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/*-------------------------------------------------------------------------
* A stack of automaton states to handle nested conditionals.
*
* This file describes a stack of automaton states which
* allow a manage nested conditionals.
*
* It is used by:
* - "psql" interpreter for handling \if ... \endif
* - "pgbench" interpreter for handling \if ... \endif
* - "pgbench" syntax checker to test for proper nesting
*
* The stack holds the state of enclosing conditionals (are we in
* a true branch? in a false branch? have we already encountered
* a true branch?) so that the interpreter knows whether to execute
* code and whether to evaluate conditions.
*
* Copyright (c) 2000-2023, PostgreSQL Global Development Group
*
* src/include/fe_utils/conditional.h
*
*-------------------------------------------------------------------------
*/
#ifndef CONDITIONAL_H
#define CONDITIONAL_H
/*
* Possible states of a single level of \if block.
*/
typedef enum ifState
{
IFSTATE_NONE = 0, /* not currently in an \if block */
IFSTATE_TRUE, /* currently in an \if or \elif that is true
* and all parent branches (if any) are true */
IFSTATE_FALSE, /* currently in an \if or \elif that is false
* but no true branch has yet been seen, and
* all parent branches (if any) are true */
IFSTATE_IGNORED, /* currently in an \elif that follows a true
* branch, or the whole \if is a child of a
* false parent branch */
IFSTATE_ELSE_TRUE, /* currently in an \else that is true and all
* parent branches (if any) are true */
IFSTATE_ELSE_FALSE /* currently in an \else that is false or
* ignored */
} ifState;
/*
* The state of nested \ifs is stored in a stack.
*
* query_len is used to determine what accumulated text to throw away at the
* end of an inactive branch. (We could, perhaps, teach the lexer to not add
* stuff to the query buffer in the first place when inside an inactive branch;
* but that would be very invasive.) We also need to save and restore the
* lexer's parenthesis nesting depth when throwing away text. (We don't need
* to save and restore any of its other state, such as comment nesting depth,
* because a backslash command could never appear inside a comment or SQL
* literal.)
*/
typedef struct IfStackElem
{
ifState if_state; /* current state, see enum above */
int query_len; /* length of query_buf at last branch start */
int paren_depth; /* parenthesis depth at last branch start */
struct IfStackElem *next; /* next surrounding \if, if any */
} IfStackElem;
typedef struct ConditionalStackData
{
IfStackElem *head;
} ConditionalStackData;
typedef struct ConditionalStackData *ConditionalStack;
extern ConditionalStack conditional_stack_create(void);
extern void conditional_stack_reset(ConditionalStack cstack);
extern void conditional_stack_destroy(ConditionalStack cstack);
extern int conditional_stack_depth(ConditionalStack cstack);
extern void conditional_stack_push(ConditionalStack cstack, ifState new_state);
extern bool conditional_stack_pop(ConditionalStack cstack);
extern ifState conditional_stack_peek(ConditionalStack cstack);
extern bool conditional_stack_poke(ConditionalStack cstack, ifState new_state);
extern bool conditional_stack_empty(ConditionalStack cstack);
extern bool conditional_active(ConditionalStack cstack);
extern void conditional_stack_set_query_len(ConditionalStack cstack, int len);
extern int conditional_stack_get_query_len(ConditionalStack cstack);
extern void conditional_stack_set_paren_depth(ConditionalStack cstack, int depth);
extern int conditional_stack_get_paren_depth(ConditionalStack cstack);
#endif /* CONDITIONAL_H */
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