--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/spandsp-0.0.3/spandsp-0.0.3/src/tone_detect.c	Fri Jun 25 16:00:21 2010 +0200
@@ -0,0 +1,121 @@
+/*
+ * SpanDSP - a series of DSP components for telephony
+ *
+ * tone_detect.c - General telephony tone detection, and specific
+ *                 detection of Bell MF, and MFC/R2.
+ *
+ * Written by Steve Underwood <steveu@coppice.org>
+ *
+ * Copyright (C) 2001-2003, 2005 Steve Underwood
+ *
+ * All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ * $Id: tone_detect.c,v 1.30 2006/11/19 14:07:25 steveu Exp $
+ */
+ 
+/*! \file tone_detect.h */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <inttypes.h>
+#include <stdlib.h>
+#if defined(HAVE_TGMATH_H)
+#include <tgmath.h>
+#endif
+#if defined(HAVE_MATH_H)
+#include <math.h>
+#endif
+#include <string.h>
+#include <stdio.h>
+#include <time.h>
+#include <fcntl.h>
+
+#include "spandsp/telephony.h"
+#include "spandsp/tone_detect.h"
+#include "spandsp/tone_generate.h"
+
+#if !defined(M_PI)
+/* C99 systems may not define M_PI */
+#define M_PI 3.14159265358979323846264338327
+#endif
+
+void make_goertzel_descriptor(goertzel_descriptor_t *t, float freq, int samples)
+{
+    t->fac = 2.0f*cosf(2.0f*M_PI*(freq/(float) SAMPLE_RATE));
+    t->samples = samples;
+}
+/*- End of function --------------------------------------------------------*/
+
+goertzel_state_t *goertzel_init(goertzel_state_t *s,
+                                goertzel_descriptor_t *t)
+{
+    if (s  ||  (s = malloc(sizeof(goertzel_state_t))))
+    {
+        s->v2 =
+        s->v3 = 0.0;
+        s->fac = t->fac;
+        s->samples = t->samples;
+        s->current_sample = 0;
+    }
+    return s;
+}
+/*- End of function --------------------------------------------------------*/
+
+void goertzel_reset(goertzel_state_t *s)
+{
+    s->v2 =
+    s->v3 = 0.0;
+    s->current_sample = 0;
+}
+/*- End of function --------------------------------------------------------*/
+
+int goertzel_update(goertzel_state_t *s,
+                    const int16_t amp[],
+                    int samples)
+{
+    int i;
+    float v1;
+
+    if (samples > s->samples - s->current_sample)
+        samples = s->samples - s->current_sample;
+    for (i = 0;  i < samples;  i++)
+    {
+        v1 = s->v2;
+        s->v2 = s->v3;
+        s->v3 = s->fac*s->v2 - v1 + amp[i];
+    }
+    s->current_sample += samples;
+    return samples;
+}
+/*- End of function --------------------------------------------------------*/
+
+float goertzel_result(goertzel_state_t *s)
+{
+    float v1;
+
+    /* Push a zero through the process to finish things off. */
+    v1 = s->v2;
+    s->v2 = s->v3;
+    s->v3 = s->fac*s->v2 - v1;
+    /* Now calculate the non-recursive side of the filter. */
+    /* The result here is not scaled down to allow for the magnification
+       effect of the filter (the usual DFT magnification effect). */
+    return s->v3*s->v3 + s->v2*s->v2 - s->v2*s->v3*s->fac;
+}
+/*- End of function --------------------------------------------------------*/
+/*- End of file ------------------------------------------------------------*/