Package org.apache.lucene.queryparser.charstream

# Class FastCharStream

java.lang.Object
org.apache.lucene.queryparser.charstream.FastCharStream

All Implemented Interfaces:
  `CharStream`

public final class FastCharStream extends Object implements CharStream
An efficient implementation of JavaCC's CharStream interface.

Note that this does not do line-number counting, but instead keeps track of the character position of the token in the input, as required by Lucene's `OffsetAttribute` API.

## Constructor Summary

Constructors
Constructor
Description
`FastCharStream(Reader r)`
Constructs from a Reader.

## Method Summary

Modifier and Type
Method
Description
`final void`
`backup(int amount)`
Backs up the input stream by amount steps.
`final char`
`BeginToken()`
Returns the next character that marks the beginning of the next token.
`final void`
`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.
`final int`
`getBeginColumn()`
Returns the column number of the first character for current token (being matched after the last call to BeginTOken).
`final int`
`getBeginLine()`
Returns the line number of the first character for current token (being matched after the last call to BeginTOken).
`final int`
`getEndColumn()`
Returns the column number of the last character for current token (being matched after the last call to BeginTOken).
`final int`
`getEndLine()`
Returns the line number of the last character for current token (being matched after the last call to BeginTOken).
`final String`
`GetImage()`
Returns a string made up of characters from the marked token beginning to the current buffer position.
`final char[]`
`GetSuffix(int len)`
Returns an array of characters that make up the suffix of length 'len' for the currently matched token.
`final char`
`readChar()`
Returns the next character from the selected input.

### Methods inherited from class java.lang.Object

`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

## Constructor Details

### FastCharStream

public FastCharStream(Reader r)
Constructs from a Reader.

## Method Details

### readChar

public final char readChar() throws IOException
Description copied from interface: `CharStream`
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 java.io.IOException.

Specified by:
  `readChar` in interface `CharStream`
Throws:
  `IOException`

### BeginToken

public final char BeginToken() throws IOException
Description copied from interface: `CharStream`
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 correctly.

Specified by:
  `BeginToken` in interface `CharStream`
Throws:
  `IOException`

### backup

public final void backup(int amount)
Description copied from interface: `CharStream`
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 implementation's responsibility to do this right.

Specified by:
  `backup` in interface `CharStream`

### GetImage

public final String GetImage()
Description copied from interface: `CharStream`
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.

Specified by:
  `GetImage` in interface `CharStream`

### GetSuffix

public final char[] GetSuffix(int len)
Description copied from interface: `CharStream`
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 = GetImage(); return t.substring(t.length() - len, t.length()).toCharArray(); }

Specified by:
  `GetSuffix` in interface `CharStream`

### Done

public final void Done()
Description copied from interface: `CharStream`
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.

Specified by:
  `Done` in interface `CharStream`

### getEndColumn

public final int getEndColumn()
Description copied from interface: `CharStream`
Returns the column number of the last character for current token (being matched after the last call to BeginTOken).

Specified by:
  `getEndColumn` in interface `CharStream`

### getEndLine

public final int getEndLine()
Description copied from interface: `CharStream`
Returns the line number of the last character for current token (being matched after the last call to BeginTOken).

Specified by:
  `getEndLine` in interface `CharStream`

### getBeginColumn

public final int getBeginColumn()
Description copied from interface: `CharStream`
Returns the column number of the first character for current token (being matched after the last call to BeginTOken).

Specified by:
  `getBeginColumn` in interface `CharStream`

### getBeginLine

public final int getBeginLine()
Description copied from interface: `CharStream`
Returns the line number of the first character for current token (being matched after the last call to BeginTOken).

Specified by:
  `getBeginLine` in interface `CharStream`