stream_reassembler.cc

#include "stream_reassembler.hh"
#include <iostream>
#include <limits>
#include <vector>

// Dummy implementation of a stream reassembler.

// For Lab 1, please replace with a real implementation that passes the
// automated checks run by `make check_lab1`.

// You will need to add private members to the class declaration in `stream_reassembler.hh`

template <typename... Targs>
void DUMMY_CODE(Targs &&... /* unused */) {}

using namespace std;

void StreamReassembler::remove_segement(const Type1 &it, size_t l, size_t r, Type2 &_erase, Type2 &_insert) {
    DUMMY_CODE(it, l, r);
    if(l >= it -> second || r <= it -> first) return;
    _erase.push_back(*it);
    if(l >= it -> first) {
        auto new_node = make_pair(r, it -> second);
        _stored_bytes += min(r, it -> second) - l;
        auto node = *it;
        node.second = l;
        if(node.second > node.first)
            _insert.push_back(node);
        if(new_node.second > new_node.first)
            _insert.push_back(new_node);
    } else {
        _stored_bytes += min(r, it -> second) - it -> first;
        auto node = *it;
        node.second = r;
        if(node.second > node.first)
            _insert.push_back(node);
    }
}

StreamReassembler::StreamReassembler(const size_t capacity) : 
    _output(capacity), _capacity(capacity), _assembled_bytes(0), _stored_bytes(0), _str_to_assemble(), _existed(), _eof(false), _used_byte{std::make_pair(0, std::numeric_limits<size_t>::max())} {}

//! \details This function accepts a substring (aka a segment) of bytes,
//! possibly out-of-order, from the logical stream, and assembles any newly
//! contiguous substrings and writes them into the output stream in order.
void StreamReassembler::push_substring(const string &data, const size_t index, const bool eof) {
    DUMMY_CODE(data, index, eof);
    if(index >= _capacity + _output.bytes_read()) return;
    string tmp(data);
    if(index + tmp.size() > _capacity + _output.bytes_read()) {
        tmp.resize(_capacity + _output.bytes_read() - index);
    } else _eof |= eof;
    
    if(index + tmp.size() <= _assembled_bytes) {
        if(empty()) _output.end_input();
        return;
    }
    
    // Calculate stored bytes
    decltype(_used_byte)::iterator it_l = _used_byte.lower_bound(make_pair(index, index));
    decltype(_used_byte)::iterator it_r = _used_byte.lower_bound(make_pair(index + tmp.size(), index + tmp.size()));

    vector<pair<size_t, size_t>> _need_to_erase{}, _need_to_insert{};

    if(it_l != _used_byte.begin()) it_l--;
    while(it_l != _used_byte.end()) {
        remove_segement(it_l, index, index + tmp.size(), _need_to_erase, _need_to_insert);
        if(it_l == it_r) break;
        it_l++;
    }
    for(auto v : _need_to_erase) _used_byte.erase(v);
    for(auto v : _need_to_insert) _used_byte.insert(v);

    decltype(_existed)::iterator it = _existed.lower_bound(index);
    if(it == _existed.end()) {
        _str_to_assemble.push_back(make_pair(tmp, index));
        _existed[index] = (--_str_to_assemble.end());
    } else {
        if(it -> first == index) {
            if(tmp.size() > (it -> second -> first).size()) {
                *(it -> second) = make_pair(tmp, index);
            }
        } else {
            _existed[index] = _str_to_assemble.insert(it -> second, make_pair(tmp, index));
        }
    }
    while(!_str_to_assemble.empty() && _str_to_assemble.front().second <= _assembled_bytes) {
        size_t _index = _str_to_assemble.front().second;
        string _data = _str_to_assemble.front().first;
        if(_index + _data.size() > _assembled_bytes) {
            _output.write(_data.substr(_assembled_bytes - _index, _index + _data.size() - _assembled_bytes));
            _assembled_bytes = _index + _data.size();
        }
        _existed.erase(_index);
        _str_to_assemble.pop_front();
    }
    if(empty()) _output.end_input();
}

size_t StreamReassembler::unassembled_bytes() const { return _stored_bytes - _assembled_bytes; }

bool StreamReassembler::empty() const { return (_stored_bytes == _assembled_bytes) && _eof; }