lib: add libxpc to implement functionality needed by xpc interfaces

lib/libxpc/buffer.c

@@ -0,0 +1,59 @@
+#include <mango/status.h>
+#include <xpc/buffer.h>
+#include <xpc/msg.h>
+
+kern_status_t xpc_buffer_read(
+	const xpc_buffer_t *buf,
+	void *out,
+	size_t max,
+	size_t *nr_read)
+{
+	if ((buf->buf_flags & (XPC_BUFFER_F_IN | XPC_BUFFER_F_REMOTE))
+	    != (XPC_BUFFER_F_IN | XPC_BUFFER_F_REMOTE)) {
+		return KERN_BAD_STATE;
+	}
+
+	size_t to_read = max;
+	if (to_read > buf->buf_len) {
+		to_read = buf->buf_len;
+	}
+
+	kern_status_t status
+		= xpc_msg_read(buf->buf_origin, buf->buf_offset, out, to_read);
+	if (status != KERN_OK) {
+		return status;
+	}
+
+	/* TODO */
+	*nr_read = to_read;
+
+	return KERN_OK;
+}
+
+kern_status_t xpc_buffer_write(
+	xpc_buffer_t *buf,
+	const void *in,
+	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)) {
+		return KERN_BAD_STATE;
+	}
+
+	size_t to_write = len;
+	if (to_write > buf->buf_max) {
+		to_write = buf->buf_max;
+	}
+
+	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;
+}