gas/hash.c: add interface for looking up non-NUL-terminated strings

[Zack Weinberg <zack@codesourcery.com>]

The appended patch adds a new interface to gas/hash.c, hash_find_n,
with exactly the same semantics as hash_find except that the length of
the key is passed in as an argument, and the key is not assumed to be
NUL-terminated.  This is more convenient when parsing an assembly
instruction: one does not need to write a NUL into the line buffer so
that hash_find knows where to stop.

Thoughts?  The only downside that I see is that the other hash_*
functions may now be marginally slower, since they have to call strlen
up front.  I thought this was better than duplicating the entire body
of hash_lookup.

zw

        * hash.c (hash_lookup): Delete unnecessary forward declaration.
        Add 'len' argument.  Do not assume 'key' is NUL-terminated.
        All callers changed to match.
        (hash_find_n): New interface.
        * hash.h: Prototype hash_find_n.

===================================================================
Index: hash.c
--- hash.c	(revision 7)
+++ hash.c	(revision 8)
@@ -120,19 +120,13 @@
    Each time we look up a string, we move it to the start of the list
    for its hash code, to take advantage of referential locality.  */
 
-static struct hash_entry *hash_lookup (struct hash_control *,
-				       const char *,
-				       struct hash_entry ***,
-				       unsigned long *);
-
 static struct hash_entry *
-hash_lookup (struct hash_control *table, const char *key,
+hash_lookup (struct hash_control *table, const char *key, size_t len,
 	     struct hash_entry ***plist, unsigned long *phash)
 {
-  register unsigned long hash;
-  unsigned int len;
-  register const unsigned char *s;
-  register unsigned int c;
+  unsigned long hash;
+  size_t n;
+  unsigned int c;
   unsigned int index;
   struct hash_entry **list;
   struct hash_entry *p;
@@ -143,13 +137,11 @@
 #endif
 
   hash = 0;
-  len = 0;
-  s = (const unsigned char *) key;
-  while ((c = *s++) != '\0')
+  for (n = 0; n < len; n++)
     {
+      c = key[n];
       hash += c + (c << 17);
       hash ^= hash >> 2;
-      ++len;
     }
   hash += len + (len << 17);
   hash ^= hash >> 2;
@@ -176,7 +168,7 @@
 	  ++table->string_compares;
 #endif
 
-	  if (strcmp (p->string, key) == 0)
+	  if (p->string[len] == '\0' && strncmp (p->string, key, len) == 0)
 	    {
 	      if (prev != NULL)
 		{
@@ -207,7 +199,7 @@
   struct hash_entry **list;
   unsigned long hash;
 
-  p = hash_lookup (table, key, &list, &hash);
+  p = hash_lookup (table, key, strlen (key), &list, &hash);
   if (p != NULL)
     return "exists";
 
@@ -237,7 +229,7 @@
   struct hash_entry **list;
   unsigned long hash;
 
-  p = hash_lookup (table, key, &list, &hash);
+  p = hash_lookup (table, key, strlen (key), &list, &hash);
   if (p != NULL)
     {
 #ifdef HASH_STATISTICS
@@ -274,7 +266,7 @@
   struct hash_entry *p;
   PTR ret;
 
-  p = hash_lookup (table, key, NULL, NULL);
+  p = hash_lookup (table, key, strlen (key), NULL, NULL);
   if (p == NULL)
     return NULL;
 
@@ -297,13 +289,28 @@
 {
   struct hash_entry *p;
 
-  p = hash_lookup (table, key, NULL, NULL);
+  p = hash_lookup (table, key, strlen (key), NULL, NULL);
   if (p == NULL)
     return NULL;
 
   return p->data;
 }
 
+/* As hash_find, but KEY is of length LEN and is not guaranteed to be
+   NUL-terminated.  */
+
+PTR
+hash_find_n (struct hash_control *table, const char *key, size_t len)
+{
+  struct hash_entry *p;
+
+  p = hash_lookup (table, key, len, NULL, NULL);
+  if (p == NULL)
+    return NULL;
+
+  return p->data;
+}
+
 /* Delete an entry from a hash table.  This returns the value stored
    for that entry, or NULL if there is no such entry.  */
 
@@ -313,7 +320,7 @@
   struct hash_entry *p;
   struct hash_entry **list;
 
-  p = hash_lookup (table, key, &list, NULL);
+  p = hash_lookup (table, key, strlen (key), &list, NULL);
   if (p == NULL)
     return NULL;
 
===================================================================
Index: hash.h
--- hash.h	(revision 7)
+++ hash.h	(revision 8)
@@ -59,6 +59,11 @@
 
 extern PTR hash_find (struct hash_control *, const char *key);
 
+/* As hash_find, but KEY is of length LEN and is not guaranteed to be
+   NUL-terminated.  */
+
+extern PTR hash_find_n (struct hash_control *, const char *key, size_t len);
+
 /* Delete an entry from a hash table.  This returns the value stored
    for that entry, or NULL if there is no such entry.  */