src/fe_utils/conditional.c

   1 /*-------------------------------------------------------------------------
   2  * A stack of automaton states to handle nested conditionals.
   3  *
   4  * Copyright (c) 2000-2021, 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 stack
  28  */
  29 void
  30 conditional_stack_destroy(ConditionalStack cstack)
  31 {
  32         while (conditional_stack_pop(cstack))
  33                 continue;
  34         free(cstack);
  35 }
  36
  37 /*
  38  * Create a new conditional branch.
  39  */
  40 void
  41 conditional_stack_push(ConditionalStack cstack, ifState new_state)
  42 {
  43         IfStackElem *p = (IfStackElem *) pg_malloc(sizeof(IfStackElem));
  44
  45         p->if_state = new_state;
  46         p->query_len = -1;
  47         p->paren_depth = -1;
  48         p->next = cstack->head;
  49         cstack->head = p;
  50 }
  51
  52 /*
  53  * Destroy the topmost conditional branch.
  54  * Returns false if there was no branch to end.
  55  */
  56 bool
  57 conditional_stack_pop(ConditionalStack cstack)
  58 {
  59         IfStackElem *p = cstack->head;
  60
  61         if (!p)
  62                 return false;
  63         cstack->head = cstack->head->next;
  64         free(p);
  65         return true;
  66 }
  67
  68 /*
  69  * Returns current stack depth, for debugging purposes.
  70  */
  71 int
  72 conditional_stack_depth(ConditionalStack cstack)
  73 {
  74         if (cstack == NULL)
  75                 return -1;
  76         else
  77         {
  78                 IfStackElem *p = cstack->head;
  79                 int                     depth = 0;
  80
  81                 while (p != NULL)
  82                 {
  83                         depth++;
  84                         p = p->next;
  85                 }
  86                 return depth;
  87         }
  88 }
  89
  90 /*
  91  * Fetch the current state of the top of the stack.
  92  */
  93 ifState
  94 conditional_stack_peek(ConditionalStack cstack)
  95 {
  96         if (conditional_stack_empty(cstack))
  97                 return IFSTATE_NONE;
  98         return cstack->head->if_state;
  99 }
 100
 101 /*
 102  * Change the state of the topmost branch.
 103  * Returns false if there was no branch state to set.
 104  */
 105 bool
 106 conditional_stack_poke(ConditionalStack cstack, ifState new_state)
 107 {
 108         if (conditional_stack_empty(cstack))
 109                 return false;
 110         cstack->head->if_state = new_state;
 111         return true;
 112 }
 113
 114 /*
 115  * True if there are no active \if-blocks.
 116  */
 117 bool
 118 conditional_stack_empty(ConditionalStack cstack)
 119 {
 120         return cstack->head == NULL;
 121 }
 122
 123 /*
 124  * True if we should execute commands normally; that is, the current
 125  * conditional branch is active, or there is no open \if block.
 126  */
 127 bool
 128 conditional_active(ConditionalStack cstack)
 129 {
 130         ifState         s = conditional_stack_peek(cstack);
 131
 132         return s == IFSTATE_NONE || s == IFSTATE_TRUE || s == IFSTATE_ELSE_TRUE;
 133 }
 134
 135 /*
 136  * Save current query buffer length in topmost stack entry.
 137  */
 138 void
 139 conditional_stack_set_query_len(ConditionalStack cstack, int len)
 140 {
 141         Assert(!conditional_stack_empty(cstack));
 142         cstack->head->query_len = len;
 143 }
 144
 145 /*
 146  * Fetch last-recorded query buffer length from topmost stack entry.
 147  * Will return -1 if no stack or it was never saved.
 148  */
 149 int
 150 conditional_stack_get_query_len(ConditionalStack cstack)
 151 {
 152         if (conditional_stack_empty(cstack))
 153                 return -1;
 154         return cstack->head->query_len;
 155 }
 156
 157 /*
 158  * Save current parenthesis nesting depth in topmost stack entry.
 159  */
 160 void
 161 conditional_stack_set_paren_depth(ConditionalStack cstack, int depth)
 162 {
 163         Assert(!conditional_stack_empty(cstack));
 164         cstack->head->paren_depth = depth;
 165 }
 166
 167 /*
 168  * Fetch last-recorded parenthesis nesting depth from topmost stack entry.
 169  * Will return -1 if no stack or it was never saved.
 170  */
 171 int
 172 conditional_stack_get_paren_depth(ConditionalStack cstack)
 173 {
 174         if (conditional_stack_empty(cstack))
 175                 return -1;
 176         return cstack->head->paren_depth;
 177 }