Decoder.h

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#ifndef BENCODING_DECODER_H
#define BENCODING_DECODER_H

#include <exception>
#include <memory>
#include <string>

#include "BItem.h"

namespace bencoding {

class BDictionary;
class BInteger;
class BList;
class BString;

class DecodingError: public std::runtime_error {
public:
    explicit DecodingError(const std::string &what);
};

class Decoder {
public:
    static std::unique_ptr<Decoder> create();

    std::unique_ptr<BItem> decode(const std::string &data);
    std::unique_ptr<BItem> decode(std::istream &input);

private:
    Decoder();

    void readExpectedChar(std::istream &input, char expected_char) const;

    std::unique_ptr<BDictionary> decodeDictionary(std::istream &input);
    std::unique_ptr<BDictionary> decodeDictionaryItemsIntoDictionary(
        std::istream &input);
    std::shared_ptr<BString> decodeDictionaryKey(std::istream &input);
    std::unique_ptr<BItem> decodeDictionaryValue(std::istream &input);

    std::unique_ptr<BInteger> decodeInteger(std::istream &input) const;
    std::string readEncodedInteger(std::istream &input) const;
    std::unique_ptr<BInteger> decodeEncodedInteger(
        const std::string &encodedInteger) const;

    std::unique_ptr<BList> decodeList(std::istream &input);
    std::unique_ptr<BList> decodeListItemsIntoList(std::istream &input);

    std::unique_ptr<BString> decodeString(std::istream &input) const;
    std::string::size_type readStringLength(std::istream &input) const;
    std::string readStringOfGivenLength(std::istream &input,
        std::string::size_type length) const;

    void validateInputDoesNotContainUndecodedCharacters(std::istream &input);
};

std::unique_ptr<BItem> decode(const std::string &data);
std::unique_ptr<BItem> decode(std::istream &input);

} // namespace bencoding

#endif