[PATCH] osmo-trx[master]: sigProcLib: Use explicit NaN check in sinc table generation

[Tom Tsou]

Review at  https://gerrit.osmocom.org/2942

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
---
M Transceiver52M/sigProcLib.cpp
1 file changed, 3 insertions(+), 9 deletions(-)


  git pull ssh://gerrit.osmocom.org:29418/osmo-trx refs/changes/42/2942/1

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 @@
 
 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;
   }
 }
 

-- 
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Gerrit-MessageType: newchange
Gerrit-Change-Id: I3a838fe3139fa977dfe906246020a14451185714
Gerrit-PatchSet: 1
Gerrit-Project: osmo-trx
Gerrit-Branch: master
Gerrit-Owner: Tom Tsou <tom at tsou.cc>