1 files changed, 109 insertions, 0 deletions
diff --git a/arm7/lib/src/SND_util.c b/arm7/lib/src/SND_util.c
new file mode 100644
index 00000000..5c0b220b
--- /dev/null
+++ b/arm7/lib/src/SND_util.c
@@ -0,0 +1,109 @@
+#include "SND_util.h"
+
+#include "syscall.h"
+
+// TODO remove this extern once the static const definition of it is here
+extern s8 sLfoSinTable[0x21];
+
+u16 SND_CalcTimer(int timer, int pitch)
+{
+    int octave = 0;
+    int pitch_normalized = -pitch;
+
+    while (pitch_normalized < 0)
+    {
+        octave--;
+        pitch_normalized += 768;
+    }
+
+    while (pitch_normalized >= 768)
+    {
+        octave++;
+        pitch_normalized -= 768;
+    }
+
+    u64 result = SVC_GetPitchTable(pitch_normalized);
+
+    result += 0x10000;
+    result *= timer;
+
+    int shift = octave - 16;
+
+    if (shift <= 0)
+    {
+        shift = -shift;
+        result >>= shift;
+    }
+    else if (shift < 32)
+    {
+        // clamp in case timer value overflows
+        u64 tmp = result & ~0uLL << (32 - shift);
+        if (tmp != 0)
+            return 0xFFFF;
+        result <<= shift;
+    }
+    else
+    {
+        return 0xFFFF;
+    }
+
+    if (result < 0x10)
+        result = 0x10;
+    else if (result > 0xFFFF)
+        result = 0xFFFF;
+
+    return (u16)result;
+}
+
+u16 SND_CalcChannelVolume(int value)
+{
+    if (value < SND_VOL_DB_MIN)
+        value = SND_VOL_DB_MIN;
+    else if (value > 0)
+        value = 0;
+
+    int result = SVC_GetVolumeTable(value + (-SND_VOL_DB_MIN));
+    int div;
+
+    if (value < -240)
+        div = 3;
+    else if (value < -120)
+        div = 2;
+    else if (value < -60)
+        div = 1;
+    else
+        div = 0;
+
+    return (u16)(result | (div << 8));
+}
+
+s8 SND_SinIdx(int x)
+{
+    // BUG: UB for out of range values
+
+    if (x < 0x20)
+    {
+        return sLfoSinTable[x];
+    }
+    else if (x < 0x40)
+    {
+        return sLfoSinTable[0x40 - x];
+    }
+    else if (x < 0x60)
+    {
+        return (s8)(-sLfoSinTable[x - 0x40]);
+    }
+    else
+    {
+        return (s8)(-sLfoSinTable[0x20 - (x - 0x60)]);
+    }
+}
+
+u16 SND_CalcRandom(void)
+{
+    static u32 state = 0x12345678;
+
+    // values from "Numerical Recipes"
+    state = state * 1664525u + 1013904223u;
+    return (u16)(state >> 16u);
+}