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-rw-r--r--lib/compression/lzxpress.c347
1 files changed, 347 insertions, 0 deletions
diff --git a/lib/compression/lzxpress.c b/lib/compression/lzxpress.c
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+++ b/lib/compression/lzxpress.c
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+/*
+ * Copyright (C) Matthieu Suiche 2008
+ *
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * 3. Neither the name of the author nor the names of its contributors
+ * may be used to endorse or promote products derived from this software
+ * without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ */
+
+#include "replace.h"
+#include "lzxpress.h"
+#include "../lib/util/byteorder.h"
+
+
+#define __CHECK_BYTES(__size, __index, __needed) do { \
+ if (unlikely(__index >= __size)) { \
+ return -1; \
+ } else { \
+ uint32_t __avail = __size - __index; \
+ if (unlikely(__needed > __avail)) { \
+ return -1; \
+ } \
+ } \
+} while(0)
+
+#define CHECK_INPUT_BYTES(__needed) \
+ __CHECK_BYTES(uncompressed_size, uncompressed_pos, __needed)
+#define CHECK_OUTPUT_BYTES(__needed) \
+ __CHECK_BYTES(max_compressed_size, compressed_pos, __needed)
+
+ssize_t lzxpress_compress(const uint8_t *uncompressed,
+ uint32_t uncompressed_size,
+ uint8_t *compressed,
+ uint32_t max_compressed_size)
+{
+ /*
+ * This is the algorithm in [MS-XCA] 2.3 "Plain LZ77 Compression".
+ *
+ * It avoids Huffman encoding by including literal bytes inline when a
+ * match is not found. Every so often it includes a uint32 bit map
+ * flagging which positions contain matches and which contain
+ * literals. The encoding of matches is of variable size, depending on
+ * the match length; they are always at least 16 bits long, and can
+ * implicitly use unused half-bytes from earlier in the stream.
+ */
+ uint32_t uncompressed_pos, compressed_pos;
+ uint32_t indic;
+ uint32_t indic_pos;
+ uint32_t indic_bit, nibble_index;
+
+ if (!uncompressed_size) {
+ return 0;
+ }
+
+ uncompressed_pos = 0;
+ compressed_pos = 0;
+ indic = 0;
+ CHECK_OUTPUT_BYTES(sizeof(uint32_t));
+ PUSH_LE_U32(compressed, compressed_pos, 0);
+ compressed_pos += sizeof(uint32_t);
+ indic_pos = 0;
+
+ indic_bit = 0;
+ nibble_index = 0;
+
+ while ((uncompressed_pos < uncompressed_size) &&
+ (compressed_pos < max_compressed_size)) {
+ bool found = false;
+
+ uint32_t best_len = 2;
+ uint32_t best_offset = 0;
+
+ int32_t offset;
+
+ const uint32_t max_offset = MIN(0x2000, uncompressed_pos);
+ /* maximum len we can encode into metadata */
+ const uint32_t max_len = MIN(0xFFFF + 3, uncompressed_size - uncompressed_pos);
+
+ /* search for the longest match in the window for the lookahead buffer */
+ for (offset = 1; (uint32_t)offset <= max_offset; offset++) {
+ uint32_t len;
+
+ for (len = 0;
+ (len < max_len) && (uncompressed[uncompressed_pos + len] ==
+ uncompressed[uncompressed_pos + len - offset]);
+ len++);
+
+ /*
+ * We check if len is better than the value found before, including the
+ * sequence of identical bytes
+ */
+ if (len > best_len) {
+ found = true;
+ best_len = len;
+ best_offset = offset;
+ if (best_len == max_len) {
+ /* We're not going to do better than this */
+ break;
+ }
+ }
+ }
+
+ if (!found) {
+ /*
+ * This is going to literal byte, which we flag by
+ * setting a bit in an indicator field somewhere
+ * earlier in the stream.
+ */
+ CHECK_INPUT_BYTES(sizeof(uint8_t));
+ CHECK_OUTPUT_BYTES(sizeof(uint8_t));
+ compressed[compressed_pos++] = uncompressed[uncompressed_pos++];
+
+ indic <<= 1;
+ indic_bit += 1;
+
+ if (indic_bit == 32) {
+ PUSH_LE_U32(compressed, indic_pos, indic);
+ indic_bit = 0;
+ CHECK_OUTPUT_BYTES(sizeof(uint32_t));
+ indic_pos = compressed_pos;
+ compressed_pos += sizeof(uint32_t);
+ }
+ } else {
+ uint32_t match_len = best_len;
+
+ uint16_t metadata;
+
+ match_len -= 3;
+ best_offset -= 1;
+
+ /* Classical meta-data */
+ CHECK_OUTPUT_BYTES(sizeof(uint16_t));
+ metadata = (uint16_t)((best_offset << 3) | MIN(match_len, 7));
+ PUSH_LE_U16(compressed, compressed_pos, metadata);
+ compressed_pos += sizeof(uint16_t);
+
+ if (match_len >= 7) {
+ match_len -= 7;
+
+ if (!nibble_index) {
+ nibble_index = compressed_pos;
+
+ CHECK_OUTPUT_BYTES(sizeof(uint8_t));
+ compressed[nibble_index] = MIN(match_len, 15);
+ compressed_pos += sizeof(uint8_t);
+ } else {
+ compressed[nibble_index] |= MIN(match_len, 15) << 4;
+ nibble_index = 0;
+ }
+
+ if (match_len >= 15) {
+ match_len -= 15;
+
+ CHECK_OUTPUT_BYTES(sizeof(uint8_t));
+ compressed[compressed_pos] = MIN(match_len, 255);
+ compressed_pos += sizeof(uint8_t);
+
+ if (match_len >= 255) {
+ /* Additional match_len */
+
+ match_len += 7 + 15;
+
+ if (match_len < (1 << 16)) {
+ CHECK_OUTPUT_BYTES(sizeof(uint16_t));
+ PUSH_LE_U16(compressed, compressed_pos, match_len);
+ compressed_pos += sizeof(uint16_t);
+ } else {
+ CHECK_OUTPUT_BYTES(sizeof(uint16_t) + sizeof(uint32_t));
+ PUSH_LE_U16(compressed, compressed_pos, 0);
+ compressed_pos += sizeof(uint16_t);
+
+ PUSH_LE_U32(compressed, compressed_pos, match_len);
+ compressed_pos += sizeof(uint32_t);
+ }
+ }
+ }
+ }
+
+ indic = (indic << 1) | 1;
+ indic_bit += 1;
+
+ if (indic_bit == 32) {
+ PUSH_LE_U32(compressed, indic_pos, indic);
+ indic_bit = 0;
+ CHECK_OUTPUT_BYTES(sizeof(uint32_t));
+ indic_pos = compressed_pos;
+ compressed_pos += sizeof(uint32_t);
+ }
+
+ uncompressed_pos += best_len;
+ }
+ }
+
+ if (indic_bit != 0) {
+ indic <<= 32 - indic_bit;
+ }
+ indic |= UINT32_MAX >> indic_bit;
+ PUSH_LE_U32(compressed, indic_pos, indic);
+
+ return compressed_pos;
+}
+
+ssize_t lzxpress_decompress(const uint8_t *input,
+ uint32_t input_size,
+ uint8_t *output,
+ uint32_t max_output_size)
+{
+ /*
+ * This is the algorithm in [MS-XCA] 2.4 "Plain LZ77 Decompression
+ * Algorithm Details".
+ */
+ uint32_t output_index, input_index;
+ uint32_t indicator, indicator_bit;
+ uint32_t nibble_index;
+
+ if (input_size == 0) {
+ return 0;
+ }
+
+ output_index = 0;
+ input_index = 0;
+ indicator = 0;
+ indicator_bit = 0;
+ nibble_index = 0;
+
+#undef CHECK_INPUT_BYTES
+#define CHECK_INPUT_BYTES(__needed) \
+ __CHECK_BYTES(input_size, input_index, __needed)
+#undef CHECK_OUTPUT_BYTES
+#define CHECK_OUTPUT_BYTES(__needed) \
+ __CHECK_BYTES(max_output_size, output_index, __needed)
+
+ do {
+ if (indicator_bit == 0) {
+ CHECK_INPUT_BYTES(sizeof(uint32_t));
+ indicator = PULL_LE_U32(input, input_index);
+ input_index += sizeof(uint32_t);
+ if (input_index == input_size) {
+ /*
+ * The compressor left room for indicator
+ * flags for data that doesn't exist.
+ */
+ break;
+ }
+ indicator_bit = 32;
+ }
+ indicator_bit--;
+
+ /*
+ * check whether the bit specified by indicator_bit is set or not
+ * set in indicator. For example, if indicator_bit has value 4
+ * check whether the 4th bit of the value in indicator is set
+ */
+ if (((indicator >> indicator_bit) & 1) == 0) {
+ CHECK_INPUT_BYTES(sizeof(uint8_t));
+ CHECK_OUTPUT_BYTES(sizeof(uint8_t));
+ output[output_index] = input[input_index];
+ input_index += sizeof(uint8_t);
+ output_index += sizeof(uint8_t);
+ } else {
+ uint32_t length;
+ uint32_t offset;
+
+ CHECK_INPUT_BYTES(sizeof(uint16_t));
+ length = PULL_LE_U16(input, input_index);
+ input_index += sizeof(uint16_t);
+ offset = (length >> 3) + 1;
+ length &= 7;
+
+ if (length == 7) {
+ if (nibble_index == 0) {
+ CHECK_INPUT_BYTES(sizeof(uint8_t));
+ nibble_index = input_index;
+ length = input[input_index] & 0xf;
+ input_index += sizeof(uint8_t);
+ } else {
+ length = input[nibble_index] >> 4;
+ nibble_index = 0;
+ }
+
+ if (length == 15) {
+ CHECK_INPUT_BYTES(sizeof(uint8_t));
+ length = input[input_index];
+ input_index += sizeof(uint8_t);
+ if (length == 255) {
+ CHECK_INPUT_BYTES(sizeof(uint16_t));
+ length = PULL_LE_U16(input, input_index);
+ input_index += sizeof(uint16_t);
+ if (length == 0) {
+ CHECK_INPUT_BYTES(sizeof(uint32_t));
+ length = PULL_LE_U32(input, input_index);
+ input_index += sizeof(uint32_t);
+ }
+
+ if (length < (15 + 7)) {
+ return -1;
+ }
+ length -= (15 + 7);
+ }
+ length += 15;
+ }
+ length += 7;
+ }
+ length += 3;
+
+ if (length == 0) {
+ return -1;
+ }
+
+ for (; length > 0; --length) {
+ if (offset > output_index) {
+ return -1;
+ }
+ CHECK_OUTPUT_BYTES(sizeof(uint8_t));
+ output[output_index] = output[output_index - offset];
+ output_index += sizeof(uint8_t);
+ }
+ }
+ } while ((output_index < max_output_size) && (input_index < (input_size)));
+
+ return output_index;
+}
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