Initial community commit

Src/external_dependencies/openmpt-trunk/soundlib/plugins/dmo/DMOUtils.cpp

@@ -0,0 +1,59 @@
+/*
+ * DMOUtils.cpp
+ * ------------
+ * Purpose: Utility functions shared by DMO plugins
+ * Notes  : none
+ * Authors: OpenMPT Devs
+ * The OpenMPT source code is released under the BSD license. Read LICENSE for more details.
+ */
+
+
+#include "stdafx.h"
+
+#include "DMOUtils.h"
+
+#ifndef NO_PLUGINS
+#include "../../Sndfile.h"
+#endif // !NO_PLUGINS
+
+OPENMPT_NAMESPACE_BEGIN
+
+#ifndef NO_PLUGINS
+
+namespace DMO
+{
+
+// Computes (log2(x) + 1) * 2 ^ (shiftL - shiftR) (x = -2^31...2^31)
+float logGain(float x, int32 shiftL, int32 shiftR)
+{
+	uint32 intSample = static_cast<uint32>(static_cast<int64>(x));
+	const uint32 sign = intSample & 0x80000000;
+	if(sign)
+		intSample = (~intSample) + 1;
+
+	// Multiply until overflow (or edge shift factor is reached)
+	while(shiftL > 0 && intSample < 0x80000000)
+	{
+		intSample += intSample;
+		shiftL--;
+	}
+	// Unsign clipped sample
+	if(intSample >= 0x80000000)
+	{
+		intSample &= 0x7FFFFFFF;
+		shiftL++;
+	}
+	intSample = (shiftL << (31 - shiftR)) | (intSample >> shiftR);
+	if(sign)
+		intSample = ~intSample | sign;
+	return static_cast<float>(static_cast<int32>(intSample));
+}
+
+} // namespace DMO
+
+#else
+MPT_MSVC_WORKAROUND_LNK4221(Distortion)
+
+#endif // !NO_PLUGINS
+
+OPENMPT_NAMESPACE_END