compress: upgraded to AudioCompress 2.0

Copied sources from
http://beesbuzz.biz/code/audiocompress/AudioCompress-2.0.tar.gz

[mk: created this patch under fluffy's name and fixed some gcc
signed/unsigned comparison warnings]

src/AudioCompress/compress.c

@@ -0,0 +1,184 @@
+/* compress.c
+ * Compressor logic
+ *
+ * (c)2007 busybee (http://beesbuzz.biz/
+ * Licensed under the terms of the LGPL. See the file COPYING for details.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "config.h"
+#include "compress.h"
+
+struct Compressor {
+        //! The compressor's preferences
+        struct CompressorConfig prefs;
+        
+        //! History of the peak values
+        int *peaks;
+                
+        //! History of the gain values
+        int *gain;
+        
+        //! History of clip amounts
+        int *clipped;
+        
+        unsigned int pos;
+        unsigned int bufsz;
+};
+
+struct Compressor *Compressor_new(unsigned int history)
+{
+	struct Compressor *obj = malloc(sizeof(struct Compressor));
+
+	obj->prefs.target = TARGET;
+	obj->prefs.maxgain = GAINMAX;
+	obj->prefs.smooth = GAINSMOOTH;
+
+        obj->peaks = obj->gain = obj->clipped = NULL;
+	obj->bufsz = 0;
+        obj->pos = 0;
+        
+        Compressor_setHistory(obj, history);
+        
+        return obj;
+}
+
+void Compressor_delete(struct Compressor *obj)
+{
+	if (obj->peaks)
+		free(obj->peaks);
+	if (obj->gain)
+		free(obj->gain);
+	if (obj->clipped)
+		free(obj->clipped);
+	free(obj);
+}
+
+static int *resizeArray(int *data, int newsz, int oldsz)
+{
+        data = realloc(data, newsz*sizeof(int));
+        if (newsz > oldsz)
+                memset(data + oldsz, 0, sizeof(int)*(newsz - oldsz));
+        return data;
+}
+
+void Compressor_setHistory(struct Compressor *obj, unsigned int history)
+{
+	if (!history)
+                history = BUCKETS;
+        
+        obj->peaks = resizeArray(obj->peaks, history, obj->bufsz);
+        obj->gain = resizeArray(obj->gain, history, obj->bufsz);
+        obj->clipped = resizeArray(obj->clipped, history, obj->bufsz);
+        obj->bufsz = history;
+}
+
+struct CompressorConfig *Compressor_getConfig(struct Compressor *obj)
+{
+        return &obj->prefs;
+}
+
+void Compressor_Process_int16(struct Compressor *obj, int16_t *audio, 
+                              unsigned int count)
+{
+        struct CompressorConfig *prefs = Compressor_getConfig(obj);
+	int16_t *ap;
+	unsigned int i;
+        int *peaks = obj->peaks;
+        int curGain = obj->gain[obj->pos];
+        int newGain;
+        int peakVal = 1;
+        int peakPos = 0;
+        int slot = (obj->pos + 1) % obj->bufsz;
+        int *clipped = obj->clipped + slot;
+        unsigned int ramp = count;
+        int delta;
+        
+	ap = audio;
+	for (i = 0; i < count; i++)
+	{
+		int val = *ap++;
+                if (val < 0)
+                        val = -val;
+		if (val > peakVal)
+                {
+			peakVal = val;
+                        peakPos = i;
+                }
+	}
+	peaks[slot] = peakVal;
+
+
+	for (i = 0; i < obj->bufsz; i++)
+	{
+		if (peaks[i] > peakVal)
+		{
+			peakVal = peaks[i];
+			peakPos = 0;
+		}
+	}
+
+	//! Determine target gain
+	newGain = (1 << 10)*prefs->target/peakVal;
+        
+        //! Adjust the gain with inertia from the previous gain value
+        newGain = (curGain*((1 << prefs->smooth) - 1) + newGain) 
+                >> prefs->smooth;
+        
+        //! Make sure it's no more than the maximum gain value
+        if (newGain > (prefs->maxgain << 10))
+                newGain = prefs->maxgain << 10;
+        
+        //! Make sure it's no less than 1:1
+	if (newGain < (1 << 10))
+		newGain = 1 << 10;
+
+        //! Make sure the adjusted gain won't cause clipping
+        if ((peakVal*newGain >> 10) > 32767)
+        {
+                newGain = (32767 << 10)/peakVal;
+                //! Truncate the ramp time
+                ramp = peakPos;
+        }
+        
+        //! Record the new gain
+        obj->gain[slot] = newGain;
+
+        if (!ramp)
+                ramp = 1;
+        if (!curGain)
+                curGain = 1 << 10;
+	delta = (newGain - curGain) / (int)ramp;
+
+	ap = audio;
+        *clipped = 0;
+	for (i = 0; i < count; i++)
+	{
+		int sample;
+
+		//! Amplify the sample
+		sample = *ap*curGain >> 10;
+		if (sample < -32768)
+		{
+			*clipped += -32768 - sample;
+			sample = -32768;
+		} else if (sample > 32767)
+		{
+			*clipped += sample - 32767;
+			sample = 32767;
+		}
+		*ap++ = sample;
+
+                //! Adjust the gain
+                if (i < ramp)
+                        curGain += delta;
+                else
+                        curGain = newGain;
+	}
+
+        obj->pos = slot;
+}
+