diff --git a/object-file.c b/object-file.c
index 7946fa5e088..9fd449693c4 100644
--- a/object-file.c
+++ b/object-file.c
@@ -2119,6 +2119,106 @@ static int freshen_packed_object(const struct object_id *oid)
 	return 1;
 }
 
+int stream_loose_object(struct input_stream *in_stream, size_t len,
+			struct object_id *oid)
+{
+	int fd, ret, err = 0, flush = 0;
+	unsigned char compressed[4096];
+	git_zstream stream;
+	git_hash_ctx c;
+	struct strbuf tmp_file = STRBUF_INIT;
+	struct strbuf filename = STRBUF_INIT;
+	int dirlen;
+	char hdr[MAX_HEADER_LEN];
+	int hdrlen;
+
+	/* Since oid is not determined, save tmp file to odb path. */
+	strbuf_addf(&filename, "%s/", get_object_directory());
+	hdrlen = format_object_header(hdr, sizeof(hdr), OBJ_BLOB, len);
+
+	/*
+	 * Common steps for write_loose_object and stream_loose_object to
+	 * start writing loose objects:
+	 *
+	 *  - Create tmpfile for the loose object.
+	 *  - Setup zlib stream for compression.
+	 *  - Start to feed header to zlib stream.
+	 */
+	fd = start_loose_object_common(&tmp_file, filename.buf, 0,
+				       &stream, compressed, sizeof(compressed),
+				       &c, hdr, hdrlen);
+	if (fd < 0) {
+		err = -1;
+		goto cleanup;
+	}
+
+	/* Then the data itself.. */
+	do {
+		unsigned char *in0 = stream.next_in;
+
+		if (!stream.avail_in && !in_stream->is_finished) {
+			const void *in = in_stream->read(in_stream, &stream.avail_in);
+			stream.next_in = (void *)in;
+			in0 = (unsigned char *)in;
+			/* All data has been read. */
+			if (in_stream->is_finished)
+				flush = 1;
+		}
+		ret = write_loose_object_common(&c, &stream, flush, in0, fd,
+						compressed, sizeof(compressed));
+		/*
+		 * Unlike write_loose_object(), we do not have the entire
+		 * buffer. If we get Z_BUF_ERROR due to too few input bytes,
+		 * then we'll replenish them in the next input_stream->read()
+		 * call when we loop.
+		 */
+	} while (ret == Z_OK || ret == Z_BUF_ERROR);
+
+	if (stream.total_in != len + hdrlen)
+		die(_("write stream object %ld != %"PRIuMAX), stream.total_in,
+		    (uintmax_t)len + hdrlen);
+
+	/* Common steps for write_loose_object and stream_loose_object to
+	 * end writing loose oject:
+	 *
+	 *  - End the compression of zlib stream.
+	 *  - Get the calculated oid.
+	 */
+	if (ret != Z_STREAM_END)
+		die(_("unable to stream deflate new object (%d)"), ret);
+	ret = end_loose_object_common(&c, &stream, oid);
+	if (ret != Z_OK)
+		die(_("deflateEnd on stream object failed (%d)"), ret);
+	close_loose_object(fd, tmp_file.buf);
+
+	if (freshen_packed_object(oid) || freshen_loose_object(oid)) {
+		unlink_or_warn(tmp_file.buf);
+		goto cleanup;
+	}
+
+	loose_object_path(the_repository, &filename, oid);
+
+	/* We finally know the object path, and create the missing dir. */
+	dirlen = directory_size(filename.buf);
+	if (dirlen) {
+		struct strbuf dir = STRBUF_INIT;
+		strbuf_add(&dir, filename.buf, dirlen);
+
+		if (mkdir_in_gitdir(dir.buf) && errno != EEXIST) {
+			err = error_errno(_("unable to create directory %s"), dir.buf);
+			strbuf_release(&dir);
+			goto cleanup;
+		}
+		strbuf_release(&dir);
+	}
+
+	err = finalize_object_file(tmp_file.buf, filename.buf);
+cleanup:
+	strbuf_release(&tmp_file);
+	strbuf_release(&filename);
+	return err;
+}
+
 int write_object_file_flags(const void *buf, unsigned long len,
 			    enum object_type type, struct object_id *oid,
 			    unsigned flags)
diff --git a/object-store.h b/object-store.h
index 539ea439046..5222ee54600 100644
--- a/object-store.h
+++ b/object-store.h
@@ -46,6 +46,12 @@ struct object_directory {
 	char *path;
 };
 
+struct input_stream {
+	const void *(*read)(struct input_stream *, unsigned long *len);
+	void *data;
+	int is_finished;
+};
+
 KHASH_INIT(odb_path_map, const char * /* key: odb_path */,
 	struct object_directory *, 1, fspathhash, fspatheq)
 
@@ -269,6 +275,8 @@ static inline int write_object_file(const void *buf, unsigned long len,
 int write_object_file_literally(const void *buf, unsigned long len,
 				const char *type, struct object_id *oid,
 				unsigned flags);
+int stream_loose_object(struct input_stream *in_stream, size_t len,
+			struct object_id *oid);
 
 /*
  * Add an object file to the in-memory object store, without writing it
