resample: Improve GCD calculation

Use Euclids algorithm to calculate the greatest common divisor to
simplify the resample ratio fraction instead of the slow iterative
method.
Signed-off-by: Tristan Matthews <tmatth@videolan.org>

libspeexdsp/resample.c

@@ -1068,6 +1068,18 @@ EXPORT void speex_resampler_get_rate(SpeexResamplerState *st, spx_uint32_t *in_r
    *out_rate = st->out_rate;
 }
 
+static inline spx_uint32_t _gcd(spx_uint32_t a, spx_uint32_t b)
+{
+   while (b != 0)
+   {
+      spx_uint32_t temp = a;
+
+      a = b;
+      b = temp % b;
+   }
+   return a;
+}
+
 EXPORT int speex_resampler_set_rate_frac(SpeexResamplerState *st, spx_uint32_t ratio_num, spx_uint32_t ratio_den, spx_uint32_t in_rate, spx_uint32_t out_rate)
 {
    spx_uint32_t fact;
@@ -1081,15 +1093,11 @@ EXPORT int speex_resampler_set_rate_frac(SpeexResamplerState *st, spx_uint32_t r
    st->out_rate = out_rate;
    st->num_rate = ratio_num;
    st->den_rate = ratio_den;
-   /* FIXME: This is terribly inefficient, but who cares (at least for now)? */
-   for (fact=2;fact<=IMIN(st->num_rate, st->den_rate);fact++)
-   {
-      while ((st->num_rate % fact == 0) && (st->den_rate % fact == 0))
-      {
-         st->num_rate /= fact;
-         st->den_rate /= fact;
-      }
-   }
+
+   fact = _gcd (st->num_rate, st->den_rate);
+
+   st->num_rate /= fact;
+   st->den_rate /= fact;
 
    if (old_den > 0)
    {