sha1: allow limiting the size of the data passed to SHA1_Update()

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>

Makefile

@@ -141,6 +141,10 @@ all::
 # Define PPC_SHA1 environment variable when running make to make use of
 # a bundled SHA1 routine optimized for PowerPC.
 #
+# Define SHA1_MAX_BLOCK_SIZE to limit the amount of data that will be hashed
+# in one call to the platform's SHA1_Update(). e.g. APPLE_COMMON_CRYPTO
+# wants 'SHA1_MAX_BLOCK_SIZE=1024L*1024L*1024L' defined.
+#
 # Define NEEDS_CRYPTO_WITH_SSL if you need -lcrypto when using -lssl (Darwin).
 #
 # Define NEEDS_SSL_WITH_CRYPTO if you need -lssl when using -lcrypto (Darwin).
@@ -1276,6 +1280,11 @@ ifdef NO_POSIX_GOODIES
 	BASIC_CFLAGS += -DNO_POSIX_GOODIES
 endif
 
+ifdef APPLE_COMMON_CRYPTO
+	# Apple CommonCrypto requires chunking
+	SHA1_MAX_BLOCK_SIZE = 1024L*1024L*1024L
+endif
+
 ifdef BLK_SHA1
 	SHA1_HEADER = "block-sha1/sha1.h"
 	LIB_OBJS += block-sha1/sha1.o
@@ -1294,6 +1303,10 @@ endif
 endif
 endif
 
+ifdef SHA1_MAX_BLOCK_SIZE
+	LIB_OBJS += compat/sha1-chunked.o
+	BASIC_CFLAGS += -DSHA1_MAX_BLOCK_SIZE="$(SHA1_MAX_BLOCK_SIZE)"
+endif
 ifdef NO_PERL_MAKEMAKER
 	export NO_PERL_MAKEMAKER
 endif

cache.h

@@ -30,6 +30,12 @@
 #define git_SHA1_Update		platform_SHA1_Update
 #define git_SHA1_Final		platform_SHA1_Final
 
+#ifdef SHA1_MAX_BLOCK_SIZE
+#include "compat/sha1-chunked.h"
+#undef git_SHA1_Update
+#define git_SHA1_Update		git_SHA1_Update_Chunked
+#endif
+
 #include <zlib.h>
 typedef struct git_zstream {
 	z_stream z;

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 { \

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;
+}

compat/sha1-chunked.h

@@ -0,0 +1,2 @@
+
+int git_SHA1_Update_Chunked(platform_SHA_CTX *c, const void *data, size_t len);