WIP

src/libfir/000_TopSource.c

@@ -8,6 +8,10 @@
 #include "fir.h"
 
 /* Below are all the includes used throughout the library. */
+#include <alloca.h>
+#include <math.h>
+#include <stdlib.h>
+#include <string.h>
 
 /* options for text editors
 vim: expandtab:ts=4:sw=4

src/libfir/100_fir.c

@@ -0,0 +1,156 @@
+/* libfir/src/libfir/100_fir.c
+ *
+ *  Copyright: ©2014, Laurence Withers.
+ *  Author: Laurence Withers <l@lwithers.me.uk>
+ *  License: GPLv3
+ */
+
+
+
+struct fir_symm_store {
+    double* d;
+    int pos, size;
+};
+
+
+
+struct fir_filter_t {
+    double* coeff;
+    int ncoeff;
+
+    int primed;
+    double* x;
+    int xpos;
+
+    enum fir_symmetry symm;
+    int nsymm;
+    struct fir_symm_store* symm_store;
+};
+
+
+
+static void
+symm_setup(struct fir_filter_t* fi, int delay)
+{
+    int i;
+
+    fi->symm_store = malloc(sizeof(struct fir_symm_store) * fi->nsymm);
+    for(i = 0; i < fi->nsymm; ++i) {
+        fi->symm_store[i].d = malloc(sizeof(double) * delay);
+        fi->symm_store[i].pos = 0;
+        fi->symm_store[i].size = delay;
+        delay -= 2;
+    }
+}
+
+
+
+struct fir_filter_t*
+fir_filter_new(const double* coeff, int ncoeff, enum fir_symmetry symm)
+{
+    struct fir_filter_t* fi = malloc(sizeof(*fi));
+
+    fi->coeff = malloc(sizeof(double) * ncoeff);
+    memcpy(fi->coeff, coeff, sizeof(double) * ncoeff);
+    fi->ncoeff = ncoeff;
+
+    fi->primed = 0;
+    fi->x = malloc(sizeof(double) * ncoeff);
+    fi->xpos = 0;
+
+    fi->symm = symm;
+    switch(symm) {
+    case fir_symmetry_none:
+        fi->nsymm = 0;
+        fi->symm_store = 0;
+        break;
+
+    case fir_symmetry_odd:
+        fi->nsymm = ncoeff - 1;
+        symm_setup(fi, 2 * ncoeff - 1);
+        break;
+
+    case fir_symmetry_even:
+        fi->nsymm = ncoeff;
+        symm_setup(fi, 2 * ncoeff);
+        break;
+    }
+
+    return fi;
+}
+
+
+
+void
+fir_filter_free(struct fir_filter_t* fi)
+{
+    int i;
+
+    if(!fi) return;
+
+    for(i = 0; i < fi->nsymm; ++i) free(fi->symm_store[i].d);
+    free(fi->symm_store);
+
+    free(fi->x);
+    free(fi->coeff);
+    free(fi);
+}
+
+
+
+struct fir_filter_t*
+fir_filter_clone(const struct fir_filter_t* fi)
+{
+    struct fir_filter_t* out = fir_filter_new(fi->coeff, fi->ncoeff, fi->symm);
+    return out;
+}
+
+
+
+double
+fir_filter(struct fir_filter_t* fi, double x)
+{
+    int i, xpos, spos;
+    double p, y = 0;
+
+    if(!fi->primed) {
+        fi->primed = 1;
+        for(i = 0; i < fi->ncoeff; ++i) fi->x[i] = x;
+        for(i = 0; i < fi->nsymm; ++i) {
+            for(spos = 0; spos < fi->symm_store[i].size; ++spos) {
+                fi->symm_store[i].d[spos] = x * fi->coeff[i];
+            }
+        }
+    }
+
+    xpos = fi->xpos;
+    fi->x[xpos] = x;
+
+    for(i = 0; i < fi->ncoeff; ++i) {
+        p = fi->x[xpos] * fi->coeff[i];
+        y += p;
+        if(!xpos--) xpos += fi->ncoeff;
+
+        if(i < fi->nsymm) {
+            spos = fi->symm_store[i].pos;
+            fi->symm_store[i].d[spos] = p;
+            if(++spos == fi->symm_store[i].size) spos = 0;
+            fi->symm_store[i].pos = spos;
+        }
+    }
+
+    if(++fi->xpos == fi->ncoeff) fi->xpos = 0;
+
+    for(i = 0; i < fi->nsymm; ++i) {
+        spos = fi->symm_store[i].pos;
+        y += fi->symm_store[i].d[spos];
+    }
+
+    return y;
+}
+
+
+
+/* options for text editors
+vim: expandtab:ts=4:sw=4
+*/

src/libfir/100_fir.h

@@ -0,0 +1,35 @@
+/* libfir/src/libfir/100_fir.h
+ *
+ *  Copyright: ©2014, Laurence Withers.
+ *  Author: Laurence Withers <l@lwithers.me.uk>
+ *  License: GPLv3
+ */
+
+
+
+struct fir_filter_t;
+
+
+
+enum fir_symmetry {
+    fir_symmetry_none,
+    fir_symmetry_odd,
+    fir_symmetry_even,
+};
+
+
+
+struct fir_filter_t* fir_filter_new(const double* coeff, int ncoeff,
+    enum fir_symmetry symm);
+
+void fir_filter_free(struct fir_filter_t* fi);
+
+struct fir_filter_t* fir_filter_clone(const struct fir_filter_t* fi);
+
+double fir_filter(struct fir_filter_t* fi, double x);
+
+
+
+/* options for text editors
+vim: expandtab:ts=4:sw=4
+*/

src/libfir/200_common_filters.c

@@ -0,0 +1,39 @@
+/* libfir/src/libfir/200_common_filters.c
+ *
+ *  Copyright: ©2014, Laurence Withers.
+ *  Author: Laurence Withers <l@lwithers.me.uk>
+ *  License: GPLv3
+ */
+
+
+
+struct fir_filter_t*
+fir_sinc_lowpass(int npoints, double corner)
+{
+    double* coeff, t;
+    int i, spoints;
+
+    /* find number of points after taking symmetry into account */
+    spoints = (npoints + 1) / 2;
+    coeff = alloca(sizeof(double) * spoints);
+
+    /* only fill out for t ≤ 0 */
+    for(i = 0; i < spoints; ++i) {
+        if((i * 2 + 1) == npoints) {
+            coeff[i] = 1;
+        } else {
+            t = i + 0.5 - npoints * 0.5;
+            t *= corner * 2;
+            coeff[i] = sin(t) / t;
+        }
+    }
+
+    return fir_filter_new(coeff, spoints,
+        (npoints & 1) ? fir_symmetry_odd : fir_symmetry_even);
+}
+
+
+
+/* options for text editors
+vim: expandtab:ts=4:sw=4
+*/

src/libfir/200_common_filters.h

@@ -0,0 +1,16 @@
+/* libfir/src/libfir/200_common_filters.h
+ *
+ *  Copyright: ©2014, Laurence Withers.
+ *  Author: Laurence Withers <l@lwithers.me.uk>
+ *  License: GPLv3
+ */
+
+
+
+struct fir_filter_t* fir_sinc_lowpass(int npoints, double corner);
+
+
+
+/* options for text editors
+vim: expandtab:ts=4:sw=4
+*/

src/libfir/build.lib

@@ -14,7 +14,7 @@ then
     libfir="obj/${libfir_BASE}.so.${SOMAJOR}.${SOMICRO}"
     libfir_DEP_CFLAGS="" # @TODO@ cflags
     libfir_DEP_LIBS="" # @TODO@ libs
-    SO_EXTRA="${libfir_DEP_CFLAGS} ${libfir_DEP_LIBS} -lc \
+    SO_EXTRA="${libfir_DEP_CFLAGS} ${libfir_DEP_LIBS} -lc -lm \
         -D_GNU_SOURCE -std=gnu99"
 
     echo "Building library ${libfir}..."