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producer.h
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producer.h
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#pragma once
#include <variant>
#include "bitreader.h"
#include "codebook.h"
#include "footer.h"
#include "header.h"
#include "huffman_decoder.h"
#include "lz77.h"
#include "sliding_window.h"
enum struct State {
Header,
Block,
Inflate,
InflateFinalBlock,
Footer,
};
using Produce = std::variant<Header, Footer, std::vector<uint8_t>>;
template <typename Read>
class Producer : public Iterator<Produce> {
public:
explicit Producer(Read &reader)
: reader_{reader}, state_{State::Header}, member_idx_{0} {}
std::optional<Produce> next() override {
switch (state_) {
case State::Header:
if (!reader_.has_data_left()) {
if (member_idx_ == 0) {
throw Error{ErrorType::EmptyInput};
}
return std::nullopt;
}
state_ = State::Block;
++member_idx_;
return read_header(reader_);
case State::Block: {
auto header = reader_.read_bits(3);
auto is_final = (header & 1) == 1;
switch (header & 0b110) {
case 0b000:
if (is_final) state_ = State::Footer;
return inflate_block0();
case 0b010:
ll_decoder_ = HuffmanDecoder{Codebook::default_ll()};
dist_decoder_ = HuffmanDecoder{Codebook::default_dist()};
state_ = is_final ? State::InflateFinalBlock : State::Inflate;
return inflate(is_final);
case 0b100:
std::tie(ll_decoder_, dist_decoder_) = read_dynamic_codebook();
state_ = is_final ? State::InflateFinalBlock : State::Inflate;
return inflate(is_final);
default:
throw Error{ErrorType::InvalidBlockType};
}
}
case State::Inflate:
return inflate(false);
case State::InflateFinalBlock:
return inflate(true);
case State::Footer:
state_ = State::Header;
window_ = SlidingWindow{}; // reset history
return read_footer(reader_);
default:
return std::nullopt; // unreachable
}
}
private:
BitReader<Read> reader_;
State state_;
std::size_t member_idx_;
SlidingWindow window_;
HuffmanDecoder ll_decoder_;
HuffmanDecoder dist_decoder_;
Produce inflate_block0() {
reader_.byte_align();
auto len = reader_.read_bits(16);
auto nlen = reader_.read_bits(16);
if ((len ^ nlen) != 0xFFFF) {
throw Error{ErrorType::BlockType0LenMismatch};
}
std::vector<uint8_t> buf(len, 0);
auto gcount = reader_.read(Slice{buf});
if (gcount != len) throw Error{ErrorType::UnexpectedEof};
auto n = std::min<std::size_t>(len, MAX_DISTANCE);
auto write_buffer = window_.write_buffer();
std::copy(&buf[len - n], &buf[len], write_buffer.begin());
window_.slide(n);
return buf;
}
Produce inflate(bool is_final) {
auto boundary = window_.boundary();
auto result =
decode(window_.buffer(), boundary, reader_, ll_decoder_, dist_decoder_);
auto n = result.n;
if (result.done) {
state_ = is_final ? State::Footer : State::Block;
}
auto begin = window_.data.begin() + window_.cur;
std::vector<uint8_t> buf(begin, begin + n);
window_.slide(n);
return buf;
}
std::pair<HuffmanDecoder, HuffmanDecoder> read_dynamic_codebook() {
std::size_t hlit = reader_.read_bits(5) + 257;
std::size_t hdist = reader_.read_bits(5) + 1;
std::size_t hclen = reader_.read_bits(4) + 4;
uint32_t cl_lengths[19];
std::fill(&cl_lengths[0], &cl_lengths[18], 0);
std::size_t indices[] = {
16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15,
};
for (std::size_t i = 0; i < hclen; ++i) {
cl_lengths[indices[i]] = reader_.read_bits(3);
}
Codebook cl_codes{Slice{cl_lengths, std::end(cl_lengths)}};
HuffmanDecoder cl_decoder{cl_codes};
auto num_codes = hlit + hdist;
std::vector<uint32_t> lengths;
lengths.reserve(num_codes);
while (lengths.size() < num_codes) {
uint32_t cl_code, len;
try {
std::tie(cl_code, len) = cl_decoder.decode(reader_.peek_bits());
} catch (std::exception &e) {
throw Error{ErrorType::ReadDynamicCodebook};
}
reader_.consume(len);
std::size_t length;
switch (cl_code) {
case 0:
case 1:
case 2:
case 3:
case 4:
case 5:
case 6:
case 7:
case 8:
case 9:
case 10:
case 11:
case 12:
case 13:
case 14:
case 15:
lengths.push_back(cl_code);
break;
case 16: {
assert(!lengths.empty());
length = 3 + reader_.read_bits(2);
auto x = lengths.back();
lengths.resize(lengths.size() + length, x);
break;
}
case 17:
length = 3 + reader_.read_bits(3);
lengths.resize(lengths.size() + length, 0);
break;
case 18:
length = 11 + reader_.read_bits(7);
lengths.resize(lengths.size() + length, 0);
break;
default:
throw Error{ErrorType::ReadDynamicCodebook};
}
}
if (lengths.size() != num_codes)
throw Error{ErrorType::ReadDynamicCodebook};
Codebook ll_codes{Slice{&lengths[0], &lengths[hlit]}};
Codebook dist_codes{Slice{&lengths[hlit], &lengths[lengths.size()]}};
return std::make_pair(HuffmanDecoder{ll_codes}, HuffmanDecoder{dist_codes});
}
};