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#include "LZW.h"
#include <stdlib.h>
LZW *AllocLZW(int maxsymbols,int reservedsymbols)
{
LZW *self=(LZW *)malloc(sizeof(LZW)+sizeof(LZWTreeNode)*maxsymbols);
if(!self) return 0;
self->maxsymbols=maxsymbols;
self->reservedsymbols=reservedsymbols;
self->buffer=NULL;
self->buffersize=0;
for(int i=0;i<256;i++)
{
self->nodes[i].chr=i;
self->nodes[i].parent=-1;
}
ClearLZWTable(self);
return self;
}
void FreeLZW(LZW *self)
{
if(self)
{
free(self->buffer);
free(self);
}
}
void ClearLZWTable(LZW *self)
{
self->numsymbols=256+self->reservedsymbols;
self->prevsymbol=-1;
self->symbolsize=9; // TODO: technically this depends on reservedsymbols
}
static uint8_t FindFirstByte(LZWTreeNode *nodes,int symbol)
{
while(nodes[symbol].parent>=0) symbol=nodes[symbol].parent;
return nodes[symbol].chr;
}
int NextLZWSymbol(LZW *self,int symbol)
{
if(self->prevsymbol<0)
{
if(symbol>=self->numsymbols) return LZWInvalidCodeError;
self->prevsymbol=symbol;
return LZWNoError;
}
int postfixbyte;
if(symbol<self->numsymbols) postfixbyte=FindFirstByte(self->nodes,symbol);
else if(symbol==self->numsymbols) postfixbyte=FindFirstByte(self->nodes,self->prevsymbol);
else return LZWInvalidCodeError;
int parent=self->prevsymbol;
self->prevsymbol=symbol;
if(!LZWSymbolListFull(self))
{
self->nodes[self->numsymbols].parent=parent;
self->nodes[self->numsymbols].chr=postfixbyte;
self->numsymbols++;
if(!LZWSymbolListFull(self))
if((self->numsymbols&self->numsymbols-1)==0) self->symbolsize++;
return LZWNoError;
}
else
{
return LZWTooManyCodesError;
}
}
int ReplaceLZWSymbol(LZW *self,int oldsymbol,int symbol)
{
if(symbol>=self->numsymbols) return LZWInvalidCodeError;
self->nodes[oldsymbol].parent=self->prevsymbol;
self->nodes[oldsymbol].chr=FindFirstByte(self->nodes,symbol);
self->prevsymbol=symbol;
return LZWNoError;
}
int LZWOutputLength(LZW *self)
{
int symbol=self->prevsymbol;
int n=0;
while(symbol>=0)
{
symbol=self->nodes[symbol].parent;
n++;
}
return n;
}
int LZWOutputToBuffer(LZW *self,uint8_t *buffer)
{
int symbol=self->prevsymbol;
int n=LZWOutputLength(self);
buffer+=n;
while(symbol>=0)
{
*--buffer=self->nodes[symbol].chr;
symbol=self->nodes[symbol].parent;
}
return n;
}
int LZWReverseOutputToBuffer(LZW *self,uint8_t *buffer)
{
int symbol=self->prevsymbol;
int n=0;
while(symbol>=0)
{
*buffer++=self->nodes[symbol].chr;
symbol=self->nodes[symbol].parent;
n++;
}
return n;
}
int LZWOutputToInternalBuffer(LZW *self)
{
int symbol=self->prevsymbol;
int n=LZWOutputLength(self);
if(n>self->buffersize)
{
free(self->buffer);
self->buffersize+=1024;
self->buffer=malloc(self->buffersize);
}
uint8_t *buffer=self->buffer+n;
while(symbol>=0)
{
*--buffer=self->nodes[symbol].chr;
symbol=self->nodes[symbol].parent;
}
return n;
}
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