symon/symon/lib/lex.c

/* $Id: lex.c,v 1.15 2002/12/15 14:27:43 dijkstra Exp $ */

/*
 * Copyright (c) 2001-2002 Willem Dijkstra
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *    - Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *    - 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 COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "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
 * COPYRIGHT HOLDERS OR CONTRIBUTORS 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.
 *
 */

/*
 * This lexical analyser was written to be smaller than flex and with less
 * features. Its attributes in random order: capable of multiple instances, one
 * token lookahead, strings delimited by ' or ", comments can start anywhere
 * with # and last until eol, max token size = _POSIX2_LINE_LENGTH. Tokens are
 * defined in lex.h, the mapping of tokens to ascii happens here.
 *
 * Usage:
 *
 *    l = open_lex(filename);
 *    while (lex_nexttoken(l)) {
 *       use l->token, l->op, l->value
 *    }
 *    close_lex(l);
 */

#include <sys/types.h>

#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "xmalloc.h"
#include "lex.h"
#include "error.h"

static struct {
    const char *name;
    int opcode;
}      keywords[] = {
    { "{", LXT_BEGIN },
    { "}", LXT_END },
    { "(", LXT_OPEN },
    { ")", LXT_CLOSE },
    { ",", LXT_COMMA },
    { "accept", LXT_ACCEPT },
    { "cpu", LXT_CPU },
    { "datadir", LXT_DATADIR },
    { "debug", LXT_DEBUG },
    { "if", LXT_IF },
    { "in", LXT_IN },
    { "io", LXT_IO },
    { "mbuf", LXT_MBUF },
    { "mem", LXT_MEM },
    { "monitor", LXT_MONITOR },
    { "mux", LXT_MUX },
    { "pf", LXT_PF },
    { "port", LXT_PORT },
    { "proc", LXT_PROC },
    { "source", LXT_SOURCE },
    { "stream", LXT_STREAM },
    { "to", LXT_TO },
    { "write", LXT_WRITE },
    { NULL, 0 }
};
#define KW_OPS "{},()"

/* Return the number of the token pointed to by cp or LXT_BADTOKEN */
int 
parse_token(const char *cp)
{
    u_int i;

    for (i = 0; keywords[i].name; i++)
	if (strcasecmp(cp, keywords[i].name) == 0)
	    return keywords[i].opcode;

    return LXT_BADTOKEN;
}
/* Return the ascii representation of an opcode */
const char *
parse_opcode(const int op)
{
    u_int i;

    for (i = 0; keywords[i].name; i++)
	if (keywords[i].opcode == op)
	    return keywords[i].name;

    return NULL;
}
/* Read a line and increase buffer if needed */
int 
lex_readline(struct lex * l)
{
    char *bp;

    bp = l->buffer;

    if (l->buffer) {
	if ((l->curpos < l->endpos) &&
	    ((l->bsize - l->endpos) < _POSIX2_LINE_MAX)) {
	    l->bsize += _POSIX2_LINE_MAX;
	    l->buffer = xrealloc(l->buffer, l->bsize);
	    bp = l->buffer;
	    bp += l->endpos;
	}
	else {
	    l->curpos = 0;
	    l->endpos = 0;
	}
    }
    else {
	l->bsize = _POSIX2_LINE_MAX;
	l->buffer = xmalloc(l->bsize);
	bp = l->buffer;
    }

    if (!fgets(bp, (l->buffer + l->bsize) - bp, l->fh))
	return 0;
    else {
	l->endpos += strlen(bp) - 1;
	return 1;
    }
}
/* Copy char out of input stream */
void 
lex_copychar(struct lex * l)
{
    l->token[l->tokpos] = l->buffer[l->curpos];

    if (++l->tokpos >= _POSIX2_LINE_MAX) {
	l->token[_POSIX2_LINE_MAX - 1] = '\0';
	fatal("%s:%d: parse error at '%s'", l->filename, l->cline, l->token);
	/* NOT REACHED */
    }
}
/* Get next char, read next line if needed */
int 
lex_nextchar(struct lex * l)
{
    l->curpos++;

    if (l->curpos > l->endpos)
	if (!lex_readline(l))
	    return 0;

    if (l->buffer[l->curpos] == '\n')
	l->cline++;

    return 1;
}
/* Close of current token with a '\0' */
void 
lex_termtoken(struct lex * l)
{
    l->token[l->tokpos] = l->token[_POSIX2_LINE_MAX - 1] = '\0';
    l->tokpos = 0;
}
/* Unget token; the lexer allows 1 look a head. */
void 
lex_ungettoken(struct lex * l)
{
    l->unget = 1;
}
/* Get the next token in lex->token. return 0 if no more tokens found. */
int 
lex_nexttoken(struct lex * l)
{
    /* return same token as last time if it has been pushed back */
    if (l->unget) {
	l->unget = 0;
	return 1;
    }

    l->op = LXT_BADTOKEN;
    l->value = 0;
    l->type = LXY_UNKNOWN;

    /* find first non whitespace */
    while (l->buffer[l->curpos] == ' ' ||
	   l->buffer[l->curpos] == '\t' ||
	   l->buffer[l->curpos] == '\r' ||
	   l->buffer[l->curpos] == '\n' ||
	   l->buffer[l->curpos] == '\0' ||
	   l->buffer[l->curpos] == '#') {
	/* flush rest of line if comment */
	if (l->buffer[l->curpos] == '#') {
	    while (l->buffer[l->curpos] != '\n')
		if (!lex_nextchar(l))
		    return 0;
	}
	else if (!lex_nextchar(l))
	    return 0;
    }

    l->type = LXY_STRING;

    /* "delimited string" */
    if (l->buffer[l->curpos] == '"') {
	if (!lex_nextchar(l)) {
	    warning("%s:%d: unbalanced '\"'", l->filename, l->cline);
	    return 0;
	}
	while (l->buffer[l->curpos] != '"') {
	    lex_copychar(l);
	    if (!lex_nextchar(l)) {
		warning("%s:%d: unbalanced '\"'", l->filename, l->cline);
		return 0;
	    }
	}
	lex_termtoken(l);
	lex_nextchar(l);
	return 1;
    }

    /* 'delimited string' */
    if (l->buffer[l->curpos] == '\'') {
	if (!lex_nextchar(l)) {
	    warning("%s:%d: unbalanced \"\'\"", l->filename, l->cline);
	    return 0;
	}
	while (l->buffer[l->curpos] != '\'') {
	    lex_copychar(l);
	    if (!lex_nextchar(l)) {
		warning("%s:%d: unbalanced \"\'\"", l->filename, l->cline);
		return 0;
	    }
	}
	lex_termtoken(l);
	lex_nextchar(l);
	return 1;
    }

    /* one char keyword */
    if (strchr(KW_OPS, l->buffer[l->curpos])) {
	lex_copychar(l);
	lex_termtoken(l);
	l->op = parse_token(l->token);
	lex_nextchar(l);
	return 1;
    }

    /* single keyword */
    while (l->buffer[l->curpos] != ' ' &&
	   l->buffer[l->curpos] != '\t' &&
	   l->buffer[l->curpos] != '\r' &&
	   l->buffer[l->curpos] != '\n' &&
	   l->buffer[l->curpos] != '\0' &&
	   l->buffer[l->curpos] != '#' &&
	   (strchr(KW_OPS, l->buffer[l->curpos]) == NULL)) {
	lex_copychar(l);
	if (!lex_nextchar(l))
	    break;
    }
    lex_termtoken(l);
    l->op = parse_token(l->token);

    /* number */
    if (l->token[0] >= '0' && l->token[0] <= '9') {
	if (strlen(l->token) == strspn(l->token, "0123456789")) {
	    l->type = LXY_NUMBER;
	    l->value = strtol(l->token, NULL, 10);
	}
    }
    return 1;
}
/* Create and initialize a lexical analyser */
struct lex *
open_lex(const char *filename)
{
    struct lex *l;

    l = xmalloc(sizeof(struct lex));
    l->buffer = NULL;
    l->cline = 1;
    l->curpos = 0;
    l->endpos = 0;
    l->filename = filename;
    l->op = LXT_BADTOKEN;
    l->token = xmalloc(_POSIX2_LINE_MAX);
    l->tokpos = 0;
    l->type = LXY_UNKNOWN;
    l->unget = 0;
    l->value = 0;

    if ((l->fh = fopen(l->filename, "r")) == NULL) {
	warning("could not open file '%s':%s",
		l->filename, strerror(errno));
	xfree(l);
	return NULL;
    }

    lex_readline(l);
    return l;
}
/* Destroy a lexical analyser */
void 
close_lex(struct lex * l)
{
    if (l == NULL)
	return;
    if (l->fh)
	fclose(l->fh);
    if (l->buffer)
	xfree(l->buffer);
    if (l->token)
	xfree(l->token);
    xfree(l);
}
/* Signal a parse error */
void 
parse_error(struct lex * l, const char *s)
{
    warning("%s:%d: expected %s (found '%.8s')",
	    l->filename, l->cline, s, l->token);
}