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/* Function for printing numbers using si prefixes (k, M, G, etc.).
* From http://www.cs.tut.fi/~jkorpela/c/eng.html */
#define PREFIX_START (-24)
/* Smallest power of then for which there is a prefix defined.
If the set of prefixes will be extended, change this constant
and update the table "prefix". */
#include <stdio.h>
#include <math.h>
static char *eng(double value, int digits, int numeric)
{
static const char *prefix[] = {
"y", "z", "a", "f", "p", "n", "u", "m", "",
"k", "M", "G", "T", "P", "E", "Z", "Y"
};
#define PREFIX_END (PREFIX_START+\
(int)((sizeof(prefix)/sizeof(char *)-1)*3))
int expof10;
static char result[100];
char *res = result;
if (value < 0.)
{
*res++ = '-';
value = -value;
}
expof10 = (int) log10(value);
if(expof10 > 0)
expof10 = (expof10/3)*3;
else
expof10 = (-expof10+3)/3*(-3);
value *= pow(10,-expof10);
if (value >= 1000.)
{ value /= 1000.0; expof10 += 3; }
else if(value >= 100.0)
digits -= 2;
else if(value >= 10.0)
digits -= 1;
if(numeric || (expof10 < PREFIX_START) ||
(expof10 > PREFIX_END))
sprintf(res, "%.*fe%d", digits-1, value, expof10);
else
sprintf(res, "%.*f %s", digits-1, value,
prefix[(expof10-PREFIX_START)/3]);
return result;
}
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