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/*
Ousía
Copyright (C) 2014 Benjamin Paaßen, Andreas Stöckel
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* @file Tokenizer.hpp
*
* Tokenizer that can be reconfigured at runtime and is used for parsing the
* plain text format.
*
* @author Andreas Stöckel (astoecke@techfak.uni-bielefeld.de)
*/
#ifndef _OUSIA_DYNAMIC_TOKENIZER_HPP_
#define _OUSIA_DYNAMIC_TOKENIZER_HPP_
#include <cstdint>
#include <string>
#include <vector>
#include <core/common/Location.hpp>
#include <core/common/Token.hpp>
#include "TokenTrie.hpp"
namespace ousia {
// Forward declarations
class CharReader;
class TokenizedData;
/**
* The Tokenizer is used to extract tokens and chunks of text from a
* CharReader. It allows to register and unregister tokens while parsing. Note
* that the Tokenizer always tries to extract the longest possible token from
* the tokenizer. Tokens can be registered as primary or non-primary token. If
* a Token is registered as a primary token, it is returned as a single Token
* instance if it occurs. In the non-primary case the token is returned as part
* of a segmented TokenizedData instance.
*/
class Tokenizer {
public:
/**
* Internally used structure describing a registered token.
*/
struct TokenDescriptor {
/**
* String describing the token.
*/
std::string string;
/**
* Set to true if this token is primary.
*/
bool primary;
/**
* Constructor of the TokenDescriptor class.
*
* @param string is the string representation of the registered token.
* @param primary specifies whether the token is a primary token that
* should be returned as a single token, or a secondary token, that
* should be returned as part of TokenizedData.
*/
TokenDescriptor(const std::string &string, bool primary)
: string(string), primary(primary)
{
}
/**
* Default constructor.
*/
TokenDescriptor() : primary(false) {}
/**
* Returns true if the TokenDescriptor represents a valid token.
*/
bool valid() { return !string.empty(); }
};
private:
/**
* Internally used token trie. This object holds all registered tokens.
*/
TokenTrie trie;
/**
* Vector containing all registered token types.
*/
std::vector<TokenDescriptor> tokens;
/**
* Next index in the tokens list where to search for a new token id.
*/
size_t nextTokenId;
/**
* Templated function used internally to read the current token. The
* function is templated in order to force optimized code generation for
* both reading and peeking.
*
* @tparam read specifies whether the method should read the token or just
* peek.
* @param reader is the CharReader instance from which the data should be
* read.
* @param token is the token structure into which the token information
* should be written.
* @param data is a reference at the TokenizedData instance to which the
* token information should be appended.
* @return false if the end of the stream has been reached, true otherwise.
*/
template <bool read>
bool next(CharReader &reader, Token &token, TokenizedData &data) const;
public:
/**
* Constructor of the Tokenizer class.
*/
Tokenizer();
/**
* Registers the given string as a token. Returns a unique identifier
* describing the registered token.
*
* @param token is the token string that should be registered.
* @param primary specifies whether the token is a primary token -- if true,
* the token will be returned as a single, standalone token. Otherwise the
* token will be returned as part of a "TokenizedData" structure.
* @return a unique identifier for the registered token or Tokens::Empty if
* an error occured.
*/
TokenId registerToken(const std::string &token, bool primary = true);
/**
* Unregisters the token belonging to the given TokenId.
*
* @param type is the token type that should be unregistered. The
* TokenId must have been returned by registerToken.
* @return true if the operation was successful, false otherwise (e.g.
* because the token with the given TokenId was already unregistered).
*/
bool unregisterToken(TokenId id);
/**
* Returns the token that was registered under the given TokenId id or
* an empty string if an invalid TokenId id is given.
*
* @param id is the TokenId for which the corresponding TokenDescriptor
* should be returned.
* @return the registered TokenDescriptor or an invalid TokenDescriptor if
* the given TokenId is invalid.
*/
const TokenDescriptor& lookupToken(TokenId id) const;
/**
* Reads a new token from the CharReader and stores it in the given
* Token instance. If the token has the id Tokens::Data, use the "getData"
* method to fetch a reference at the underlying TokenizedData instance
* storing the data.
*
* @param reader is the CharReader instance from which the data should be
* read.
* @param token is a reference at the token instance into which the Token
* information should be written.
* @param data is a reference at the TokenizedData instance to which the
* token information should be appended.
* @return true if a token could be read, false if the end of the stream
* has been reached.
*/
bool read(CharReader &reader, Token &token, TokenizedData &data) const;
/**
* The peek method does not advance the read position of the char reader,
* but reads the next token from the current char reader peek position.
*
* @param reader is the CharReader instance from which the data should be
* read.
* @param token is a reference at the token instance into which the Token
* information should be written.
* @param data is a reference at the TokenizedData instance to which the
* token information should be appended.
* @return true if a token could be read, false if the end of the stream
* has been reached.
*/
bool peek(CharReader &reader, Token &token, TokenizedData &data) const;
};
}
#endif /* _OUSIA_DYNAMIC_TOKENIZER_HPP_ */
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