WordDict3

Usage

#include <mifluz.h>
WordList* words = ...;
WordDict* dict = words->Dict();

Overview

WordDict maps strings to unique identifiers and frequency in the inverted index. Whenever a new word is found, the WordDict class can be asked to assign it a serial number. When doing so, an entry is created in the dictionary with a frequency of zero. The application may then increment or decrement the frequency to reflect the inverted index content.

The serial numbers range from 1 to 2^32 inclusive.

A WordDict object is automatically created by the WordList object and should not be created directly by the application.

Methods

WordDict()

Private constructor.

int Initialize(WordList* words)

Bind the object a WordList inverted index. Return OK on success, NOTOK otherwise.

int Open()

Open the underlying Berkeley DB sub-database. The enclosing file is given by the words data member. Return OK on success, NOTOK otherwise.

int Remove()

Destroy the underlying Berkeley DB sub-database. Return OK on success, NOTOK otherwise.

int Close()

Close the underlying Berkeley DB sub-database. Return OK on success, NOTOK otherwise.

int Serial(const String& word, unsigned int& serial)

If the word argument exists in the dictionnary, return its serial number in the serial argument. If it does not already exists, assign it a serial number, create an entry with a frequency of zero and return the new serial in the serial argument. Return OK on success, NOTOK otherwise.

int SerialExists(const String& word, unsigned int& serial)

If the word argument exists in the dictionnary, return its serial number in the serial argument. If it does not exists set the serial argument to WORD_DICT_SERIAL_INVALID. Return OK on success, NOTOK otherwise.

int SerialRef(const String& word, unsigned int& serial)

Short hand for Serial() followed by Ref(). Return OK on success, NOTOK otherwise.

int Noccurrence(const String& word, unsigned int& noccurrence) const

Return the frequency of the word argument in the noccurrence argument. Return OK on success, NOTOK otherwise.

int Normalize(String& word) const

Short hand for words->GetContext()->GetType()->Normalize(word). Return OK on success, NOTOK otherwise.

int Ref(const String& word)

Short hand for Incr(word, 1)

int Incr(const String& word, unsigned int incr)

Add incr to the frequency of the word Return OK on success, NOTOK otherwise.

int Unref(const String& word)

Short hand for Decr(word, 1)

int Decr(const String& word, unsigned int decr)

Subtract decr to the frequency of the word the frequency becomes lower or equal to zero, remove the entry from the dictionnary and lose the association between the word and its serial number. Return OK on success, NOTOK otherwise.

int Put(const String& word, unsigned int noccurrence)

Set the frequency of word with the value of the noccurrence argument.

int Exists(const String& word) const

Return true if word exists in the dictionnary, false otherwise.

List* Words() const

Return a pointer to the associated WordList object.

WordDictCursor* Cursor() const

Return a cursor to sequentially walk the dictionnary using the Next method.

int Next(WordDictCursor* cursor, String& word, WordDictRecord& record)

Return the next entry in the dictionnary. The cursor argument must have been created using the Cursor method. The word is returned in the word argument and the record is returned in the record argument. On success the function returns 0, at the end of the dictionnary it returns DB_NOTFOUND. The cursor argument is deallocated when the function hits the end of the dictionnary or an error occurs.

WordDictCursor* CursorPrefix(const String& prefix) const

Return a cursor to sequentially walk the entries of the dictionnary that start with the prefix argument, using the NextPrefix method.

int NextPrefix(WordDictCursor* cursor, String& word, WordDictRecord& record)

Return the next prefix from the dictionnary. The cursor argument must have been created using the CursorPrefix method. The word is returned in the word argument and the record is returned in the record argument. The word is guaranteed to start with the prefix specified to the CursorPrefix method. On success the function returns 0, at the end of the dictionnary it returns DB_NOTFOUND. The cursor argument is deallocated when the function hits the end of the dictionnary or an error occurs.

int Write(FILE* f)

Dump the complete dictionary in the file descriptor f. The format of the dictionary is word serial frequency , one by line.