mirror of https://github.com/postgres/postgres
This patch adds nestable conditional blocks to psql. The control structure feature per se is complete, but the boolean expressions understood by \if and \elif are pretty primitive; basically, after variable substitution and backtick expansion, the result has to be "true" or "false" or one of the other standard spellings of a boolean value. But that's enough for many purposes, since you can always do the heavy lifting on the server side; and we can extend it later. Along the way, pay down some of the technical debt that had built up around psql/command.c: * Refactor exec_command() into a function per command, instead of being a 1500-line monstrosity. This makes the file noticeably longer because of repetitive function header/trailer overhead, but it seems much more readable. * Teach psql_get_variable() and psqlscanslash.l to suppress variable substitution and backtick expansion on the basis of the conditional stack state, thereby allowing removal of the OT_NO_EVAL kluge. * Fix the no-doubt-once-expedient hack of sometimes silently substituting mainloop.c's previous_buf for query_buf when calling HandleSlashCmds. (It's a bit remarkable that commands like \r worked at all with that.) Recall of a previous query is now done explicitly in the slash commands where that should happen. Corey Huinker, reviewed by Fabien Coelho, further hacking by me Discussion: https://postgr.es/m/CADkLM=c94OSRTnat=LX0ivNq4pxDNeoomFfYvBKM5N_xfmLtAA@mail.gmail.compull/3/merge
Tom Lane
8 years ago
parent
ffae6733db
commit
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/*
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* psql - the PostgreSQL interactive terminal |
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* |
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* Copyright (c) 2000-2017, PostgreSQL Global Development Group |
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* |
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* src/bin/psql/conditional.c |
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*/ |
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#include "postgres_fe.h" |
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#include "conditional.h" |
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/*
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* create stack |
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*/ |
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ConditionalStack |
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conditional_stack_create(void) |
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{ |
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ConditionalStack cstack = pg_malloc(sizeof(ConditionalStackData)); |
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cstack->head = NULL; |
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return cstack; |
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} |
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/*
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* destroy stack |
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*/ |
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void |
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conditional_stack_destroy(ConditionalStack cstack) |
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{ |
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while (conditional_stack_pop(cstack)) |
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continue; |
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free(cstack); |
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} |
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/*
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* Create a new conditional branch. |
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*/ |
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void |
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conditional_stack_push(ConditionalStack cstack, ifState new_state) |
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{ |
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IfStackElem *p = (IfStackElem *) pg_malloc(sizeof(IfStackElem)); |
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p->if_state = new_state; |
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p->query_len = -1; |
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p->paren_depth = -1; |
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p->next = cstack->head; |
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cstack->head = p; |
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} |
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/*
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* Destroy the topmost conditional branch. |
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* Returns false if there was no branch to end. |
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*/ |
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bool |
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conditional_stack_pop(ConditionalStack cstack) |
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{ |
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IfStackElem *p = cstack->head; |
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if (!p) |
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return false; |
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cstack->head = cstack->head->next; |
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free(p); |
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return true; |
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} |
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/*
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* Fetch the current state of the top of the stack. |
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*/ |
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ifState |
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conditional_stack_peek(ConditionalStack cstack) |
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{ |
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if (conditional_stack_empty(cstack)) |
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return IFSTATE_NONE; |
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return cstack->head->if_state; |
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} |
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/*
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* Change the state of the topmost branch. |
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* Returns false if there was no branch state to set. |
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*/ |
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bool |
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conditional_stack_poke(ConditionalStack cstack, ifState new_state) |
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{ |
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if (conditional_stack_empty(cstack)) |
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return false; |
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cstack->head->if_state = new_state; |
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return true; |
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} |
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/*
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* True if there are no active \if-blocks. |
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*/ |
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bool |
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conditional_stack_empty(ConditionalStack cstack) |
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{ |
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return cstack->head == NULL; |
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} |
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/*
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* True if we should execute commands normally; that is, the current |
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* conditional branch is active, or there is no open \if block. |
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*/ |
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bool |
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conditional_active(ConditionalStack cstack) |
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{ |
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ifState s = conditional_stack_peek(cstack); |
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return s == IFSTATE_NONE || s == IFSTATE_TRUE || s == IFSTATE_ELSE_TRUE; |
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} |
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/*
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* Save current query buffer length in topmost stack entry. |
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*/ |
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void |
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conditional_stack_set_query_len(ConditionalStack cstack, int len) |
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{ |
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Assert(!conditional_stack_empty(cstack)); |
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cstack->head->query_len = len; |
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} |
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/*
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* Fetch last-recorded query buffer length from topmost stack entry. |
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* Will return -1 if no stack or it was never saved. |
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*/ |
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int |
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conditional_stack_get_query_len(ConditionalStack cstack) |
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{ |
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if (conditional_stack_empty(cstack)) |
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return -1; |
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return cstack->head->query_len; |
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} |
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/*
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* Save current parenthesis nesting depth in topmost stack entry. |
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*/ |
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void |
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conditional_stack_set_paren_depth(ConditionalStack cstack, int depth) |
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{ |
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Assert(!conditional_stack_empty(cstack)); |
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cstack->head->paren_depth = depth; |
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} |
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/*
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* Fetch last-recorded parenthesis nesting depth from topmost stack entry. |
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* Will return -1 if no stack or it was never saved. |
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*/ |
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int |
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conditional_stack_get_paren_depth(ConditionalStack cstack) |
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{ |
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if (conditional_stack_empty(cstack)) |
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return -1; |
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return cstack->head->paren_depth; |
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} |
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@ -0,0 +1,83 @@ |
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/*
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* psql - the PostgreSQL interactive terminal |
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* |
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* Copyright (c) 2000-2017, PostgreSQL Global Development Group |
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* |
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* src/bin/psql/conditional.h |
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*/ |
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#ifndef CONDITIONAL_H |
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#define CONDITIONAL_H |
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/*
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* Possible states of a single level of \if block. |
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*/ |
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typedef enum ifState |
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{ |
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IFSTATE_NONE = 0, /* not currently in an \if block */ |
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IFSTATE_TRUE, /* currently in an \if or \elif that is true
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* and all parent branches (if any) are true */ |
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IFSTATE_FALSE, /* currently in an \if or \elif that is false
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* but no true branch has yet been seen, and |
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* all parent branches (if any) are true */ |
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IFSTATE_IGNORED, /* currently in an \elif that follows a true
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* branch, or the whole \if is a child of a |
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* false parent branch */ |
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IFSTATE_ELSE_TRUE, /* currently in an \else that is true and all
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* parent branches (if any) are true */ |
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IFSTATE_ELSE_FALSE /* currently in an \else that is false or
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* ignored */ |
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} ifState; |
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/*
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* The state of nested \ifs is stored in a stack. |
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* |
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* query_len is used to determine what accumulated text to throw away at the |
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* end of an inactive branch. (We could, perhaps, teach the lexer to not add |
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* stuff to the query buffer in the first place when inside an inactive branch; |
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* but that would be very invasive.) We also need to save and restore the |
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* lexer's parenthesis nesting depth when throwing away text. (We don't need |
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* to save and restore any of its other state, such as comment nesting depth, |
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* because a backslash command could never appear inside a comment or SQL |
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* literal.) |
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*/ |
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typedef struct IfStackElem |
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{ |
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ifState if_state; /* current state, see enum above */ |
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int query_len; /* length of query_buf at last branch start */ |
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int paren_depth; /* parenthesis depth at last branch start */ |
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struct IfStackElem *next; /* next surrounding \if, if any */ |
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} IfStackElem; |
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typedef struct ConditionalStackData |
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{ |
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IfStackElem *head; |
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} ConditionalStackData; |
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typedef struct ConditionalStackData *ConditionalStack; |
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extern ConditionalStack conditional_stack_create(void); |
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extern void conditional_stack_destroy(ConditionalStack cstack); |
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extern void conditional_stack_push(ConditionalStack cstack, ifState new_state); |
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extern bool conditional_stack_pop(ConditionalStack cstack); |
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extern ifState conditional_stack_peek(ConditionalStack cstack); |
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extern bool conditional_stack_poke(ConditionalStack cstack, ifState new_state); |
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extern bool conditional_stack_empty(ConditionalStack cstack); |
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extern bool conditional_active(ConditionalStack cstack); |
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extern void conditional_stack_set_query_len(ConditionalStack cstack, int len); |
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extern int conditional_stack_get_query_len(ConditionalStack cstack); |
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extern void conditional_stack_set_paren_depth(ConditionalStack cstack, int depth); |
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extern int conditional_stack_get_paren_depth(ConditionalStack cstack); |
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#endif /* CONDITIONAL_H */ |
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