sigProcLib: Use explicit NaN check in sinc table generation

Using "x < 0.01" is a crude check for detecting NaN condition, which
occurs in a sinc call when x = 0 due to divide-by-zero. Use stdlib
isnan() call for this purpose. Also, as the table is created only
once during initialization, use double floats for table value
generation.

Change-Id: I3a838fe3139fa977dfe906246020a14451185714

1 files changed, 3 insertions, 9 deletions

diff --git a/Transceiver52M/sigProcLib.cpp b/Transceiver52M/sigProcLib.cpp
index c776501..9d1ef49 100644
--- a/Transceiver52M/sigProcLib.cpp
+++ b/Transceiver52M/sigProcLib.cpp
@@ -979,16 +979,10 @@ signalVector *modulateBurst(const BitVector &wBurst, int guardPeriodLength,
 
 static void generateSincTable()
 {
-  float x;
-
   for (int i = 0; i < TABLESIZE; i++) {
-    x = (float) i / TABLESIZE * 8 * M_PI;
-    if (fabs(x) < 0.01) {
-      sincTable[i] = 1.0f;
-      continue;
-    }
-
-    sincTable[i] = sinf(x) / x;
+    auto x = (double) i / TABLESIZE * 8 * M_PI;
+    auto y = sin(x) / x;
+    sincTable[i] = isnan(y) ? 1.0 : y;
   }
 }