# [PATCH 2/3] Micro-optimize prepare_alt_odb

1 messages from 2007-05-26 to 2007-05-26. Participants: Shawn O. Pearce.
Thread: https://gitlist.dev/t/8321

## Shawn O. Pearce, 2007-05-26 05:24

Subject: [PATCH 2/3] Micro-optimize prepare_alt_odb
Message-ID: <20070526052440.GB11957@spearce.org>
URL: https://gitlist.dev/e/20070526052440.GB11957%40spearce.org

```
Calling getenv() is not that expensive, but its also not free,
and its certainly not cheaper than testing to see if alt_odb_tail
is not null.

Because we are calling prepare_alt_odb() from within find_sha1_file
every time we cannot find an object file locally we want to skip out
of prepare_alt_odb() as early as possible once we have initialized
our alternate list.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
---
 sha1_file.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/sha1_file.c b/sha1_file.c
index 6a5ba63..a3637d7 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -376,11 +376,12 @@ void prepare_alt_odb(void)
 {
 	const char *alt;
 
+	if (alt_odb_tail)
+		return;
+
 	alt = getenv(ALTERNATE_DB_ENVIRONMENT);
 	if (!alt) alt = "";
 
-	if (alt_odb_tail)
-		return;
 	alt_odb_tail = &alt_odb_list;
 	link_alt_odb_entries(alt, alt + strlen(alt), ':', NULL, 0);
 
-- 
1.5.2.789.g8ee1

```