src/fe_utils/conditional.c

   1 /*-------------------------------------------------------------------------
   2  * A stack of automaton states to handle nested conditionals.
   3  *
   4  * Copyright (c) 2000-2023, PostgreSQL Global Development Group
   5  *
   6  * src/fe_utils/conditional.c
   7  *
   8  *-------------------------------------------------------------------------
   9  */
  10 #include "postgres_fe.h"
  11
  12 #include "fe_utils/conditional.h"
  13
  14 /*
  15  * create stack
  16  */
  17 ConditionalStack
  18 conditional_stack_create(void)
  19 {
  20         ConditionalStack cstack = pg_malloc(sizeof(ConditionalStackData));
  21
  22         cstack->head = NULL;
  23         return cstack;
  24 }
  25
  26 /*
  27  * Destroy all the elements from the stack. The stack itself is not freed.
  28  */
  29 void
  30 conditional_stack_reset(ConditionalStack cstack)
  31 {
  32         if (!cstack)
  33                 return;                                 /* nothing to do here */
  34
  35         while (conditional_stack_pop(cstack))
  36                 continue;
  37 }
  38
  39 /*
  40  * destroy stack
  41  */
  42 void
  43 conditional_stack_destroy(ConditionalStack cstack)
  44 {
  45         conditional_stack_reset(cstack);
  46         free(cstack);
  47 }
  48
  49 /*
  50  * Create a new conditional branch.
  51  */
  52 void
  53 conditional_stack_push(ConditionalStack cstack, ifState new_state)
  54 {
  55         IfStackElem *p = (IfStackElem *) pg_malloc(sizeof(IfStackElem));
  56
  57         p->if_state = new_state;
  58         p->query_len = -1;
  59         p->paren_depth = -1;
  60         p->next = cstack->head;
  61         cstack->head = p;
  62 }
  63
  64 /*
  65  * Destroy the topmost conditional branch.
  66  * Returns false if there was no branch to end.
  67  */
  68 bool
  69 conditional_stack_pop(ConditionalStack cstack)
  70 {
  71         IfStackElem *p = cstack->head;
  72
  73         if (!p)
  74                 return false;
  75         cstack->head = cstack->head->next;
  76         free(p);
  77         return true;
  78 }
  79
  80 /*
  81  * Returns current stack depth, for debugging purposes.
  82  */
  83 int
  84 conditional_stack_depth(ConditionalStack cstack)
  85 {
  86         if (cstack == NULL)
  87                 return -1;
  88         else
  89         {
  90                 IfStackElem *p = cstack->head;
  91                 int                     depth = 0;
  92
  93                 while (p != NULL)
  94                 {
  95                         depth++;
  96                         p = p->next;
  97                 }
  98                 return depth;
  99         }
 100 }
 101
 102 /*
 103  * Fetch the current state of the top of the stack.
 104  */
 105 ifState
 106 conditional_stack_peek(ConditionalStack cstack)
 107 {
 108         if (conditional_stack_empty(cstack))
 109                 return IFSTATE_NONE;
 110         return cstack->head->if_state;
 111 }
 112
 113 /*
 114  * Change the state of the topmost branch.
 115  * Returns false if there was no branch state to set.
 116  */
 117 bool
 118 conditional_stack_poke(ConditionalStack cstack, ifState new_state)
 119 {
 120         if (conditional_stack_empty(cstack))
 121                 return false;
 122         cstack->head->if_state = new_state;
 123         return true;
 124 }
 125
 126 /*
 127  * True if there are no active \if-blocks.
 128  */
 129 bool
 130 conditional_stack_empty(ConditionalStack cstack)
 131 {
 132         return cstack->head == NULL;
 133 }
 134
 135 /*
 136  * True if we should execute commands normally; that is, the current
 137  * conditional branch is active, or there is no open \if block.
 138  */
 139 bool
 140 conditional_active(ConditionalStack cstack)
 141 {
 142         ifState         s = conditional_stack_peek(cstack);
 143
 144         return s == IFSTATE_NONE || s == IFSTATE_TRUE || s == IFSTATE_ELSE_TRUE;
 145 }
 146
 147 /*
 148  * Save current query buffer length in topmost stack entry.
 149  */
 150 void
 151 conditional_stack_set_query_len(ConditionalStack cstack, int len)
 152 {
 153         Assert(!conditional_stack_empty(cstack));
 154         cstack->head->query_len = len;
 155 }
 156
 157 /*
 158  * Fetch last-recorded query buffer length from topmost stack entry.
 159  * Will return -1 if no stack or it was never saved.
 160  */
 161 int
 162 conditional_stack_get_query_len(ConditionalStack cstack)
 163 {
 164         if (conditional_stack_empty(cstack))
 165                 return -1;
 166         return cstack->head->query_len;
 167 }
 168
 169 /*
 170  * Save current parenthesis nesting depth in topmost stack entry.
 171  */
 172 void
 173 conditional_stack_set_paren_depth(ConditionalStack cstack, int depth)
 174 {
 175         Assert(!conditional_stack_empty(cstack));
 176         cstack->head->paren_depth = depth;
 177 }
 178
 179 /*
 180  * Fetch last-recorded parenthesis nesting depth from topmost stack entry.
 181  * Will return -1 if no stack or it was never saved.
 182  */
 183 int
 184 conditional_stack_get_paren_depth(ConditionalStack cstack)
 185 {
 186         if (conditional_stack_empty(cstack))
 187                 return -1;
 188         return cstack->head->paren_depth;
 189 }