Add a utility library for downconverting to fp16.

[movit] / fp16.h

diff --git a/fp16.h b/fp16.h
new file mode 100644 (file)
index 0000000..9f7eff9
--- /dev/null
+++ b/fp16.h
@@ -0,0 +1,27 @@
+#ifndef _MOVIT_FP16_H
+#define _MOVIT_FP16_H 1
+
+// Code for converting to and from fp16 (from fp64), without any particular
+// machine support, with proper IEEE round-to-even behavior (and correct
+// handling of NaNs and infinities). This is needed because some OpenGL
+// drivers don't properly round off when asked to convert data themselves.
+//
+// These routines are not particularly fast.
+
+namespace movit {
+
+typedef unsigned int fp32_int_t;
+typedef unsigned short fp16_int_t;
+
+double fp16_to_fp64(fp16_int_t x);
+fp16_int_t fp64_to_fp16(double x);
+
+// These are not very useful by themselves, but are implemented using the same
+// code as the fp16 ones (just with different constants), so they are useful
+// for verifying against the FPU in unit tests.
+double fp32_to_fp64(fp32_int_t x);
+fp32_int_t fp64_to_fp32(double x);
+
+}  // namespace movit
+
+#endif  // _MOVIT_FP16_H