From f6b26e770ffae621408532c5b2c1aae4fa1c9e49 Mon Sep 17 00:00:00 2001
From: Michael Schubert <schu@schu.io>
Date: Fri, 27 Jul 2012 10:53:09 +0200
Subject: [PATCH] git_oid_cmp: inline memcmp by hand to optimize

git.git uses an inlined hashcmp function instead of memcmp, since it
performes much better when comparing hashes (most hashes compared
diverge within the first byte).

Measurements and rationale for the curious reader:
http://thread.gmane.org/gmane.comp.version-control.git/172286
---
 include/git2/oid.h | 26 +++++++++++++++++++++++++-
 src/oid.c          |  5 -----
 src/oidmap.h       |  7 +------
 3 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/include/git2/oid.h b/include/git2/oid.h
index a05b40a37..d6b2d1e7f 100644
--- a/include/git2/oid.h
+++ b/include/git2/oid.h
@@ -136,7 +136,31 @@ GIT_EXTERN(void) git_oid_cpy(git_oid *out, const git_oid *src);
  * @param b second oid structure.
  * @return <0, 0, >0 if a < b, a == b, a > b.
  */
-GIT_EXTERN(int) git_oid_cmp(const git_oid *a, const git_oid *b);
+GIT_INLINE(int) git_oid_cmp(const git_oid *a, const git_oid *b)
+{
+	const unsigned char *sha1 = a->id;
+	const unsigned char *sha2 = b->id;
+	int i;
+
+	for (i = 0; i < GIT_OID_RAWSZ; i++, sha1++, sha2++) {
+		if (*sha1 != *sha2)
+			return *sha1 - *sha2;
+	}
+
+	return 0;
+}
+
+/**
+ * Compare two oid structures for equality
+ *
+ * @param a first oid structure.
+ * @param b second oid structure.
+ * @return true if equal, false otherwise
+ */
+GIT_INLINE(int) git_oid_equal(const git_oid *a, const git_oid *b)
+{
+	return !git_oid_cmp(a, b);
+}
 
 /**
  * Compare the first 'len' hexadecimal characters (packets of 4 bits)
diff --git a/src/oid.c b/src/oid.c
index 87756010b..556a2cf85 100644
--- a/src/oid.c
+++ b/src/oid.c
@@ -161,11 +161,6 @@ void git_oid_cpy(git_oid *out, const git_oid *src)
 	memcpy(out->id, src->id, sizeof(out->id));
 }
 
-int git_oid_cmp(const git_oid *a, const git_oid *b)
-{
-	return memcmp(a->id, b->id, sizeof(a->id));
-}
-
 int git_oid_ncmp(const git_oid *oid_a, const git_oid *oid_b, unsigned int len)
 {
 	const unsigned char *a = oid_a->id;
diff --git a/src/oidmap.h b/src/oidmap.h
index 5a0bab6ec..1791adb16 100644
--- a/src/oidmap.h
+++ b/src/oidmap.h
@@ -28,13 +28,8 @@ GIT_INLINE(khint_t) hash_git_oid(const git_oid *oid)
 	return h;
 }
 
-GIT_INLINE(int) hash_git_oid_equal(const git_oid *a, const git_oid *b)
-{
-	return (memcmp(a->id, b->id, sizeof(a->id)) == 0);
-}
-
 #define GIT__USE_OIDMAP \
-	__KHASH_IMPL(oid, static kh_inline, const git_oid *, void *, 1, hash_git_oid, hash_git_oid_equal)
+	__KHASH_IMPL(oid, static kh_inline, const git_oid *, void *, 1, hash_git_oid, git_oid_equal)
 
 #define git_oidmap_alloc() kh_init(oid)
 #define git_oidmap_free(h) kh_destroy(oid,h), h = NULL