bool CompressLZW::CompressImpl(const ByteBuffer& input, ByteBuffer& output)
{
dict<std::string, int>::type_dense_hash_map dictionary;
dict<std::string, int>::init(dictionary, "");
int dictSize = DEFAULT_DICTIONARY_SIZE;
for (int i = 0; i < DEFAULT_DICTIONARY_SIZE; i++)
dictionary[std::string(1, i)] = i;
const char* in = (const char*)input.Data();
char c;
std::string w, wc;
dict<std::string, int>::type_dense_hash_map::iterator itr;
for (size_t i = 0; i < input.Size(); ++i)
{
c = input[i];
wc = w + c;
itr = dictionary.find(wc);
if (itr != dictionary.end())
w = wc;
else
{
output.WriteDynInt(dictionary[w]);
dictionary.insert(itr, std::make_pair(wc, dictSize++));
w = std::string(1, c);
}
}
if (!w.empty())
output.WriteDynInt(dictionary[w]);
return true;
}
void ByteBuffer::Append(const ByteBuffer& from) {
Write(from.Data(), from.Size());
}