/*	$Id: lexer.c,v 1.9 2001/08/10 15:18:08 sandro Exp $	*/

/*
 * Copyright (c) 1997-2001 Sandro Sigala.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include "config.h"

#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "slisp.h"
#include "extern.h"

FILE *input_file;
int lineno;

#define LEX_BUF_MAX 16
static int lex_buf[LEX_BUF_MAX];
static int *lex_bufp;
#define xgetc()		(lex_bufp > lex_buf ? *--lex_bufp : fgetc(input_file))
#define xungetc(c)	*lex_bufp++ = c

char *token_buffer;
static int token_buffer_max;

void
init_lex(void)
{
	lineno = 1;
	token_buffer_max = 10;
	token_buffer = (char *)xmalloc(token_buffer_max);
	lex_bufp = lex_buf;
}

void
done_lex(void)
{
	free(token_buffer);
}

static char *
extend_buf(char *p)
{
	int off = p - token_buffer;

	token_buffer_max += 10;
	token_buffer = (char *)xrealloc(token_buffer, token_buffer_max);

	return token_buffer + off;
}

int
gettoken(void)
{
	char *p;
	int c;

	for (;;) {
		c = xgetc();
		switch (c) {
		case '\n':
			++lineno;
			break;

		case ' ': case '\f': case '\t': case '\v': case '\r':
			break;

		case ';':
			/* Comment: ";".*"\n" */
			while ((c = xgetc()) != '\n')
				;
			++lineno;
			break;

		case '?':
			/* Character: "?". */
			c = xgetc();
			sprintf(token_buffer, "%d", c);
			return INTEGER;

		case '-':
			/* Minus sign: "-". */
			c = xgetc();
			if (!isdigit(c)) {
				xungetc(c);
				c = '-';
				goto got_id;
			}
			xungetc(c);
			c = '-';
			/* FALLTRHU */

		case '0':
		case '1': case '2': case '3':
		case '4': case '5': case '6':
		case '7': case '8': case '9':
			/* Integer: [0-9]+ */
			p = token_buffer;
			do {
				if (p - token_buffer >= token_buffer_max)
					p = extend_buf(p);
				*p++ = c;
				c = xgetc();
			} while (isdigit(c));
			xungetc(c);
			*p = '\0';
			return INTEGER;

		got_id:
		case '_': case '+': case '*': case '/': case '%':
		case '<': case '>': case '=': case '&':
		case 'a': case 'b': case 'c': case 'd': case 'e': case 'f':
		case 'g': case 'h': case 'i': case 'j': case 'k': case 'l':
		case 'm': case 'n': case 'o': case 'p': case 'q': case 'r':
		case 's': case 't': case 'u': case 'v': case 'w': case 'x':
		case 'y': case 'z':
		case 'A': case 'B': case 'C': case 'D': case 'E': case 'F':
		case 'G': case 'H': case 'I': case 'J': case 'K': case 'L':
		case 'M': case 'N': case 'O': case 'P': case 'Q': case 'R':
		case 'S': case 'T': case 'U': case 'V': case 'W': case 'X':
		case 'Y': case 'Z':
			/* Identifier: [-/+*%<>=&a-zA-Z_][-/+*%<>=&a-zA-Z_0-9]* */
			p = token_buffer;
			do {
				if (p - token_buffer >= token_buffer_max)
					p = extend_buf(p);
				*p++ = c;
				c = xgetc();
			} while (isalnum(c) || strchr("_-+*/%<>=&", c) != NULL);
			xungetc(c);
			*p = '\0';
			return IDENTIFIER;

		case '"':
			/* String: "\""([^"]|"\\".)*"\"" */
			p = token_buffer;
			while ((c = xgetc()) != '"' && c != EOF) {
				if (p - token_buffer >= token_buffer_max)
					p = extend_buf(p);
				if (c == '\\') {
					c = xgetc();
					switch (c) {
					case '\n': ++lineno; break;
					case 'a': *p++ = '\a'; break;
					case 'b': *p++ = '\b'; break;
					case 'f': *p++ = '\f'; break;
					case 'n': *p++ = '\n'; break;
					case 'r': *p++ = '\r'; break;
					case 't': *p++ = '\t'; break;
					case 'v': *p++ = '\v'; break;
					default: *p++ = c;
					}
				} else {
					if (c == '\n')
						++lineno;
					*p++ = c;
				}
			}
			*p = '\0';
			return STRING;

		default:
			return c;
		}
	}
}