odb: make it clearer that the id is calculated in the frontend

The frontend is in charge of calculating the id of the objects. Thus
the backends should treat it as a read-only value. The positioning in
the function signature made it seem as though it was an output
parameter.

Make the id const and move it from the front to behind the subject
(backend or stream).

4 files changed, 8 insertions, 12 deletions

diff --git a/include/git2/odb_backend.h b/include/git2/odb_backend.h
index d004238a4..5696ee07d 100644
--- a/include/git2/odb_backend.h
+++ b/include/git2/odb_backend.h
@@ -75,7 +75,7 @@ struct git_odb_stream {
 
 	int (*read)(git_odb_stream *stream, char *buffer, size_t len);
 	int (*write)(git_odb_stream *stream, const char *buffer, size_t len);
-	int (*finalize_write)(git_oid *oid_p, git_odb_stream *stream);
+	int (*finalize_write)(git_odb_stream *stream, const git_oid *oid);
 	void (*free)(git_odb_stream *stream);
 };
 
diff --git a/include/git2/sys/odb_backend.h b/include/git2/sys/odb_backend.h
index 3cd2734c0..2d06613d2 100644
--- a/include/git2/sys/odb_backend.h
+++ b/include/git2/sys/odb_backend.h
@@ -48,12 +48,8 @@ struct git_odb_backend {
 	int (* read_header)(
 		size_t *, git_otype *, git_odb_backend *, const git_oid *);
 
-	/* The writer may assume that the object
-	 * has already been hashed and is passed
-	 * in the first parameter.
-	 */
 	int (* write)(
-		git_oid *, git_odb_backend *, const void *, size_t, git_otype);
+		git_odb_backend *, const git_oid *, const void *, size_t, git_otype);
 
 	int (* writestream)(
 		git_odb_stream **, git_odb_backend *, size_t, git_otype);
diff --git a/src/odb.c b/src/odb.c
index b7f64dfc9..d2be60f97 100644
--- a/src/odb.c
+++ b/src/odb.c
@@ -291,10 +291,10 @@ typedef struct {
 	git_otype type;
 } fake_wstream;
 
-static int fake_wstream__fwrite(git_oid *oid, git_odb_stream *_stream)
+static int fake_wstream__fwrite(git_odb_stream *_stream, const git_oid *oid)
 {
 	fake_wstream *stream = (fake_wstream *)_stream;
-	return _stream->backend->write(oid, _stream->backend, stream->buffer, stream->size, stream->type);
+	return _stream->backend->write(_stream->backend, oid, stream->buffer, stream->size, stream->type);
 }
 
 static int fake_wstream__write(git_odb_stream *_stream, const char *data, size_t len)
@@ -851,7 +851,7 @@ int git_odb_write(
 			continue;
 
 		if (b->write != NULL)
-			error = b->write(oid, b, data, len, type);
+			error = b->write(b, oid, data, len, type);
 	}
 
 	if (!error || error == GIT_PASSTHROUGH)
@@ -931,7 +931,7 @@ int git_odb_stream_write(git_odb_stream *stream, const char *buffer, size_t len)
 int git_odb_stream_finalize_write(git_oid *out, git_odb_stream *stream)
 {
 	git_hash_final(out, stream->hash_ctx);
-	return stream->finalize_write(out, stream);
+	return stream->finalize_write(stream, out);
 }
 
 int git_odb_stream_read(git_odb_stream *stream, char *buffer, size_t len)
diff --git a/src/odb_loose.c b/src/odb_loose.c
index 35f53fb7d..d1ca18edb 100644
--- a/src/odb_loose.c
+++ b/src/odb_loose.c
@@ -769,7 +769,7 @@ static int loose_backend__foreach(git_odb_backend *_backend, git_odb_foreach_cb
 	return state.cb_error ? state.cb_error : error;
 }
 
-static int loose_backend__stream_fwrite(git_oid *oid, git_odb_stream *_stream)
+static int loose_backend__stream_fwrite(git_odb_stream *_stream, const git_oid *oid)
 {
 	loose_writestream *stream = (loose_writestream *)_stream;
 	loose_backend *backend = (loose_backend *)_stream->backend;
@@ -850,7 +850,7 @@ static int loose_backend__stream(git_odb_stream **stream_out, git_odb_backend *_
 	return !stream ? -1 : 0;
 }
 
-static int loose_backend__write(git_oid *oid, git_odb_backend *_backend, const void *data, size_t len, git_otype type)
+static int loose_backend__write(git_odb_backend *_backend, const git_oid *oid, const void *data, size_t len, git_otype type)
 {
 	int error = 0, header_len;
 	git_buf final_path = GIT_BUF_INIT;