static bool ReadBlock(JPEGCompressor *self,JPEGBlock *block,int comp)
{
int dcindex=self->jpeg.scancomponents[comp].dcindex;
int acindex=self->jpeg.scancomponents[comp].acindex;
int dcmagnitude=ReadHuffmanCode(&self->bitstream,&self->dctables[dcindex]);
if(dcmagnitude<0) return false;
int dcremainder=ReadBitString(&self->bitstream,dcmagnitude);
if(dcremainder<0) return false;
int delta=DecodeValue(dcmagnitude,dcremainder);
block->c[0]=self->predicted[comp]+delta;
self->predicted[comp]+=delta;
int coeff=1;
while(coeff<64)
{
int val=ReadHuffmanCode(&self->bitstream,&self->actables[acindex]);
if(val<0) return false;
if(val==0x00) break;
int zeroes=val>>4;
int acmagnitude=val&0x0f;
int acremainder=ReadBitString(&self->bitstream,acmagnitude);
if(acremainder<0) return false;
// TODO: range checks
for(int i=0;i<zeroes;i++) block->c[coeff++]=0;
block->c[coeff++]=DecodeValue(acmagnitude,acremainder);
}
for(int i=coeff;i<64;i++) block->c[i]=0;
block->eob=coeff-1;
return true;
}
void DecompressData(FILE *fh,uint8_t *buf,uint32_t size,
int typeshift,int literalshift,int lengthshift1,int lengthshift2,int offsetshift1,int offsetshift2)
{
RangeDecoder dec;
InitializeRangeDecoder(&dec,STDIOReadFunction,fh);
int typeweight=0x800;
int lengthweights1[32],lengthweights2[32];
int offsetweights1[32],offsetweights2[32];
for(int i=0;i<32;i++)
lengthweights1[i]=lengthweights2[i]=offsetweights1[i]=offsetweights2[i]=0x800;
int literalbitweights[256];
for(int i=0;i<256;i++)
literalbitweights[i]=0x800;
int pos=0;
while(pos<size)
{
int length,offs;
if(ReadDynamicBit(&dec,&typeweight,typeshift)==1)
{
int length=(ReadUniversalCode2(&dec,size-pos-3,lengthweights1,lengthshift1,lengthweights2,lengthshift2)+3);
int offs=(ReadUniversalCode2(&dec,pos-1,offsetweights1,offsetshift1,offsetweights2,offsetshift2)+1);
CopyMemory(&buf[pos],&buf[pos-offs],length);
pos+=length;
}
else
{
buf[pos++]=ReadBitString(&dec,8,literalbitweights,literalshift);
}
}
}
void CObjectIStreamJson::SkipBitString(void)
{
CBitString obj;
ReadBitString(obj);
}
