restore C app for Es/No est test

unittest/CMakeLists.txt

@@ -118,3 +118,6 @@ target_link_libraries(mksine m)
 
 add_executable(vq_mbest vq_mbest.c)
 target_link_libraries(vq_mbest codec2)
+
+add_executable(tesno_est tesno_est.c)
+target_link_libraries(tesno_est m codec2)

unittest/tesno_est.c

@@ -0,0 +1,31 @@
+/*---------------------------------------------------------------------------*\
+
+  FILE........: tesno_est.c
+  AUTHORS.....: David Rowe
+  DATE CREATED: Mar 2021
+
+  Test for C port of Es/No estimator.
+  
+\*---------------------------------------------------------------------------*/
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+#include "ofdm_internal.h"
+
+int main(int argc, char *argv[])
+{
+    FILE *fin = fopen(argv[1],"rb"); assert(fin != NULL);
+    size_t nsym = atoi(argv[2]); assert(nsym >= 0);
+    complex float rx_sym[nsym];
+    size_t nread = fread(rx_sym, sizeof(complex float), nsym, fin);
+    assert(nread == nsym);
+    fclose(fin);
+    
+    float EsNodB = ofdm_esno_est_calc(rx_sym, nsym);
+    printf("%f\n",EsNodB);
+
+    return 0;
+}