inline unsigned int HuffmanDecoder::Decode(code_t code, /* out */ value_t &value) const
{
assert(m_codeToValue.size() > 0);
LookupEntry &entry = m_cache[code & m_cacheMask];
code_t normalizedCode;
if (entry.type != 1)
normalizedCode = BitReverse(code);
if (entry.type == 0)
FillCacheEntry(entry, normalizedCode);
if (entry.type == 1)
{
value = entry.value;
return entry.len;
}
else
{
const CodeInfo &codeInfo = (entry.type == 2)
? entry.begin[(normalizedCode << m_cacheBits) >> (MAX_CODE_BITS - (entry.len - m_cacheBits))]
: *(std::upper_bound(entry.begin, entry.end, normalizedCode, CodeLessThan())-1);
value = codeInfo.value;
return codeInfo.len;
}
}
void HuffmanDecoder::FillCacheEntry(LookupEntry &entry, code_t normalizedCode) const
{
normalizedCode &= m_normalizedCacheMask;
const CodeInfo &codeInfo = *(std::upper_bound(m_codeToValue.begin(), m_codeToValue.end(), normalizedCode, CodeLessThan())-1);
if (codeInfo.len <= m_cacheBits)
{
entry.type = 1;
entry.value = codeInfo.value;
entry.len = codeInfo.len;
}
else
{
entry.begin = &codeInfo;
const CodeInfo *last = & *(std::upper_bound(m_codeToValue.begin(), m_codeToValue.end(), normalizedCode + ~m_normalizedCacheMask, CodeLessThan())-1);
if (codeInfo.len == last->len)
{
entry.type = 2;
entry.len = codeInfo.len;
}
else
{
entry.type = 3;
entry.end = last+1;
}
}
}
