Module openj9.dtfj
Package com.ibm.dtfj.javacore.parser.framework.parser

Interface ILookAheadBuffer

All Known Implementing Classes:
LookAheadBuffer
public interface ILookAheadBuffer
Prediction buffer that holds a certain number of tokens. Tokens are consumed when the are matched, and the buffer is kept filled all the time until end of token stream is reached.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    allConsumed()
     
    void
    consume()
    Consumes the first element of the buffer.
    void
    init()
     
    int
    length()
     
    IParserToken
    lookAhead(int depth)
    Looks ahead by a depth amount.
    boolean
    match(String type)
    Matches a given type to the token type found at the first element of the buffer.
    int
    maxDepth()
     
    void
    setLookAheadDepth(int depth)
    Depth of the lookahead can be changed after creation.

  • Method Details

    • match

      boolean match(String type)
      Matches a given type to the token type found at the first element of the buffer.
      Parameters:
      type - to match against first element in buffer
      Returns:
      true if match is successful

    • consume

      void consume() throws IOException, ScannerException
      Consumes the first element of the buffer.
      Throws:
      ScannerException
      IOException

    • allConsumed

      boolean allConsumed()
      Returns:
      true if all tokens from both the input stream and the lookahead buffer have been consumed

    • lookAhead

      IParserToken lookAhead(int depth) throws IOException, ScannerException, IndexOutOfBoundsException
      Looks ahead by a depth amount. The lowest depth to look ahead is 1. Note that in some cases, a lookahead may be attempted on an earlier error condition that lead to an empty buffer (e.g., an exception was thrown during a fill process, and although more tokens may remain in the input source, the lookahead value may itself be null. Consequently, the lookahead buffer refills first before attempting the lookahead.
      Parameters:
      depth - to lookahead
      Returns:
      token at specified lookahead depth or IndexOutOfBoundsException.
      Throws:
      ScannerException
      IOException
      IndexOutOfBoundsException - if depth is outside the depth range of the buffer. Minimum depth is always 1.

    • length

      int length()

    • maxDepth

      int maxDepth()

    • init

      void init() throws IOException, ScannerException
      Throws:
      ScannerException
      IOException

    • setLookAheadDepth

      void setLookAheadDepth(int depth) throws IOException, ScannerException
      Depth of the lookahead can be changed after creation.
      If the new depth is less that the current depth, no new tokens will be read until the outstanding tokens (current depth - new depth) are first consumed.
      If the new depth is greater than the current depth, the lookahead will read new tokens to fill the delta.
      Parameters:
      depth - to change
      Throws:
      ScannerException - as increasing the current depth of the buffer requires to fill the buffer to the new length
      IOException