diff --git a/ChangeLog b/ChangeLog
index 945dbff57..3190bf7f5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,19 @@
+2004-05-14 Richard Frith-Macdonald <rfm@gnu.org>
+
+	* Source/GSFormat.h:
+	* Source/GSFormat.m:
+	* Source/GSPrivate.h:
+	* Source/GSString.m:
+	* Source/GSeq.h:
+	* Source/NSString.m:
+	Updates to allow GSFormat to write directly into an existing string
+	in either 16bit or 8bit format.  Also tidyups and modifications to
+	use temporary buffers on stack rather than malloc/free as long as
+	the buffers are reasonably sized.
+	* Source/benchmark.m: Trivial string format benchmarks ...
+	Performance improvement of 10% for initWithFormat and 90% for
+	appendFormat operations.
+
 2004-05-13 Richard Frith-Macdonald <rfm@gnu.org>
 
 	* Source/NSCalendarDate.m: ([initWithString:calendarFormat:locale:])
diff --git a/Source/GSFormat.h b/Source/GSFormat.h
index 4e4bbe1f8..4780d7f85 100644
--- a/Source/GSFormat.h
+++ b/Source/GSFormat.h
@@ -26,18 +26,12 @@
 #define __GSFormat_H_
 
 #include	<Foundation/NSZone.h>
+#include	"GSPrivate.h"
 
 @class	NSDictionary;
 
-typedef struct {
-  unichar	*buf;
-  size_t	len;
-  size_t	size;
-  NSZone	*z;
-} FormatBuf_t;
-
 void 
-GSFormat(FormatBuf_t *fb, const unichar *fmt, va_list ap, NSDictionary *loc);
+GSFormat(GSStr fb, const unichar *fmt, va_list ap, NSDictionary *loc);
 
 #endif
 
diff --git a/Source/GSFormat.m b/Source/GSFormat.m
index 917c34c73..24822c063 100644
--- a/Source/GSFormat.m
+++ b/Source/GSFormat.m
@@ -127,7 +127,7 @@ struct printf_info
 };
 
 /* Type of a printf specifier-handler function.
-   STREAM is the FormatBuf_t on which to write output.
+   STREAM is the GSStr on which to write output.
    INFO gives information about the format specification.
    ARGS is a vector of pointers to the argument data;
    the number of pointers will be the number returned
@@ -733,32 +733,8 @@ parse_one_spec (const unichar *format, size_t posn, struct printf_spec *spec,
 }
 
 
-#define	outchar(Ch)							      \
-  do									      \
-    {									      \
-      register const wint_t outc = (Ch);				      \
-      if (s->len+1 >= s->size) {					      \
-        s->size += s->size / 2;						      \
-	s->buf = NSZoneRealloc(s->z, s->buf, s->size*sizeof(s->buf[0]));      \
-      }                                                                       \
-      s->buf[s->len++] = outc;                                                \
-      ++done;								      \
-    }									      \
-  while (0)
-
-#define outstring(String, Len)						      \
-  do									      \
-    {									      \
-      unsigned i;							      \
-      									      \
-      if (s->len+((unsigned)(Len)) >= s->size) {			      \
-      	s->size += s->size/2 > ((unsigned)(Len))? s->size/2: (unsigned)(Len); \
-	s->buf = NSZoneRealloc(s->z, s->buf, s->size*sizeof(s->buf[0]));      \
-      }									      \
-      for (i=0; i < ((unsigned)(Len)); i++) s->buf[s->len++] = (String)[i];   \
-      done += (unsigned)(Len);						      \
-    }									      \
-  while (0)
+#define	outchar(Ch)		GSStrAppendUnichar(s, Ch)
+#define outstring(String, Len)	GSStrAppendUnichars(s, String, Len)
 
 /* For handling long_double and longlong we use the same flag.  If
    `long' and `long long' are effectively the same type define it to
@@ -787,7 +763,7 @@ static const unichar null[] = {'(','n','u','l','l',')','\0'};
 
 
 /* Handle unknown format specifier.  */
-static int printf_unknown (FormatBuf_t *, const struct printf_info *,
+static int printf_unknown (GSStr, const struct printf_info *,
 				const void *const *);
 
 /* Group digits of number string.  */
@@ -796,7 +772,7 @@ static unichar *group_number (unichar *, unichar *, const char *, NSString *);
 
 /* The function itself.  */
 void
-GSFormat (FormatBuf_t *s, const unichar *format, va_list ap,
+GSFormat (GSStr s, const unichar *format, va_list ap,
 NSDictionary *locale)
 {
   /* The character used as thousands separator.  */
@@ -866,12 +842,6 @@ NSDictionary *locale)
 #define CHAR_CLASS(Ch) (jump_table[(wint_t) (Ch) - ' '])
 # define JUMP_TABLE_TYPE const void *const
 
-  if (s->size == 0)
-    {
-      s->buf = NSZoneMalloc(s->z, 100*sizeof(unichar));
-      s->size = 100;
-    }
-
   /* Initialize local variables.  */
   done = 0;
   grouping = (const char *) -1;
@@ -1768,7 +1738,7 @@ NSDictionary *locale)
 	    /* Allocate dynamically an array which definitely is long
 	       enough for the wide character version.  */
 	    if (len < 8192
-	      || ((string = (unichar *) NSZoneMalloc(s->z, len * sizeof (unichar)))
+	      || ((string = (unichar *) NSZoneMalloc(s->_zone, len * sizeof (unichar)))
 		    == NULL))
 	      string = (unichar *) alloca (len * sizeof (unichar));
 	    else
@@ -1795,7 +1765,7 @@ NSDictionary *locale)
 	    /* Allocate dynamically an array which definitely is long
 	       enough for the wide character version.  */
 	    if (len < 8192
-	      || ((string = (unichar *) NSZoneMalloc(s->z, len * sizeof (unichar)))
+	      || ((string = (unichar *) NSZoneMalloc(s->_zone, len * sizeof (unichar)))
 		    == NULL))
 	      string = (unichar *) alloca (len * sizeof (unichar));
 	    else
@@ -1819,7 +1789,7 @@ NSDictionary *locale)
 	      PAD (' ');
 	  }
 	if (string_malloced)
-	  NSZoneFree(s->z, string);
+	  NSZoneFree(s->_zone, string);
       }
       break;
 
@@ -1851,7 +1821,7 @@ NSDictionary *locale)
 	    /* Allocate dynamically an array which definitely is long
 	       enough for the wide character version.  */
 	    if (len < 8192
-	      || ((string = (unichar *) NSZoneMalloc(s->z, len * sizeof (unichar)))
+	      || ((string = (unichar *) NSZoneMalloc(s->_zone, len * sizeof (unichar)))
 		    == NULL))
 	      string = (unichar *) alloca (len * sizeof (unichar));
 	    else
@@ -1875,7 +1845,7 @@ NSDictionary *locale)
 	      PAD (' ');
 	  }
 	if (string_malloced)
-	  NSZoneFree(s->z, string);
+	  NSZoneFree(s->_zone, string);
       }
       break;
 
@@ -1919,7 +1889,7 @@ all_done:
 /* Handle an unknown format specifier.  This prints out a canonicalized
    representation of the format spec itself.  */
 static int
-printf_unknown (FormatBuf_t *s, const struct printf_info *info,
+printf_unknown (GSStr s, const struct printf_info *info,
 		const void *const *args)
 
 {
diff --git a/Source/GSPrivate.h b/Source/GSPrivate.h
index 38505c93b..b8193f5f9 100644
--- a/Source/GSPrivate.h
+++ b/Source/GSPrivate.h
@@ -106,6 +106,42 @@ GS_EXPORT BOOL		GSIsByteEncoding(NSStringEncoding encoding);
 }
 @end
 
+/*
+ * GSMutableString - concrete mutable string, capable of changing its storage
+ * from holding 8-bit to 16-bit character set.
+ */
+@interface GSMutableString : NSMutableString
+{
+  union {
+    unichar		*u;
+    unsigned char	*c;
+  } _contents;
+  unsigned int	_count;
+  struct {
+    unsigned int	wide: 1;
+    unsigned int	free: 1;
+    unsigned int	unused: 2;
+    unsigned int	hash: 28;
+  } _flags;
+  NSZone	*_zone;
+  unsigned int	_capacity;
+}
+@end
+
+/*
+ * Typedef for access to internals of concrete string objects.
+ */
+typedef struct {
+  @defs(GSMutableString)
+} GSStr_t;
+typedef	GSStr_t	*GSStr;
+
+/*
+ * Functions to append to GSStr
+ */
+extern void GSStrAppendUnichar(GSStr s, unichar);
+extern void GSStrAppendUnichars(GSStr s, const unichar *u, unsigned l);
+
 /*
  * Enumeration for MacOS-X compatibility user defaults settings.
  * For efficiency, we save defaults information which is used by the
diff --git a/Source/GSString.m b/Source/GSString.m
index 8bc12479f..30ed0ea6c 100644
--- a/Source/GSString.m
+++ b/Source/GSString.m
@@ -180,35 +180,6 @@ instance.
 @end
 
 
-/*
- * GSMutableString - concrete mutable string, capable of changing its storage
- * from holding 8-bit to 16-bit character set.
- */
-@interface GSMutableString : NSMutableString
-{
-  union {
-    unichar		*u;
-    unsigned char	*c;
-  } _contents;
-  unsigned int	_count;
-  struct {
-    unsigned int	wide: 1;
-    unsigned int	free: 1;
-    unsigned int	unused: 2;
-    unsigned int	hash: 28;
-  } _flags;
-  NSZone	*_zone;
-  unsigned int	_capacity;
-}
-@end
-
-/*
- * Typedef for access to internals of concrete string objects.
- */
-typedef struct {
-  @defs(GSMutableString)
-} *ivars;
-
 /*
  *	Include sequence handling code with instructions to generate search
  *	and compare functions for NSString objects.
@@ -378,9 +349,9 @@ setup(void)
 - (id) initWithCharacters: (const unichar*)chars
 		   length: (unsigned)length
 {
-  ivars	me;
+  GSStr	me;
 
-  me = (ivars)NSAllocateObject(GSUnicodeInlineStringClass,
+  me = (GSStr)NSAllocateObject(GSUnicodeInlineStringClass,
     length*sizeof(unichar), GSObjCZone(self));
   me->_contents.u = (unichar*)&((GSUnicodeInlineString*)me)[1];
   me->_count = length;
@@ -397,9 +368,9 @@ setup(void)
 			 length: (unsigned)length
 		   freeWhenDone: (BOOL)flag
 {
-  ivars	me;
+  GSStr	me;
 
-  me = (ivars)NSAllocateObject(GSUnicodeBufferStringClass, 0, GSObjCZone(self));
+  me = (GSStr)NSAllocateObject(GSUnicodeBufferStringClass, 0, GSObjCZone(self));
   me->_contents.u = chars;
   me->_count = length;
   me->_flags.wide = 1;
@@ -418,9 +389,9 @@ setup(void)
 {
   if (defEnc == intEnc)
     {
-      ivars	me;
+      GSStr	me;
 
-      me = (ivars)NSAllocateObject(GSCInlineStringClass, length,
+      me = (GSStr)NSAllocateObject(GSCInlineStringClass, length,
 	GSObjCZone(self));
       me->_contents.c = (unsigned char*)&((GSCInlineString*)me)[1];
       me->_count = length;
@@ -451,9 +422,9 @@ setup(void)
 {
   if (defEnc == intEnc)
     {
-      ivars	me;
+      GSStr	me;
 
-      me = (ivars)NSAllocateObject(GSCBufferStringClass, 0, GSObjCZone(self));
+      me = (GSStr)NSAllocateObject(GSCBufferStringClass, 0, GSObjCZone(self));
       me->_contents.c = (unsigned char*)chars;
       me->_count = length;
       me->_flags.wide = 0;
@@ -492,7 +463,7 @@ setup(void)
 {
   unsigned	length;
   Class		c;
-  ivars		me;
+  GSStr		me;
 
   if (string == nil)
     [NSException raise: NSInvalidArgumentException
@@ -505,19 +476,19 @@ setup(void)
   length = [string length];
   if (GSObjCIsKindOf(c, GSCStringClass) == YES || c == NSConstantStringClass
     || (GSObjCIsKindOf(c, GSMutableStringClass) == YES
-      && ((ivars)string)->_flags.wide == 0))
+      && ((GSStr)string)->_flags.wide == 0))
     {
       /*
        * For a GSCString subclass, and ??ConstantString, or an 8-bit
        * GSMutableString, we can copy the bytes directly into a GSCString.
        */
-      me = (ivars)NSAllocateObject(GSCInlineStringClass,
+      me = (GSStr)NSAllocateObject(GSCInlineStringClass,
 	length, GSObjCZone(self));
       me->_contents.c = (unsigned char*)&((GSCInlineString*)me)[1];
       me->_count = length;
       me->_flags.wide = 0;
       me->_flags.free = 1;
-      memcpy(me->_contents.c, ((ivars)string)->_contents.c, length);
+      memcpy(me->_contents.c, ((GSStr)string)->_contents.c, length);
     }
   else if (GSObjCIsKindOf(c, GSUnicodeStringClass) == YES
     || GSObjCIsKindOf(c, GSMutableStringClass) == YES)
@@ -526,13 +497,13 @@ setup(void)
        * For a GSUnicodeString subclass, or a 16-bit GSMutableString,
        * we can copy the bytes directly into a GSUnicodeString.
        */
-      me = (ivars)NSAllocateObject(GSUnicodeInlineStringClass,
+      me = (GSStr)NSAllocateObject(GSUnicodeInlineStringClass,
 	length*sizeof(unichar), GSObjCZone(self));
       me->_contents.u = (unichar*)&((GSUnicodeInlineString*)me)[1];
       me->_count = length;
       me->_flags.wide = 1;
       me->_flags.free = 1;
-      memcpy(me->_contents.u, ((ivars)string)->_contents.u,
+      memcpy(me->_contents.u, ((GSStr)string)->_contents.u,
 	length*sizeof(unichar));
     }
   else
@@ -541,7 +512,7 @@ setup(void)
        * For a string with an unknown class, we can initialise by
        * having the string copy its content directly into our buffer.
        */
-      me = (ivars)NSAllocateObject(GSUnicodeInlineStringClass,
+      me = (GSStr)NSAllocateObject(GSUnicodeInlineStringClass,
 	length*sizeof(unichar), GSObjCZone(self));
       me->_contents.u = (unichar*)&((GSUnicodeInlineString*)me)[1];
       me->_count = length;
@@ -588,7 +559,7 @@ setup(void)
  */
 
 static inline char*
-UTF8String_c(ivars self)
+UTF8String_c(GSStr self)
 {
   unsigned char *r;
 
@@ -637,7 +608,7 @@ UTF8String_c(ivars self)
 }
 
 static inline char*
-UTF8String_u(ivars self)
+UTF8String_u(GSStr self)
 {
   unsigned	c = self->_count;
 
@@ -661,7 +632,7 @@ UTF8String_u(ivars self)
 }
 
 static inline BOOL
-boolValue_c(ivars self)
+boolValue_c(GSStr self)
 {
   if (self->_count == 0)
     {
@@ -698,7 +669,7 @@ boolValue_c(ivars self)
 }
 
 static inline BOOL
-boolValue_u(ivars self)
+boolValue_u(GSStr self)
 {
   if (self->_count == 0)
     {
@@ -734,7 +705,7 @@ boolValue_u(ivars self)
 }
 
 static inline BOOL
-canBeConvertedToEncoding_c(ivars self, NSStringEncoding enc)
+canBeConvertedToEncoding_c(GSStr self, NSStringEncoding enc)
 {
   if (enc == intEnc)
     {
@@ -749,15 +720,53 @@ canBeConvertedToEncoding_c(ivars self, NSStringEncoding enc)
 }
 
 static inline BOOL
-canBeConvertedToEncoding_u(ivars self, NSStringEncoding enc)
+canBeConvertedToEncoding_u(GSStr self, NSStringEncoding enc)
 {
-  BOOL	result = (*convertImp)((id)self, convertSel, enc);
+  BOOL	result = YES;
 
+  if (enc == NSISOLatin1StringEncoding)
+    {
+      unsigned	i;
+
+      /*
+       * If all the unicode characters are in the 0 to 255 range
+       * they are all latin1.
+       */
+      for (i = 0; i < self->_count; i++)
+	{
+	  if (self->_contents.u[i] > 255)
+	    {
+	      result = NO;
+	      break;
+	    }
+	}
+    }
+  else if (enc == NSASCIIStringEncoding)
+    {
+      unsigned	i;
+
+      /*
+       * If all the unicode characters are in the 0 to 127 range
+       * they are all ascii.
+       */
+      for (i = 0; i < self->_count; i++)
+	{
+	  if (self->_contents.u[i] > 127)
+	    {
+	      result = NO;
+	      break;
+	    }
+	}
+    }
+  else
+    {
+      result = (*convertImp)((id)self, convertSel, enc);
+    }
   return result;
 }
 
 static inline unichar
-characterAtIndex_c(ivars self, unsigned index)
+characterAtIndex_c(GSStr self, unsigned index)
 {
   unichar	c;
 
@@ -772,7 +781,7 @@ characterAtIndex_c(ivars self, unsigned index)
 }
 
 static inline unichar
-characterAtIndex_u(ivars self,unsigned index)
+characterAtIndex_u(GSStr self,unsigned index)
 {
   if (index >= self->_count)
     [NSException raise: NSRangeException format: @"Invalid index."];
@@ -780,7 +789,7 @@ characterAtIndex_u(ivars self,unsigned index)
 }
 
 static inline NSComparisonResult
-compare_c(ivars self, NSString *aString, unsigned mask, NSRange aRange)
+compare_c(GSStr self, NSString *aString, unsigned mask, NSRange aRange)
 {
   Class	c;
 
@@ -791,18 +800,18 @@ compare_c(ivars self, NSString *aString, unsigned mask, NSRange aRange)
 
   c = GSObjCClass(aString);
   if (GSObjCIsKindOf(c, GSUnicodeStringClass) == YES
-    || (c == GSMutableStringClass && ((ivars)aString)->_flags.wide == 1))
+    || (c == GSMutableStringClass && ((GSStr)aString)->_flags.wide == 1))
     return strCompCsUs((id)self, aString, mask, aRange);
   else if (GSObjCIsKindOf(c, GSCStringClass) == YES
     || c == NSConstantStringClass
-    || (c == GSMutableStringClass && ((ivars)aString)->_flags.wide == 0))
+    || (c == GSMutableStringClass && ((GSStr)aString)->_flags.wide == 0))
     return strCompCsCs((id)self, aString, mask, aRange);
   else
     return strCompCsNs((id)self, aString, mask, aRange);
 }
 
 static inline NSComparisonResult
-compare_u(ivars self, NSString *aString, unsigned mask, NSRange aRange)
+compare_u(GSStr self, NSString *aString, unsigned mask, NSRange aRange)
 {
   Class	c;
 
@@ -813,18 +822,18 @@ compare_u(ivars self, NSString *aString, unsigned mask, NSRange aRange)
 
   c = GSObjCClass(aString);
   if (GSObjCIsKindOf(c, GSUnicodeStringClass)
-    || (c == GSMutableStringClass && ((ivars)aString)->_flags.wide == 1))
+    || (c == GSMutableStringClass && ((GSStr)aString)->_flags.wide == 1))
     return strCompUsUs((id)self, aString, mask, aRange);
   else if (GSObjCIsKindOf(c, GSCStringClass)
     || c == NSConstantStringClass
-    || (c == GSMutableStringClass && ((ivars)aString)->_flags.wide == 0))
+    || (c == GSMutableStringClass && ((GSStr)aString)->_flags.wide == 0))
     return strCompUsCs((id)self, aString, mask, aRange);
   else
     return strCompUsNs((id)self, aString, mask, aRange);
 }
 
 static inline char*
-cString_c(ivars self)
+cString_c(GSStr self)
 {
   unsigned char *r;
 
@@ -873,7 +882,7 @@ cString_c(ivars self)
 }
 
 static inline char*
-cString_u(ivars self)
+cString_u(GSStr self)
 {
   unsigned	c = self->_count;
 
@@ -897,7 +906,7 @@ cString_u(ivars self)
 }
 
 static inline unsigned int
-cStringLength_c(ivars self)
+cStringLength_c(GSStr self)
 {
   if (defEnc == intEnc)
     {
@@ -939,7 +948,7 @@ cStringLength_c(ivars self)
 }
 
 static inline unsigned int
-cStringLength_u(ivars self)
+cStringLength_u(GSStr self)
 {
   unsigned	c = self->_count;
 
@@ -962,7 +971,7 @@ cStringLength_u(ivars self)
 }
 
 static inline NSData*
-dataUsingEncoding_c(ivars self, NSStringEncoding encoding, BOOL flag)
+dataUsingEncoding_c(GSStr self, NSStringEncoding encoding, BOOL flag)
 {
   unsigned	len = self->_count;
 
@@ -1027,7 +1036,7 @@ dataUsingEncoding_c(ivars self, NSStringEncoding encoding, BOOL flag)
 }
 
 static inline NSData*
-dataUsingEncoding_u(ivars self, NSStringEncoding encoding, BOOL flag)
+dataUsingEncoding_u(GSStr self, NSStringEncoding encoding, BOOL flag)
 {
   unsigned	len = self->_count;
 
@@ -1064,7 +1073,7 @@ dataUsingEncoding_u(ivars self, NSStringEncoding encoding, BOOL flag)
 extern BOOL GSScanDouble(unichar*, unsigned, double*);
 
 static inline double
-doubleValue_c(ivars self)
+doubleValue_c(GSStr self)
 {
   if (self->_count == 0)
     {
@@ -1084,7 +1093,7 @@ doubleValue_c(ivars self)
 }
 
 static inline double
-doubleValue_u(ivars self)
+doubleValue_u(GSStr self)
 {
   if (self->_count == 0)
     {
@@ -1100,7 +1109,7 @@ doubleValue_u(ivars self)
 }
 
 static inline void
-fillHole(ivars self, unsigned index, unsigned size)
+fillHole(GSStr self, unsigned index, unsigned size)
 {
   NSCAssert(size > 0, @"size <= zero");
   NSCAssert(index + size <= self->_count, @"index + size > length");
@@ -1121,7 +1130,7 @@ fillHole(ivars self, unsigned index, unsigned size)
 }
 
 static inline void
-getCharacters_c(ivars self, unichar *buffer, NSRange aRange)
+getCharacters_c(GSStr self, unichar *buffer, NSRange aRange)
 {
   unsigned	len = aRange.length;
 
@@ -1137,14 +1146,14 @@ getCharacters_c(ivars self, unichar *buffer, NSRange aRange)
 }
 
 static inline void
-getCharacters_u(ivars self, unichar *buffer, NSRange aRange)
+getCharacters_u(GSStr self, unichar *buffer, NSRange aRange)
 {
   memcpy(buffer, self->_contents.u + aRange.location,
     aRange.length*sizeof(unichar));
 }
 
 static inline void
-getCString_c(ivars self, char *buffer, unsigned int maxLength,
+getCString_c(GSStr self, char *buffer, unsigned int maxLength,
   NSRange aRange, NSRange *leftoverRange)
 {
   int len;
@@ -1177,7 +1186,7 @@ getCString_c(ivars self, char *buffer, unsigned int maxLength,
 }
 
 static inline void
-getCString_u(ivars self, char *buffer, unsigned int maxLength,
+getCString_u(GSStr self, char *buffer, unsigned int maxLength,
   NSRange aRange, NSRange *leftoverRange)
 {
   /* The primitive we have for converting from unicode, GSFromUnicode,
@@ -1259,7 +1268,7 @@ getCString_u(ivars self, char *buffer, unsigned int maxLength,
 }
 
 static inline int
-intValue_c(ivars self)
+intValue_c(GSStr self)
 {
   if (self->_count == 0)
     {
@@ -1277,7 +1286,7 @@ intValue_c(ivars self)
 }
 
 static inline int
-intValue_u(ivars self)
+intValue_u(GSStr self)
 {
   if (self->_count == 0)
     {
@@ -1295,7 +1304,7 @@ intValue_u(ivars self)
 }
 
 static inline BOOL
-isEqual_c(ivars self, id anObject)
+isEqual_c(GSStr self, id anObject)
 {
   Class	c;
 
@@ -1314,16 +1323,16 @@ isEqual_c(ivars self, id anObject)
   c = GSObjCClass(anObject);
   if (c == NSConstantStringClass)
     {
-      ivars	other = (ivars)anObject;
+      GSStr	other = (GSStr)anObject;
       NSRange	r = {0, self->_count};
 
       if (strCompCsCs((id)self, (id)other, 0, r) == NSOrderedSame)
 	return YES;
       return NO;
     }
-  else if (GSObjCIsKindOf(c, GSStringClass) == YES)
+  else if (GSObjCIsKindOf(c, GSStringClass) == YES || c == GSMutableStringClass)
     {
-      ivars	other = (ivars)anObject;
+      GSStr	other = (GSStr)anObject;
       NSRange	r = {0, self->_count};
 
       /*
@@ -1362,7 +1371,7 @@ isEqual_c(ivars self, id anObject)
 }
 
 static inline BOOL
-isEqual_u(ivars self, id anObject)
+isEqual_u(GSStr self, id anObject)
 {
   Class	c;
 
@@ -1381,16 +1390,16 @@ isEqual_u(ivars self, id anObject)
   c = GSObjCClass(anObject);
   if (c == NSConstantStringClass)
     {
-      ivars	other = (ivars)anObject;
+      GSStr	other = (GSStr)anObject;
       NSRange	r = {0, self->_count};
 
       if (strCompUsCs((id)self, (id)other, 0, r) == NSOrderedSame)
 	return YES;
       return NO;
     }
-  else if (GSObjCIsKindOf(c, GSStringClass) == YES)
+  else if (GSObjCIsKindOf(c, GSStringClass) == YES || c == GSMutableStringClass)
     {
-      ivars	other = (ivars)anObject;
+      GSStr	other = (GSStr)anObject;
       NSRange	r = {0, self->_count};
 
       /*
@@ -1429,7 +1438,7 @@ isEqual_u(ivars self, id anObject)
 }
 
 static inline const char*
-lossyCString_c(ivars self)
+lossyCString_c(GSStr self)
 {
   char *r;
 
@@ -1478,7 +1487,7 @@ lossyCString_c(ivars self)
 }
 
 static inline const char*
-lossyCString_u(ivars self)
+lossyCString_u(GSStr self)
 {
   unsigned	l = 0;
   unsigned char	*r = 0;
@@ -1488,75 +1497,150 @@ lossyCString_u(ivars self)
   return (const char*)r;
 }
 
-static inline void
-makeHole(ivars self, unsigned int index, unsigned int size)
+static void GSStrMakeSpace(GSStr s, unsigned size)
 {
   unsigned	want;
 
-  NSCAssert(size > 0, @"size < zero");
-  NSCAssert(index <= self->_count, @"index > length");
-
-  want = size + self->_count + 1;
-  if (want > self->_capacity)
+  want = size + s->_count + 1;
+  s->_capacity += s->_capacity/2;
+  if (want > s->_capacity)
     {
-      self->_capacity += self->_capacity/2;
-      if (want > self->_capacity)
+      s->_capacity = want;
+    }
+  if (s->_flags.free == 1)
+    {
+      /*
+       * If we own the character buffer, we can simply realloc.
+       */
+      if (s->_flags.wide == 1)
 	{
-	  self->_capacity = want;
+	  s->_contents.u = NSZoneRealloc(s->_zone,
+	    s->_contents.u, s->_capacity*sizeof(unichar));
 	}
-      if (self->_flags.free == 1)
+      else
 	{
-	  /*
-	   * If we own the character buffer, we can simply realloc.
-	   */
-	  if (self->_flags.wide == 1)
+	  s->_contents.c = NSZoneRealloc(s->_zone,
+	    s->_contents.c, s->_capacity);
+	}
+    }
+  else
+    {
+      /*
+       * If the initial data was not to be freed, we must allocate new
+       * buffer, copy the data, and set up the zone we are using.
+       */
+      if (s->_zone == 0)
+	{
+#if	GS_WITH_GC
+	  s->_zone = GSAtomicMallocZone();
+#else
+	  if (s->isa == 0)
 	    {
-	      self->_contents.u = NSZoneRealloc(self->_zone,
-		self->_contents.u, self->_capacity*sizeof(unichar));
+	      s->_zone = NSDefaultMallocZone();
 	    }
 	  else
 	    {
-	      self->_contents.c = NSZoneRealloc(self->_zone,
-		self->_contents.c, self->_capacity);
+	      s->_zone = GSObjCZone((NSString*)s);
+	    }
+#endif
+	}
+      if (s->_flags.wide == 1)
+	{
+	  unichar	*tmp = s->_contents.u;
+
+	  s->_contents.u = NSZoneMalloc(s->_zone,
+	    s->_capacity*sizeof(unichar));
+	  if (s->_count > 0)
+	    {
+	      memcpy(s->_contents.u, tmp, s->_count*sizeof(unichar));
 	    }
 	}
       else
 	{
-	  /*
-	   * If the initial data was not to be freed, we must allocate new
-	   * buffer, copy the data, and set up the zone we are using.
-	   */
-	  if (self->_zone == 0)
-	    {
-#if	GS_WITH_GC
-	      self->_zone = GSAtomicMallocZone();
-#else
-	      self->_zone = GSObjCZone((NSString*)self);
-#endif
-	    }
-	  if (self->_flags.wide == 1)
-	    {
-	      unichar	*tmp = self->_contents.u;
+	  unsigned char	*tmp = s->_contents.c;
 
-	      self->_contents.u = NSZoneMalloc(self->_zone,
-		self->_capacity*sizeof(unichar));
-	      if (self->_count > 0)
-		{
-		  memcpy(self->_contents.u, tmp, self->_count*sizeof(unichar));
-		}
-	    }
-	  else
+	  s->_contents.c = NSZoneMalloc(s->_zone, s->_capacity);
+	  if (s->_count > 0)
 	    {
-	      unsigned char	*tmp = self->_contents.c;
-
-	      self->_contents.c = NSZoneMalloc(self->_zone, self->_capacity);
-	      if (self->_count > 0)
-		{
-		  memcpy(self->_contents.c, tmp, self->_count);
-		}
+	      memcpy(s->_contents.c, tmp, s->_count);
 	    }
-	  self->_flags.free = 1;
 	}
+      s->_flags.free = 1;
+    }
+}
+
+static void GSStrWiden(GSStr s)
+{
+  unichar	*tmp = 0;
+  int		len = 0;
+
+  NSCAssert(s->_flags.wide == 0, @"string is not wide");
+
+  /*
+   * As a special case, where we are ascii or latin1 and the buffer size
+   * is big enough, we can widen to unicode without having to allocate
+   * more memory or call a character conversion function.
+   */
+  if (s->_count <= s->_capacity / 2)
+    {
+      if (intEnc == NSISOLatin1StringEncoding
+	|| intEnc == NSASCIIStringEncoding)
+	{
+	  len = s->_count;
+	  while (len-- > 0)
+	    {
+	      s->_contents.u[len] = s->_contents.c[len];
+	    }
+	  s->_capacity /= 2;
+	  s->_flags.wide = 1;
+	  return;
+	}
+    }
+
+  if (!s->_zone)
+    {
+#if GS_WITH_GC
+      s->_zone = GSAtomicMallocZone();
+#else
+      if (s->isa == 0)
+	{
+	  s->_zone = NSDefaultMallocZone();
+	}
+      else
+	{
+	  s->_zone = GSObjCZone((NSString*)s);
+	}
+#endif
+    }
+
+  if (!GSToUnicode(&tmp, &len, s->_contents.c, s->_count, intEnc, s->_zone, 0))
+    {
+      [NSException raise: NSInternalInconsistencyException
+		  format: @"widen of string failed"];
+    }
+  if (s->_flags.free == 1)
+    {
+      NSZoneFree(s->_zone, s->_contents.c);
+    }
+  else
+    {
+      s->_flags.free = 1;
+    }
+  s->_contents.u = tmp;
+  s->_flags.wide = 1;
+  s->_count = len;
+  s->_capacity = len;
+}
+
+static inline void
+makeHole(GSStr self, unsigned int index, unsigned int size)
+{
+  NSCAssert(size > 0, @"size < zero");
+  NSCAssert(index <= self->_count, @"index > length");
+
+  if (self->_count + size + 1 >= self->_capacity)
+    {
+      GSStrMakeSpace((GSStr)self, size);
     }
 
   if (index < self->_count)
@@ -1580,7 +1664,7 @@ makeHole(ivars self, unsigned int index, unsigned int size)
 }
 
 static inline NSRange
-rangeOfSequence_c(ivars self, unsigned anIndex)
+rangeOfSequence_c(GSStr self, unsigned anIndex)
 {
   if (anIndex >= self->_count)
     [NSException raise: NSRangeException format:@"Invalid location."];
@@ -1589,7 +1673,7 @@ rangeOfSequence_c(ivars self, unsigned anIndex)
 }
 
 static inline NSRange
-rangeOfSequence_u(ivars self, unsigned anIndex)
+rangeOfSequence_u(GSStr self, unsigned anIndex)
 {
   unsigned	start;
   unsigned	end;
@@ -1608,7 +1692,7 @@ rangeOfSequence_u(ivars self, unsigned anIndex)
 }
 
 static inline NSRange
-rangeOfCharacter_c(ivars self, NSCharacterSet *aSet, unsigned mask,
+rangeOfCharacter_c(GSStr self, NSCharacterSet *aSet, unsigned mask,
   NSRange aRange)
 {
   int		i;
@@ -1655,7 +1739,7 @@ rangeOfCharacter_c(ivars self, NSCharacterSet *aSet, unsigned mask,
 }
 
 static inline NSRange
-rangeOfCharacter_u(ivars self, NSCharacterSet *aSet, unsigned mask,
+rangeOfCharacter_u(GSStr self, NSCharacterSet *aSet, unsigned mask,
   NSRange aRange)
 {
   int		i;
@@ -1698,7 +1782,7 @@ rangeOfCharacter_u(ivars self, NSCharacterSet *aSet, unsigned mask,
 }
 
 static inline NSRange
-rangeOfString_c(ivars self, NSString *aString, unsigned mask, NSRange aRange)
+rangeOfString_c(GSStr self, NSString *aString, unsigned mask, NSRange aRange)
 {
   Class	c;
 
@@ -1709,18 +1793,18 @@ rangeOfString_c(ivars self, NSString *aString, unsigned mask, NSRange aRange)
 
   c = GSObjCClass(aString);
   if (GSObjCIsKindOf(c, GSUnicodeStringClass) == YES
-    || (c == GSMutableStringClass && ((ivars)aString)->_flags.wide == 1))
+    || (c == GSMutableStringClass && ((GSStr)aString)->_flags.wide == 1))
     return strRangeCsUs((id)self, aString, mask, aRange);
   else if (GSObjCIsKindOf(c, GSCStringClass) == YES
     || c == NSConstantStringClass
-    || (c == GSMutableStringClass && ((ivars)aString)->_flags.wide == 0))
+    || (c == GSMutableStringClass && ((GSStr)aString)->_flags.wide == 0))
     return strRangeCsCs((id)self, aString, mask, aRange);
   else
     return strRangeCsNs((id)self, aString, mask, aRange);
 }
 
 static inline NSRange
-rangeOfString_u(ivars self, NSString *aString, unsigned mask, NSRange aRange)
+rangeOfString_u(GSStr self, NSString *aString, unsigned mask, NSRange aRange)
 {
   Class	c;
 
@@ -1731,18 +1815,18 @@ rangeOfString_u(ivars self, NSString *aString, unsigned mask, NSRange aRange)
 
   c = GSObjCClass(aString);
   if (GSObjCIsKindOf(c, GSUnicodeStringClass) == YES
-    || (c == GSMutableStringClass && ((ivars)aString)->_flags.wide == 1))
+    || (c == GSMutableStringClass && ((GSStr)aString)->_flags.wide == 1))
     return strRangeUsUs((id)self, aString, mask, aRange);
   else if (GSObjCIsKindOf(c, GSCStringClass) == YES
     || c == NSConstantStringClass
-    || (c == GSMutableStringClass && ((ivars)aString)->_flags.wide == 0))
+    || (c == GSMutableStringClass && ((GSStr)aString)->_flags.wide == 0))
     return strRangeUsCs((id)self, aString, mask, aRange);
   else
     return strRangeUsNs((id)self, aString, mask, aRange);
 }
 
 static inline NSString*
-substring_c(ivars self, NSRange aRange)
+substring_c(GSStr self, NSRange aRange)
 {
   id	sub;
 
@@ -1765,7 +1849,7 @@ substring_c(ivars self, NSRange aRange)
 }
 
 static inline NSString*
-substring_u(ivars self, NSRange aRange)
+substring_u(GSStr self, NSRange aRange)
 {
   id	sub;
 
@@ -1792,25 +1876,22 @@ substring_u(ivars self, NSRange aRange)
  * Function to examine the given string and see if it is one of our concrete
  * string classes.  Converts the mutable string (self) from 8-bit to 16-bit
  * representation if necessary in order to contain the data in aString.
- * Returns a pointer to aStrings ivars if aString is a concrete class
+ * Returns a pointer to aStrings GSStr if aString is a concrete class
  * from which contents may be copied directly without conversion.
  */
-static inline ivars
-transmute(ivars self, NSString *aString)
+static inline GSStr
+transmute(GSStr self, NSString *aString)
 {
-  ivars	other;
-  BOOL	transmute;
+  GSStr	other = (GSStr)aString;
+  BOOL	transmute = YES;
   Class	c = GSObjCClass(aString);	// NB aString must not be nil
 
-  other = (ivars)aString;
-  transmute = YES;
-
   if (self->_flags.wide == 1)
     {
       /*
        * This is already a unicode string, so we don't need to transmute,
        * but we still need to know if the other string is a unicode
-       * string whose ivars we can access directly.
+       * string whose GSStr we can access directly.
        */
       transmute = NO;
       if (GSObjCIsKindOf(c, GSUnicodeStringClass) == NO
@@ -1829,7 +1910,7 @@ transmute(ivars self, NSString *aString)
 	{
 	  /*
 	   * The other string is also held in the internal 8-bit encoding,
-	   * so we don't need to transmute, and we can use its ivars.
+	   * so we don't need to transmute, and we can use its GSStr.
 	   */
 	  transmute = NO;
 	}
@@ -1839,7 +1920,7 @@ transmute(ivars self, NSString *aString)
 	  /*
 	   * The other string can be converted to the internal 8-bit encoding,
 	   * via the cString method, so we don't need to transmute, but we
-	   * can *not* use its ivars.
+	   * can *not* use its GSStr.
 	   * NB. If 'intEnc != defEnc' the cString method of the other string
 	   * will not return data in the internal encoding.
 	   */
@@ -1852,7 +1933,7 @@ transmute(ivars self, NSString *aString)
 	  /*
 	   * The other string can not be converted to the internal 8-bit
 	   * encoding, so we need to transmute, and will then be able to
-	   * use its ivars.
+	   * use its GSStr.
 	   */
 	  transmute = YES;
 	}
@@ -1861,7 +1942,7 @@ transmute(ivars self, NSString *aString)
 	  /*
 	   * The other string can not be converted to the internal 8-bit
 	   * character string, so we need to transmute, but even then we
-	   * will not be able to use the other strings ivars because that
+	   * will not be able to use the other strings GSStr because that
 	   * string is not a known GSString subclass.
 	   */
 	  other = 0;
@@ -1870,37 +1951,7 @@ transmute(ivars self, NSString *aString)
 
   if (transmute == YES)
     {
-      unichar	*tmp = 0;
-      int	len = 0;
-
-      if (!self->_zone)
-	{
-#if GS_WITH_GC
-	  self->_zone = GSAtomicMallocZone();
-#else
-	  self->_zone = GSObjCZone((NSString*)self);
-#endif
-	}
-
-      if (!GSToUnicode(&tmp, &len, self->_contents.c, self->_count, intEnc,
-		       self->_zone, 0))
-	{
-	  [NSException raise: NSInternalInconsistencyException
-		      format: @"transmute of string failed"];
-	  return 0;
-	}
-      if (self->_flags.free == 1)
-	{
-	  NSZoneFree(self->_zone, self->_contents.c);
-	}
-      else
-	{
-	  self->_flags.free = 1;
-	}
-      self->_contents.u = tmp;
-      self->_flags.wide = 1;
-      self->_count = len;
-      self->_capacity = len;
+      GSStrWiden((GSStr)self);
     }
 
   return other;
@@ -1964,50 +2015,50 @@ transmute(ivars self, NSString *aString)
 @implementation GSCString
 - (const char *) UTF8String
 {
-  return UTF8String_c((ivars)self);
+  return UTF8String_c((GSStr)self);
 }
 
 - (BOOL) boolValue
 {
-  return boolValue_c((ivars)self);
+  return boolValue_c((GSStr)self);
 }
 
 - (BOOL) canBeConvertedToEncoding: (NSStringEncoding)enc
 {
-  return canBeConvertedToEncoding_c((ivars)self, enc);
+  return canBeConvertedToEncoding_c((GSStr)self, enc);
 }
 
 - (unichar) characterAtIndex: (unsigned int)index
 {
-  return characterAtIndex_c((ivars)self, index);
+  return characterAtIndex_c((GSStr)self, index);
 }
 
 - (NSComparisonResult) compare: (NSString*)aString
 		       options: (unsigned int)mask
 			 range: (NSRange)aRange
 {
-  return compare_c((ivars)self, aString, mask, aRange);
+  return compare_c((GSStr)self, aString, mask, aRange);
 }
 
 - (const char *) cString
 {
-  return cString_c((ivars)self);
+  return cString_c((GSStr)self);
 }
 
 - (unsigned int) cStringLength
 {
-  return cStringLength_c((ivars)self);
+  return cStringLength_c((GSStr)self);
 }
 
 - (NSData*) dataUsingEncoding: (NSStringEncoding)encoding
 	 allowLossyConversion: (BOOL)flag
 {
-  return dataUsingEncoding_c((ivars)self, encoding, flag);
+  return dataUsingEncoding_c((GSStr)self, encoding, flag);
 }
 
 - (double) doubleValue
 {
-  return doubleValue_c((ivars)self);
+  return doubleValue_c((GSStr)self);
 }
 
 - (void) encodeWithCoder: (NSCoder*)aCoder
@@ -2029,30 +2080,30 @@ transmute(ivars self, NSString *aString)
 
 - (float) floatValue
 {
-  return doubleValue_c((ivars)self);
+  return doubleValue_c((GSStr)self);
 }
 
 - (void) getCharacters: (unichar*)buffer
 {
-  getCharacters_c((ivars)self, buffer, (NSRange){0, _count});
+  getCharacters_c((GSStr)self, buffer, (NSRange){0, _count});
 }
 
 - (void) getCharacters: (unichar*)buffer range: (NSRange)aRange
 {
   GS_RANGE_CHECK(aRange, _count);
-  getCharacters_c((ivars)self, buffer, aRange);
+  getCharacters_c((GSStr)self, buffer, aRange);
 }
 
 - (void) getCString: (char*)buffer
 {
-  getCString_c((ivars)self, buffer, NSMaximumStringLength,
+  getCString_c((GSStr)self, buffer, NSMaximumStringLength,
     (NSRange){0, _count}, 0);
 }
 
 - (void) getCString: (char*)buffer
 	  maxLength: (unsigned int)maxLength
 {
-  getCString_c((ivars)self, buffer, maxLength, (NSRange){0, _count}, 0);
+  getCString_c((GSStr)self, buffer, maxLength, (NSRange){0, _count}, 0);
 }
 
 - (void) getCString: (char*)buffer
@@ -2061,7 +2112,7 @@ transmute(ivars self, NSString *aString)
      remainingRange: (NSRange*)leftoverRange
 {
   GS_RANGE_CHECK(aRange, _count);
-  getCString_c((ivars)self, buffer, maxLength, aRange, leftoverRange);
+  getCString_c((GSStr)self, buffer, maxLength, aRange, leftoverRange);
 }
 
 - (unsigned) hash
@@ -2075,17 +2126,17 @@ transmute(ivars self, NSString *aString)
 
 - (int) intValue
 {
-  return intValue_c((ivars)self);
+  return intValue_c((GSStr)self);
 }
 
 - (BOOL) isEqual: (id)anObject
 {
-  return isEqual_c((ivars)self, anObject);
+  return isEqual_c((GSStr)self, anObject);
 }
 
 - (BOOL) isEqualToString: (NSString*)anObject
 {
-  return isEqual_c((ivars)self, anObject);
+  return isEqual_c((GSStr)self, anObject);
 }
 
 - (unsigned int) length
@@ -2095,7 +2146,7 @@ transmute(ivars self, NSString *aString)
 
 - (const char*) lossyCString
 {
-  return lossyCString_c((ivars)self);
+  return lossyCString_c((GSStr)self);
 }
 
 - (id) mutableCopy
@@ -2119,7 +2170,7 @@ transmute(ivars self, NSString *aString)
 
 - (NSRange) rangeOfComposedCharacterSequenceAtIndex: (unsigned)anIndex
 {
-  return rangeOfSequence_c((ivars)self, anIndex);
+  return rangeOfSequence_c((GSStr)self, anIndex);
 }
 
 - (NSRange) rangeOfCharacterFromSet: (NSCharacterSet*)aSet
@@ -2127,14 +2178,14 @@ transmute(ivars self, NSString *aString)
 			      range: (NSRange)aRange
 {
   GS_RANGE_CHECK(aRange, _count);
-  return rangeOfCharacter_c((ivars)self, aSet, mask, aRange);
+  return rangeOfCharacter_c((GSStr)self, aSet, mask, aRange);
 }
 
 - (NSRange) rangeOfString: (NSString*)aString
 		  options: (unsigned)mask
 		    range: (NSRange)aRange
 {
-  return rangeOfString_c((ivars)self, aString, mask, aRange);
+  return rangeOfString_c((GSStr)self, aString, mask, aRange);
 }
 
 - (NSStringEncoding) smallestEncoding
@@ -2145,13 +2196,13 @@ transmute(ivars self, NSString *aString)
 - (NSString*) substringFromRange: (NSRange)aRange
 {
   GS_RANGE_CHECK(aRange, _count);
-  return substring_c((ivars)self, aRange);
+  return substring_c((GSStr)self, aRange);
 }
 
 - (NSString*) substringWithRange: (NSRange)aRange
 {
   GS_RANGE_CHECK(aRange, _count);
-  return substring_c((ivars)self, aRange);
+  return substring_c((GSStr)self, aRange);
 }
 
 // private method for Unicode level 3 implementation
@@ -2283,50 +2334,50 @@ agree, create a new GSCInlineString otherwise.
 @implementation GSUnicodeString
 - (const char *) UTF8String
 {
-  return UTF8String_u((ivars)self);
+  return UTF8String_u((GSStr)self);
 }
 
 - (BOOL) boolValue
 {
-  return boolValue_u((ivars)self);
+  return boolValue_u((GSStr)self);
 }
 
 - (BOOL) canBeConvertedToEncoding: (NSStringEncoding)enc
 {
-  return canBeConvertedToEncoding_u((ivars)self, enc);
+  return canBeConvertedToEncoding_u((GSStr)self, enc);
 }
 
 - (unichar) characterAtIndex: (unsigned int)index
 {
-  return characterAtIndex_u((ivars)self, index);
+  return characterAtIndex_u((GSStr)self, index);
 }
 
 - (NSComparisonResult) compare: (NSString*)aString
 		       options: (unsigned int)mask
 			 range: (NSRange)aRange
 {
-  return compare_u((ivars)self, aString, mask, aRange);
+  return compare_u((GSStr)self, aString, mask, aRange);
 }
 
 - (const char *) cString
 {
-  return cString_u((ivars)self);
+  return cString_u((GSStr)self);
 }
 
 - (unsigned int) cStringLength
 {
-  return cStringLength_u((ivars)self);
+  return cStringLength_u((GSStr)self);
 }
 
 - (NSData*) dataUsingEncoding: (NSStringEncoding)encoding
 	 allowLossyConversion: (BOOL)flag
 {
-  return dataUsingEncoding_u((ivars)self, encoding, flag);
+  return dataUsingEncoding_u((GSStr)self, encoding, flag);
 }
 
 - (double) doubleValue
 {
-  return doubleValue_u((ivars)self);
+  return doubleValue_u((GSStr)self);
 }
 
 - (void) encodeWithCoder: (NSCoder*)aCoder
@@ -2350,30 +2401,30 @@ agree, create a new GSCInlineString otherwise.
 
 - (float) floatValue
 {
-  return doubleValue_u((ivars)self);
+  return doubleValue_u((GSStr)self);
 }
 
 - (void) getCharacters: (unichar*)buffer
 {
-  getCharacters_u((ivars)self, buffer, (NSRange){0, _count});
+  getCharacters_u((GSStr)self, buffer, (NSRange){0, _count});
 }
 
 - (void) getCharacters: (unichar*)buffer range: (NSRange)aRange
 {
   GS_RANGE_CHECK(aRange, _count);
-  getCharacters_u((ivars)self, buffer, aRange);
+  getCharacters_u((GSStr)self, buffer, aRange);
 }
 
 - (void) getCString: (char*)buffer
 {
-  getCString_u((ivars)self, buffer, NSMaximumStringLength,
+  getCString_u((GSStr)self, buffer, NSMaximumStringLength,
     (NSRange){0, _count}, 0);
 }
 
 - (void) getCString: (char*)buffer
 	  maxLength: (unsigned int)maxLength
 {
-  getCString_u((ivars)self, buffer, maxLength, (NSRange){0, _count}, 0);
+  getCString_u((GSStr)self, buffer, maxLength, (NSRange){0, _count}, 0);
 }
 
 - (void) getCString: (char*)buffer
@@ -2383,7 +2434,7 @@ agree, create a new GSCInlineString otherwise.
 {
   GS_RANGE_CHECK(aRange, _count);
 
-  getCString_u((ivars)self, buffer, maxLength, aRange, leftoverRange);
+  getCString_u((GSStr)self, buffer, maxLength, aRange, leftoverRange);
 }
 
 - (unsigned) hash
@@ -2397,17 +2448,17 @@ agree, create a new GSCInlineString otherwise.
 
 - (int) intValue
 {
-  return intValue_u((ivars)self);
+  return intValue_u((GSStr)self);
 }
 
 - (BOOL) isEqual: (id)anObject
 {
-  return isEqual_u((ivars)self, anObject);
+  return isEqual_u((GSStr)self, anObject);
 }
 
 - (BOOL) isEqualToString: (NSString*)anObject
 {
-  return isEqual_u((ivars)self, anObject);
+  return isEqual_u((GSStr)self, anObject);
 }
 
 - (unsigned int) length
@@ -2417,7 +2468,7 @@ agree, create a new GSCInlineString otherwise.
 
 - (const char*) lossyCString
 {
-  return lossyCString_u((ivars)self);
+  return lossyCString_u((GSStr)self);
 }
 
 - (id) mutableCopy
@@ -2441,7 +2492,7 @@ agree, create a new GSCInlineString otherwise.
 
 - (NSRange) rangeOfComposedCharacterSequenceAtIndex: (unsigned)anIndex
 {
-  return rangeOfSequence_u((ivars)self, anIndex);
+  return rangeOfSequence_u((GSStr)self, anIndex);
 }
 
 - (NSRange) rangeOfCharacterFromSet: (NSCharacterSet*)aSet
@@ -2449,14 +2500,14 @@ agree, create a new GSCInlineString otherwise.
 			      range: (NSRange)aRange
 {
   GS_RANGE_CHECK(aRange, _count);
-  return rangeOfCharacter_u((ivars)self, aSet, mask, aRange);
+  return rangeOfCharacter_u((GSStr)self, aSet, mask, aRange);
 }
 
 - (NSRange) rangeOfString: (NSString*)aString
 		  options: (unsigned)mask
 		    range: (NSRange)aRange
 {
-  return rangeOfString_u((ivars)self, aString, mask, aRange);
+  return rangeOfString_u((GSStr)self, aString, mask, aRange);
 }
 
 - (NSStringEncoding) smallestEncoding
@@ -2467,13 +2518,13 @@ agree, create a new GSCInlineString otherwise.
 - (NSString*) substringFromRange: (NSRange)aRange
 {
   GS_RANGE_CHECK(aRange, _count);
-  return substring_u((ivars)self, aRange);
+  return substring_u((GSStr)self, aRange);
 }
 
 - (NSString*) substringWithRange: (NSRange)aRange
 {
   GS_RANGE_CHECK(aRange, _count);
-  return substring_u((ivars)self, aRange);
+  return substring_u((GSStr)self, aRange);
 }
 
 // private method for Unicode level 3 implementation
@@ -2630,73 +2681,42 @@ agree, create a new GSUnicodeInlineString otherwise.
 - (void) appendFormat: (NSString*)format, ...
 {
   va_list	ap;
+  unichar	buf[1024];
+  unichar	*fmt = buf;
+  size_t	len;
 
   va_start(ap, format);
+
   /*
-   * If this is a unicode string, we can write the formatted data directly
-   * into its buffer.
+   * Make sure we have the format string in a nul terminated array of
+   * unichars for passing to GSFormat.  Use on-stack memory for performance
+   * unless the size of the format string is really big (a rare occurrance).
    */
-  if (_flags.wide == 1)
+  len = [format length];
+  if (len >= 1024)
     {
-      FormatBuf_t	f;
-      unichar		*fmt;
-      size_t		len;
-
-      len = [format length];
       fmt = objc_malloc((len+1)*sizeof(unichar));
-      [format getCharacters: fmt];
-      fmt[len] = '\0';
-      /*
-       * If the buffer can't be freed, replace it with one which can before
-       * we attempt to append to the string (and possibly extend buffer)
-       */
-      if (_flags.free == NO)
-	{
-	  unichar	*u;
-
-	  if (_zone == 0)
-	    {
-	      _zone = [self zone];
-	    }
-	  u = NSZoneMalloc(_zone, _capacity * sizeof(unichar));
-	  memcpy(u, _contents.u, _count * sizeof(unichar));
-	  _contents.u = u;
-	  _flags.free = YES;
-	}
-      f.z = _zone;
-      f.buf = _contents.u;
-      f.len = _count;
-      f.size = _capacity;
-      GSFormat(&f, fmt, ap, nil);
-      _contents.u = f.buf;
-      _count = f.len;
-      _capacity = f.size;
-      _flags.hash = 0;
-      objc_free(fmt);
     }
-  else
-    {
-      NSRange	aRange;
-      NSString	*t;
+  [format getCharacters: fmt];
+  fmt[len] = '\0';
 
-      /*
-       * Get the abstract class to give us the default placeholder string.
-       */
-      t = (NSString*)[NSStringClass allocWithZone: NSDefaultMallocZone()];
-      /*
-       * Now initialise with the format information ... the placeholder
-       * can decide whether to create a concrete 8-bit character string
-       * or unicode string.
-       */
-      t = [t initWithFormat: format arguments: ap];
-      /*
-       * Now append the created string to this one ... the appending
-       * method will make this string wide if necessary.
-       */
-      aRange.location = _count;
-      aRange.length = 0;
-      [self replaceCharactersInRange: aRange withString: t];
-      RELEASE(t);
+  /*
+   * If no zone is set, make sure we have one so any memory mangement
+   * (buffer growth) is done with the correct zone.
+   */
+  if (_zone == 0)
+    {
+#if	GS_WITH_GC
+      _zone = GSAtomicMallocZone();
+#else
+      _zone = GSObjCZone(self);
+#endif
+    }
+  GSFormat((GSStr)self, fmt, ap, nil);
+  _flags.hash = 0;	// Invalidate the hash for this string.
+  if (fmt != buf)
+    {
+      objc_free(fmt);
     }
   va_end(ap);
 }
@@ -2704,25 +2724,25 @@ agree, create a new GSUnicodeInlineString otherwise.
 - (BOOL) boolValue
 {
   if (_flags.wide == 1)
-    return boolValue_u((ivars)self);
+    return boolValue_u((GSStr)self);
   else
-    return boolValue_c((ivars)self);
+    return boolValue_c((GSStr)self);
 }
 
 - (BOOL) canBeConvertedToEncoding: (NSStringEncoding)enc
 {
   if (_flags.wide == 1)
-    return canBeConvertedToEncoding_u((ivars)self, enc);
+    return canBeConvertedToEncoding_u((GSStr)self, enc);
   else
-    return canBeConvertedToEncoding_c((ivars)self, enc);
+    return canBeConvertedToEncoding_c((GSStr)self, enc);
 }
 
 - (unichar) characterAtIndex: (unsigned int)index
 {
   if (_flags.wide == 1)
-    return characterAtIndex_u((ivars)self, index);
+    return characterAtIndex_u((GSStr)self, index);
   else
-    return characterAtIndex_c((ivars)self, index);
+    return characterAtIndex_c((GSStr)self, index);
 }
 
 - (NSComparisonResult) compare: (NSString*)aString
@@ -2730,9 +2750,9 @@ agree, create a new GSUnicodeInlineString otherwise.
 			 range: (NSRange)aRange
 {
   if (_flags.wide == 1)
-    return compare_u((ivars)self, aString, mask, aRange);
+    return compare_u((GSStr)self, aString, mask, aRange);
   else
-    return compare_c((ivars)self, aString, mask, aRange);
+    return compare_c((GSStr)self, aString, mask, aRange);
 }
 
 - (id) copyWithZone: (NSZone*)z
@@ -2756,26 +2776,26 @@ agree, create a new GSUnicodeInlineString otherwise.
 - (const char *) cString
 {
   if (_flags.wide == 1)
-    return cString_u((ivars)self);
+    return cString_u((GSStr)self);
   else
-    return cString_c((ivars)self);
+    return cString_c((GSStr)self);
 }
 
 - (unsigned int) cStringLength
 {
   if (_flags.wide == 1)
-    return cStringLength_u((ivars)self);
+    return cStringLength_u((GSStr)self);
   else
-    return cStringLength_c((ivars)self);
+    return cStringLength_c((GSStr)self);
 }
 
 - (NSData*) dataUsingEncoding: (NSStringEncoding)encoding
 	 allowLossyConversion: (BOOL)flag
 {
   if (_flags.wide == 1)
-    return dataUsingEncoding_u((ivars)self, encoding, flag);
+    return dataUsingEncoding_u((GSStr)self, encoding, flag);
   else
-    return dataUsingEncoding_c((ivars)self, encoding, flag);
+    return dataUsingEncoding_c((GSStr)self, encoding, flag);
 }
 
 - (void) dealloc
@@ -2794,16 +2814,16 @@ agree, create a new GSUnicodeInlineString otherwise.
   GS_RANGE_CHECK(range, _count);
   if (range.length > 0)
     {
-      fillHole((ivars)self, range.location, range.length);
+      fillHole((GSStr)self, range.location, range.length);
     }
 }
 
 - (double) doubleValue
 {
   if (_flags.wide == 1)
-    return doubleValue_u((ivars)self);
+    return doubleValue_u((GSStr)self);
   else
-    return doubleValue_c((ivars)self);
+    return doubleValue_c((GSStr)self);
 }
 
 - (void) encodeWithCoder: (NSCoder*)aCoder
@@ -2841,17 +2861,17 @@ agree, create a new GSUnicodeInlineString otherwise.
 - (float) floatValue
 {
   if (_flags.wide == 1)
-    return doubleValue_u((ivars)self);
+    return doubleValue_u((GSStr)self);
   else
-    return doubleValue_c((ivars)self);
+    return doubleValue_c((GSStr)self);
 }
 
 - (void) getCharacters: (unichar*)buffer
 {
   if (_flags.wide == 1)
-    getCharacters_u((ivars)self, buffer, (NSRange){0, _count});
+    getCharacters_u((GSStr)self, buffer, (NSRange){0, _count});
   else
-    getCharacters_c((ivars)self, buffer, (NSRange){0, _count});
+    getCharacters_c((GSStr)self, buffer, (NSRange){0, _count});
 }
 
 - (void) getCharacters: (unichar*)buffer range: (NSRange)aRange
@@ -2859,21 +2879,21 @@ agree, create a new GSUnicodeInlineString otherwise.
   GS_RANGE_CHECK(aRange, _count);
   if (_flags.wide == 1)
     {
-      getCharacters_u((ivars)self, buffer, aRange);
+      getCharacters_u((GSStr)self, buffer, aRange);
     }
   else
     {
-      getCharacters_c((ivars)self, buffer, aRange);
+      getCharacters_c((GSStr)self, buffer, aRange);
     }
 }
 
 - (void) getCString: (char*)buffer
 {
   if (_flags.wide == 1)
-    getCString_u((ivars)self, buffer, NSMaximumStringLength,
+    getCString_u((GSStr)self, buffer, NSMaximumStringLength,
       (NSRange){0, _count}, 0);
   else
-    getCString_c((ivars)self, buffer, NSMaximumStringLength,
+    getCString_c((GSStr)self, buffer, NSMaximumStringLength,
       (NSRange){0, _count}, 0);
 }
 
@@ -2881,9 +2901,9 @@ agree, create a new GSUnicodeInlineString otherwise.
 	  maxLength: (unsigned int)maxLength
 {
   if (_flags.wide == 1)
-    getCString_u((ivars)self, buffer, maxLength, (NSRange){0, _count}, 0);
+    getCString_u((GSStr)self, buffer, maxLength, (NSRange){0, _count}, 0);
   else
-    getCString_c((ivars)self, buffer, maxLength, (NSRange){0, _count}, 0);
+    getCString_c((GSStr)self, buffer, maxLength, (NSRange){0, _count}, 0);
 }
 
 - (void) getCString: (char*)buffer
@@ -2894,11 +2914,11 @@ agree, create a new GSUnicodeInlineString otherwise.
   GS_RANGE_CHECK(aRange, _count);
   if (_flags.wide == 1)
     {
-      getCString_u((ivars)self, buffer, maxLength, aRange, leftoverRange);
+      getCString_u((GSStr)self, buffer, maxLength, aRange, leftoverRange);
     }
   else
     {
-      getCString_c((ivars)self, buffer, maxLength, aRange, leftoverRange);
+      getCString_c((GSStr)self, buffer, maxLength, aRange, leftoverRange);
     }
 }
 
@@ -3007,25 +3027,25 @@ agree, create a new GSUnicodeInlineString otherwise.
 - (int) intValue
 {
   if (_flags.wide == 1)
-    return intValue_u((ivars)self);
+    return intValue_u((GSStr)self);
   else
-    return intValue_c((ivars)self);
+    return intValue_c((GSStr)self);
 }
 
 - (BOOL) isEqual: (id)anObject
 {
   if (_flags.wide == 1)
-    return isEqual_u((ivars)self, anObject);
+    return isEqual_u((GSStr)self, anObject);
   else
-    return isEqual_c((ivars)self, anObject);
+    return isEqual_c((GSStr)self, anObject);
 }
 
 - (BOOL) isEqualToString: (NSString*)anObject
 {
   if (_flags.wide == 1)
-    return isEqual_u((ivars)self, anObject);
+    return isEqual_u((GSStr)self, anObject);
   else
-    return isEqual_c((ivars)self, anObject);
+    return isEqual_c((GSStr)self, anObject);
 }
 
 - (unsigned int) length
@@ -3036,9 +3056,9 @@ agree, create a new GSUnicodeInlineString otherwise.
 - (const char*) lossyCString
 {
   if (_flags.wide == 1)
-    return lossyCString_u((ivars)self);
+    return lossyCString_u((GSStr)self);
   else
-    return lossyCString_c((ivars)self);
+    return lossyCString_c((GSStr)self);
 }
 
 - (id) makeImmutableCopyOnFail: (BOOL)force
@@ -3090,9 +3110,9 @@ agree, create a new GSUnicodeInlineString otherwise.
 - (NSRange) rangeOfComposedCharacterSequenceAtIndex: (unsigned)anIndex
 {
   if (_flags.wide == 1)
-    return rangeOfSequence_u((ivars)self, anIndex);
+    return rangeOfSequence_u((GSStr)self, anIndex);
   else
-    return rangeOfSequence_c((ivars)self, anIndex);
+    return rangeOfSequence_c((GSStr)self, anIndex);
 }
 
 - (NSRange) rangeOfCharacterFromSet: (NSCharacterSet*)aSet
@@ -3101,9 +3121,9 @@ agree, create a new GSUnicodeInlineString otherwise.
 {
   GS_RANGE_CHECK(aRange, _count);
   if (_flags.wide == 1)
-    return rangeOfCharacter_u((ivars)self, aSet, mask, aRange);
+    return rangeOfCharacter_u((GSStr)self, aSet, mask, aRange);
   else
-    return rangeOfCharacter_c((ivars)self, aSet, mask, aRange);
+    return rangeOfCharacter_c((GSStr)self, aSet, mask, aRange);
 }
 
 - (NSRange) rangeOfString: (NSString*)aString
@@ -3111,15 +3131,15 @@ agree, create a new GSUnicodeInlineString otherwise.
 		    range: (NSRange)aRange
 {
   if (_flags.wide == 1)
-    return rangeOfString_u((ivars)self, aString, mask, aRange);
+    return rangeOfString_u((GSStr)self, aString, mask, aRange);
   else
-    return rangeOfString_c((ivars)self, aString, mask, aRange);
+    return rangeOfString_c((GSStr)self, aString, mask, aRange);
 }
 
 - (void) replaceCharactersInRange: (NSRange)aRange
 		       withString: (NSString*)aString
 {
-  ivars		other = 0;
+  GSStr		other = 0;
   int		offset;
   unsigned	length = 0;
 
@@ -3145,16 +3165,16 @@ agree, create a new GSUnicodeInlineString otherwise.
    */
   if (length > 0)
     {
-      other = transmute((ivars)self, aString);
+      other = transmute((GSStr)self, aString);
     }
 
   if (offset < 0)
     {
-      fillHole((ivars)self, NSMaxRange(aRange) + offset, -offset);
+      fillHole((GSStr)self, NSMaxRange(aRange) + offset, -offset);
     }
   else if (offset > 0)
     {
-      makeHole((ivars)self, NSMaxRange(aRange), (unsigned int)offset);
+      makeHole((GSStr)self, NSMaxRange(aRange), (unsigned int)offset);
     }
 
   if (length > 0)
@@ -3228,17 +3248,17 @@ agree, create a new GSUnicodeInlineString otherwise.
 - (void) setString: (NSString*)aString
 {
   unsigned int	len = (aString == nil) ? 0 : [aString length];
-  ivars	other;
+  GSStr	other;
 
   if (len == 0)
     {
       _count = 0;
       return;
     }
-  other = transmute((ivars)self, aString);
+  other = transmute((GSStr)self, aString);
   if (_count < len)
     {
-      makeHole((ivars)self, _count, (unsigned int)(len - _count));
+      makeHole((GSStr)self, _count, (unsigned int)(len - _count));
     }
   else
     {
@@ -3543,53 +3563,53 @@ agree, create a new GSUnicodeInlineString otherwise.
 
 - (BOOL) canBeConvertedToEncoding: (NSStringEncoding)enc
 {
-  if (((ivars)_parent)->_flags.wide == 1)
-    return canBeConvertedToEncoding_u((ivars)_parent, enc);
+  if (((GSStr)_parent)->_flags.wide == 1)
+    return canBeConvertedToEncoding_u((GSStr)_parent, enc);
   else
-    return canBeConvertedToEncoding_c((ivars)_parent, enc);
+    return canBeConvertedToEncoding_c((GSStr)_parent, enc);
 }
 
 - (unichar) characterAtIndex: (unsigned int)index
 {
-  if (((ivars)_parent)->_flags.wide == 1)
-    return characterAtIndex_u((ivars)_parent, index);
+  if (((GSStr)_parent)->_flags.wide == 1)
+    return characterAtIndex_u((GSStr)_parent, index);
   else
-    return characterAtIndex_c((ivars)_parent, index);
+    return characterAtIndex_c((GSStr)_parent, index);
 }
 
 - (NSComparisonResult) compare: (NSString*)aString
 		       options: (unsigned int)mask
 			 range: (NSRange)aRange
 {
-  if (((ivars)_parent)->_flags.wide == 1)
-    return compare_u((ivars)_parent, aString, mask, aRange);
+  if (((GSStr)_parent)->_flags.wide == 1)
+    return compare_u((GSStr)_parent, aString, mask, aRange);
   else
-    return compare_c((ivars)_parent, aString, mask, aRange);
+    return compare_c((GSStr)_parent, aString, mask, aRange);
 }
 
 - (const char *) cString
 {
-  if (((ivars)_parent)->_flags.wide == 1)
-    return cString_u((ivars)_parent);
+  if (((GSStr)_parent)->_flags.wide == 1)
+    return cString_u((GSStr)_parent);
   else
-    return cString_c((ivars)_parent);
+    return cString_c((GSStr)_parent);
 }
 
 - (unsigned int) cStringLength
 {
-  if (((ivars)_parent)->_flags.wide == 1)
-    return cStringLength_u((ivars)_parent);
+  if (((GSStr)_parent)->_flags.wide == 1)
+    return cStringLength_u((GSStr)_parent);
   else
-    return cStringLength_c((ivars)_parent);
+    return cStringLength_c((GSStr)_parent);
 }
 
 - (NSData*) dataUsingEncoding: (NSStringEncoding)encoding
 	 allowLossyConversion: (BOOL)flag
 {
-  if (((ivars)_parent)->_flags.wide == 1)
-    return dataUsingEncoding_u((ivars)_parent, encoding, flag);
+  if (((GSStr)_parent)->_flags.wide == 1)
+    return dataUsingEncoding_u((GSStr)_parent, encoding, flag);
   else
-    return dataUsingEncoding_c((ivars)_parent, encoding, flag);
+    return dataUsingEncoding_c((GSStr)_parent, encoding, flag);
 }
 
 - (void) encodeWithCoder: (NSCoder*)aCoder
@@ -3599,7 +3619,7 @@ agree, create a new GSUnicodeInlineString otherwise.
 
 - (NSStringEncoding) fastestEncoding
 {
-  if (((ivars)_parent)->_flags.wide == 1)
+  if (((GSStr)_parent)->_flags.wide == 1)
     return NSUnicodeStringEncoding;
   else
     return intEnc;
@@ -3607,101 +3627,101 @@ agree, create a new GSUnicodeInlineString otherwise.
 
 - (void) getCharacters: (unichar*)buffer
 {
-  if (((ivars)_parent)->_flags.wide == 1)
+  if (((GSStr)_parent)->_flags.wide == 1)
     {
-      getCharacters_u((ivars)_parent, buffer,
-	(NSRange){0, ((ivars)_parent)->_count});
+      getCharacters_u((GSStr)_parent, buffer,
+	(NSRange){0, ((GSStr)_parent)->_count});
     }
   else
     {
-      getCharacters_c((ivars)_parent, buffer,
-	(NSRange){0, ((ivars)_parent)->_count});
+      getCharacters_c((GSStr)_parent, buffer,
+	(NSRange){0, ((GSStr)_parent)->_count});
     }
 }
 
 - (void) getCharacters: (unichar*)buffer range: (NSRange)aRange
 {
-  GS_RANGE_CHECK(aRange, ((ivars)_parent)->_count);
-  if (((ivars)_parent)->_flags.wide == 1)
+  GS_RANGE_CHECK(aRange, ((GSStr)_parent)->_count);
+  if (((GSStr)_parent)->_flags.wide == 1)
     {
-      getCharacters_u((ivars)_parent, buffer, aRange);
+      getCharacters_u((GSStr)_parent, buffer, aRange);
     }
   else
     {
-      getCharacters_c((ivars)_parent, buffer, aRange);
+      getCharacters_c((GSStr)_parent, buffer, aRange);
     }
 }
 
 - (unsigned) hash
 {
-  if (((ivars)_parent)->_flags.hash == 0)
+  if (((GSStr)_parent)->_flags.hash == 0)
     {
-      ((ivars)_parent)->_flags.hash = (*hashImp)((id)_parent, hashSel);
+      ((GSStr)_parent)->_flags.hash = (*hashImp)((id)_parent, hashSel);
     }
-  return ((ivars)_parent)->_flags.hash;
+  return ((GSStr)_parent)->_flags.hash;
 }
 
 - (BOOL) isEqual: (id)anObject
 {
-  if (((ivars)_parent)->_flags.wide == 1)
-    return isEqual_u((ivars)_parent, anObject);
+  if (((GSStr)_parent)->_flags.wide == 1)
+    return isEqual_u((GSStr)_parent, anObject);
   else
-    return isEqual_c((ivars)_parent, anObject);
+    return isEqual_c((GSStr)_parent, anObject);
 }
 
 - (BOOL) isEqualToString: (NSString*)anObject
 {
-  if (((ivars)_parent)->_flags.wide == 1)
-    return isEqual_u((ivars)_parent, anObject);
+  if (((GSStr)_parent)->_flags.wide == 1)
+    return isEqual_u((GSStr)_parent, anObject);
   else
-    return isEqual_c((ivars)_parent, anObject);
+    return isEqual_c((GSStr)_parent, anObject);
 }
 
 - (unsigned int) length
 {
-  return ((ivars)_parent)->_count;
+  return ((GSStr)_parent)->_count;
 }
 
 - (const char*) lossyCString
 {
-  if (((ivars)_parent)->_flags.wide == 1)
-    return lossyCString_u((ivars)_parent);
+  if (((GSStr)_parent)->_flags.wide == 1)
+    return lossyCString_u((GSStr)_parent);
   else
-    return lossyCString_c((ivars)_parent);
+    return lossyCString_c((GSStr)_parent);
 }
 
 - (NSRange) rangeOfComposedCharacterSequenceAtIndex: (unsigned)anIndex
 {
-  if (((ivars)_parent)->_flags.wide == 1)
-    return rangeOfSequence_u((ivars)_parent, anIndex);
+  if (((GSStr)_parent)->_flags.wide == 1)
+    return rangeOfSequence_u((GSStr)_parent, anIndex);
   else
-    return rangeOfSequence_c((ivars)_parent, anIndex);
+    return rangeOfSequence_c((GSStr)_parent, anIndex);
 }
 
 - (NSRange) rangeOfCharacterFromSet: (NSCharacterSet*)aSet
 			    options: (unsigned)mask
 			      range: (NSRange)aRange
 {
-  GS_RANGE_CHECK(aRange, ((ivars)_parent)->_count);
-  if (((ivars)_parent)->_flags.wide == 1)
-    return rangeOfCharacter_u((ivars)_parent, aSet, mask, aRange);
+  GS_RANGE_CHECK(aRange, ((GSStr)_parent)->_count);
+  if (((GSStr)_parent)->_flags.wide == 1)
+    return rangeOfCharacter_u((GSStr)_parent, aSet, mask, aRange);
   else
-    return rangeOfCharacter_c((ivars)_parent, aSet, mask, aRange);
+    return rangeOfCharacter_c((GSStr)_parent, aSet, mask, aRange);
 }
 
 - (NSRange) rangeOfString: (NSString*)aString
 		  options: (unsigned)mask
 		    range: (NSRange)aRange
 {
-  if (((ivars)_parent)->_flags.wide == 1)
-    return rangeOfString_u((ivars)_parent, aString, mask, aRange);
+  if (((GSStr)_parent)->_flags.wide == 1)
+    return rangeOfString_u((GSStr)_parent, aString, mask, aRange);
   else
-    return rangeOfString_c((ivars)_parent, aString, mask, aRange);
+    return rangeOfString_c((GSStr)_parent, aString, mask, aRange);
 }
 
 - (NSStringEncoding) smallestEncoding
 {
-  if (((ivars)_parent)->_flags.wide == 1)
+  if (((GSStr)_parent)->_flags.wide == 1)
     {
       return NSUnicodeStringEncoding;
     }
@@ -3718,7 +3738,7 @@ agree, create a new GSUnicodeInlineString otherwise.
  * strings, as such its ivar layout is determined by the compiler
  * and consists of a pointer (_contents.c) and a character count
  * (_count).  So, while this class inherits GSCString behavior,
- * the code must make sure not to use any other GSCString ivars
+ * the code must make sure not to use any other GSCString GSStr
  * when accesssing an NXConstantString.</p>
  */
 @implementation NXConstantString
@@ -3736,7 +3756,7 @@ agree, create a new GSUnicodeInlineString otherwise.
  * Access instance variables of NXConstantString class consistently
  * with other concrete NSString subclasses.
  */
-#define _self	((ivars)self)
+#define _self	((GSStr)self)
 
 - (id) initWithCharacters: (unichar*)byteString
 		   length: (unsigned int)length
@@ -3864,9 +3884,9 @@ agree, create a new GSUnicodeInlineString otherwise.
 
   if (GSObjCIsKindOf(c, GSCStringClass) == YES
     || c == NSConstantStringClass
-    || (c == GSMutableStringClass && ((ivars)anObject)->_flags.wide == 0))
+    || (c == GSMutableStringClass && ((GSStr)anObject)->_flags.wide == 0))
     {
-      ivars	other = (ivars)anObject;
+      GSStr	other = (GSStr)anObject;
 
       if (_self->_count != other->_count)
 	return NO;
@@ -3914,9 +3934,9 @@ agree, create a new GSUnicodeInlineString otherwise.
 
   if (GSObjCIsKindOf(c, GSCStringClass) == YES
     || c == NSConstantStringClass
-    || (c == GSMutableStringClass && ((ivars)anObject)->_flags.wide == 0))
+    || (c == GSMutableStringClass && ((GSStr)anObject)->_flags.wide == 0))
     {
-      ivars	other = (ivars)anObject;
+      GSStr	other = (GSStr)anObject;
 
       if (_self->_count != other->_count)
 	return NO;
@@ -4074,3 +4094,113 @@ agree, create a new GSUnicodeInlineString otherwise.
 }
 @end
 
+
+/**
+ * Append characters to a string.
+ */
+void GSStrAppendUnichars(GSStr s, const unichar *u, unsigned l)
+{
+  /*
+   * Make the string wide if necessary.
+   */
+  if (s->_flags.wide == 0)
+    {
+      BOOL	widen = NO;
+
+      if (intEnc == NSISOLatin1StringEncoding)
+	{
+	  unsigned	i;
+
+	  for (i = 0; i < l; i++)
+	    {
+	      if (u[i] > 255)
+		{
+		  widen = YES;
+		  break;
+		}
+	    }
+	}
+      else
+	{
+	  unsigned	i;
+
+	  for (i = 0; i < l; i++)
+	    {
+	      if (u[i] > 127)
+		{
+		  widen = YES;
+		  break;
+		}
+	    }
+	}
+      if (widen == YES)
+	{
+	  GSStrWiden(s);
+	}
+    }
+
+  /*
+   * Make room for the characters we are appending.
+   */
+  if (s->_count + l + 1 >= s->_capacity)
+    {
+      GSStrMakeSpace(s, l);
+    }
+
+  /*
+   * Copy the characters into place.
+   */
+  if (s->_flags.wide == 1)
+    {
+      unsigned 	i;
+
+      for (i = 0; i < l; i++)
+	{
+	  s->_contents.u[s->_count++] = u[i];
+	}
+    }
+  else
+    {
+      unsigned 	i;
+
+      for (i = 0; i < l; i++)
+	{
+	  s->_contents.c[s->_count++] = u[i];
+	}
+    }
+}
+
+void GSStrAppendUnichar(GSStr s, unichar u)
+{
+  /*
+   * Make the string wide if necessary.
+   */
+  if (s->_flags.wide == 0)
+    {
+      if (u > 255 || (u > 127 && intEnc != NSISOLatin1StringEncoding))
+	{
+	  GSStrWiden(s);
+	}
+    }
+
+  /*
+   * Make room for the characters we are appending.
+   */
+  if (s->_count + 2 >= s->_capacity)
+    {
+      GSStrMakeSpace(s, 1);
+    }
+
+  /*
+   * Copy the characters into place.
+   */
+  if (s->_flags.wide == 1)
+    {
+      s->_contents.u[s->_count++] = u;
+    }
+  else
+    {
+      s->_contents.c[s->_count++] = u;
+    }
+}
+
diff --git a/Source/GSeq.h b/Source/GSeq.h
index 49f627fae..34513e929 100644
--- a/Source/GSeq.h
+++ b/Source/GSeq.h
@@ -290,14 +290,14 @@ static inline void GSeq_uppercase(GSeq seq)
  * Set up macros for dealing with 'self' on the basis of GSQ_S
  */
 #if	GSEQ_S == GSEQ_US
-#define	GSEQ_ST	ivars
+#define	GSEQ_ST	GSStr
 #define	GSEQ_SLEN	s->_count
 #define	GSEQ_SGETC(I)	s->_contents.u[I]
 #define	GSEQ_SGETR(B,R)	memcpy(B, &s->_contents.u[R.location], 2*(R).length)
 #define	GSEQ_SRANGE(I)	(*srImp)((id)s, ranSel, I)
 #else
 #if	GSEQ_S == GSEQ_CS
-#define	GSEQ_ST	ivars
+#define	GSEQ_ST	GSStr
 #define	GSEQ_SLEN	s->_count
 #define	GSEQ_SGETC(I)	(unichar)s->_contents.c[I]
 #define	GSEQ_SGETR(B,R)	( { \
@@ -322,14 +322,14 @@ static inline void GSeq_uppercase(GSeq seq)
  * Set up macros for dealing with 'other' string on the basis of GSQ_O
  */
 #if	GSEQ_O == GSEQ_US
-#define	GSEQ_OT	ivars
+#define	GSEQ_OT	GSStr
 #define	GSEQ_OLEN	o->_count
 #define	GSEQ_OGETC(I)	o->_contents.u[I]
 #define	GSEQ_OGETR(B,R)	memcpy(B, &o->_contents.u[R.location], 2*(R).length)
 #define	GSEQ_ORANGE(I)	(*orImp)((id)o, ranSel, I)
 #else
 #if	GSEQ_O == GSEQ_CS
-#define	GSEQ_OT	ivars
+#define	GSEQ_OT	GSStr
 #define	GSEQ_OLEN	o->_count
 #define	GSEQ_OGETC(I)	(unichar)o->_contents.c[I]
 #define	GSEQ_OGETR(B,R)	( { \
diff --git a/Source/NSString.m b/Source/NSString.m
index 105ac98fc..4b7716433 100644
--- a/Source/NSString.m
+++ b/Source/NSString.m
@@ -69,6 +69,7 @@
 // For private method _decodePropertyListForKey:
 #include "Foundation/NSKeyedArchiver.h"
 #include "GNUstepBase/GSMime.h"
+#include "GSPrivate.h"
 #include "GSFormat.h"
 #include <limits.h>
 #include <sys/stat.h>
@@ -1153,321 +1154,70 @@ handle_printf_atsign (FILE *stream,
                locale: (NSDictionary*)locale
             arguments: (va_list)argList
 {
-  FormatBuf_t	f;
-  unichar	*fmt;
+  unsigned char	buf[2048];
+  GSStr_t	f;
+  unichar	fbuf[1024];
+  unichar	*fmt = fbuf;
   size_t	len;
 
+  /*
+   * First we provide an array of unichar characters containing the
+   * format string.  For performance reasons we try to use an on-stack
+   * buffer if the format string is small enough ... it almost always
+   * will be.
+   */
   len = [format length];
-  fmt = objc_malloc((len+1)*sizeof(unichar));
+  if (len >= 1024)
+    {
+      fmt = objc_malloc((len+1)*sizeof(unichar));
+    }
   [format getCharacters: fmt];
   fmt[len] = '\0';
-  f.z = NSDefaultMallocZone();
-  f.buf = NSZoneMalloc(f.z, 100*sizeof(unichar));
-  f.len = 0;
-  f.size = 100;
+
+  /*
+   * Now set up 'f' as a GSMutableString object whose initial buffer is
+   * allocated on the stack.  The GSFormat function can write into it.
+   */
+  f.isa = GSMutableStringClass;
+  f._zone = NSDefaultMallocZone();
+  f._contents.c = buf;
+  f._capacity = sizeof(buf);
+  f._count = 0;
+  f._flags.wide = 0;
+  f._flags.free = 0;
   GSFormat(&f, fmt, argList, locale);
-  objc_free(fmt);
-  // don't use noCopy because f.size > f.len!
-  self = [self initWithCharacters: f.buf length: f.len];
-  NSZoneFree(f.z, f.buf);
-  return self;
-}
-
-#if 0
-/* xxx Change this when we have non-CString classes */
-- (id) initWithFormat: (NSString*)format
-               locale: (NSDictionary*)locale
-            arguments: (va_list)argList
-{
-#if defined(HAVE_VSPRINTF) || defined(HAVE_VASPRINTF)
-  const char *format_cp = [format lossyCString];
-  int format_len = strlen (format_cp);
-#ifdef HAVE_VASPRINTF
-  char *buf;
-  int printed_len = 0;
-  NSString *ret;
-
-#ifndef HAVE_REGISTER_PRINTF_FUNCTION
-  NSZone *z = GSObjCZone(self);
-
-  /* If the available libc doesn't have `register_printf_function()', then
-     the `%@' printf directive isn't available with printf() and friends.
-     Here we make a feable attempt to handle it. */
-  {
-    /* We need a local copy since we change it.  (Changing and undoing
-       the change doesn't work because some format strings are constant
-       strings, placed in a non-writable section of the executable, and
-       writing to them will cause a segfault.) */
-    char format_cp_copy[format_len+1];
-    char *atsign_pos;	     /* points to a location inside format_cp_copy */
-    char *format_to_go = format_cp_copy;
-    char *buf_l;
-#define _PRINTF_BUF_LEN 256
-    int printed_local_len, avail_len = _PRINTF_BUF_LEN;
-    int cstring_len;
-
-    buf = NSZoneMalloc(z, _PRINTF_BUF_LEN);
-    strcpy (format_cp_copy, format_cp);
-    /* Loop once for each `%@' in the format string. */
-    while ((atsign_pos = strstr (format_to_go, "%@")))
-      {
-        const char *cstring;
-        char *formatter_pos; // Position for formatter.
-
-        /* If there is a "%%@", then do the right thing: print it literally. */
-        if ((*(atsign_pos-1) == '%')
-            && atsign_pos != format_cp_copy)
-          continue;
-        /* Temporarily terminate the string before the `%@'. */
-        *atsign_pos = '\0';
-        /* Print the part before the '%@' */
-        printed_local_len = VASPRINTF_LENGTH (vasprintf (&buf_l,
-	  format_to_go, argList));
-        if(buf_l)
-          {
-            if(avail_len < printed_local_len+1)
-              {
-                NS_DURING
-                  {
-                    buf = NSZoneRealloc(z, buf,
-		      printed_len+printed_local_len+_PRINTF_BUF_LEN);
-                    avail_len += _PRINTF_BUF_LEN;
-                  }
-                NS_HANDLER
-                  {
-                    free(buf_l);
-                    [localException raise];
-                  }
-                NS_ENDHANDLER
-              }
-            memcpy(&buf[printed_len], buf_l, printed_local_len+1);
-            avail_len -= printed_local_len;
-            printed_len += printed_local_len;
-            free(buf_l);
-          }
-        else
-          {
-            [NSException raise: NSMallocException
-                        format: @"No available memory"];
-          }
-        /* Skip arguments used in last vsprintf(). */
-        while ((formatter_pos = strchr(format_to_go, '%')))
-          {
-            char *spec_pos; // Position of conversion specifier.
-
-            if (*(formatter_pos+1) == '%')
-              {
-                format_to_go = formatter_pos+2;
-                continue;
-              }
-            spec_pos = strpbrk(formatter_pos+1, "dioxXucsfeEgGpn\0");
-            switch (*spec_pos)
-              {
-#ifndef powerpc
-	      /* FIXME: vsprintf on powerpc apparently advances the arg list
-             so this doesn't need to be done. Make a more general check
-             for this */
-              case 'd': case 'i': case 'o':
-              case 'x': case 'X': case 'u': case 'c':
-                va_arg(argList, int);
-                break;
-              case 's':
-                if (*(spec_pos - 1) == '*')
-                  va_arg(argList, int*);
-                va_arg(argList, char*);
-                break;
-              case 'f': case 'e': case 'E': case 'g': case 'G':
-                va_arg(argList, double);
-                break;
-              case 'p':
-                va_arg(argList, void*);
-                break;
-              case 'n':
-                va_arg(argList, int*);
-                break;
-#endif /* NOT powerpc */
-              case '\0':
-                spec_pos--;
-                break;
-              }
-            format_to_go = spec_pos+1;
-          }
-        /* Get a C-string (char*) from the String object, and print it. */
-        cstring = [[(id) va_arg (argList, id) description] lossyCString];
-        if (!cstring)
-          cstring = "<null string>";
-        cstring_len = strlen(cstring);
-
-        if(cstring_len)
-          {
-            if(avail_len < cstring_len+1)
-              {
-                buf = NSZoneRealloc(z, buf,
-                                    printed_len+cstring_len+_PRINTF_BUF_LEN);
-                avail_len += _PRINTF_BUF_LEN;
-              }
-            memcpy(&buf[printed_len], cstring, cstring_len+1);
-            avail_len -= cstring_len;
-            printed_len += cstring_len;
-          }
-        /* Skip over this `%@', and look for another one. */
-        format_to_go = atsign_pos + 2;
-      }
-    /* Print the rest of the string after the last `%@'. */
-    printed_local_len = VASPRINTF_LENGTH (vasprintf (&buf_l,
-      format_to_go, argList));
-    if(buf_l)
-      {
-        if(avail_len < printed_local_len+1)
-          {
-            NS_DURING
-              {
-                buf = NSZoneRealloc(z, buf,
-		  printed_len+printed_local_len+_PRINTF_BUF_LEN);
-                avail_len += _PRINTF_BUF_LEN;
-              }
-            NS_HANDLER
-              {
-                free(buf_l);
-                [localException raise];
-              }
-            NS_ENDHANDLER
-          }
-        memcpy(&buf[printed_len], buf_l, printed_local_len+1);
-        avail_len -= printed_local_len;
-        printed_len += printed_local_len;
-        free(buf_l);
-      }
-    else
-      {
-        [NSException raise: NSMallocException
-                     format: @"No available memory"];
-      }
-  }
-#else /* HAVE_VSPRINTF */
-  /* The available libc has `register_printf_function()', so the `%@'
-     printf directive is handled by printf and friends. */
-  printed_len = VASPRINTF_LENGTH (vasprintf (&buf, format_cp, argList));
-
-  if(!buf)
+  if (fmt != fbuf)
     {
-      [NSException raise: NSMallocException
-                   format: @"No available memory"];
+      objc_free(fmt);
     }
-#endif /* !HAVE_REGISTER_PRINTF_FUNCTION */
 
-  ret = [self initWithCString: buf];
-#ifndef HAVE_REGISTER_PRINTF_FUNCTION
-  NSZoneFree(z, buf);
-#else
-  free(buf);
-#endif
-  return ret;
-#else
-  /* xxx horrible disgusting BUFFER_EXTRA arbitrary limit; fix this! */
-  #define BUFFER_EXTRA 1024*500
-  char buf[format_len + BUFFER_EXTRA];
-  int printed_len = 0;
+  /*
+   * Don't use noCopy because f._contents.u may be memory on the stack,
+   * and even if it wasn't f._capacity may be greater than f._count so
+   * we could be wasting quite a bit of space.  Better to accept a
+   * performance hit due to copying data (and allocating/deallocating
+   * the temporary buffer) for large strings.  For most strings, the
+   * on-stack memory will have been used, so we will get better performance.
+   */
+  if (f._flags.wide == 1)
+    {
+      self = [self initWithCharacters: f._contents.u length: f._count];
+    }
+  else
+    {
+      self = [self initWithCString: f._contents.c length: f._count];
+    }
 
-#ifndef HAVE_REGISTER_PRINTF_FUNCTION
-  /* If the available libc doesn't have `register_printf_function()', then
-     the `%@' printf directive isn't available with printf() and friends.
-     Here we make a feable attempt to handle it. */
-  {
-    /* We need a local copy since we change it.  (Changing and undoing
-       the change doesn't work because some format strings are constant
-       strings, placed in a non-writable section of the executable, and
-       writing to them will cause a segfault.) */
-    char format_cp_copy[format_len+1];
-    char *atsign_pos;	     /* points to a location inside format_cp_copy */
-    char *format_to_go = format_cp_copy;
-    strcpy (format_cp_copy, format_cp);
-    /* Loop once for each `%@' in the format string. */
-    while ((atsign_pos = strstr (format_to_go, "%@")))
-      {
-	const char *cstring;
-	char *formatter_pos; // Position for formatter.
-
-	/* If there is a "%%@", then do the right thing: print it literally. */
-	if ((*(atsign_pos-1) == '%')
-	    && atsign_pos != format_cp_copy)
-	  continue;
-	/* Temporarily terminate the string before the `%@'. */
-	*atsign_pos = '\0';
-	/* Print the part before the '%@' */
-	printed_len += VSPRINTF_LENGTH (vsprintf (buf+printed_len,
-						  format_to_go, argList));
-	/* Skip arguments used in last vsprintf(). */
-	while ((formatter_pos = strchr(format_to_go, '%')))
-	  {
-	    char *spec_pos; // Position of conversion specifier.
-
-	    if (*(formatter_pos+1) == '%')
-	      {
-		format_to_go = formatter_pos+2;
-		continue;
-	      }
-	    spec_pos = strpbrk(formatter_pos+1, "dioxXucsfeEgGpn\0");
-	    switch (*spec_pos)
-	      {
-#ifndef powerpc
-	      /* FIXME: vsprintf on powerpc apparently advances the arg list
-	      so this doesn't need to be done. Make a more general check
-	      for this */
-	      case 'd': case 'i': case 'o':
-	      case 'x': case 'X': case 'u': case 'c':
-		(void)va_arg(argList, int);
-		break;
-	      case 's':
-		if (*(spec_pos - 1) == '*')
-		  (void)va_arg(argList, int*);
-		(void)va_arg(argList, char*);
-		break;
-	      case 'f': case 'e': case 'E': case 'g': case 'G':
-		(void)va_arg(argList, double);
-		break;
-	      case 'p':
-		(void)va_arg(argList, void*);
-		break;
-	      case 'n':
-		(void)va_arg(argList, int*);
-		break;
-#endif /* NOT powerpc */
-	      case '\0':
-		spec_pos--;
-		break;
-	      }
-	    format_to_go = spec_pos+1;
-	  }
-	/* Get a C-string (char*) from the String object, and print it. */
-	cstring = [[(id) va_arg (argList, id) description] lossyCString];
-	if (!cstring)
-	  cstring = "<null string>";
-	strcat (buf+printed_len, cstring);
-	printed_len += strlen (cstring);
-	/* Skip over this `%@', and look for another one. */
-	format_to_go = atsign_pos + 2;
-      }
-    /* Print the rest of the string after the last `%@'. */
-    printed_len += VSPRINTF_LENGTH (vsprintf (buf+printed_len,
-					      format_to_go, argList));
-  }
-#else
-  /* The available libc has `register_printf_function()', so the `%@'
-     printf directive is handled by printf and friends. */
-  printed_len = VSPRINTF_LENGTH (vsprintf (buf, format_cp, argList));
-#endif /* !HAVE_REGISTER_PRINTF_FUNCTION */
-
-  /* Raise an exception if we overran our buffer. */
-  NSParameterAssert (printed_len < format_len + BUFFER_EXTRA - 1);
-  return [self initWithCString: buf];
-#endif /* HAVE_VASPRINTF */
-#else /* HAVE_VSPRINTF || HAVE_VASPRINTF */
-  [self notImplemented: _cmd];
+  /*
+   * If the string had to grow beyond the initial buffer size, we must
+   * release any allocated memory.
+   */
+  if (f._flags.free == 1)
+    {
+      NSZoneFree(f._zone, f._contents.c);
+    }
   return self;
-#endif
 }
-#endif
 
 /**
  * Initialises the receiver with the supplied data, using the
diff --git a/Testing/benchmark.m b/Testing/benchmark.m
index 7ce8a5a23..66fc4edbd 100755
--- a/Testing/benchmark.m
+++ b/Testing/benchmark.m
@@ -371,6 +371,7 @@ bench_str()
 {
   int i;
   NSString *str;
+  NSMutableString	*ms;
   id plist;
   NSString *plstr;
   Class	arc = [NSArchiver class];
@@ -408,6 +409,25 @@ bench_str()
   plstr = [plist description];
  
   printf("NSString\n");
+
+  START_TIMER;
+  for (i = 0; i < MAX_COUNT; i++)
+    {
+      str = [[stringClass alloc] initWithFormat: @"Hello %d", i];
+      RELEASE(str);
+    }
+  END_TIMER;
+  PRINT_TIMER("NSString (1 initWithFormat:) \t");
+
+  ms = [NSMutableString stringWithCapacity: 0];
+  START_TIMER;
+  for (i = 0; i < MAX_COUNT; i++)
+    {
+      [ms appendFormat: @"%d", i];
+    }
+  END_TIMER;
+  PRINT_TIMER("NSString (1 appendFormat:) \t\t");
+
   START_TIMER;
   for (i = 0; i < MAX_COUNT; i++)
     {