summaryrefslogtreecommitdiff
path: root/src/include/fe_utils/psqlscan_int.h
blob: 4905aae40885608a688c1a0185c9944dc81d95bb (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
/*-------------------------------------------------------------------------
 *
 * psqlscan_int.h
 *	  lexical scanner internal declarations
 *
 * This file declares the PsqlScanStateData structure used by psqlscan.l
 * and shared by other lexers compatible with it, such as psqlscanslash.l.
 *
 * One difficult aspect of this code is that we need to work in multibyte
 * encodings that are not ASCII-safe.  A "safe" encoding is one in which each
 * byte of a multibyte character has the high bit set (it's >= 0x80).  Since
 * all our lexing rules treat all high-bit-set characters alike, we don't
 * really need to care whether such a byte is part of a sequence or not.
 * In an "unsafe" encoding, we still expect the first byte of a multibyte
 * sequence to be >= 0x80, but later bytes might not be.  If we scan such
 * a sequence as-is, the lexing rules could easily be fooled into matching
 * such bytes to ordinary ASCII characters.  Our solution for this is to
 * substitute 0xFF for each non-first byte within the data presented to flex.
 * The flex rules will then pass the FF's through unmolested.  The
 * psqlscan_emit() subroutine is responsible for looking back to the original
 * string and replacing FF's with the corresponding original bytes.
 *
 * Another interesting thing we do here is scan different parts of the same
 * input with physically separate flex lexers (ie, lexers written in separate
 * .l files).  We can get away with this because the only part of the
 * persistent state of a flex lexer that depends on its parsing rule tables
 * is the start state number, which is easy enough to manage --- usually,
 * in fact, we just need to set it to INITIAL when changing lexers.  But to
 * make that work at all, we must use re-entrant lexers, so that all the
 * relevant state is in the yyscan_t attached to the PsqlScanState;
 * if we were using lexers with separate static state we would soon end up
 * with dangling buffer pointers in one or the other.  Also note that this
 * is unlikely to work very nicely if the lexers aren't all built with the
 * same flex version, or if they don't use the same flex options.
 *
 *
 * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/fe_utils/psqlscan_int.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef PSQLSCAN_INT_H
#define PSQLSCAN_INT_H

#include "fe_utils/psqlscan.h"

/*
 * These are just to allow this file to be compilable standalone for header
 * validity checking; in actual use, this file should always be included
 * from the body of a flex file, where these symbols are already defined.
 */
#ifndef YY_TYPEDEF_YY_BUFFER_STATE
#define YY_TYPEDEF_YY_BUFFER_STATE
typedef struct yy_buffer_state *YY_BUFFER_STATE;
#endif
#ifndef YY_TYPEDEF_YY_SCANNER_T
#define YY_TYPEDEF_YY_SCANNER_T
typedef void *yyscan_t;
#endif

/*
 * We use a stack of flex buffers to handle substitution of psql variables.
 * Each stacked buffer contains the as-yet-unread text from one psql variable.
 * When we pop the stack all the way, we resume reading from the outer buffer
 * identified by scanbufhandle.
 */
typedef struct StackElem
{
	YY_BUFFER_STATE buf;		/* flex input control structure */
	char	   *bufstring;		/* data actually being scanned by flex */
	char	   *origstring;		/* copy of original data, if needed */
	char	   *varname;		/* name of variable providing data, or NULL */
	struct StackElem *next;
} StackElem;

/*
 * All working state of the lexer must be stored in PsqlScanStateData
 * between calls.  This allows us to have multiple open lexer operations,
 * which is needed for nested include files.  The lexer itself is not
 * recursive, but it must be re-entrant.
 */
typedef struct PsqlScanStateData
{
	yyscan_t	scanner;		/* Flex's state for this PsqlScanState */

	PQExpBuffer output_buf;		/* current output buffer */

	StackElem  *buffer_stack;	/* stack of variable expansion buffers */

	/*
	 * These variables always refer to the outer buffer, never to any stacked
	 * variable-expansion buffer.
	 */
	YY_BUFFER_STATE scanbufhandle;
	char	   *scanbuf;		/* start of outer-level input buffer */
	const char *scanline;		/* current input line at outer level */

	/* safe_encoding, curline, refline are used by emit() to replace FFs */
	int			encoding;		/* encoding being used now */
	bool		safe_encoding;	/* is current encoding "safe"? */
	bool		std_strings;	/* are string literals standard? */
	const char *curline;		/* actual flex input string for cur buf */
	const char *refline;		/* original data for cur buffer */

	/*
	 * All this state lives across successive input lines, until explicitly
	 * reset by psql_scan_reset.  start_state is adopted by yylex() on entry,
	 * and updated with its finishing state on exit.
	 */
	int			start_state;	/* yylex's starting/finishing state */
	int			state_before_str_stop;	/* start cond. before end quote */
	int			paren_depth;	/* depth of nesting in parentheses */
	int			xcdepth;		/* depth of nesting in slash-star comments */
	char	   *dolqstart;		/* current $foo$ quote start string */

	/*
	 * State to track boundaries of BEGIN ... END blocks in function
	 * definitions, so that semicolons do not send query too early.
	 */
	int			identifier_count;	/* identifiers since start of statement */
	char		identifiers[4]; /* records the first few identifiers */
	int			begin_depth;	/* depth of begin/end pairs */

	/*
	 * Callback functions provided by the program making use of the lexer,
	 * plus a void* callback passthrough argument.
	 */
	const PsqlScanCallbacks *callbacks;
	void	   *cb_passthrough;
} PsqlScanStateData;


/*
 * Functions exported by psqlscan.l, but only meant for use within
 * compatible lexers.
 */
extern void psqlscan_push_new_buffer(PsqlScanState state,
									 const char *newstr, const char *varname);
extern void psqlscan_pop_buffer_stack(PsqlScanState state);
extern void psqlscan_select_top_buffer(PsqlScanState state);
extern bool psqlscan_var_is_current_source(PsqlScanState state,
										   const char *varname);
extern YY_BUFFER_STATE psqlscan_prepare_buffer(PsqlScanState state,
											   const char *txt, int len,
											   char **txtcopy);
extern void psqlscan_emit(PsqlScanState state, const char *txt, int len);
extern char *psqlscan_extract_substring(PsqlScanState state,
										const char *txt, int len);
extern void psqlscan_escape_variable(PsqlScanState state,
									 const char *txt, int len,
									 PsqlScanQuoteType quote);
extern void psqlscan_test_variable(PsqlScanState state,
								   const char *txt, int len);

#endif							/* PSQLSCAN_INT_H */