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Diffstat (limited to 'src/formats/osdm/DynamicTokenizer.hpp')
-rw-r--r-- | src/formats/osdm/DynamicTokenizer.hpp | 252 |
1 files changed, 252 insertions, 0 deletions
diff --git a/src/formats/osdm/DynamicTokenizer.hpp b/src/formats/osdm/DynamicTokenizer.hpp new file mode 100644 index 0000000..0cac2e8 --- /dev/null +++ b/src/formats/osdm/DynamicTokenizer.hpp @@ -0,0 +1,252 @@ +/* + 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 DynamicTokenizer.hpp + * + * Tokenizer that can be reconfigured at runtime 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 <set> +#include <string> +#include <vector> + +#include <core/common/Location.hpp> + +#include "TokenTrie.hpp" + +namespace ousia { + +// Forward declarations +class CharReader; + +/** + * The DynamicToken structure describes a token discovered by the Tokenizer. + */ +struct DynamicToken { + /** + * Id of the type of this token. + */ + TokenTypeId type; + + /** + * String that was matched. + */ + std::string content; + + /** + * Location from which the string was extracted. + */ + SourceLocation location; + + /** + * Default constructor. + */ + DynamicToken() : type(EmptyToken) {} + + /** + * Constructor of the DynamicToken struct. + * + * @param id represents the token type. + * @param content is the string content that has been extracted. + * @param location is the location of the extracted string content in the + * source file. + */ + DynamicToken(TokenTypeId type, const std::string &content, + SourceLocation location) + : type(type), content(content), location(location) + { + } + + /** + * Constructor of the DynamicToken struct, only initializes the token type + * + * @param type is the id corresponding to the type of the token. + */ + DynamicToken(TokenTypeId type) : type(type) {} + + /** + * The getLocation function allows the tokens to be directly passed as + * parameter to Logger or LoggableException instances. + * + * @return a reference at the location field + */ + const SourceLocation &getLocation() const { return location; } +}; + +/** + * Enum specifying the whitespace handling of the DynamicTokenizer class when + * reading non-token text. + */ +enum class WhitespaceMode { + /** + * Preserves all whitespaces as they are found in the source file. + */ + PRESERVE, + + /** + * Trims whitespace at the beginning and the end of the found text. + */ + TRIM, + + /** + * Whitespaces are trimmed and collapsed, multiple whitespace characters + * are replaced by a single space character. + */ + COLLAPSE +}; + +/** + * The DynamicTokenizer is used to extract tokens and chunks of text from a + * CharReader. It allows to register and unregister tokens while parsing and + * to modify the handling of whitespace characters. Note that the + * DynamicTokenizer always tries to extract the longest possible token from the + * tokenizer. + */ +class DynamicTokenizer { +private: + /** + * Internally used token trie. This object holds all registered tokens. + */ + TokenTrie trie; + + /** + * Flag defining whether whitespaces should be preserved or not. + */ + WhitespaceMode whitespaceMode; + + /** + * Vector containing all registered token types. + */ + std::vector<std::string> tokens; + + /** + * Next index in the tokens list where to search for a new token id. + */ + size_t nextTokenTypeId; + + /** + * Templated function used internally to read the current token. The + * function is templated in order to force code generation for all six + * combiations of whitespace modes and reading/peeking. + * + * @tparam TextHandler is the type to be used for the textHandler instance. + * @tparam read specifies whether the function should start from and advance + * the read pointer of the char reader. + * @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. + * @return false if the end of the stream has been reached, true otherwise. + */ + template <typename TextHandler, bool read> + bool next(CharReader &reader, DynamicToken &token); + +public: + /** + * Constructor of the DynamicTokenizer class. + * + * @param whitespaceMode specifies how whitespace should be handled. + */ + DynamicTokenizer(WhitespaceMode whitespaceMode = WhitespaceMode::COLLAPSE); + + /** + * Registers the given string as a token. Returns a const pointer at a + * TokenDescriptor that will be used to reference the newly created token. + * + * @param token is the token string that should be registered. + * @return a unique identifier for the registered token or EmptyToken if + * an error occured. + */ + TokenTypeId registerToken(const std::string &token); + + /** + * Unregisters the token belonging to the given TokenTypeId. + * + * @param type is the token type that should be unregistered. The + *TokenTypeId + * must have been returned by registerToken. + * @return true if the operation was successful, false otherwise (e.g. + * because the given TokenDescriptor was already unregistered). + */ + bool unregisterToken(TokenTypeId type); + + /** + * Returns the token that was registered under the given TokenTypeId id or + *an + * empty string if an invalid TokenTypeId id is given. + * + * @param type is the TokenTypeId id for which the corresponding token + *string + * should be returned. + * @return the registered token string or an empty string if the given type + * was invalid. + */ + std::string getTokenString(TokenTypeId type); + + /** + * Sets the whitespace mode. + * + * @param whitespaceMode defines how whitespace should be treated in text + * tokens. + */ + void setWhitespaceMode(WhitespaceMode mode); + + /** + * Returns the current value of the whitespace mode. + * + * @return the whitespace mode. + */ + WhitespaceMode getWhitespaceMode(); + + /** + * Reads a new token from the CharReader and stores it in the given + * DynamicToken instance. + * + * @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. + * @return true if a token could be read, false if the end of the stream + * has been reached. + */ + bool read(CharReader &reader, DynamicToken &token); + + /** + * 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. + * @return true if a token could be read, false if the end of the stream + * has been reached. + */ + bool peek(CharReader &reader, DynamicToken &token); +}; +} + +#endif /* _OUSIA_DYNAMIC_TOKENIZER_HPP_ */ + |