ntp_scanner.h revision 290001 
1/* ntp_scanner.h
2 *
3 * The header file for a simple lexical analyzer.
4 *
5 * Written By:	Sachin Kamboj
6 *		University of Delaware
7 *		Newark, DE 19711
8 * Copyright (c) 2006
9 */
10
11#ifndef NTP_SCANNER_H
12#define NTP_SCANNER_H
13
14#include "ntp_config.h"
15
16/*
17 * ntp.conf syntax is slightly irregular in that some tokens such as
18 * hostnames do not require quoting even if they might otherwise be
19 * recognized as T_ terminal tokens.  This hand-crafted lexical scanner
20 * uses a "followed by" value associated with each keyword to indicate
21 * normal scanning of the next token, forced scanning of the next token
22 * alone as a T_String, or forced scanning of all tokens to the end of
23 * the command as T_String.
24 * In the past the identifiers for this functionality ended in _ARG:
25 *
26 * NO_ARG	->	FOLLBY_TOKEN
27 * SINGLE_ARG	->	FOLLBY_STRING
28 * MULTIPLE_ARG	->	FOLLBY_STRINGS_TO_EOC
29 *
30 * Note that some tokens use FOLLBY_TOKEN even though they sometimes
31 * are followed by strings.  FOLLBY_STRING is used only when needed to
32 * avoid the keyword scanner matching a token where a string is needed.
33 *
34 * FOLLBY_NON_ACCEPT is an overloading of this field to distinguish
35 * non-accepting states (where the state number does not match a T_
36 * value).
37 */
38typedef enum {
39	FOLLBY_TOKEN = 0,
40	FOLLBY_STRING,
41	FOLLBY_STRINGS_TO_EOC,
42	FOLLBY_NON_ACCEPTING
43} follby;
44
45#define MAXLINE		1024	/* maximum length of line */
46#define MAXINCLUDELEVEL	5	/* maximum include file levels */
47
48/* STRUCTURES
49 * ----------
50 */
51
52/*
53 * Define a structure to hold the FSA for the keywords.
54 * The structure is actually a trie.
55 *
56 * To save space, a single u_int32 encodes four fields, and a fifth
57 * (the token completed for terminal states) is implied by the index of
58 * the rule within the scan state array, taking advantage of the fact
59 * there are more scan states than the highest T_ token number.
60 *
61 * The lowest 8 bits hold the character the state matches on.
62 * Bits 8 and 9 hold the followedby value (0 - 3).  For non-accepting
63 *   states (which do not match a completed token) the followedby
64 *   value 3 (FOLLBY_NONACCEPTING) denotes that fact.  For accepting
65 *   states, values 0 - 2 control whether the scanner forces the
66 *   following token(s) to strings.
67 * Bits 10 through 20 hold the next state to check not matching
68 * this state's character.
69 * Bits 21 through 31 hold the next state to check matching the char.
70 */
71
72#define S_ST(ch, fb, match_n, other_n) (			\
73	(u_char)((ch) & 0xff) |					\
74	((u_int32)(fb) << 8) |					\
75	((u_int32)(match_n) << 10) |				\
76	((u_int32)(other_n) << 21)				\
77)
78
79#define SS_CH(ss)	((char)(u_char)((ss) & 0xff))
80#define SS_FB(ss)	(((u_int)(ss) >>  8) & 0x3)
81#define SS_MATCH_N(ss)	(((u_int)(ss) >> 10) & 0x7ff)
82#define SS_OTHER_N(ss)	(((u_int)(ss) >> 21) & 0x7ff)
83
84typedef u_int32 scan_state;
85
86struct LCPOS {
87	int nline;
88	int ncol;
89};
90
91/* Structure to hold a filename, file pointer and positional info.
92 * Instances are dynamically allocated, and the file name is copied by
93 * value into a dynamic extension of the 'fname' array. (Which *must* be
94 * the last field for that reason!)
95 */
96struct FILE_INFO {
97	struct FILE_INFO * st_next;	/* next on stack */
98	FILE *		   fpi;		/* File Descriptor */
99	int                force_eof;	/* locked or not */
100	int                backch;	/* ungetch buffer */
101
102	struct LCPOS       curpos;	/* current scan position */
103	struct LCPOS       bakpos;	/* last line end for ungetc */
104	struct LCPOS       tokpos;	/* current token position */
105	struct LCPOS       errpos;	/* error position */
106
107	char               fname[1];	/* (formal only) buffered name */
108};
109
110
111/* SCANNER GLOBAL VARIABLES
112 * ------------------------
113 */
114extern config_tree cfgt;	  /* Parser output stored here */
115
116/* VARIOUS EXTERNAL DECLARATIONS
117 * -----------------------------
118 */
119extern int old_config_style;
120
121/* VARIOUS SUBROUTINE DECLARATIONS
122 * -------------------------------
123 */
124extern const char *keyword(int token);
125extern char *quote_if_needed(char *str);
126int yylex(void);
127
128/* managing the input source stack itself */
129extern int/*BOOL*/ lex_init_stack(const char * path, const char * mode);
130extern void        lex_drop_stack(void);
131extern int/*BOOL*/ lex_flush_stack(void);
132
133/* add/remove a nested input source */
134extern int/*BOOL*/ lex_push_file(const char * path, const char * mode);
135extern int/*BOOL*/ lex_pop_file(void);
136
137/* input stack state query functions */
138extern size_t      lex_level(void);
139extern int/*BOOL*/ lex_from_file(void);
140extern struct FILE_INFO * lex_current(void);
141
142#endif	/* NTP_SCANNER_H */
143