[src/trunk]: src/lib/libc/stdlib Double the size of the allocate environment ...

[tron <tron%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/f1decf8fe0d2
branches:  trunk
changeset: 758179:f1decf8fe0d2
user:      tron <tron%NetBSD.org@localhost>
date:      Sun Oct 24 17:53:27 2010 +0000

description:
Double the size of the allocate environment vector when we resize it.
This should speed up extending the environment via setenv(3).

diffstat:

 lib/libc/stdlib/getenv.c |  37 +++++++++++++++++++++++--------------
 1 files changed, 23 insertions(+), 14 deletions(-)

diffs (81 lines):

diff -r 4bbc6bdfc219 -r f1decf8fe0d2 lib/libc/stdlib/getenv.c
--- a/lib/libc/stdlib/getenv.c  Sun Oct 24 17:44:32 2010 +0000
+++ b/lib/libc/stdlib/getenv.c  Sun Oct 24 17:53:27 2010 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: getenv.c,v 1.25 2010/10/02 10:51:07 tron Exp $ */
+/*     $NetBSD: getenv.c,v 1.26 2010/10/24 17:53:27 tron Exp $ */
 
 /*
  * Copyright (c) 1987, 1993
@@ -34,7 +34,7 @@
 #if 0
 static char sccsid[] = "@(#)getenv.c   8.1 (Berkeley) 6/4/93";
 #else
-__RCSID("$NetBSD: getenv.c,v 1.25 2010/10/02 10:51:07 tron Exp $");
+__RCSID("$NetBSD: getenv.c,v 1.26 2010/10/24 17:53:27 tron Exp $");
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -105,7 +105,7 @@
 __allocenv(int offset)
 {
        char **p;
-       size_t nl;
+       size_t required_len, new_len;
 
        if (offset == -1 || saveenv != environ) {
                char **ptr;
@@ -113,33 +113,42 @@
                        offset++;
        }
 
-       nl = offset + 2;        /* one for potentially new entry one for NULL */
-       if (nl <= environ_malloced_len && saveenv == environ)
+       /* one for potentially new entry one for NULL */
+       required_len = offset + 2;
+
+       if (required_len <= environ_malloced_len && saveenv == environ)
                return 0;
 
+       /* Make sure we at least double the size of the arrays. */
+       new_len = (environ_malloced_len >= 16) ?
+           (environ_malloced_len << 1) : 16;
+       while (new_len < required_len)
+               new_len = new_len << 1;
+
        if (saveenv == environ) {               /* just increase size */
-               if ((p = realloc(saveenv, nl * sizeof(*p))) == NULL)
+               if ((p = realloc(saveenv, new_len * sizeof(*p))) == NULL)
                        return -1;
                (void)memset(&p[environ_malloced_len], 0,
-                   (nl - environ_malloced_len) * sizeof(*p));
+                   (new_len - environ_malloced_len) * sizeof(*p));
                saveenv = p;
        } else {                                /* get new space */
                free(saveenv);
-               if ((saveenv = malloc(nl * sizeof(*saveenv))) == NULL)
+               if ((saveenv = malloc(new_len * sizeof(*saveenv))) == NULL)
                        return -1;
-               (void)memcpy(saveenv, environ, (nl - 2) * sizeof(*saveenv));
-               saveenv[nl - 2] = NULL;
-               saveenv[nl - 1] = NULL;
+               (void)memcpy(saveenv, environ,
+                   (required_len - 2) * sizeof(*saveenv));
+               (void)memset(&saveenv[required_len - 2], 0,
+                   (new_len - (required_len - 2)) * sizeof(*saveenv));
        }
        environ = saveenv;
 
-       p = realloc(__environ_malloced, nl * sizeof(*p));
+       p = realloc(__environ_malloced, new_len * sizeof(*p));
        if (p == NULL)
                return -1;
 
        (void)memset(&p[environ_malloced_len], 0,
-           (nl - environ_malloced_len) * sizeof(*p));
-       environ_malloced_len = nl;
+           (new_len - environ_malloced_len) * sizeof(*p));
+       environ_malloced_len = new_len;
        __environ_malloced = p;
 
        return 0;