146 lines
3.3 KiB
C#
146 lines
3.3 KiB
C#
using System;
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namespace antlr
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{
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/*ANTLR Translator Generator
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* Project led by Terence Parr at http://www.jGuru.com
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* Software rights: http://www.antlr.org/license.html
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*
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* $Id:$
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*/
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//
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// ANTLR C# Code Generator by Micheal Jordan
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// Kunle Odutola : kunle UNDERSCORE odutola AT hotmail DOT com
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// Anthony Oguntimehin
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//
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// With many thanks to Eric V. Smith from the ANTLR list.
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//
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/*A Stream of Token objects fed to the parser from a Tokenizer that can
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* be rewound via mark()/rewind() methods.
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* <p>
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* A dynamic array is used to buffer up all the input tokens. Normally,
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* "k" tokens are stored in the buffer. More tokens may be stored during
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* guess mode (testing syntactic predicate), or when LT(i>k) is referenced.
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* Consumption of tokens is deferred. In other words, reading the next
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* token is not done by conume(), but deferred until needed by LA or LT.
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* <p>
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*
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* @see antlr.Token
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* @see antlr.Tokenizer
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* @see antlr.TokenQueue
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*/
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public class TokenBuffer
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{
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// Token source
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protected internal TokenStream input;
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// Number of active markers
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protected internal int nMarkers = 0;
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// Additional offset used when markers are active
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protected internal int markerOffset = 0;
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// Number of calls to consume() since last LA() or LT() call
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protected internal int numToConsume = 0;
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// Circular queue
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internal TokenQueue queue;
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/*Create a token buffer */
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public TokenBuffer(TokenStream input_)
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{
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input = input_;
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queue = new TokenQueue(1);
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}
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/*Reset the input buffer to empty state */
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public virtual void reset()
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{
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nMarkers = 0;
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markerOffset = 0;
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numToConsume = 0;
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queue.reset();
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}
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/*Mark another token for deferred consumption */
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public virtual void consume()
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{
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numToConsume++;
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}
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/*Ensure that the token buffer is sufficiently full */
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protected virtual void fill(int amount)
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{
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syncConsume();
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// Fill the buffer sufficiently to hold needed tokens
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while (queue.nbrEntries < (amount + markerOffset))
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{
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// Append the next token
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queue.append(input.nextToken());
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}
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}
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/*return the Tokenizer (needed by ParseView) */
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public virtual TokenStream getInput()
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{
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return input;
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}
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/*Get a lookahead token value */
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public virtual int LA(int i)
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{
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fill(i);
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return queue.elementAt(markerOffset + i - 1).Type;
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}
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/*Get a lookahead token */
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public virtual IToken LT(int i)
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{
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fill(i);
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return queue.elementAt(markerOffset + i - 1);
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}
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/*Return an integer marker that can be used to rewind the buffer to
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* its current state.
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*/
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public virtual int mark()
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{
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syncConsume();
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nMarkers++;
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return markerOffset;
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}
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/*Rewind the token buffer to a marker.
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* @param mark Marker returned previously from mark()
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*/
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public virtual void rewind(int mark)
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{
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syncConsume();
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markerOffset = mark;
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nMarkers--;
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}
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/*Sync up deferred consumption */
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protected virtual void syncConsume()
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{
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while (numToConsume > 0)
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{
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if (nMarkers > 0)
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{
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// guess mode -- leave leading tokens and bump offset.
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markerOffset++;
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}
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else
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{
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// normal mode -- remove first token
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queue.removeFirst();
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}
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numToConsume--;
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}
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}
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}
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} |