lib: add libxpc to implement functionality needed by xpc interfaces

lib/libxpc/string.c

@@ -0,0 +1,60 @@
+#include <mango/status.h>
+#include <xpc/msg.h>
+#include <xpc/string.h>
+
+xpc_status_t xpc_string_read(
+	const xpc_string_t *s,
+	char *out,
+	size_t max,
+	size_t *nr_read)
+{
+	if ((s->s_flags & (XPC_STRING_F_IN | XPC_STRING_F_REMOTE))
+	    != (XPC_STRING_F_IN | XPC_STRING_F_REMOTE)) {
+		return KERN_BAD_STATE;
+	}
+
+	size_t to_read = max - 1;
+	if (to_read > s->s_len) {
+		to_read = s->s_len;
+	}
+
+	kern_status_t status
+		= xpc_msg_read(s->s_origin, s->s_offset, out, to_read);
+	if (status != KERN_OK) {
+		return status;
+	}
+
+	out[to_read] = '\0';
+	/* TODO */
+	*nr_read = to_read;
+
+	return KERN_OK;
+}
+
+xpc_status_t xpc_string_write(
+	xpc_string_t *s,
+	const char *in,
+	size_t len,
+	size_t *nr_written)
+{
+	if ((s->s_flags & (XPC_STRING_F_OUT | XPC_STRING_F_REMOTE))
+	    != (XPC_STRING_F_IN | XPC_STRING_F_REMOTE)) {
+		return KERN_BAD_STATE;
+	}
+
+	size_t to_write = len;
+	if (to_write > s->s_max - 1) {
+		to_write = s->s_max - 1;
+	}
+
+	kern_status_t status
+		= xpc_msg_write(s->s_origin, s->s_offset, in, to_write);
+	if (status != KERN_OK) {
+		return status;
+	}
+
+	/* TODO */
+	*nr_written = to_write;
+
+	return KERN_OK;
+}