~0 << 10);
    > > > > + v >>= 10;
    > > > > + }
    > > > > +
    > > > > + if (!u)
    > > > > + return sprintf(buf, "%llu", v);
    > > > > +
    > > > > + if (v < 100 && v > -100)
    > > > > + sprintf(dec, ".%i", t / 100);
    > > > > +
    > > > > + return sprintf(buf, "%lli%s%c", v, dec, units[u]);
    > > > > +}
    > > > > +EXPORT_SYMBOL_GPL(hprint);
    > > >
    > > > Not your fault but maybe we want integer vsnprintf modifier for this.
    > >
    > > Yes.
    >
    > or maybe yet another lib/vsprintf pointer extension
    > like %pD with some descriptors after the %pD for
    > type, width and precision.

    Integer modifier makes more sense to me - it's an integer you're
    printing in the first place, anyways...

    This code seems to work - it produces the same output as my hprint(),
    anyways:

    ---
    lib/vsprintf.c | 24 +++++++++++++++++++++++-
    1 files changed, 23 insertions(+), 1 deletions(-)

    diff --git a/lib/vsprintf.c b/lib/vsprintf.c
    index 38e612e..9225857 100644
    --- a/lib/vsprintf.c
    +++ b/lib/vsprintf.c
    @@ -219,6 +219,7 @@ char *put_dec(char *buf, unsigned long long num)
    #define LEFT 16 /* left justified */
    #define SMALL 32 /* use lowercase in hex (must be 32 == 0x20) */
    #define SPECIAL 64 /* prefix hex with "0x", octal with "0" */
    +#define HUNITS 128 /* Human readable units, i.e. k/M/G/T */

    enum format_type {
    FORMAT_TYPE_NONE, /* Just a string part */
    @@ -258,6 +259,7 @@ char *number(char *buf, char *end, unsigned long long num,
    {
    /* we are called with base 8, 10 or 16, only, thus don't need "G..." */
    static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
    + static const char units[] = "?kMGTPEZY";

    char tmp[66];
    char sign;
    @@ -310,7 +312,26 @@ char *number(char *buf, char *end, unsigned long long num,
    num >>= shift;
    } while (num);
    } else { /* base 10 */
    - i = put_dec(tmp, num) - tmp;
    + if (spec.flags & HUNITS) {
    + int u, rem = 0;
    +
    + for (u = 0; num >= 1024; u++) {
    + rem = num & ~(~0 << 10);
    + num >>= 10;
    + }
    +
    + if (u) {
    + tmp[i++] = units[u];
    +
    + if (num < 100) {
    + rem /= 100;
    + i = put_dec(tmp + i, rem) - tmp;
    + tmp[i++] = '.';
    + }
    + }
    + }
    +
    + i = put_dec(tmp + i, num) - tmp;
    }

    /* printing 100 using %2d gives "100", not "00" */
    @@ -1002,6 +1023,7 @@ int format_decode(const char *fmt, struct printf_spec *spec)
    case ' ': spec->flags |= SPACE; break;
    case '#': spec->flags |= SPECIAL; break;
    case '0': spec->flags |= ZEROPAD; break;
    + case 'h': spec->flags |= HUNITS; break;
    default: found = false;
    }

    --
    1.7.9.rc2


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