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oot/tools/yaz0.c
2020-03-17 00:31:30 -04:00

238 lines
6.1 KiB
C

#include <assert.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include "yaz0.h"
// decoder implementation by thakis of http://www.amnoid.de
// src points to the yaz0 source data (to the "real" source data, not at the header!)
// dst points to a buffer uncompressedSize bytes large (you get uncompressedSize from
// the second 4 bytes in the Yaz0 header).
void yaz0_decode(uint8_t* src, uint8_t* dst, int uncompressedSize)
{
int srcPlace = 0, dstPlace = 0; // current read/write positions
unsigned int validBitCount = 0; // number of valid bits left in "code" byte
uint8_t currCodeByte;
while (dstPlace < uncompressedSize)
{
// read new "code" byte if the current one is used up
if (validBitCount == 0)
{
currCodeByte = src[srcPlace];
++srcPlace;
validBitCount = 8;
}
if ((currCodeByte & 0x80) != 0)
{
// straight copy
dst[dstPlace] = src[srcPlace];
dstPlace++;
srcPlace++;
}
else
{
// RLE part
uint8_t byte1 = src[srcPlace];
uint8_t byte2 = src[srcPlace + 1];
srcPlace += 2;
unsigned int dist = ((byte1 & 0xF) << 8) | byte2;
unsigned int copySource = dstPlace - (dist + 1);
unsigned int numBytes = byte1 >> 4;
if (numBytes == 0)
{
numBytes = src[srcPlace] + 0x12;
srcPlace++;
}
else
{
numBytes += 2;
}
// copy run
for (unsigned int i = 0; i < numBytes; ++i)
{
dst[dstPlace] = dst[copySource];
copySource++;
dstPlace++;
}
}
// use next bit from "code" byte
currCodeByte <<= 1;
validBitCount -= 1;
}
}
// encoder implementation by shevious, with bug fixes by notwa
typedef uint32_t uint32_t;
typedef uint8_t uint8_t;
#define MAX_RUNLEN (0xFF + 0x12)
// simple and straight encoding scheme for Yaz0
static uint32_t simpleEnc(uint8_t *src, int size, int pos, uint32_t *pMatchPos)
{
int numBytes = 1;
int matchPos = 0;
int startPos = pos - 0x1000;
int end = size - pos;
if (startPos < 0)
startPos = 0;
// maximum runlength for 3 byte encoding
if (end > MAX_RUNLEN)
end = MAX_RUNLEN;
for (int i = startPos; i < pos; i++)
{
int j;
for (j = 0; j < end; j++)
{
if (src[i + j] != src[j + pos])
break;
}
if (j > numBytes)
{
numBytes = j;
matchPos = i;
}
}
*pMatchPos = matchPos;
if (numBytes == 2)
numBytes = 1;
return numBytes;
}
// a lookahead encoding scheme for ngc Yaz0
static uint32_t nintendoEnc(uint8_t *src, int size, int pos, uint32_t *pMatchPos)
{
uint32_t numBytes = 1;
static uint32_t numBytes1;
static uint32_t matchPos;
static int prevFlag = 0;
// if prevFlag is set, it means that the previous position
// was determined by look-ahead try.
// so just use it. this is not the best optimization,
// but nintendo's choice for speed.
if (prevFlag == 1)
{
*pMatchPos = matchPos;
prevFlag = 0;
return numBytes1;
}
prevFlag = 0;
numBytes = simpleEnc(src, size, pos, &matchPos);
*pMatchPos = matchPos;
// if this position is RLE encoded, then compare to copying 1 byte and next position(pos+1) encoding
if (numBytes >= 3)
{
numBytes1 = simpleEnc(src, size, pos + 1, &matchPos);
// if the next position encoding is +2 longer than current position, choose it.
// this does not guarantee the best optimization, but fairly good optimization with speed.
if (numBytes1 >= numBytes + 2)
{
numBytes = 1;
prevFlag = 1;
}
}
return numBytes;
}
int yaz0_encode(uint8_t *src, uint8_t *dst, int srcSize)
{
int srcPos = 0;
int dstPos = 0;
int bufPos = 0;
uint8_t buf[24]; // 8 codes * 3 bytes maximum
uint32_t validBitCount = 0; // number of valid bits left in "code" byte
uint8_t currCodeByte = 0; // a bitfield, set bits meaning copy, unset meaning RLE
while (srcPos < srcSize)
{
uint32_t numBytes;
uint32_t matchPos;
numBytes = nintendoEnc(src, srcSize, srcPos, &matchPos);
if (numBytes < 3)
{
// straight copy
buf[bufPos] = src[srcPos];
bufPos++;
srcPos++;
//set flag for straight copy
currCodeByte |= (0x80 >> validBitCount);
}
else
{
//RLE part
uint32_t dist = srcPos - matchPos - 1;
uint8_t byte1, byte2, byte3;
if (numBytes >= 0x12) // 3 byte encoding
{
byte1 = 0 | (dist >> 8);
byte2 = dist & 0xFF;
buf[bufPos++] = byte1;
buf[bufPos++] = byte2;
// maximum runlength for 3 byte encoding
if (numBytes > MAX_RUNLEN)
numBytes = MAX_RUNLEN;
byte3 = numBytes - 0x12;
buf[bufPos++] = byte3;
}
else // 2 byte encoding
{
byte1 = ((numBytes - 2) << 4) | (dist >> 8);
byte2 = dist & 0xFF;
buf[bufPos++] = byte1;
buf[bufPos++] = byte2;
}
srcPos += numBytes;
}
validBitCount++;
// write eight codes
if (validBitCount == 8)
{
dst[dstPos++] = currCodeByte;
for (int j = 0; j < bufPos; j++)
dst[dstPos++] = buf[j];
currCodeByte = 0;
validBitCount = 0;
bufPos = 0;
}
}
if (validBitCount > 0)
{
dst[dstPos++] = currCodeByte;
for (int j = 0; j < bufPos; j++)
dst[dstPos++] = buf[j];
currCodeByte = 0;
validBitCount = 0;
bufPos = 0;
}
return dstPos;
}