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From: Derrick Stolee <dstolee@microsoft.com>
To: git@vger.kernel.org
Cc: johannes.schindelin@gmx.de, git@jeffhostetler.com,
	kewillf@microsoft.com, Derrick Stolee <dstolee@microsoft.com>
Subject: [PATCH 3/3] sha1_name: Parse less while finding common prefix
Date: Fri, 15 Sep 2017 12:57:50 -0400	[thread overview]
Message-ID: <20170915165750.198201-4-dstolee@microsoft.com> (raw)
In-Reply-To: <20170915165750.198201-1-dstolee@microsoft.com>

Create get_hex_char_from_oid() to parse oids one hex character at a
time. This prevents unnecessary copying of hex characters in
extend_abbrev_len() when finding the length of a common prefix.

This change decreases the time to run test-abbrev by up to 40% on
large repos.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 sha1_name.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index f2a1ebe49..bb47b6702 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -480,13 +480,22 @@ struct min_abbrev_data {
 	char *hex;
 };
 
+static inline char get_hex_char_from_oid(const struct object_id *oid, int i)
+{
+	static const char hex[] = "0123456789abcdef";
+
+	if ((i & 1) == 0)
+		return hex[oid->hash[i >> 1] >> 4];
+	else
+		return hex[oid->hash[i >> 1] & 0xf];
+}
+
 static int extend_abbrev_len(const struct object_id *oid, void *cb_data)
 {
 	struct min_abbrev_data *mad = cb_data;
 
-	char *hex = oid_to_hex(oid);
 	unsigned int i = mad->init_len;
-	while (mad->hex[i] && mad->hex[i] == hex[i])
+	while (mad->hex[i] && mad->hex[i] == get_hex_char_from_oid(oid, i))
 		i++;
 
 	if (i < GIT_MAX_RAWSZ && i >= mad->cur_len)
-- 
2.14.1.538.g56ec8fc98.dirty


  parent reply	other threads:[~2017-09-15 16:58 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-09-15 16:57 [PATCH 0/3] Improve abbreviation disambiguation Derrick Stolee
2017-09-15 16:57 ` [PATCH 1/3] sha1_name: Create perf test for find_unique_abbrev() Derrick Stolee
2017-09-18  0:51   ` Junio C Hamano
2017-09-18 11:36     ` Derrick Stolee
2017-09-19  0:51       ` Junio C Hamano
2017-09-15 16:57 ` [PATCH 2/3] sha1_name: Unroll len loop in find_unique_abbrev_r Derrick Stolee
2017-09-15 16:57 ` Derrick Stolee [this message]
2017-09-15 17:08 ` [PATCH 0/3] Improve abbreviation disambiguation Jonathan Nieder

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