From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: libc-alpha@sourceware.org, Wilco Dijkstra <Wilco.Dijkstra@arm.com>
Subject: [PATCH 2/7] stdlib: Simplify getenv
Date: Mon, 13 Feb 2023 10:55:53 -0300 [thread overview]
Message-ID: <20230213135558.3328727-3-adhemerval.zanella@linaro.org> (raw)
In-Reply-To: <20230213135558.3328727-1-adhemerval.zanella@linaro.org>
And remove _STRING_ARCH_unaligned usage. The small size optimization
just adds boilerplate code.
Checked on x86_64-linux-gnu and i686-linux-gnu.
---
stdlib/getenv.c | 63 ++++---------------------------------------------
1 file changed, 4 insertions(+), 59 deletions(-)
diff --git a/stdlib/getenv.c b/stdlib/getenv.c
index e3157ce2f3..449bba1e16 100644
--- a/stdlib/getenv.c
+++ b/stdlib/getenv.c
@@ -15,76 +15,21 @@
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
-#include <endian.h>
-#include <errno.h>
-#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
-
-/* 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 (const char *name)
{
- char **ep;
- uint16_t name_start;
-
if (__environ == NULL || name[0] == '\0')
return NULL;
- 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 || !_STRING_ARCH_unaligned
- name_start = ('=' << 8) | *(const unsigned char *) name;
-#else
- name_start = '=' | ((*(const unsigned char *) name) << 8);
-#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
+ size_t len = __strchrnul (name, '=') - name;
+ for (char **ep = __environ; *ep != NULL; ++ep)
{
- size_t len = strlen (name);
-#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];
- }
+ if (strncmp (name, *ep, len) == 0 && (*ep)[len] == '=')
+ return *ep + len + 1;
}
return NULL;
--
2.34.1
next prev parent reply other threads:[~2023-02-13 13:56 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-13 13:55 [PATCH 0/7] Remove _STRING_ARCH_unaligned Adhemerval Zanella
2023-02-13 13:55 ` [PATCH 1/7] crypto: Remove _STRING_ARCH_unaligned usage Adhemerval Zanella
2023-02-15 17:55 ` Wilco Dijkstra
2023-02-13 13:55 ` Adhemerval Zanella [this message]
2023-02-15 17:50 ` [PATCH 2/7] stdlib: Simplify getenv Wilco Dijkstra
2023-02-16 13:49 ` Adhemerval Zanella Netto
2023-02-16 14:02 ` Andreas Schwab
2023-02-16 18:02 ` Wilco Dijkstra
2023-02-16 18:38 ` Adhemerval Zanella Netto
2023-02-16 18:47 ` Wilco Dijkstra
2023-02-16 19:29 ` Adhemerval Zanella Netto
2023-02-17 17:13 ` Wilco Dijkstra
2023-02-13 13:55 ` [PATCH 3/7] nscd: Remove _STRING_ARCH_unaligned usage Adhemerval Zanella
2023-02-15 17:59 ` Wilco Dijkstra
2023-02-13 13:55 ` [PATCH 4/7] resolv: " Adhemerval Zanella
2023-02-15 18:04 ` Wilco Dijkstra
2023-02-13 13:55 ` [PATCH 5/7] iconv: Remove _STRING_ARCH_unaligned usage for get/set macros Adhemerval Zanella
2023-02-13 14:05 ` Andreas Schwab
2023-02-15 18:34 ` Wilco Dijkstra
2023-02-13 13:55 ` [PATCH 6/7] iconv: Remove _STRING_ARCH_unaligned usage Adhemerval Zanella
2023-02-15 19:02 ` Wilco Dijkstra
2023-02-13 13:55 ` [PATCH 7/7] string: Remove string_private.h Adhemerval Zanella
2023-02-15 19:04 ` Wilco Dijkstra
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