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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 05-23-2012, 04:50 AM
Kent Overstreet
 
Default 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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