pic/symtab.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include <ctype.h>
   4 #include <string.h>
   5 #include "pic.h"
   6 #include "y.tab.h"
   7
   8 YYSTYPE getvar(char *s) /* return value of variable s (usually pointer) */
   9 {
  10         struct symtab *p;
  11         static YYSTYPE bug;
  12
  13         p = lookup(s);
  14         if (p == NULL) {
  15                 if (islower(s[0]))
  16                         ERROR "no such variable as %s", s WARNING;
  17                 else
  18                         ERROR "no such place as %s", s WARNING;
  19                 return(bug);
  20         }
  21         return(p->s_val);
  22 }
  23
  24 double getfval(char *s) /* return float value of variable s */
  25 {
  26         YYSTYPE y;
  27
  28         y = getvar(s);
  29         return y.f;
  30 }
  31
  32 void setfval(char *s, double f) /* set variable s to f */
  33 {
  34         struct symtab *p;
  35
  36         if ((p = lookup(s)) != NULL)
  37                 p->s_val.f = f;
  38 }
  39
  40 struct symtab *makevar(char *s, int t, YYSTYPE v)       /* make variable named s in table */
  41                 /* assumes s is static or from tostring */
  42 {
  43         struct symtab *p;
  44
  45         for (p = stack[nstack].p_symtab; p != NULL; p = p->s_next)
  46                 if (strcmp(s, p->s_name) == 0)
  47                         break;
  48         if (p == NULL) {        /* it's a new one */
  49                 p = (struct symtab *) malloc(sizeof(struct symtab));
  50                 if (p == NULL)
  51                         ERROR "out of symtab space with %s", s FATAL;
  52                 p->s_next = stack[nstack].p_symtab;
  53                 stack[nstack].p_symtab = p;     /* stick it at front */
  54         }
  55         p->s_name = s;
  56         p->s_type = t;
  57         p->s_val = v;
  58         return(p);
  59 }
  60
  61 struct symtab *lookup(char *s)  /* find s in symtab */
  62 {
  63         int i;
  64         struct symtab *p;
  65
  66         for (i = nstack; i >= 0; i--)   /* look in each active symtab */
  67                 for (p = stack[i].p_symtab; p != NULL; p = p->s_next)
  68                         if (strcmp(s, p->s_name) == 0)
  69                                 return(p);
  70         return(NULL);
  71 }
  72
  73 void freesymtab(struct symtab *p)       /* free space used by symtab at p */
  74 {
  75         struct symtab *q;
  76
  77         for ( ; p != NULL; p = q) {
  78                 q = p->s_next;
  79                 free(p->s_name);        /* assumes done with tostring */
  80                 free((char *)p);
  81         }
  82 }
  83
  84 void freedef(char *s)   /* free definition for string s */
  85 {
  86         struct symtab *p, *q, *op;
  87
  88         for (p = op = q = stack[nstack].p_symtab; p != NULL; p = p->s_next) {
  89                 if (strcmp(s, p->s_name) == 0) {        /* got it */
  90                         if (p->s_type != DEFNAME)
  91                                 break;
  92                         if (p == op)    /* 1st elem */
  93                                 stack[nstack].p_symtab = p->s_next;
  94                         else
  95                                 q->s_next = p->s_next;
  96                         free(p->s_name);
  97                         free(p->s_val.p);
  98                         free((char *)p);
  99                         return;
 100                 }
 101                 q = p;
 102         }
 103         /* ERROR "%s is not defined at this point", s WARNING; */
 104 }