hash algorithms: use size_t for section lengths

Continue walking the code path for the >4GB `hash-object --literally`
test to the hash algorithm step for LLP64 systems.

This patch lets the SHA1DC code use `size_t`, making it compatible with
LLP64 data models (as used e.g. by Windows).

The interested reader of this patch will note that we adjust the
signature of the `git_SHA1DCUpdate()` function without updating _any_
call site. This certainly puzzled at least one reviewer already, so here
is an explanation:

This function is never called directly, but always via the macro
`platform_SHA1_Update`, which is usually called via the macro
`git_SHA1_Update`. However, we never call `git_SHA1_Update()` directly
in `struct git_hash_algo`. Instead, we call `git_hash_sha1_update()`,
which is defined thusly:

    static void git_hash_sha1_update(git_hash_ctx *ctx,
                                     const void *data, size_t len)
    {
        git_SHA1_Update(&ctx->sha1, data, len);
    }

i.e. it contains an implicit downcast from `size_t` to `unsigned long`
(before this here patch). With this patch, there is no downcast anymore.

With this patch, finally, the t1007-hash-object.sh "files over 4GB hash
literally" test case is fixed.

Signed-off-by: Philip Oakley <philipoakley@iee.email>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

object-file.c

@@ -1864,7 +1864,7 @@ void *read_object_with_reference(struct repository *r,
 }
 
 static void hash_object_body(const struct git_hash_algo *algo, git_hash_ctx *c,
-			     const void *buf, unsigned long len,
+			     const void *buf, size_t len,
 			     struct object_id *oid,
 			     char *hdr, size_t *hdrlen)
 {
@@ -1884,7 +1884,7 @@ static void write_object_file_prepare(const struct git_hash_algo *algo,
 	/* Generate the header */
 	*hdrlen = format_object_header(hdr, *hdrlen, type, len);
 
-	/* Sha1.. */
+	/* Hash (function pointers) computation */
 	hash_object_body(algo, &c, buf, len, oid, hdr, hdrlen);
 }
 

sha1dc_git.c

@@ -27,10 +27,9 @@ void git_SHA1DCFinal(unsigned char hash[20], SHA1_CTX *ctx)
 /*
  * Same as SHA1DCUpdate, but adjust types to match git's usual interface.
  */
-void git_SHA1DCUpdate(SHA1_CTX *ctx, const void *vdata, unsigned long len)
+void git_SHA1DCUpdate(SHA1_CTX *ctx, const void *vdata, size_t len)
 {
 	const char *data = vdata;
-	/* We expect an unsigned long, but sha1dc only takes an int */
 	while (len > INT_MAX) {
 		SHA1DCUpdate(ctx, data, INT_MAX);
 		data += INT_MAX;

sha1dc_git.h

@@ -15,7 +15,7 @@ void git_SHA1DCInit(SHA1_CTX *);
 #endif
 
 void git_SHA1DCFinal(unsigned char [20], SHA1_CTX *);
-void git_SHA1DCUpdate(SHA1_CTX *ctx, const void *data, unsigned long len);
+void git_SHA1DCUpdate(SHA1_CTX *ctx, const void *data, size_t len);
 
 #define platform_SHA_IS_SHA1DC /* used by "test-tool sha1-is-sha1dc" */
 #define platform_SHA_CTX SHA1_CTX

t/t1007-hash-object.sh

@@ -269,7 +269,7 @@ test_expect_success '--stdin outside of repository (uses SHA-1)' '
 	test_cmp expect actual
 '
 
-test_expect_failure EXPENSIVE,SIZE_T_IS_64BIT,!LONG_IS_64BIT \
+test_expect_success EXPENSIVE,SIZE_T_IS_64BIT,!LONG_IS_64BIT \
 		'files over 4GB hash literally' '
 	test-tool genzeros $((5*1024*1024*1024)) >big &&
 	test_oid large5GB >expect &&