Add DMR2M17

DMR2M17/codec2/pack.cpp

@@ -0,0 +1,139 @@
+/*
+  Copyright (C) 2010 Perens LLC <bruce@perens.com>
+
+  All rights reserved.
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU Lesser General Public License version 2.1, as
+  published by the Free Software Foundation.  This program is
+  distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or
+  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
+  License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with this program; if not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "defines.h"
+#include "quantise.h"
+#include <stdio.h>
+
+/* Compile-time constants */
+/* Size of unsigned char in bits. Assumes 8 bits-per-char. */
+static const unsigned int	WordSize = 8;
+
+/* Mask to pick the bit component out of bitIndex. */
+static const unsigned int	IndexMask = 0x7;
+
+/* Used to pick the word component out of bitIndex. */
+static const unsigned int	ShiftRight = 3;
+
+/** Pack a bit field into a bit string, encoding the field in Gray code.
+ *
+ * The output is an array of unsigned char data. The fields are efficiently
+ * packed into the bit string. The Gray coding is a naive attempt to reduce
+ * the effect of single-bit errors, we expect to do a better job as the
+ * codec develops.
+ *
+ * This code would be simpler if it just set one bit at a time in the string,
+ * but would hit the same cache line more often. I'm not sure the complexity
+ * gains us anything here.
+ *
+ * Although field is currently of int type rather than unsigned for
+ * compatibility with the rest of the code, indices are always expected to
+ * be >= 0.
+ */
+void CQuantize::pack(
+	unsigned char *bitArray,  /* The output bit string. */
+	unsigned int  *bitIndex,  /* Index into the string in BITS, not bytes.*/
+	int			   field,	  /* The bit field to be packed. */
+	unsigned int   fieldWidth /* Width of the field in BITS, not bytes. */
+)
+{
+	pack_natural_or_gray(bitArray, bitIndex, field, fieldWidth, 1);
+}
+
+void CQuantize::pack_natural_or_gray(
+	unsigned char *bitArray,   /* The output bit string. */
+	unsigned int  *bitIndex,   /* Index into the string in BITS, not bytes.*/
+	int			   field,	   /* The bit field to be packed. */
+	unsigned int   fieldWidth, /* Width of the field in BITS, not bytes. */
+	unsigned int   gray        /* non-zero for gray coding */
+)
+{
+	if (gray)
+	{
+		/* Convert the field to Gray code */
+		field = (field >> 1) ^ field;
+	}
+
+	do
+	{
+		unsigned int bI = *bitIndex;
+		unsigned int bitsLeft = WordSize - (bI & IndexMask);
+		unsigned int sliceWidth = bitsLeft < fieldWidth ? bitsLeft : fieldWidth;
+		unsigned int wordIndex = bI >> ShiftRight;
+
+		bitArray[wordIndex] |= ((unsigned char)((field >> (fieldWidth - sliceWidth)) << (bitsLeft - sliceWidth)));
+
+		*bitIndex = bI + sliceWidth;
+		fieldWidth -= sliceWidth;
+	}
+	while ( fieldWidth != 0 );
+}
+
+/** Unpack a field from a bit string, converting from Gray code to binary.
+ *
+ */
+int CQuantize::unpack(
+	const unsigned char *bitArray, /* The input bit string. */
+	unsigned int        *bitIndex, /* Index into the string in BITS, not bytes.*/
+	unsigned int		 fieldWidth/* Width of the field in BITS, not bytes. */
+)
+{
+	return unpack_natural_or_gray(bitArray, bitIndex, fieldWidth, 1);
+}
+
+/** Unpack a field from a bit string, to binary, optionally using
+ * natural or Gray code.
+ *
+ */
+int CQuantize::unpack_natural_or_gray(
+	const unsigned char *bitArray,  /* The input bit string. */
+	unsigned int        *bitIndex,  /* Index into the string in BITS, not bytes.*/
+	unsigned int		 fieldWidth,/* Width of the field in BITS, not bytes. */
+	unsigned int         gray       /* non-zero for Gray coding */
+)
+{
+	unsigned int	field = 0;
+	unsigned int	t;
+
+	do
+	{
+		unsigned int bI = *bitIndex;
+		unsigned int bitsLeft = WordSize - (bI & IndexMask);
+		unsigned int sliceWidth = bitsLeft < fieldWidth ? bitsLeft : fieldWidth;
+
+		field |= (((bitArray[bI >> ShiftRight] >> (bitsLeft - sliceWidth)) & ((1 << sliceWidth) - 1)) << (fieldWidth - sliceWidth));
+
+		*bitIndex = bI + sliceWidth;
+		fieldWidth -= sliceWidth;
+	}
+	while ( fieldWidth != 0 );
+
+	if (gray)
+	{
+		/* Convert from Gray code to binary. Works for maximum 8-bit fields. */
+		t = field ^ (field >> 8);
+		t ^= (t >> 4);
+		t ^= (t >> 2);
+		t ^= (t >> 1);
+	}
+	else
+	{
+		t = field;
+	}
+
+	return t;
+}