sha256: add an SHA-256 implementation using libgcrypt
Generally, one gets better performance out of cryptographic routines
written in assembly than C, and this is also true for SHA-256. In
addition, most Linux distributions cannot distribute Git linked against
OpenSSL for licensing reasons.
Most systems with GnuPG will also have libgcrypt, since it is a
dependency of GnuPG. libgcrypt is also faster than the SHA1DC
implementation for messages of a few KiB and larger.
For comparison, on a Core i7-6600U, this implementation processes 16 KiB
chunks at 355 MiB/s while SHA1DC processes equivalent chunks at 337
MiB/s.
In addition, libgcrypt is licensed under the LGPL 2.1, which is
compatible with the GPL. Add an implementation of SHA-256 that uses
libgcrypt.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/hash.h b/hash.h
index a9bc624..2ef0980 100644
--- a/hash.h
+++ b/hash.h
@@ -15,7 +15,11 @@
#include "block-sha1/sha1.h"
#endif
+#if defined(SHA256_GCRYPT)
+#include "sha256/gcrypt.h"
+#else
#include "sha256/block/sha256.h"
+#endif
#ifndef platform_SHA_CTX
/*
