mirror of
https://github.com/sehugg/8bitworkshop.git
synced 2024-11-12 10:07:00 +00:00
71 lines
1.7 KiB
C
71 lines
1.7 KiB
C
/*
|
|
LZG decompression library.
|
|
See lzh.h and https://liblzg.bitsnbites.eu/
|
|
*/
|
|
|
|
#include <string.h>
|
|
|
|
const unsigned char LZG_LENGTH_DECODE_LUT[32] = {
|
|
2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,
|
|
18,19,20,21,22,23,24,25,26,27,28,29,35,48,72,128
|
|
};
|
|
|
|
#pragma codesize (200) // make code faster?
|
|
|
|
unsigned char* lzg_decode_vram(const unsigned char* _src,
|
|
unsigned char* _dest,
|
|
unsigned char* _end) {
|
|
// copy params to static locals
|
|
register const unsigned char* src = _src;
|
|
register unsigned char* dest = _dest;
|
|
unsigned char* end = _end;
|
|
// more locals
|
|
char marker[4];
|
|
unsigned int length, offset;
|
|
unsigned char sym, b, b2;
|
|
|
|
// copy 4 marker bytes to locals
|
|
memcpy(marker, src, 4);
|
|
src += 4;
|
|
// loop until we run out of buffer space
|
|
while (dest < end) {
|
|
sym = src[0];
|
|
b = src[1];
|
|
src += 2;
|
|
// copy commands
|
|
offset = 0;
|
|
b2 = b & 0x1f;
|
|
length = LZG_LENGTH_DECODE_LUT[b2]; // required for aaaa,y
|
|
// look for marker symbols
|
|
if (sym == marker[0]) {
|
|
if (b == 0) goto literal;
|
|
b2 = *src++;
|
|
offset = ((b2 << 8) | *src++) + 2056; // 16-bit value
|
|
} else if (sym == marker[1]) {
|
|
if (b == 0) goto literal;
|
|
b2 = *src++;
|
|
offset = (((b & 0xe0) << 3) | b2) + 8;
|
|
} else if (sym == marker[2]) {
|
|
length = (b >> 6) + 3;
|
|
offset = (b & 0x3f) + 8;
|
|
} else if (sym == marker[3]) {
|
|
offset = (b >> 5) + 1;
|
|
} else {
|
|
src--;
|
|
literal:
|
|
*dest++ = sym;
|
|
continue;
|
|
}
|
|
// escape marker symbol
|
|
if (b == 0) goto literal;
|
|
// check for dest. overflow
|
|
if (dest + length > end) {
|
|
length = end - dest;
|
|
}
|
|
// copy bytes
|
|
memcpy(dest, dest - offset, length);
|
|
dest += length;
|
|
}
|
|
return dest;
|
|
}
|