bool readReference(IBitStream& bstr, unsigned& reference, unsigned huffmanNumber) {
int code = bstr.read(2);
if (code == 3) {
reference = bstr.read(32);
return true;
}
int bitlen = BitLength(huffmanNumber);
assert(bitlen >= 2);
reference = (code << (bitlen - 2)) | bstr.read(bitlen - 2);
return true;
}
void LenTable::Read(IBitStream &bitstr) {
symidx2nodeidx.clear();
nodes.clear();
int count = bitstr.read(32);
int bitsPerLen = bitstr.read(8);
int idxBitSize = BitLength(count);
symidx2nodeidx.resize(count);
for (unsigned& nodeIdx : symidx2nodeidx) {
nodeIdx = -1; // in case the root has a leaf as a child
}
nodes.resize(count - 1);
int rootIdx = nodes.size() - 1;
nodes.at(rootIdx) = {0,0,-1,-1};
nextNodePosition = 0;
for (int i = 0; i < count; ++i) {
int symidx = bitstr.read(idxBitSize);
int len = bitstr.read(bitsPerLen);
placeSymidx(symidx, rootIdx, len);
}
}
int LenTable::Decode(IBitStream &bitstr, unsigned &symIdx) const {
const HuffmanNode* node = &nodes.back();
int len = 0;
for (;;) {
len++;
int bit = bitstr.read(1);
if (bit) { // right
if (node->right < 0) { // leaf
symIdx = -1 - node->right;
return len;
}
node = &nodes.at(node->right - 1);
} else { // left
if (node->left < 0) { // leaf
symIdx = -1 - node->left;
return len;
}
node = &nodes.at(node->left - 1);
}
}
// unreachable
}