diff options
Diffstat (limited to 'src/base/compression')
| -rw-r--r-- | src/base/compression/lzss_compression.cc | 171 | ||||
| -rw-r--r-- | src/base/compression/lzss_compression.hh | 101 | ||||
| -rw-r--r-- | src/base/compression/null_compression.hh | 76 |
3 files changed, 348 insertions, 0 deletions
diff --git a/src/base/compression/lzss_compression.cc b/src/base/compression/lzss_compression.cc new file mode 100644 index 000000000..3ffdf7e95 --- /dev/null +++ b/src/base/compression/lzss_compression.cc @@ -0,0 +1,171 @@ +/* + * Copyright (c) 2003-2005 The Regents of The University of Michigan + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer; + * 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; + * neither the name of the copyright holders 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 COPYRIGHT HOLDERS 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 COPYRIGHT + * OWNER 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. + */ + +/** @file + * LZSSCompression definitions. + */ + +#include <assert.h> + +#include "base/compression/lzss_compression.hh" + +#include "base/misc.hh" //for fatal + +void +LZSSCompression::findSubString(uint8_t *src, int back, int size, uint16_t &L, + uint16_t &P) +{ + int front = 0; + int max_length = size - back; + L = 0; + P = back - 1; + while (front < back) { + while (src[front] != src[back] && front < back) ++front; + if (front >= back) { + return; + } + int i = 1; + while (src[front+i] == src[back+i] && i < max_length) ++i; + if (i >= L) { + L = i; + P = front; + } + if (src[front+i] != src[back+i-1]) { + // can't find a longer substring until past this point. + front += i; + } else { + ++front; + } + } +} + +int +LZSSCompression::emitByte(uint8_t *dest, uint8_t byte) +{ + if ((byte >> 5 & 0x7) == 0 || (byte >> 5 & 0x7) == 7) { + // If the top 3 bits are the same, emit 00<6bits> + dest[0] = byte & 0x3f; + return 1; + } else { + // emit 01XXXXXX <8 bits> + dest[0] = 0x40; + dest[1] = byte; + return 2; + } +} + +void +LZSSCompression::emitString(uint8_t *dest, uint16_t P, uint16_t L) +{ + // Emit 1<7P> <5P><3L> <8L> + dest[0] = 1<<7 | (P >> 5 & 0x7f); + dest[1] = ((P & 0x1f) << 3) | (L>>8 & 0x3); + dest[2] = L & 0xFF; +} + +int +LZSSCompression::compress(uint8_t *dest, uint8_t *src, int size) +{ + if (size > 4096) { + fatal("Compression can only handle block sizes of 4096 bytes or less"); + } + + // Encode the first byte. + int dest_index = emitByte(dest, src[0]); + int i = 1; + // A 11 bit field + uint16_t L; + // A 12 bit field + uint16_t P = 0; + + while (i < size && dest_index < size) { + L = 0; + + if (dest_index+3 >= size) { + dest_index = size; + continue; + } + + if (i == size - 1) { + // Output the character + dest_index += emitByte(&dest[dest_index], src[i]); + ++i; + continue; + } + findSubString(src, i, size, L, P); + if (L > 1) { + // Output the string reference + emitString(&dest[dest_index], P, L); + dest_index += 3; + i = i+L; + } else { + // Output the character + dest_index += emitByte(&dest[dest_index], src[i]); + ++i; + } + } + + if (dest_index >= size) { + // Have expansion instead of compression, just copy. + memcpy(dest,src,size); + return size; + } + return dest_index; +} + +int +LZSSCompression::uncompress(uint8_t *dest, uint8_t *src, int size) +{ + int index = 0; + int i = 0; + while (i < size) { + if (src[i] & 1<<7 ) { + // We have a string + // Extract P + int start = (src[i] & 0x3f)<<5 | ((src[i+1] >> 3) & 0x1f); + // Extract L + int len = (src[i+1] & 0x07)<<8 | src[i+2]; + i += 3; + for (int j = start; j < start+len; ++j) { + dest[index++] = dest[j]; + } + } else { + // We have a character + if (src[i] & 1<<6) { + // Value is in the next byte + dest[index++] = src[i+1]; + i += 2; + } else { + // just extend the lower 6 bits + dest[index++] = (src[i] & 0x3f) | ((src[i] & 1<<5) ? 0xC0 : 0); + ++i; + } + } + } + return index; +} diff --git a/src/base/compression/lzss_compression.hh b/src/base/compression/lzss_compression.hh new file mode 100644 index 000000000..c136c6d60 --- /dev/null +++ b/src/base/compression/lzss_compression.hh @@ -0,0 +1,101 @@ +/* + * Copyright (c) 2003-2005 The Regents of The University of Michigan + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer; + * 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; + * neither the name of the copyright holders 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 COPYRIGHT HOLDERS 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 COPYRIGHT + * OWNER 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. + */ + +#ifndef __LZSS_COMPRESSION_HH__ +#define __LZSS_COMPRESSION_HH__ + +/** @file + * LZSSCompression declarations. + */ + +#include "sim/host.hh" // for uint8_t + +/** + * Simple LZSS compression scheme. + */ +class LZSSCompression +{ + /** + * Finds the longest substring for the given offset. + * @param src The source block that we search for substrings. + * @param back The larger offset. + * @param size The size of the source block. + * @param L The length of the largest substring. + * @param P The starting offset of the largest substring. + */ + void findSubString(uint8_t *src, int back, int size, uint16_t &L, + uint16_t &P); + + /** + * Emit an encoded byte to the compressed data array. If the 2 high + * order bits can be signed extended, use 1 byte encoding, if not use 2 + * bytes. + * @param dest The compressed data. + * @param byte The byte to emit. + * @return The number of bytes used to encode. + */ + int emitByte(uint8_t *dest, uint8_t byte); + + /** + * Emit a string reference to the compressed data array. A string reference + * always uses 3 bytes. 1 flag bit, 12 bits for the starting position, and + * 11 bits for the length of the string. This allows compression of 4096 + * byte blocks with string lengths of up to 2048 bytes. + * @param dest The compressed data. + * @param P The starting position in the uncompressed data. + * @param L The length in bytes of the string. + */ + void emitString(uint8_t *dest, uint16_t P, uint16_t L); + + public: + /** + * Compresses the source block and stores it in the destination block. If + * the compressed block grows to larger than the source block, it aborts + * and just performs a copy. + * @param dest The destination block. + * @param src The block to be compressed. + * @param size The size of the source block. + * @return The size of the compressed block. + * + * @pre Destination has enough storage to hold the compressed block. + */ + int compress(uint8_t *dest, uint8_t *src, int size); + + /** + * Unompresses the source block and stores it in the destination block. + * @param dest The destination block. + * @param src The block to be uncompressed. + * @param size The size of the source block. + * @return The size of the uncompressed block. + * + * @pre Destination has enough storage to hold the uncompressed block. + */ + int uncompress(uint8_t *dest, uint8_t *src, int size); +}; + +#endif //__LZSS_COMPRESSION_HH__ diff --git a/src/base/compression/null_compression.hh b/src/base/compression/null_compression.hh new file mode 100644 index 000000000..5fbcf562b --- /dev/null +++ b/src/base/compression/null_compression.hh @@ -0,0 +1,76 @@ +/* + * Copyright (c) 2003-2005 The Regents of The University of Michigan + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions are + * met: redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer; + * 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; + * neither the name of the copyright holders 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 COPYRIGHT HOLDERS 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 COPYRIGHT + * OWNER 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. + */ + +#ifndef __BASE_COMPRESSION_NULL_COMPRESSION_HH__ +#define __BASE_COMPRESSION_NULL_COMPRESSION_HH__ + +/** + * @file + * This file defines a doNothing compression algorithm. + */ + +#include "base/misc.hh" // for fatal() +#include "sim/host.hh" + + +/** + * A dummy compression class to use when no data compression is desired. + */ +class NullCompression +{ + public: + /** + * Uncompress the data, causes a fatal since no data should be compressed. + * @param dest The output buffer. + * @param src The compressed data. + * @param size The number of bytes in src. + * + * @retval The size of the uncompressed data. + */ + static int uncompress(uint8_t * dest, uint8_t *src, int size) + { + fatal("Can't uncompress data"); + } + + /** + * Compress the data, just returns the source data. + * @param dest The output buffer. + * @param src The data to be compressed. + * @param size The number of bytes in src. + * + * @retval The size of the compressed data. + */ + + static int compress(uint8_t *dest, uint8_t *src, int size) + { + memcpy(dest,src,size); + return size; + } +}; + +#endif //__BASE_COMPRESSION_NULL_COMPRESSION_HH__ |