Initial community commit

Src/external_dependencies/openmpt-trunk/include/lhasa/lib/lzs_decoder.c

@@ -0,0 +1,156 @@
+/*
+
+Copyright (c) 2011, 2012, Simon Howard
+
+Permission to use, copy, modify, and/or distribute this software
+for any purpose with or without fee is hereby granted, provided
+that the above copyright notice and this permission notice appear
+in all copies.
+
+THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
+AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR
+CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
+NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+ */
+
+#include <stdlib.h>
+#include <string.h>
+#include <inttypes.h>
+
+#include "lha_decoder.h"
+
+#include "bit_stream_reader.c"
+
+// Parameters for ring buffer, used for storing history.  This acts
+// as the dictionary for copy operations.
+
+#define RING_BUFFER_SIZE 2048
+#define START_OFFSET 17
+
+// Threshold offset.  In the copy operation, the copy length is a 4-bit
+// value, giving a range 0..15.  The threshold offsets this so that it
+// is interpreted as 2..17 - a more useful range.
+
+#define THRESHOLD 2
+
+// Size of output buffer.  Must be large enough to hold the results of
+// the maximum copy operation.
+
+#define OUTPUT_BUFFER_SIZE (15 + THRESHOLD)
+
+// Decoder for the -lzs- compression method used by old versions of LArc.
+//
+// The input stream consists of commands, each of which is either "output
+// a literal byte value" or "copy block". A bit at the start of each
+// command signals which command it is.
+
+typedef struct {
+	BitStreamReader bit_stream_reader;
+	uint8_t ringbuf[RING_BUFFER_SIZE];
+	unsigned int ringbuf_pos;
+} LHALZSDecoder;
+
+static int lha_lzs_init(void *data, LHADecoderCallback callback,
+                        void *callback_data)
+{
+	LHALZSDecoder *decoder = data;
+
+	memset(decoder->ringbuf, ' ', RING_BUFFER_SIZE);
+	decoder->ringbuf_pos = RING_BUFFER_SIZE - START_OFFSET;
+	bit_stream_reader_init(&decoder->bit_stream_reader, callback,
+	                       callback_data);
+
+	return 1;
+}
+
+// Add a single byte to the output buffer.
+
+static void output_byte(LHALZSDecoder *decoder, uint8_t *buf,
+                        size_t *buf_len, uint8_t b)
+{
+	buf[*buf_len] = b;
+	++*buf_len;
+
+	decoder->ringbuf[decoder->ringbuf_pos] = b;
+	decoder->ringbuf_pos = (decoder->ringbuf_pos + 1) % RING_BUFFER_SIZE;
+}
+
+// Output a "block" of data from the specified range in the ring buffer.
+
+static void output_block(LHALZSDecoder *decoder,
+                         uint8_t *buf,
+                         size_t *buf_len,
+                         unsigned int start,
+                         unsigned int len)
+{
+	unsigned int i;
+
+	for (i = 0; i < len; ++i) {
+		output_byte(decoder, buf, buf_len,
+		            decoder->ringbuf[(start + i) % RING_BUFFER_SIZE]);
+	}
+}
+
+// Process a single command from the LZS input stream.
+
+static size_t lha_lzs_read(void *data, uint8_t *buf)
+{
+	LHALZSDecoder *decoder = data;
+	int bit;
+	size_t result;
+
+	// Start from an empty buffer.
+
+	result = 0;
+
+	// Each command starts with a bit that signals the type:
+
+	bit = read_bit(&decoder->bit_stream_reader);
+
+	if (bit < 0) {
+		return 0;
+	}
+
+	// What type of command is this?
+
+	if (bit) {
+		int b;
+
+		b = read_bits(&decoder->bit_stream_reader, 8);
+
+		if (b < 0) {
+			return 0;
+		}
+
+		output_byte(decoder, buf, &result, (uint8_t) b);
+	} else {
+		int pos, len;
+
+		pos = read_bits(&decoder->bit_stream_reader, 11);
+		len = read_bits(&decoder->bit_stream_reader, 4);
+
+		if (pos < 0 || len < 0) {
+			return 0;
+		}
+
+		output_block(decoder, buf, &result, (unsigned int) pos,
+		             (unsigned int) len + THRESHOLD);
+	}
+
+	return result;
+}
+
+LHADecoderType lha_lzs_decoder = {
+	lha_lzs_init,
+	NULL,
+	lha_lzs_read,
+	sizeof(LHALZSDecoder),
+	OUTPUT_BUFFER_SIZE,
+	RING_BUFFER_SIZE
+};
+