1 files changed, 34 insertions, 0 deletions
diff --git a/libpsn00b/psxgte/isin.c b/libpsn00b/psxgte/isin.c
new file mode 100644
index 0000000..79e2970
--- /dev/null
+++ b/libpsn00b/psxgte/isin.c
@@ -0,0 +1,34 @@
+/* Based on isin_S4 implementation from coranac:
+ *	http://www.coranac.com/2009/07/sines/
+ *
+ */
+
+#define qN	10
+#define qA	12
+#define B	19900
+#define	C	3516
+
+int isin(int x) {
+
+    int c, x2, y;
+
+    c= x<<(30-qN);              // Semi-circle info into carry.
+    x -= 1<<qN;                 // sine -> cosine calc
+
+    x= x<<(31-qN);              // Mask with PI
+    x= x>>(31-qN);              // Note: SIGNED shift! (to qN)
+
+    x= x*x>>(2*qN-14);          // x=x^2 To Q14
+
+    y= B - (x*C>>14);           // B - x^2*C
+    y= (1<<qA)-(x*y>>16);       // A - x^2*(B-x^2*C)
+
+    return c>=0 ? y : -y;
+
+}
+
+int icos(int x) {
+
+    return isin( x+1024 );
+
+}