1 files changed, 109 insertions, 0 deletions
diff --git a/gpr/source/lib/vc5_decoder/vlc.c b/gpr/source/lib/vc5_decoder/vlc.c
new file mode 100755
index 0000000..646fc59
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+++ b/gpr/source/lib/vc5_decoder/vlc.c
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+/*! @file vlc.c
+ *
+ *  @brief Implementation of routines to parse a variable-length encoded bitstream.
+ *
+ *  (C) Copyright 2018 GoPro Inc (http://gopro.com/).
+ *
+ *  Licensed under either:
+ *  - Apache License, Version 2.0, http://www.apache.org/licenses/LICENSE-2.0
+ *  - MIT license, http://opensource.org/licenses/MIT
+ *  at your option.
+ *
+ *  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.
+ */
+
+#include "headers.h"
+
+/*!
+	@brief Parse a run length coded magnitude in the bitstream
+*/
+CODEC_ERROR GetRlv(BITSTREAM *stream, CODEBOOK *codebook, RUN *run)
+{
+	BITWORD bitstream_bits = 0;			// Buffer of bits read from the stream
+	BITCOUNT bitstream_count = 0;		// Number of bits read from the stream
+
+	// Get the length of the codebook and initialize a pointer to its entries
+	int codebook_length = codebook->length;
+	RLV *codebook_entry = (RLV *)((uint8_t *)codebook + sizeof(CODEBOOK));
+
+	// Index into the codebook
+	int codeword_index = 0;
+
+	// Search the codebook for the run length and value
+	while (codeword_index < codebook_length)
+	{
+		// Get the size of the current word in the codebook
+		BITCOUNT codeword_count = codebook_entry[codeword_index].size;
+
+		// Need to read more bits from the stream?
+		if (bitstream_count < codeword_count)
+		{
+			// Calculate the number of additional bits to read from the stream
+			BITCOUNT read_count = codeword_count - bitstream_count;
+			bitstream_bits = AddBits(stream, bitstream_bits, read_count);
+			bitstream_count = codeword_count;
+		}
+
+		// Examine the run length table entries that have the same bit field length
+		for (; (codeword_index < codebook_length) && (bitstream_count == codebook_entry[codeword_index].size);
+				codeword_index++) {
+			if (bitstream_bits == codebook_entry[codeword_index].bits) {
+				run->count = codebook_entry[codeword_index].count;
+				run->value = codebook_entry[codeword_index].value;
+				goto found;
+			}
+		}
+	}
+
+	// Did not find a matching code in the codebook
+	return CODEC_ERROR_NOTFOUND;
+
+found:
+
+	// Found a valid codeword in the bitstream
+	return CODEC_ERROR_OKAY;
+}
+
+/*!
+	Parse a run length coded signed value in the bitstream
+*/
+CODEC_ERROR GetRun(BITSTREAM *stream, CODEBOOK *codebook, RUN *run)
+{
+	CODEC_ERROR error = CODEC_ERROR_OKAY;
+	int32_t value;
+
+	// Get the magnitude of the number from the bitstream
+	error = GetRlv(stream, codebook, run);
+
+	// Error while parsing the bitstream?
+	if (error != CODEC_ERROR_OKAY) {
+		return error;
+	}
+
+	// Restore the sign to the magnitude of the run value
+	value = run->value;
+
+	// Signed quantity?
+	if (value != 0)
+	{
+		BITWORD sign;
+
+		// Something is wrong if the value is already negative
+		assert(value > 0);
+
+		// Get the codeword for the sign of the value
+		sign = GetBits(stream, VLC_SIGNCODE_SIZE);
+
+		// Change the sign if the codeword signalled a negative value
+		value = ((sign == VLC_NEGATIVE_CODE) ? neg(value) : value);
+	}
+
+	// Return the signed value of the coefficient
+	run->value = value;
+
+	return CODEC_ERROR_OKAY;
+}