Micro-optimize num2str()

Instead of selecting an element from the thousand[] array several times,
perform the choice between 1000 and 1024 once. This patch does not change
any functionality.

Signed-off-by: Bart Van Assche <bvanassche@acm.org>

diff --git a/lib/num2str.c b/lib/num2str.c
index 40fb3aec923d3ce6199b64d0cf4c791c92e2151a..ff8a365bcaed516e07c69aac91f96e73952faa2b 100644 (file)
--- a/lib/num2str.c
+++ b/lib/num2str.c
@@ -30,7 +30,7 @@ char *num2str(uint64_t num, int maxlen, int base, int pow2, enum n2s_unit units)
                [N2S_BYTEPERSEC]= "B/s",
                [N2S_BITPERSEC] = "bit/s"
        };
-       const unsigned int thousand[] = { 1000, 1024 };
+       const unsigned int thousand = pow2 ? 1024 : 1000;
        unsigned int modulo;
        int post_index, carry = 0;
        char tmp[32], fmt[32];
@@ -49,7 +49,7 @@ char *num2str(uint64_t num, int maxlen, int base, int pow2, enum n2s_unit units)
                unitprefix = sistr;
 
        for (post_index = 0; base > 1; post_index++)
-               base /= thousand[!!pow2];
+               base /= thousand;
 
        switch (units) {
        case N2S_NONE:
@@ -77,9 +77,9 @@ char *num2str(uint64_t num, int maxlen, int base, int pow2, enum n2s_unit units)
                if (strlen(tmp) <= maxlen)
                        break;
 
-               modulo = num % thousand[!!pow2];
-               num /= thousand[!!pow2];
-               carry = modulo >= thousand[!!pow2] / 2;
+               modulo = num % thousand;
+               num /= thousand;
+               carry = modulo >= thousand / 2;
                post_index++;
        }
 
@@ -110,9 +110,9 @@ done:
         * Fill in everything and return the result.
         */
        assert(maxlen - strlen(tmp) - 1 > 0);
-       assert(modulo < thousand[!!pow2]);
+       assert(modulo < thousand);
        sprintf(fmt, "%%.%df", (int)(maxlen - strlen(tmp) - 1));
-       sprintf(tmp, fmt, (double)modulo / (double)thousand[!!pow2]);
+       sprintf(tmp, fmt, (double)modulo / (double)thousand);
 
        sprintf(buf, "%llu.%s%s%s", (unsigned long long) num, &tmp[2],
                        unitprefix[post_index], unitstr[units]);