Optimise fetching ascii or utf8 from literal string

git-svn-id: svn+ssh://svn.gna.org/svn/gnustep/libs/base/trunk@39915 72102866-910b-0410-8b05-ffd578937521

ChangeLog

@@ -1,3 +1,8 @@
+2016-06-23  Richard Frith-Macdonald <rfm@gnu.org>
+
+	* Source/GSString.m: Optimise getting ascii or utf8 characters
+	from a literal string.
+
 2016-06-22  Richard Frith-Macdonald <rfm@gnu.org>
 
 	* Source/NSObject.m: Make sure we treat the reference count as a

Source/GSString.m

@@ -5916,6 +5916,67 @@ literalIsEqual(NXConstantString *self, id anObject)
     }
 }
 
+- (BOOL) getCString: (char*)buffer
+	  maxLength: (NSUInteger)maxLength
+	   encoding: (NSStringEncoding)encoding
+{
+  const uint8_t *ptr = (const uint8_t*)nxcsptr;
+  int           length = nxcslen;
+  int           index;
+
+  if (0 == maxLength || 0 == buffer)
+    {
+      return NO;	// Can't fit in here
+    }
+  if (NSUTF8StringEncoding == encoding)
+    {
+      /* We are already using UTF-8 so we can just copy directly.
+       */
+      if (maxLength <= length)
+        {
+          length = maxLength - 1;
+        }
+      for (index = 0; index < length; index++)
+        {
+          buffer[index] = (char)ptr[index];
+        }
+      /* Step back before any multibyte sequence
+       */
+      while (index > 0 && (ptr[index - 1] & 0x80))
+	{
+          index--;
+        }
+      buffer[index] = '\0';
+      return YES;
+    }
+  else if (isByteEncoding(encoding))
+    {
+      /* We want a single-byte encoding (ie ascii is a subset),
+       * so as long as this constant string is ascii, we can just
+       * copy directly.
+       */
+      if (maxLength <= length)
+        {
+          length = maxLength - 1;
+        }
+      for (index = 0; index < length; index++)
+        {
+          buffer[index] = (char)ptr[index];
+          if (ptr[index] & 0x80)
+            {
+              break;    // Not ascii 
+            }
+        }
+      if (index == length)
+        {
+          buffer[index] = '\0';
+          return YES;                   // All copied.
+        }
+      // Fall through to use superclass method.
+    }
+  return [super getCString: buffer maxLength: maxLength encoding: encoding];
+}
+
 /* Must match the implementation in NSString
  * To avoid allocating memory, we build the hash incrementally.
  */

Source/NSString.m

@@ -3665,6 +3665,7 @@ static BOOL             (*nbImp)(id, SEL, unichar) = 0;
 	  maxLength: (NSUInteger)maxLength
 	   encoding: (NSStringEncoding)encoding
 {
+  if (0 == maxLength || 0 == buffer) return NO;
   if (encoding == NSUnicodeStringEncoding)
     {
       unsigned	length = [self length];