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ASSEMBLY & COMPILE TOOLS/PLM-2-C 2/plm/scope.c

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+/* literal symbol table for PL/M.
+
+$Id: scope.c,v 1.1 1994/02/28 20:55:56 hays Exp $
+
+Copyright 1994 by Kirk Hays (hays@ichips.intel.com)
+
+USE AT YOUR OWN RISK. NO WARRANTY EXPRESSED OR IMPLIED.
+This code is distributed in the hope that it will be useful,
+but without any warranty.  Further, there is no implied warranty of
+merchantability or fitness for a particular purpose.
+
+This code implements a scoped symbol table.  It depends on Paul
+Vixie's PD AVL Tree code, distributed in comp.sources.unix, Volume 27,
+Issue 34.
+
+*/
+
+#include <stdlib.h>
+#include <stdio.h>
+#include "tree.h"
+#include "scope.h"
+
+typedef struct lit_table_stack_t_elem {
+  struct lit_table_stack_t_elem *next;
+  tree * literal_table;
+} lit_table_stack_t;
+
+/* innermost scope for scope list */
+static lit_table_stack_t  *lit_table_stack;
+
+typedef struct {
+  char * identifier;
+  char * string;
+} literal_t;
+
+/* static forward references */
+static void new_scope (lit_table_stack_t *);
+static int literal_compar (literal_t *, literal_t *);
+static void literal_error (literal_t *);
+static void literal_t_delete (literal_t *);
+
+/* lookup an identifier in the scoped symbol table */
+char *
+lookup_literal (char * identifier)
+{
+  literal_t * datum;
+  literal_t * node;
+  lit_table_stack_t * scope;
+  
+  node = alloca (sizeof (literal_t));
+  node->identifier = identifier;
+  
+  for (scope = lit_table_stack; scope; scope=scope->next)
+    {
+      datum = tree_srch(&(scope->literal_table), literal_compar, node);
+      if (datum)
+        {
+          return datum->string;
+        }
+    }
+  
+  return 0;
+  
+}
+
+/* enter an identifier in the current scoping level */
+void
+enter_literal (char * identifier, char * string)
+{  
+  literal_t * datum;
+  
+  datum = malloc (sizeof (literal_t));
+  datum->identifier = identifier;
+  datum->string = string;
+  tree_add (&(lit_table_stack->literal_table),
+            literal_compar,
+            datum,
+            literal_error);
+}
+
+/* increase scope depth by one level - creates a new symbol table
+   for the current scope */
+void 
+push_scope (void)
+{
+  new_scope (lit_table_stack);
+}
+
+/* remove the innermost scope of the symbol table - releases all
+   allocated storage for that scope */
+void 
+pop_scope (void)
+{
+  lit_table_stack_t * p;
+  
+  p = lit_table_stack;
+  lit_table_stack = lit_table_stack->next;
+  tree_mung (&(p->literal_table), literal_t_delete);
+  if (p->literal_table)
+    {
+      free(p->literal_table);
+    }
+  free(p);
+}
+
+/* initialize this module, creating the outermost scope */
+void 
+init_scope (void) 
+{
+  new_scope (0);
+}
+
+/* work procedure to create a new scope */
+static void 
+new_scope (lit_table_stack_t * next)
+{
+  lit_table_stack = malloc (sizeof (lit_table_stack_t));
+  lit_table_stack->next = next;
+  tree_init (&(lit_table_stack->literal_table));
+}
+
+/* internal procedure to free storage when a symbol table entry is
+   deleted */
+static 
+void literal_t_delete (literal_t * datum)
+{
+  free (datum->string);
+  free (datum->identifier);
+}
+
+/* internal procedure to determine the match order for two symbol
+   table entries */
+
+static int 
+literal_compar (literal_t * left, literal_t * right)
+{
+  return strcmp (left->identifier, right->identifier);
+}
+
+/* assertion procedure to assure that duplicate literals are never
+   added at a single scoping level */
+
+static void 
+literal_error (literal_t * in_error)
+{
+  fprintf (stderr, 
+	   "literal table error - attempt to enter same identifier twice\n");
+  exit (255);
+}
+
+