/* ANTLRTokenBuffer.h
 *
 * SOFTWARE RIGHTS
 *
 * We reserve no LEGAL rights to the Purdue Compiler Construction Tool
 * Set (PCCTS) -- PCCTS is in the public domain.  An individual or
 * company may do whatever they wish with source code distributed with
 * PCCTS or the code generated by PCCTS, including the incorporation of
 * PCCTS, or its output, into commerical software.
 * 
 * We encourage users to develop software with PCCTS.  However, we do ask
 * that credit is given to us for developing PCCTS.  By "credit",
 * we mean that if you incorporate our source code into one of your
 * programs (commercial product, research project, or otherwise) that you
 * acknowledge this fact somewhere in the documentation, research report,
 * etc...  If you like PCCTS and have developed a nice tool with the
 * output, please mention that you developed it using PCCTS.  In
 * addition, we ask that this header remain intact in our source code.
 * As long as these guidelines are kept, we expect to continue enhancing
 * this system and expect to make other tools available as they are
 * completed.
 *
 * ANTLR 1.33
 * Terence Parr
 * Parr Research Corporation
 * with Purdue University and AHPCRC, University of Minnesota
 * 1989-1995
 */

#ifndef ATOKENBUFFER_H_GATE
#define ATOKENBUFFER_H_GATE

#include "config.h"
#include ATOKEN_H
#include ATOKENSTREAM_H
#include <stdlib.h>

/*
 * The parser is "attached" to an ANTLRTokenBuffer via interface
 * functions: getToken() and bufferedToken().  The object that actually
 * consumes characters and constructs tokens is connected to the
 * ANTLRTokenBuffer via interface function ANTLRTokenStream::getToken();
 * where ANTLRTokenStream is really just a behavior (class with no data).
 * C++ does not have this abstraction and hence we simply have come up
 * with a fancy name for "void *".  See the note in ANTLRTokenStream.h on
 * the "behavior" of ANTLRTokenStream.
 */

class ANTLRTokenBuffer {
protected:
	ANTLRTokenStream *input;        // where do I get tokens
	int buffer_size;
	int chunk_size;
	int num_markers;
	int k;                          // Need at least this many tokens in buffer
	_ANTLRTokenPtr *buffer;	// buffer used for arbitrary lookahead
	_ANTLRTokenPtr *tp;        // pts into buffer; current token ptr
	_ANTLRTokenPtr *last;      // pts to last valid token in buffer
	_ANTLRTokenPtr *next;      // place to put token from getANTLRToken()
	_ANTLRTokenPtr *end_of_buffer;
	/* when you try to write a token past this and there are no markers
	   set, then move k-1 tokens back to the beginning of the buffer.
	   We want to stay away from the end of the buffer because we have
	   to extend it if a marker is set and we reach the end (we cannot
	   move tokens to the beginning of the buffer in this case).
	 */
	_ANTLRTokenPtr *threshold;
	unsigned char _deleteTokens;

	// This function is filled in by the subclass; it initiates fetch of input
	virtual _ANTLRTokenPtr getANTLRToken() { return input->getToken(); }
	void makeRoom();
	void extendBuffer();

public:
	ANTLRTokenBuffer(ANTLRTokenStream *in, int k=1, int chksz=50);
	virtual ~ANTLRTokenBuffer();
	virtual _ANTLRTokenPtr getToken();
	virtual void rewind(int pos);
	virtual int mark();
	virtual _ANTLRTokenPtr bufferedToken(int i);

	void noGarbageCollectTokens()	{ _deleteTokens=0; }
	void garbageCollectTokens()		{ _deleteTokens=1; }

	virtual bufferSize() { return buffer_size; }
	virtual int minTokens() { return k; }
	virtual void setMinTokens(int k_new) { k = k_new; }

	virtual void panic(char *msg) { exit(PCCTS_EXIT_FAILURE); }
};

#endif