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authorUlrich Drepper <drepper@redhat.com>1998-06-08 13:37:25 +0000
committerUlrich Drepper <drepper@redhat.com>1998-06-08 13:37:25 +0000
commit31f7410f5c413605f039e898151f01231f11efa5 (patch)
tree3c920d642b67b6d739877f2f22faf2d8b9ee6e84 /sysdeps/generic/getenv.c
parentc0fb8a563c1c49e5fbec9bc22deac618910a3ff4 (diff)
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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.
Diffstat (limited to 'sysdeps/generic/getenv.c')
-rw-r--r--sysdeps/generic/getenv.c68
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;
}