libmisc: obj.h: Use LM_DEFAPPEND() to implement magic LO_BOX()

6 files changed, 129 insertions, 1 deletions

diff --git a/.editorconfig b/.editorconfig
index b7ad057..565f8b9 100644
--- a/.editorconfig
+++ b/.editorconfig
@@ -45,7 +45,7 @@ _mode = gitignore
 
 # By specific filename (non-lib9p) #############################################
 
-[{build-aux/embed-sources.h.gen,build-aux/valgrind}]
+[{build-aux/embed-sources.h.gen,build-aux/valgrind,libmisc/tests/test_obj_autobox.c.gen}]
 _mode = sh
 
 [{build-aux/lint-{src,bin},build-aux/gcov-prune,libusb/include/libusb/tusb_helpers.h.gen}]
diff --git a/GNUmakefile b/GNUmakefile
index fa76266..c2cf709 100644
--- a/GNUmakefile
+++ b/GNUmakefile
@@ -33,6 +33,10 @@ generate/files += 3rd-party/COPYING.newlib.txt
 3rd-party/COPYING.newlib.txt: /usr/share/licenses/arm-none-eabi-newlib/COPYING.NEWLIB
 	cp $< $@
 
+generate/files += libmisc/tests/test_obj_autobox.c
+libmisc/tests/test_obj_autobox.c: %: %.gen libmisc/tests/test_obj_nest.c
+	$^ $@
+
 generate/files += 3rd-party/linux-errno.txt
 3rd-party/linux-errno.txt: lib9p/linux-errno.txt.gen
 	$< $(linux.git) $@
diff --git a/libmisc/CMakeLists.txt b/libmisc/CMakeLists.txt
index 07f154b..ef254f9 100644
--- a/libmisc/CMakeLists.txt
+++ b/libmisc/CMakeLists.txt
@@ -33,5 +33,6 @@ add_lib_test(libmisc test_macro)
 add_lib_test(libmisc test_map)
 add_lib_test(libmisc test_obj)
 add_lib_test(libmisc test_obj_nest)
+add_lib_test(libmisc test_obj_autobox)
 add_lib_test(libmisc test_private)
 add_lib_test(libmisc test_rand)
diff --git a/libmisc/include/libmisc/obj.h b/libmisc/include/libmisc/obj.h
index 749a9fc..3467d5b 100644
--- a/libmisc/include/libmisc/obj.h
+++ b/libmisc/include/libmisc/obj.h
@@ -64,6 +64,8 @@
 
 #define _LO_IFACE_PROTO(_ARG_iface_name, _tuple_typ, ...) _LO_IFACE_PROTO_##_tuple_typ(_ARG_iface_name, __VA_ARGS__)
 #define _LO_IFACE_PROTO_lo_nest(_ARG_iface_name, _ARG_child_iface_name)                           \
+	LM_DEFAPPEND(_LO_REGISTRY_##_ARG_child_iface_name,                                        \
+	             (lo_interface _ARG_iface_name, _ARG_iface_name));                            \
 	LM_ALWAYS_INLINE static lo_interface _ARG_child_iface_name                                \
 	lo_box_##_ARG_iface_name##_as_##_ARG_child_iface_name(lo_interface _ARG_iface_name obj) { \
 		return (lo_interface _ARG_child_iface_name){                                      \
@@ -75,6 +77,25 @@
 	/* empty */
 
 /**
+ * `LO_BOX(iface_name, obj)` boxes `obj` as a `lo_interface
+ * iface_name`; if `obj` is not already a `lo_interface iface_name`
+ * box, then it simply calls the appropriate
+ * lo_box_{XXX}_as_{iface_name}() function/macro.
+ */
+#define LO_BOX(_ARG_iface_name, obj) _Generic((obj),     \
+	lo_interface _ARG_iface_name: obj                \
+	LM_FOREACH_TUPLE(_LO_REGISTRY_##_ARG_iface_name, \
+	                 _LO_BOX, _ARG_iface_name, obj))
+#define LO_BOX2(_ARG_iface_name, obj) _Generic((obj),     \
+	lo_interface _ARG_iface_name: obj                 \
+	LM_FOREACH_TUPLE2(_LO_REGISTRY_##_ARG_iface_name, \
+	                  _LO_BOX, _ARG_iface_name, obj))
+#define _LO_BOX(_ARG_iface_name, _ARG_obj, _ARG_typ, _ARG_typnam) \
+	, _ARG_typ: lo_box_##_ARG_typnam##_as_##_ARG_iface_name(_LO_coerce(_ARG_typ, _ARG_obj))
+#define _LO_coerce(typ, obj) \
+	_Generic((obj), typ: (obj), default: *((typ*)0))
+
+/**
  * `LO_NULL(iface_name)` is the null/nil/zero value for `lo_interface {iface_name}`.
  */
 #define LO_NULL(_ARG_iface_name) ((lo_interface _ARG_iface_name){})
@@ -112,6 +133,8 @@
 	extern const struct _lo_##_ARG_iface_name##_vtable                            \
 	_lo_##_ARG_impl_name##_##_ARG_iface_name##_vtable;                            \
 	/* Boxing.  */                                                                \
+	LM_DEFAPPEND(_LO_REGISTRY_##_ARG_iface_name,                                  \
+	             (_ARG_impl_type *, _ARG_impl_name));                             \
 	LM_DEFAPPEND(lo_box_##_ARG_impl_name##_as_##_ARG_iface_name(_ARG_self), (     \
 		(lo_interface _ARG_iface_name){                                       \
 			.self   = (_ARG_self),                                        \
diff --git a/libmisc/tests/test_obj_autobox.c b/libmisc/tests/test_obj_autobox.c
new file mode 100644
index 0000000..1bf442d
--- /dev/null
+++ b/libmisc/tests/test_obj_autobox.c
@@ -0,0 +1,83 @@
+/* libmisc/tests/test_obj_autobox.c - Generated by `libmisc/tests/test_obj_nest.c libmisc/tests/test_obj_autobox.c`.  DO NOT EDIT!  */
+/* libmisc/tests/test_obj_nest.c - Tests for <libmisc/obj.h> nesting
+ *
+ * Copyright (C) 2025  Luke T. Shumaker <lukeshu@lukeshu.com>
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+#include <string.h> /* for memcpy() */
+
+#include <libmisc/obj.h>
+
+#include "test.h"
+
+/* interfaces *****************************************************************/
+
+#define reader_LO_IFACE \
+	LO_FUNC(ssize_t, read, void *, size_t)
+LO_INTERFACE(reader);
+
+#define writer_LO_IFACE \
+	LO_FUNC(ssize_t, write, void *, size_t)
+LO_INTERFACE(writer);
+
+#define read_writer_LO_IFACE \
+	LO_NEST(reader) \
+	LO_NEST(writer)
+LO_INTERFACE(read_writer);
+
+/* implementation header ******************************************************/
+
+struct myclass {
+	size_t len;
+	char   buf[512];
+};
+LO_IMPLEMENTATION_H(reader, struct myclass, myclass);
+LO_IMPLEMENTATION_H(writer, struct myclass, myclass);
+LO_IMPLEMENTATION_H(read_writer, struct myclass, myclass);
+
+/* implementation main ********************************************************/
+
+LO_IMPLEMENTATION_C(reader, struct myclass, myclass, static);
+LO_IMPLEMENTATION_C(writer, struct myclass, myclass, static);
+LO_IMPLEMENTATION_C(read_writer, struct myclass, myclass, static);
+
+static ssize_t myclass_read(struct myclass *self, void *buf, size_t count) {
+	test_assert(self);
+	if (count > self->len)
+		count = self->len;
+	memcpy(buf, self->buf, count);
+	return count;
+}
+
+static ssize_t myclass_write(struct myclass *self, void *buf, size_t count) {
+	test_assert(self);
+	if (self->len)
+		return -1;
+	if (count > sizeof(self->buf))
+		count = sizeof(self->buf);
+	memcpy(self->buf, buf, count);
+	self->len = count;
+	return count;
+}
+
+/* main test body *************************************************************/
+
+int main() {
+	struct myclass _obj = {};
+	lo_interface read_writer obj = LO_BOX(read_writer, &_obj);
+	test_assert(LO_CALL(obj, write, "Hello", 6) == 6);
+	char buf[6] = {};
+	test_assert(LO_CALL(obj, read, buf, 3) == 3);
+	test_assert(memcmp(buf, "Hel\0\0\0", 6) == 0);
+
+	lo_interface reader rd = LO_BOX(reader, &_obj);
+	rd = LO_BOX(reader, obj);
+	(void) rd;
+
+	lo_interface writer wr = LO_BOX(writer, &_obj);
+	wr = LO_BOX(writer, obj);
+	(void) wr;
+
+	return 0;
+}
diff --git a/libmisc/tests/test_obj_autobox.c.gen b/libmisc/tests/test_obj_autobox.c.gen
new file mode 100755
index 0000000..3cfa3d4
--- /dev/null
+++ b/libmisc/tests/test_obj_autobox.c.gen
@@ -0,0 +1,17 @@
+#!/bin/sh
+# libmisc/tests/test_obj_autobox.c.gen - Generate tests for LO_BOX()
+#
+# Copyright (C) 2025  Luke T. Shumaker <lukeshu@lukeshu.com>
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+infile=$1
+outfile=$2
+
+grep --quiet lo_box_ -- "$infile"
+
+{
+	echo "/* ${outfile} - Generated by \`$*\`.  DO NOT EDIT!  */"
+	sed -E 's/lo_box_([a-z0-9_]+)_as_([a-z0-9_]+)\(/LO_BOX(\2, /g' <"$infile"
+} >"$outfile"
+
+! grep -H lo_box_ -- "$outfile"