Add bc6 and bc7 compressors from nvidia.

src/nvtt/bc7/bits.h

@@ -0,0 +1,73 @@
+/*
+Copyright 2007 nVidia, Inc.
+Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. 
+
+You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 
+
+Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, 
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
+
+See the License for the specific language governing permissions and limitations under the License.
+*/
+
+#ifndef _BITS_H
+#define _BITS_H
+
+// read/write a bitstream
+
+#include <assert.h>
+
+class Bits
+{
+public:
+
+	Bits(char *data, int maxdatabits) { assert (data && maxdatabits > 0); bptr = bend = 0; bits = data; maxbits = maxdatabits; readonly = 0;}
+	Bits(const char *data, int availdatabits) { assert (data && availdatabits > 0); bptr = 0; bend = availdatabits; cbits = data; maxbits = availdatabits; readonly = 1;}
+
+	void write(int value, int nbits) {
+		assert (nbits >= 0 && nbits < 32);
+		assert (sizeof(int)>= 4);
+		for (int i=0; i<nbits; ++i)
+			writeone(value>>i);
+	}
+	int read(int nbits) { 
+		assert (nbits >= 0 && nbits < 32);
+		assert (sizeof(int)>= 4);
+		int out = 0;
+		for (int i=0; i<nbits; ++i)
+			out |= readone() << i;
+		return out;
+	}
+	int getptr() { return bptr; }
+	void setptr(int ptr) { assert (ptr >= 0 && ptr < maxbits); bptr = ptr; }
+	int getsize() { return bend; }
+
+private:
+	int	bptr;		// next bit to read
+	int bend;		// last written bit + 1
+	char *bits;		// ptr to user bit stream
+	const char *cbits;	// ptr to const user bit stream
+	int maxbits;	// max size of user bit stream
+	char readonly;	// 1 if this is a read-only stream
+
+	int readone() {
+		assert (bptr < bend);
+		if (bptr >= bend) return 0;
+		int bit = (readonly ? cbits[bptr>>3] : bits[bptr>>3]) & (1 << (bptr & 7));
+		++bptr;
+		return bit != 0;
+	}
+	void writeone(int bit) {
+		if (readonly)
+			throw "Writing a read-only bit stream";
+		assert (bptr < maxbits);
+		if (bptr >= maxbits) return;
+		if (bit&1)
+			bits[bptr>>3] |= 1 << (bptr & 7);
+		else
+			bits[bptr>>3] &= ~(1 << (bptr & 7));
+		if (bptr++ >= bend) bend = bptr;
+	}
+};
+
+#endif