altos/lisp: Add save/restore infrastructure. Needs OS support to work.

This sticks a few globals past the end of the heap and then asks the
OS to save the heap. On restore, the heap is re-populated by the OS
and then various global variables reset.

Signed-off-by: Keith Packard <keithp@keithp.com>

6 files changed, 119 insertions, 3 deletions

diff --git a/src/lisp/Makefile b/src/lisp/Makefile
index aa542021..dac11f66 100644
--- a/src/lisp/Makefile
+++ b/src/lisp/Makefile
@@ -20,6 +20,7 @@ SRCS=\
 	ao_lisp_lambda.c \
 	ao_lisp_eval.c \
 	ao_lisp_rep.c \
+	ao_lisp_save.c \
 	ao_lisp_error.c 
 
 OBJS=$(SRCS:.c=.o)
diff --git a/src/lisp/ao_lisp.h b/src/lisp/ao_lisp.h
index 7a165cd8..44838a34 100644
--- a/src/lisp/ao_lisp.h
+++ b/src/lisp/ao_lisp.h
@@ -20,6 +20,26 @@
 //#include <stdio.h>
 #include <ao_lisp_os.h>
 
+typedef uint16_t	ao_poly;
+typedef int16_t		ao_signed_poly;
+
+#ifdef AO_LISP_SAVE
+
+struct ao_lisp_os_save {
+	ao_poly	ao_lisp_atoms;
+	ao_poly	ao_lisp_globals;
+};
+
+#define AO_LISP_POOL	(AO_LISP_POOL_TOTAL - sizeof (struct ao_lisp_os_save))
+
+int
+ao_lisp_os_save(void);
+
+int
+ao_lisp_os_restore(void);
+
+#endif
+
 #ifdef AO_LISP_MAKE_CONST
 #define AO_LISP_POOL_CONST	16384
 extern uint8_t ao_lisp_const[AO_LISP_POOL_CONST];
@@ -85,9 +105,6 @@ extern uint16_t		ao_lisp_top;
 
 extern uint8_t		ao_lisp_exception;
 
-typedef uint16_t	ao_poly;
-typedef int16_t		ao_signed_poly;
-
 static inline int
 ao_lisp_is_const(ao_poly poly) {
 	return poly & AO_LISP_CONST;
@@ -228,6 +245,8 @@ enum ao_lisp_builtin_id {
 	builtin_flush,
 	builtin_delay,
 	builtin_led,
+	builtin_save,
+	builtin_restore,
 	_builtin_last
 };
 
@@ -468,6 +487,12 @@ ao_lisp_poly_move(ao_poly *p, uint8_t note_cons);
 
 /* eval */
 
+void
+ao_lisp_eval_clear_globals(void);
+
+int
+ao_lisp_eval_restart(void);
+
 ao_poly
 ao_lisp_eval(ao_poly p);
 
@@ -542,6 +567,14 @@ ao_lisp_macro(struct ao_lisp_cons *cons);
 ao_poly
 ao_lisp_lambda_eval(void);
 
+/* save */
+
+ao_poly
+ao_lisp_save(struct ao_lisp_cons *cons);
+
+ao_poly
+ao_lisp_restore(struct ao_lisp_cons *cons);
+
 /* error */
 
 void
diff --git a/src/lisp/ao_lisp_builtin.c b/src/lisp/ao_lisp_builtin.c
index 30631980..ebc69f77 100644
--- a/src/lisp/ao_lisp_builtin.c
+++ b/src/lisp/ao_lisp_builtin.c
@@ -82,6 +82,9 @@ static const ao_poly builtin_names[] = {
 	[builtin_flush] = _ao_lisp_atom_flush,
 	[builtin_delay] = _ao_lisp_atom_delay,
 	[builtin_led] = _ao_lisp_atom_led,
+	[builtin_save] = _ao_lisp_atom_save,
+	[builtin_restore] = _ao_lisp_atom_restore,
+
 };
 
 static char *
@@ -591,5 +594,7 @@ const ao_lisp_func_t ao_lisp_builtins[] = {
 	[builtin_flush] = ao_lisp_flush,
 	[builtin_led] = ao_lisp_led,
 	[builtin_delay] = ao_lisp_delay,
+	[builtin_save] = ao_lisp_save,
+	[builtin_restore] = ao_lisp_restore,
 };
 
diff --git a/src/lisp/ao_lisp_eval.c b/src/lisp/ao_lisp_eval.c
index 1c929869..f945bc16 100644
--- a/src/lisp/ao_lisp_eval.c
+++ b/src/lisp/ao_lisp_eval.c
@@ -546,6 +546,24 @@ static int (*const evals[])(void) = {
 	[eval_while_test] = ao_lisp_eval_while_test,
 };
 
+/*
+ * Called at restore time to reset all execution state
+ */
+
+void
+ao_lisp_eval_clear_globals(void)
+{
+	ao_lisp_stack = NULL;
+	ao_lisp_frame_current = NULL;
+	ao_lisp_v = AO_LISP_NIL;
+}
+
+int
+ao_lisp_eval_restart(void)
+{
+	return ao_lisp_stack_push();
+}
+
 ao_poly
 ao_lisp_eval(ao_poly _v)
 {
diff --git a/src/lisp/ao_lisp_make_const.c b/src/lisp/ao_lisp_make_const.c
index 0b3e25a6..0a8c9d07 100644
--- a/src/lisp/ao_lisp_make_const.c
+++ b/src/lisp/ao_lisp_make_const.c
@@ -67,6 +67,8 @@ struct builtin_func funcs[] = {
 	"flush",	AO_LISP_FUNC_LAMBDA,	builtin_flush,
 	"delay",	AO_LISP_FUNC_LAMBDA,	builtin_delay,
 	"led",		AO_LISP_FUNC_LEXPR,	builtin_led,
+	"save",		AO_LISP_FUNC_LAMBDA,	builtin_save,
+	"restore",	AO_LISP_FUNC_LAMBDA,	builtin_restore,
 };
 
 #define N_FUNC (sizeof funcs / sizeof funcs[0])
diff --git a/src/lisp/ao_lisp_save.c b/src/lisp/ao_lisp_save.c
new file mode 100644
index 00000000..2b19fdcb
--- /dev/null
+++ b/src/lisp/ao_lisp_save.c
@@ -0,0 +1,57 @@
+/*
+ * Copyright © 2016 Keith Packard <keithp@keithp.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ */
+
+#include <ao_lisp.h>
+
+ao_poly
+ao_lisp_save(struct ao_lisp_cons *cons)
+{
+#ifdef AO_LISP_SAVE
+	struct ao_lisp_os_save *os = (struct ao_lisp_os_save *) &ao_lisp_pool[AO_LISP_POOL];
+
+	ao_lisp_collect();
+	os->ao_lisp_atoms = ao_lisp_atom_poly(ao_lisp_atoms);
+	os->ao_lisp_globals = ao_lisp_frame_poly(ao_lisp_frame_global);
+	if (ao_lisp_os_save())
+		return _ao_lisp_atom_t;
+#endif
+	return AO_LISP_NIL;
+}
+
+ao_poly
+ao_lisp_restore(struct ao_lisp_cons *cons)
+{
+#ifdef AO_LISP_SAVE
+	struct ao_lisp_os_save *os = (struct ao_lisp_os_save *) &ao_lisp_pool[AO_LISP_POOL];
+
+	if (ao_lisp_os_restore()) {
+
+		ao_lisp_atoms = ao_lisp_poly_atom(os->ao_lisp_atoms);
+		ao_lisp_frame_global = ao_lisp_poly_frame(os->ao_lisp_globals);
+
+		/* Clear the eval global variabls */
+		ao_lisp_eval_clear_globals();
+
+		/* Reset the allocator */
+		ao_lisp_top = AO_LISP_POOL;
+		ao_lisp_collect();
+
+		/* Re-create the evaluator stack */
+		if (!ao_lisp_eval_restart())
+			return AO_LISP_NIL;
+		return _ao_lisp_atom_t;
+	}
+#endif
+	return AO_LISP_NIL;
+}