Initial revisionHEADoriginmaster

1 files changed, 119 insertions, 0 deletions

diff --git a/symbol.c b/symbol.c
new file mode 100644
index 0000000..85be039
--- /dev/null
+++ b/symbol.c
@@ -0,0 +1,119 @@
+/* $Id: symbol.c,v 1.1 2004-05-03 05:17:48 behdad Exp $
+ *
+ * Symbol table maintenance. Implements an abstract data type called
+ * the symbol table.
+ */
+#include "c2man.h"
+#include "symbol.h"
+
+/* Create a symbol table.
+ * Return a pointer to the symbol table or NULL if an error occurs.
+ */
+SymbolTable *
+create_symbol_table ()
+{
+    SymbolTable *symtab;
+    int i;
+
+    symtab = (SymbolTable *)safe_malloc(sizeof(SymbolTable));
+
+    for (i = 0; i < SYM_MAX_HASH; ++i)
+	symtab->bucket[i] = NULL;
+
+    return symtab;
+}
+
+
+/* Free the memory allocated to the symbol table.
+ */
+void
+destroy_symbol_table (symtab)
+SymbolTable *symtab;
+{
+    int i;
+    Symbol *sym, *next;
+
+    for (i = 0; i < SYM_MAX_HASH; ++i) {
+	sym = symtab->bucket[i];
+	while (sym != NULL) {
+	    next = sym->next;
+	    free(sym->name);
+	    free(sym);
+	    sym = next;
+	}
+    }
+    free(symtab);
+}
+
+
+/* This is a simple hash function mapping a symbol name to a hash bucket. */
+
+static unsigned int
+hash (name)
+char *name;
+{
+    char *s;
+    unsigned int h;
+
+    h = 0;
+    s = name;
+    while (*s != '\0')
+	h = (h << 1) ^ *s++;
+    return h % SYM_MAX_HASH;
+}
+
+
+/* Search the list of symbols <list> for the symbol <name>.
+ * Return a pointer to the symbol or NULL if not found.
+ */
+static Symbol *
+search_symbol_list (list, name)
+Symbol *list;
+char *name;
+{
+    Symbol *sym;
+
+    for (sym = list; sym != NULL; sym = sym->next) {
+	if (strcmp(sym->name, name) == 0)
+	    return sym;
+    }
+    return NULL;
+}
+
+
+/* Look for symbol <name> in symbol table <symtab>.
+ * Return a pointer to the symbol or NULL if not found.
+ */
+Symbol *
+find_symbol (symtab, name)
+SymbolTable *symtab;
+char *name;
+{
+    return search_symbol_list(symtab->bucket[hash(name)], name);
+}
+
+
+/* If the symbol <name> does not already exist in symbol table <symtab>,
+ * then add the symbol to the symbol table.
+ * Return a pointer to the symbol or NULL on an error.
+ */
+Symbol *
+new_symbol (symtab, name, flags)
+SymbolTable *symtab;	/* symbol table */
+char *name;		/* symbol name */
+int flags;		/* symbol attributes */
+{
+    Symbol *sym;
+    int i;
+
+    if ((sym = find_symbol(symtab, name)) == NULL) {
+	sym = (Symbol *)safe_malloc(sizeof(Symbol));
+	sym->name = strduplicate(name);
+	sym->flags = flags;
+	sym->valtype = SYMVAL_NONE;
+	i = hash(name);
+	sym->next = symtab->bucket[i];
+	symtab->bucket[i] = sym;
+    }
+    return sym;
+}