Interface ICharStream

This interface describes a character stream that maintains line and column number positions of the characters. It also has the capability to backup the stream to some extent. An implementation of this interface is used in the TokenManager implementation generated by JavaCCParser.

All the methods except BackUp(Int32) can be implemented in any fashion. BackUp(Int32) needs to be implemented correctly for the correct operation of the lexer. Rest of the methods are all used to get information like line number, column number and the string that constitutes a token and are not used by the lexer. Hence their implementation won't affect the generated lexer's operation.

Namespace: Lucene.Net.QueryParsers.Classic
Assembly: Lucene.Net.QueryParser.dll
Syntax
public interface ICharStream

Properties

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BeginColumn

Returns the column number of the first character for current token (being matched after the last call to BeginTOken).

Declaration
int BeginColumn { get; }
Property Value
Type Description
System.Int32
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BeginLine

Returns the line number of the first character for current token (being matched after the last call to BeginTOken).

Declaration
int BeginLine { get; }
Property Value
Type Description
System.Int32
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Column

Returns the column position of the character last read.

Declaration
int Column { get; }
Property Value
Type Description
System.Int32
See Also
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EndColumn

Returns the column number of the last character for current token (being matched after the last call to BeginTOken).

Declaration
int EndColumn { get; }
Property Value
Type Description
System.Int32
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EndLine

Returns the line number of the last character for current token (being matched after the last call to BeginTOken).

Declaration
int EndLine { get; }
Property Value
Type Description
System.Int32
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Image

Returns a string made up of characters from the marked token beginning to the current buffer position. Implementations have the choice of returning anything that they want to. For example, for efficiency, one might decide to just return null, which is a valid implementation.

Declaration
string Image { get; }
Property Value
Type Description
System.String
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Line

Returns the line number of the character last read.

Declaration
int Line { get; }
Property Value
Type Description
System.Int32
See Also

Methods

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BackUp(Int32)

Backs up the input stream by amount steps. Lexer calls this method if it had already read some characters, but could not use them to match a (longer) token. So, they will be used again as the prefix of the next token and it is the implemetation's responsibility to do this right.

Declaration
void BackUp(int amount)
Parameters
Type Name Description
System.Int32 amount
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BeginToken()

Returns the next character that marks the beginning of the next token. All characters must remain in the buffer between two successive calls to this method to implement BackUp(Int32) correctly.

Declaration
char BeginToken()
Returns
Type Description
System.Char
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Done()

The lexer calls this function to indicate that it is done with the stream and hence implementations can free any resources held by this class. Again, the body of this function can be just empty and it will not affect the lexer's operation.

Declaration
void Done()
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GetSuffix(Int32)

Returns an array of characters that make up the suffix of length 'len' for the currently matched token. This is used to build up the matched string for use in actions in the case of MORE. A simple and inefficient implementation of this is as follows :

{
    string t = Image;
    return t.Substring(t.Length - len, len).ToCharArray();
}
Declaration
char[] GetSuffix(int len)
Parameters
Type Name Description
System.Int32 len
Returns
Type Description
System.Char[]
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ReadChar()

Returns the next character from the selected input. The method of selecting the input is the responsibility of the class implementing this interface. Can throw any .

Declaration
char ReadChar()
Returns
Type Description
System.Char