initial commit

src/symtab.c

@@ -0,0 +1,122 @@
+/****************************************************/
+/* File: symtab.c                                   */
+/* Symbol table implementation for the TINY compiler*/
+/* (allows only one symbol table)                   */
+/* Symbol table is implemented as a chained         */
+/* hash table                                       */
+/* Compiler Construction: Principles and Practice   */
+/* Kenneth C. Louden                                */
+/****************************************************/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "symtab.h"
+
+/* SIZE is the size of the hash table */
+#define SIZE 211
+
+/* SHIFT is the power of two used as multiplier
+   in hash function  */
+#define SHIFT 4
+
+/* the hash function */
+static int hash ( char * key )
+{ int temp = 0;
+  int i = 0;
+  while (key[i] != '\0')
+  { temp = ((temp << SHIFT) + key[i]) % SIZE;
+    ++i;
+  }
+  return temp;
+}
+
+/* the list of line numbers of the source 
+ * code in which a variable is referenced
+ */
+typedef struct LineListRec
+   { int lineno;
+     struct LineListRec * next;
+   } * LineList;
+
+/* The record in the bucket lists for
+ * each variable, including name, 
+ * assigned memory location, and
+ * the list of line numbers in which
+ * it appears in the source code
+ */
+typedef struct BucketListRec
+   { char * name;
+     LineList lines;
+     int memloc ; /* memory location for variable */
+     struct BucketListRec * next;
+   } * BucketList;
+
+/* the hash table */
+static BucketList hashTable[SIZE];
+
+/* Procedure st_insert inserts line numbers and
+ * memory locations into the symbol table
+ * loc = memory location is inserted only the
+ * first time, otherwise ignored
+ */
+void st_insert( char * name, int lineno, int loc )
+{ int h = hash(name);
+  BucketList l =  hashTable[h];
+  while ((l != NULL) && (strcmp(name,l->name) != 0))
+    l = l->next;
+  if (l == NULL) /* variable not yet in table */
+  { l = (BucketList) malloc(sizeof(struct BucketListRec));
+    l->name = name;
+    l->lines = (LineList) malloc(sizeof(struct LineListRec));
+    l->lines->lineno = lineno;
+    l->memloc = loc;
+    l->lines->next = NULL;
+    l->next = hashTable[h];
+    hashTable[h] = l; }
+  else /* found in table, so just add line number */
+  { LineList t = l->lines;
+    while (t->next != NULL) t = t->next;
+    t->next = (LineList) malloc(sizeof(struct LineListRec));
+    t->next->lineno = lineno;
+    t->next->next = NULL;
+  }
+} /* st_insert */
+
+/* Function st_lookup returns the memory 
+ * location of a variable or -1 if not found
+ */
+int st_lookup ( char * name )
+{ int h = hash(name);
+  BucketList l =  hashTable[h];
+  while ((l != NULL) && (strcmp(name,l->name) != 0))
+    l = l->next;
+  if (l == NULL) return -1;
+  else return l->memloc;
+}
+
+/* Procedure printSymTab prints a formatted 
+ * listing of the symbol table contents 
+ * to the listing file
+ */
+void printSymTab(FILE * listing)
+{ int i;
+  fprintf(listing,"Variable Name  Location   Line Numbers\n");
+  fprintf(listing,"-------------  --------   ------------\n");
+  for (i=0;i<SIZE;++i)
+  { if (hashTable[i] != NULL)
+    { BucketList l = hashTable[i];
+      while (l != NULL)
+      { LineList t = l->lines;
+        fprintf(listing,"%-14s ",l->name);
+        fprintf(listing,"%-8d  ",l->memloc);
+        while (t != NULL)
+        { fprintf(listing,"%4d ",t->lineno);
+          t = t->next;
+        }
+        fprintf(listing,"\n");
+        l = l->next;
+      }
+    }
+  }
+} /* printSymTab */