diff --git a/lib/libxpc/buffer.c b/lib/libxpc/buffer.c
index 594b218..9a6da88 100644
--- a/lib/libxpc/buffer.c
+++ b/lib/libxpc/buffer.c
@@ -52,14 +52,10 @@ kern_status_t xpc_buffer_write(
 		return KERN_OK;
 	}
 
-	kern_status_t status
-		= xpc_msg_write(buf->buf_origin, buf->buf_offset, in, to_write);
-	if (status != KERN_OK) {
-		return status;
-	}
-
-	/* TODO */
-	*nr_written = to_write;
-
-	return KERN_OK;
+	return xpc_msg_write(
+		buf->buf_origin,
+		buf->buf_offset,
+		in,
+		to_write,
+		nr_written);
 }
diff --git a/lib/libxpc/include/xpc/buffer.h b/lib/libxpc/include/xpc/buffer.h
index 519cf10..47051b0 100644
--- a/lib/libxpc/include/xpc/buffer.h
+++ b/lib/libxpc/include/xpc/buffer.h
@@ -16,14 +16,13 @@
 		.buf_flags = XPC_BUFFER_F_OUT | XPC_BUFFER_F_REMOTE,           \
 		.buf_origin = (msg),                                           \
 		.buf_offset = (offset),                                        \
-		.buf_len = (size),                                             \
+		.buf_max = (size),                                             \
 	}
 #define XPC_LOCAL_BUFFER_OUT(ptr, size)                                        \
 	{                                                                      \
 		.buf_flags = XPC_BUFFER_F_OUT,                                 \
 		.buf_ptr = (ptr),                                              \
 		.buf_max = (size),                                             \
-		.buf_len = (size),                                             \
 	}
 
 struct xpc_msg;
@@ -46,27 +45,18 @@ typedef enum xpc_buffer_flags {
 
 typedef struct xpc_buffer {
 	xpc_buffer_flags_t buf_flags;
-	union {
-		/* fields that are only valid if F_OUT is set */
-		struct {
-			/* only valid if F_OUT is set. specifies the maximum
-			 * number of chars that can be written to buf_buf,
-			 * including the null terminator. */
-			size_t buf_max;
-			/* only valid if F_OUT is set.
-			 * if F_FREE_ON_DISCARD is set, must be either NULL or
-			 * allocated via xpc_context_alloc */
-			void *buf_ptr;
-		};
-
-		/* fields that are only valid if F_IN is set */
-		struct {
-			/* only valid if F_IN is set. offset of the buffer data
-			 * within the associated message. used when reading
-			 * buffer data from a message. */
-			size_t buf_offset;
-		};
-	};
+	/* only valid if F_OUT is set. specifies the maximum
+	 * number of chars that can be written to buf_buf,
+	 * including the null terminator. */
+	size_t buf_max;
+	/* only valid if F_OUT is set.
+	 * if F_FREE_ON_DISCARD is set, must be either NULL or
+	 * allocated via xpc_context_alloc */
+	void *buf_ptr;
+	/* valid for F_IN and F_OUT. offset of the buffer data
+	 * within the associated message. used when reading
+	 * buffer data from a message. */
+	size_t buf_offset;
 
 	/* only valid if F_REMOTE is set.
 	 * used to read/write buffer data from/to the sender's address