lib: xpc: implement writing to local buffers

lib/libxpc/buffer.c

@@ -1,4 +1,5 @@
 #include <mango/status.h>
+#include <string.h>
 #include <xpc/buffer.h>
 #include <xpc/msg.h>
 
@@ -36,8 +37,7 @@ kern_status_t xpc_buffer_write(
 	size_t len,
 	size_t *nr_written)
 {
-	if ((buf->buf_flags & (XPC_BUFFER_F_OUT | XPC_BUFFER_F_REMOTE))
-	    != (XPC_BUFFER_F_OUT | XPC_BUFFER_F_REMOTE)) {
+	if (!(buf->buf_flags & XPC_BUFFER_F_OUT)) {
 		return KERN_BAD_STATE;
 	}
 
@@ -46,6 +46,12 @@ kern_status_t xpc_buffer_write(
 		to_write = buf->buf_max;
 	}
 
+	if (!(buf->buf_flags & XPC_BUFFER_F_REMOTE)) {
+		memcpy(buf->buf_ptr, in, to_write);
+		*nr_written = to_write;
+		return KERN_OK;
+	}
+
 	kern_status_t status
 		= xpc_msg_write(buf->buf_origin, buf->buf_offset, in, to_write);
 	if (status != KERN_OK) {

lib/libxpc/include/xpc/buffer.h

@@ -18,6 +18,13 @@
 		.buf_offset = (offset),                                        \
 		.buf_len = (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;
 
@@ -49,7 +56,7 @@ typedef struct xpc_buffer {
 			/* only valid if F_OUT is set.
 			 * if F_FREE_ON_DISCARD is set, must be either NULL or
 			 * allocated via xpc_context_alloc */
-			const char *buf_ptr;
+			void *buf_ptr;
 		};
 
 		/* fields that are only valid if F_IN is set */