token.c

linux下的Ｃ语言开发

/********************************************************
 * token -- token handling module			*
 *							*
 * Functions:						*
 *	next_token -- get the next token from the input	*
 ********************************************************/
#include <stdio.h>
#include <stdlib.h>

#include "ch_type.h"
#include "in_file.h"
#include "token.h"

static int in_comment = FALSE;	/* True if we're in a comment */

/********************************************************
 * read_comment -- read in a comment			*
 *							*
 * Returns						*
 *	Token read.  Can be a T_COMMENT or T_NEW_LINE	*
 *	depending on what we read.			*
 *							*
 *	Multi-line comments are split into multiple 	*
 *	tokens.						*
 ********************************************************/
static enum TOKEN_TYPE read_comment(void)
{
    if (in_cur_char() == '\n') {
	in_read_char();
	return (T_NEWLINE);
    }
    while (1) {
	in_comment = TRUE;
	if (in_cur_char() == EOF) {
	    fprintf(stderr, "Error: EOF inside comment\n");
	    return (T_EOF);
	}
	if (in_cur_char() == '\n')
	    return (T_COMMENT);
	if ((in_cur_char() == '*') && 
	    (in_next_char() == '/')) {
	    in_comment = FALSE;
	    /* Skip past the ending */
	    in_read_char();
	    in_read_char();
	    return (T_COMMENT);
	}
	in_read_char();
    }
}
/********************************************************
 * next_token -- read the next token in an input stream	*
 *							*
 * Returns						*
 *	next token					*
 ********************************************************/
enum TOKEN_TYPE next_token(void)
{
    if (in_comment)
	return (read_comment());

    while (is_char_type(in_cur_char(), C_WHITE)) {
	in_read_char();
    }
    if (in_cur_char() == EOF)
	return (T_EOF);

    switch (get_char_type(in_cur_char())) {
	case C_NEWLINE:
	    in_read_char();
	    return (T_NEWLINE);
	case C_ALPHA:
	    while (is_char_type(in_cur_char(), C_ALPHA_NUMERIC))
		in_read_char();
	    return (T_ID);
	case C_DIGIT:
	    in_read_char();
	    if ((in_cur_char() == 'X') || (in_cur_char() == 'x')) {
		in_read_char();
		while (is_char_type(in_cur_char(), C_HEX_DIGIT))
		    in_read_char();
		return (T_NUMBER);
	    }
	    while (is_char_type(in_cur_char(), C_DIGIT))
		in_read_char();
	    return (T_NUMBER);
	case C_SLASH:
	    /* Check for  '/', '*' characters  */
	    if (in_next_char() == '*') {
		return (read_comment());
	    }
	    /* Fall through */
	case C_OPERATOR:
	    in_read_char();
	    return (T_OPERATOR);
	case C_L_PAREN:
	    in_read_char();
	    return (T_L_PAREN);
	case C_R_PAREN:
	    in_read_char();
	    return (T_R_PAREN);
	case C_L_CURLY:
	    in_read_char();
	    return (T_L_CURLY);
	case C_R_CURLY:
	    in_read_char();
	    return (T_R_CURLY);
	case C_DOUBLE:
	    while (1) {
		in_read_char();
		/* Check for end of string */
		if (in_cur_char() == '"')
		    break;

		/* Escape character, then skip the next character */
		if (in_cur_char() == '\\')
		    in_read_char();
	    }
	    in_read_char();
	    return (T_STRING);
	case C_SINGLE:
	    while (1) {
		in_read_char();
		/* Check for end of character */
		if (in_cur_char() == '\'')
		    break;

		/* Escape character, then skip the next character */
		if (in_cur_char() == '\\')
		    in_read_char();
	    }
	    in_read_char();
	    return (T_STRING);
	default:
	    fprintf(stderr, "Internal error: Very strange character\n");
	    abort();
    }
    fprintf(stderr, "Internal error: We should never get here\n");
    abort();
    return (T_EOF);	/* Should never get here either */
			/* But we put in the return to avoid a compiler */
			/* warning. */
}