Update.

1998-06-08 13:34  Ulrich Drepper  <drepper@cygnus.com>

	* elf/sprof.c: Implement call graph profiling.

	* sysdeps/generic/getenv.c: Optimize to use strncmp less often.

1998-06-07  Andreas Jaeger  <aj@arthur.rhein-neckar.de>

	* pwd/fgetpwent_r.c (__fgetpwent_r): Correct buffer overflow fix.
	* grp/fgetgrent_r.c (__fgetgrent_r): Likewise.
	* shadow/fgetspent_r.c (__fgetspent_r): Likewise.
	Noticed by Jake Garver <garver@valkyrie.net>.

1998-06-07  Andreas Schwab  <schwab@issan.informatik.uni-dortmund.de>

	* libio/genops.c (__underflow): Read character from read pointer
	as unsigned.
	(__uflow): Likewise.

1 files changed, 62 insertions, 6 deletions

diff --git a/sysdeps/generic/getenv.c b/sysdeps/generic/getenv.c
index 990ddfd..b6f405d 100644
--- a/sysdeps/generic/getenv.c
+++ b/sysdeps/generic/getenv.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1991, 1992, 1994, 1996 Free Software Foundation, Inc.
+/* Copyright (C) 1991, 1992, 1994, 1996, 1998 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -16,7 +16,9 @@
    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
    Boston, MA 02111-1307, USA.  */
 
+#include <endian.h>
 #include <errno.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
@@ -25,20 +27,74 @@
 #define	__environ	environ
 #endif
 
-/* Return the value of the environment variable NAME.  */
+/* Return the value of the environment variable NAME.  This implementation
+   is tuned a bit in that it assumes no environment variable has an empty
+   name which of course should always be true.  We have a special case for
+   one character names so that for the general case we can assume at least
+   two characters which we can access.  By doing this we can avoid using the
+   `strncmp' most of the time.  */
 char *
 getenv (name)
      const char *name;
 {
   const size_t len = strlen (name);
   char **ep;
+  uint16_t name_start;
 
-  if (__environ == NULL)
+  if (__environ == NULL || name[0] == '\0')
     return NULL;
 
-  for (ep = __environ; *ep != NULL; ++ep)
-    if (!strncmp (*ep, name, len) && (*ep)[len] == '=')
-      return &(*ep)[len + 1];
+  if (name[1] == '\0')
+    {
+      /* The name of the variable consists of only one character.  Therefore
+	 the first two characters of the environment entry are this character
+	 and a '=' character.  */
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+      name_start = ('=' << 8) | *(const unsigned char *) name;
+#else
+# if __BYTE_ORDER == __BIG_ENDIAN
+      name_start = '=' | ((*(const unsigned char *) name) << 8);
+# else
+ #error "Funny byte order."
+# endif
+#endif
+      for (ep = __environ; *ep != NULL; ++ep)
+	{
+#if _STRING_ARCH_unaligned
+	  uint16_t ep_start = *(uint16_t *) *ep;
+#else
+	  uint16_t ep_start = (((unsigned char *) *ep)[0]
+			       | (((unsigned char *) *ep)[1] << 8));
+#endif
+	  if (name_start == ep_start)
+	    return &(*ep)[2];
+	}
+    }
+  else
+    {
+#if _STRING_ARCH_unaligned
+      name_start = *(const uint16_t *) name;
+#else
+      name_start = (((const unsigned char *) name)[0]
+		    | (((const unsigned char *) name)[1] << 8));
+#endif
+      len -= 2;
+      name += 2;
+
+      for (ep = __environ; *ep != NULL; ++ep)
+	{
+#if _STRING_ARCH_unaligned
+	  uint16_t ep_start = *(uint16_t *) *ep;
+#else
+	  uint16_t ep_start = (((unsigned char *) *ep)[0]
+			       | (((unsigned char *) *ep)[1] << 8));
+#endif
+
+	  if (name_start == ep_start && !strncmp (*ep + 2, name, len)
+	      && (*ep)[len + 2] == '=')
+	    return &(*ep)[len + 3];
+	}
+    }
 
   return NULL;
 }