RunLengthEncoder.hpp

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#pragma once

#include <tudocomp/util.hpp>
#include <tudocomp/util/vbyte.hpp>
#include <tudocomp/Env.hpp>
#include <tudocomp/Compressor.hpp>

namespace tdc {

template<class char_type>
void rle_encode(std::basic_istream<char_type>& is, std::basic_ostream<char_type>& os, size_t offset = 0) {
    char_type prev;
    if(tdc_unlikely(!is.get(prev))) return;
    os << prev;
    char_type c;
    while(is.get(c)) {
        if(prev == c) {
            size_t run = 0;
            while(is.peek() == c) { ++run; is.get(); }
            os << c;
            write_vbyte(os, run+offset);
        } else {
            os << c;
        }
        prev = c;
    }
}
template<class char_type>
void rle_decode(std::basic_istream<char_type>& is, std::basic_ostream<char_type>& os, size_t offset = 0) {
    char_type prev;
    if(tdc_unlikely(!is.get(prev))) return;
    os << prev;
    char_type c;
    while(is.get(c)) {
        if(prev == c) {
            size_t run = read_vbyte<size_t>(is)-offset;
            while(run-- > 0) { os << c; }
        }
        os << c;
        prev = c;
    }
}

class RunLengthEncoder : public Compressor {
public:
    inline static Meta meta() {
        Meta m("compressor", "rle", "Run Length Encoding Compressor");
        m.option("offset").dynamic(0);
        return m;
    }
    const size_t m_offset;
    inline RunLengthEncoder(Env&& env)
        : Compressor(std::move(env)), m_offset(this->env().option("offset").as_integer()) {
    }

    inline virtual void compress(Input& input, Output& output) override {
        auto is = input.as_stream();
        auto os = output.as_stream();
        rle_encode(is,os,m_offset);
    }
    inline virtual void decompress(Input& input, Output& output) override {
        auto is = input.as_stream();
        auto os = output.as_stream();
        rle_decode(is,os,m_offset);
    }
};


}//ns