mirror of https://github.com/bsnes-emu/bsnes.git
82 lines
2.4 KiB
C++
82 lines
2.4 KiB
C++
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#ifndef NALL_LZSS_HPP
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#define NALL_LZSS_HPP
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#include <nall/array.hpp>
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#include <nall/new.hpp>
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#include <nall/stdint.hpp>
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namespace nall {
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class lzss {
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public:
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static bool encode(uint8_t *&output, unsigned &outlength, const uint8_t *input, unsigned inlength) {
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output = new(zeromemory) uint8_t[inlength * 9 / 8 + 9];
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unsigned i = 0, o = 0;
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while(i < inlength) {
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unsigned flagoffset = o++;
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uint8_t flag = 0x00;
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for(unsigned b = 0; b < 8 && i < inlength; b++) {
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unsigned longest = 0, pointer;
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for(unsigned index = 1; index < 4096; index++) {
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unsigned count = 0;
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while(true) {
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if(count >= 15 + 3) break; //verify pattern match is not longer than max length
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if(i + count >= inlength) break; //verify pattern match does not read past end of input
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if(i + count < index) break; //verify read is not before start of input
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if(input[i + count] != input[i + count - index]) break; //verify pattern still matches
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count++;
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}
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if(count > longest) {
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longest = count;
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pointer = index;
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}
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}
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if(longest < 3) output[o++] = input[i++];
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else {
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flag |= 1 << b;
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uint16_t x = ((longest - 3) << 12) + pointer;
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output[o++] = x;
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output[o++] = x >> 8;
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i += longest;
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}
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}
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output[flagoffset] = flag;
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}
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outlength = o;
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return true;
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}
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static bool decode(uint8_t *&output, const uint8_t *input, unsigned length) {
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output = new(zeromemory) uint8_t[length];
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unsigned i = 0, o = 0;
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while(o < length) {
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uint8_t flag = input[i++];
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for(unsigned b = 0; b < 8 && o < length; b++) {
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if(!(flag & (1 << b))) output[o++] = input[i++];
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else {
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uint16_t offset = input[i++];
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offset += input[i++] << 8;
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uint16_t lookuplength = (offset >> 12) + 3;
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offset &= 4095;
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for(unsigned index = 0; index < lookuplength && o + index < length; index++) {
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output[o + index] = output[o + index - offset];
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}
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o += lookuplength;
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}
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}
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}
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return true;
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}
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};
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}
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#endif
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