sha1: provide another level of indirection for the SHA-1 functions

The git source uses git_SHA1_Update() and friends to call into the
code that computes the hashes.  Traditionally, we used to map these
directly to underlying implementation of the SHA-1 hash (e.g.
SHA1_Update() from OpenSSL or blk_SHA1_Update() from block-sha1/).

This arrangement however makes it hard to tweak behaviour of the
underlying implementation without fully replacing.  If we want to
introduce a tweaked_SHA1_Update() wrapper to implement the "Update"
in a slightly different way, for example, the implementation of the
wrapper still would want to call into the underlying implementation,
but tweaked_SHA1_Update() cannot call git_SHA1_Update() to get to
the underlying implementation (often but not always SHA1_Update()).

Add another level of indirection that maps platform_SHA1_Update()
and friends to their underlying implementations, and by default make
git_SHA1_Update() and friends map to platform_SHA1_* functions.

Doing it this way will later allow us to map git_SHA1_Update() to
tweaked_SHA1_Update(), and the latter can use platform_SHA1_Update()
in its implementation.

Signed-off-by: Atousa Pahlevan Duprat <apahlevan@ieee.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 4 insertions, 4 deletions

diff --git a/block-sha1/sha1.h b/block-sha1/sha1.h
index b864df623e..4df6747752 100644
--- a/block-sha1/sha1.h
+++ b/block-sha1/sha1.h
@@ -16,7 +16,7 @@ void blk_SHA1_Init(blk_SHA_CTX *ctx);
 void blk_SHA1_Update(blk_SHA_CTX *ctx, const void *dataIn, unsigned long len);
 void blk_SHA1_Final(unsigned char hashout[20], blk_SHA_CTX *ctx);
 
-#define git_SHA_CTX	blk_SHA_CTX
-#define git_SHA1_Init	blk_SHA1_Init
-#define git_SHA1_Update	blk_SHA1_Update
-#define git_SHA1_Final	blk_SHA1_Final
+#define platform_SHA_CTX	blk_SHA_CTX
+#define platform_SHA1_Init	blk_SHA1_Init
+#define platform_SHA1_Update	blk_SHA1_Update
+#define platform_SHA1_Final	blk_SHA1_Final