1 files changed, 88 insertions, 0 deletions
diff --git a/src/sample-util.c b/src/sample-util.c
new file mode 100644
index 00000000..7a3c267a
--- /dev/null
+++ b/src/sample-util.c
@@ -0,0 +1,88 @@
+#include <string.h>
+#include <assert.h>
+
+#include "sample-util.h"
+
+struct pa_sample_spec default_sample_spec = {
+    .format = SAMPLE_S16NE,
+    .rate = 44100,
+    .channels = 2
+};
+
+struct memblock *silence_memblock(struct memblock* b, struct pa_sample_spec *spec) {
+    assert(b && b->data && spec);
+    memblock_assert_exclusive(b);
+    silence_memory(b->data, b->length, spec);
+    return b;
+}
+
+void silence_memchunk(struct memchunk *c, struct pa_sample_spec *spec) {
+    assert(c && c->memblock && c->memblock->data && spec && c->length);
+    memblock_assert_exclusive(c->memblock);
+    silence_memory(c->memblock->data+c->index, c->length, spec);
+}
+
+void silence_memory(void *p, size_t length, struct pa_sample_spec *spec) {
+    char c = 0;
+    assert(p && length && spec);
+
+    switch (spec->format) {
+        case SAMPLE_U8:
+            c = 127;
+            break;
+        case SAMPLE_S16LE:
+        case SAMPLE_S16BE:
+        case SAMPLE_FLOAT32:
+            c = 0;
+            break;
+        case SAMPLE_ALAW:
+        case SAMPLE_ULAW:
+            c = 80;
+            break;
+    }
+                
+    memset(p, c, length);
+}
+
+size_t mix_chunks(struct mix_info channels[], unsigned nchannels, void *data, size_t length, struct pa_sample_spec *spec, uint8_t volume) {
+    unsigned c, d;
+    assert(channels && data && length && spec);
+    assert(spec->format == SAMPLE_S16NE);
+
+    for (d = 0;; d += sizeof(int16_t)) {
+        int32_t sum = 0;
+
+        if (d >= length)
+            return d;
+        
+        for (c = 0; c < nchannels; c++) {
+            int32_t v;
+            uint8_t volume = channels[c].volume;
+            
+            if (d >= channels[c].chunk.length)
+                return d;
+
+            if (volume == 0)
+                v = 0;
+            else {
+                v = *((int16_t*) (channels[c].chunk.memblock->data + channels[c].chunk.index + d));
+
+                if (volume != 0xFF)
+                    v = v*volume/0xFF;
+            }
+
+            sum += v;
+        }
+
+        if (volume == 0)
+            sum = 0;
+        else if (volume != 0xFF)
+            sum = sum*volume/0xFF;
+        
+        if (sum < -0x8000) sum = -0x8000;
+        if (sum > 0x7FFF) sum = 0x7FFF;
+        
+        *((int16_t*) data) = sum;
+        data += sizeof(int16_t);
+    }
+}