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