Allow setting a suffix for constants and trigonometric functions

In order to use constants or trigonometric functions with a type other than
double, a suffix ('f' for float or 'l' for long double) has to be used in C.
This commit adds a preprocessor macro 'kiss_fft_suffix' which can be set to
either 'f' or 'l' and which will be added to floating point constants and to
the trigonometric functions (sin and cos).

Without this suffix, the code will use a too high precision for float and a
too low precision for long double.

Author: steffen-kiess

_kiss_fft_guts.h

@@ -119,6 +119,46 @@ struct kiss_fft_state{
     }while(0)
 
 
+// If kiss_fft_suffix is not provided, determine it automatically based on kiss_fft_scalar
+#if !defined (kiss_fft_suffix) && !defined (kiss_fft_suffix_empty)
+#ifdef FIXED_POINT
+#undef kiss_fft_suffix
+#define kiss_fft_suffix_empty 1
+#endif
+
+#define KISS_X_float_X 1
+#define KISS_X__X 2
+#define KISS_X_long_X 3
+#define KISS_concat2(a, b, c) a##b##c
+#define KISS_concat(a, b, c) KISS_concat2(a, b, c)
+
+#define double // This is because otherwise KISS_concat(KISS_X_, long double, _X) would produce two tokens which would break the preprocessor comparison
+
+#if KISS_concat(KISS_X_, kiss_fft_scalar, _X) == KISS_X_float_X // float
+#define kiss_fft_suffix f
+#elif KISS_concat(KISS_X_, kiss_fft_scalar, _X) == KISS_X__X // double
+#undef kiss_fft_suffix
+#define kiss_fft_suffix_empty 1
+#elif KISS_concat(KISS_X_, kiss_fft_scalar, _X) == KISS_X_long_X // long double
+#define kiss_fft_suffix l
+#else
+#undef kiss_fft_suffix
+#define kiss_fft_suffix_empty 1
+#warning "Unknown kiss_fft_scalar type"
+#endif
+
+#undef double
+#endif
+
+
+#ifdef kiss_fft_suffix_empty
+#define KISS_ADD_SUFFIX(x) x
+#else
+#define KISS_ADD_SUFFIX2(x, y) x##y
+#define KISS_ADD_SUFFIX1(x, y) KISS_ADD_SUFFIX2(x, y)
+#define KISS_ADD_SUFFIX(x) KISS_ADD_SUFFIX1(x, kiss_fft_suffix)
+#endif
+
 #ifdef FIXED_POINT
 #  define KISS_FFT_COS(phase)  floor(.5+SAMP_MAX * cos (phase))
 #  define KISS_FFT_SIN(phase)  floor(.5+SAMP_MAX * sin (phase))
@@ -128,9 +168,9 @@ struct kiss_fft_state{
 #  define KISS_FFT_SIN(phase) _mm_set1_ps( sin(phase) )
 #  define HALF_OF(x) ((x)*_mm_set1_ps(.5))
 #else
-#  define KISS_FFT_COS(phase) (kiss_fft_scalar) cos(phase)
-#  define KISS_FFT_SIN(phase) (kiss_fft_scalar) sin(phase)
-#  define HALF_OF(x) ((x)*.5)
+#  define KISS_FFT_COS(phase) (kiss_fft_scalar) KISS_ADD_SUFFIX(cos)(phase)
+#  define KISS_FFT_SIN(phase) (kiss_fft_scalar) KISS_ADD_SUFFIX(sin)(phase)
+#  define HALF_OF(x) ((x)*KISS_ADD_SUFFIX(.5))
 #endif
 
 #define  kf_cexp(x,phase) \

kiss_fft.c

@@ -349,8 +349,8 @@ kiss_fft_cfg kiss_fft_alloc(int nfft,int inverse_fft,void * mem,size_t * lenmem
         st->inverse = inverse_fft;
 
         for (i=0;i<nfft;++i) {
-            const double pi=3.141592653589793238462643383279502884197169399375105820974944;
-            double phase = -2*pi*i / nfft;
+            const kiss_fft_scalar pi=KISS_ADD_SUFFIX(3.141592653589793238462643383279502884197169399375105820974944);
+            kiss_fft_scalar phase = -2*pi*i / nfft;
             if (st->inverse)
                 phase *= -1;
             kf_cexp(st->twiddles+i, phase );

tools/kiss_fftr.c

@@ -49,8 +49,8 @@ kiss_fftr_cfg kiss_fftr_alloc(int nfft,int inverse_fft,void * mem,size_t * lenme
     kiss_fft_alloc(nfft, inverse_fft, st->substate, &subsize);
 
     for (i = 0; i < nfft/2; ++i) {
-        double phase =
-            -3.14159265358979323846264338327 * ((double) (i+1) / nfft + .5);
+        kiss_fft_scalar phase =
+            KISS_ADD_SUFFIX(-3.14159265358979323846264338327) * ((kiss_fft_scalar) (i+1) / nfft + .5);
         if (inverse_fft)
             phase *= -1;
         kf_cexp (st->super_twiddles+i,phase);