sha1: allow limiting the size of the data passed to SHA1_Update()ad/sha1-update-chunked

Using the previous commit's inredirection mechanism for SHA1,
support a chunked implementation of SHA1_Update() that limits the
amount of data in the chunk passed to SHA1_Update().

This is enabled by using the Makefile variable SHA1_MAX_BLOCK_SIZE
to specify chunk size.  When using Apple's CommonCrypto library this
is set to 1GiB (the implementation cannot handle more 4GiB).

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

3 files changed, 25 insertions, 0 deletions

diff --git a/compat/apple-common-crypto.h b/compat/apple-common-crypto.h
index c8b9b0e1a6..d3fb264181 100644
--- a/compat/apple-common-crypto.h
+++ b/compat/apple-common-crypto.h
@@ -16,6 +16,10 @@
 #undef TYPE_BOOL
 #endif
 
+#ifndef SHA1_MAX_BLOCK_SIZE
+#error Using Apple Common Crypto library requires setting SHA1_MAX_BLOCK_SIZE
+#endif
+
 #ifdef APPLE_LION_OR_NEWER
 #define git_CC_error_check(pattern, err) \
 	do { \
diff --git a/compat/sha1-chunked.c b/compat/sha1-chunked.c
new file mode 100644
index 0000000000..6adfcfd540
--- /dev/null
+++ b/compat/sha1-chunked.c
@@ -0,0 +1,19 @@
+#include "cache.h"
+
+int git_SHA1_Update_Chunked(platform_SHA_CTX *c, const void *data, size_t len)
+{
+	size_t nr;
+	size_t total = 0;
+	const char *cdata = (const char*)data;
+
+	while (len) {
+		nr = len;
+		if (nr > SHA1_MAX_BLOCK_SIZE)
+			nr = SHA1_MAX_BLOCK_SIZE;
+		platform_SHA1_Update(c, cdata, nr);
+		total += nr;
+		cdata += nr;
+		len -= nr;
+	}
+	return total;
+}
diff --git a/compat/sha1-chunked.h b/compat/sha1-chunked.h
new file mode 100644
index 0000000000..7b2df28eec
--- /dev/null
+++ b/compat/sha1-chunked.h
@@ -0,0 +1,2 @@
+
+int git_SHA1_Update_Chunked(platform_SHA_CTX *c, const void *data, size_t len);