001: /* Generated By:JavaCC: Do not edit this line. CharStream.java Version 3.0 */
002: package org.apache.lucene.queryParser;
003:
004: /**
005: * This interface describes a character stream that maintains line and
006: * column number positions of the characters. It also has the capability
007: * to backup the stream to some extent. An implementation of this
008: * interface is used in the TokenManager implementation generated by
009: * JavaCCParser.
010: *
011: * All the methods except backup can be implemented in any fashion. backup
012: * needs to be implemented correctly for the correct operation of the lexer.
013: * Rest of the methods are all used to get information like line number,
014: * column number and the String that constitutes a token and are not used
015: * by the lexer. Hence their implementation won't affect the generated lexer's
016: * operation.
017: */
018:
019: public interface CharStream {
020:
021: /**
022: * Returns the next character from the selected input. The method
023: * of selecting the input is the responsibility of the class
024: * implementing this interface. Can throw any java.io.IOException.
025: */
026: char readChar() throws java.io.IOException;
027:
028: /**
029: * Returns the column position of the character last read.
030: * @deprecated
031: * @see #getEndColumn
032: */
033: int getColumn();
034:
035: /**
036: * Returns the line number of the character last read.
037: * @deprecated
038: * @see #getEndLine
039: */
040: int getLine();
041:
042: /**
043: * Returns the column number of the last character for current token (being
044: * matched after the last call to BeginTOken).
045: */
046: int getEndColumn();
047:
048: /**
049: * Returns the line number of the last character for current token (being
050: * matched after the last call to BeginTOken).
051: */
052: int getEndLine();
053:
054: /**
055: * Returns the column number of the first character for current token (being
056: * matched after the last call to BeginTOken).
057: */
058: int getBeginColumn();
059:
060: /**
061: * Returns the line number of the first character for current token (being
062: * matched after the last call to BeginTOken).
063: */
064: int getBeginLine();
065:
066: /**
067: * Backs up the input stream by amount steps. Lexer calls this method if it
068: * had already read some characters, but could not use them to match a
069: * (longer) token. So, they will be used again as the prefix of the next
070: * token and it is the implemetation's responsibility to do this right.
071: */
072: void backup(int amount);
073:
074: /**
075: * Returns the next character that marks the beginning of the next token.
076: * All characters must remain in the buffer between two successive calls
077: * to this method to implement backup correctly.
078: */
079: char BeginToken() throws java.io.IOException;
080:
081: /**
082: * Returns a string made up of characters from the marked token beginning
083: * to the current buffer position. Implementations have the choice of returning
084: * anything that they want to. For example, for efficiency, one might decide
085: * to just return null, which is a valid implementation.
086: */
087: String GetImage();
088:
089: /**
090: * Returns an array of characters that make up the suffix of length 'len' for
091: * the currently matched token. This is used to build up the matched string
092: * for use in actions in the case of MORE. A simple and inefficient
093: * implementation of this is as follows :
094: *
095: * {
096: * String t = GetImage();
097: * return t.substring(t.length() - len, t.length()).toCharArray();
098: * }
099: */
100: char[] GetSuffix(int len);
101:
102: /**
103: * The lexer calls this function to indicate that it is done with the stream
104: * and hence implementations can free any resources held by this class.
105: * Again, the body of this function can be just empty and it will not
106: * affect the lexer's operation.
107: */
108: void Done();
109:
110: }
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