From 2dd48b4dc0f76bcec0968509cc603c06528e40fa Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Fri, 19 Sep 2014 16:41:49 +0900
Subject: [PATCH] add pic_escape

---
 cont.c                | 100 ++++++++++++++++++++++++++++++++++++++++++
 error.c               |   2 +-
 include/picrin/cont.h |   1 +
 3 files changed, 102 insertions(+), 1 deletion(-)

diff --git a/cont.c b/cont.c
index 838cafce..d01281ad 100644
--- a/cont.c
+++ b/cont.c
@@ -57,6 +57,106 @@ pic_dynamic_wind(pic_state *pic, struct pic_proc *in, struct pic_proc *thunk, st
   return val;
 }
 
+struct pic_escape {
+  jmp_buf jmp;
+
+  bool valid;
+
+  struct pic_winder *wind;
+
+  ptrdiff_t sp_offset;
+  ptrdiff_t ci_offset;
+  ptrdiff_t xp_offset;
+  int arena_idx;
+
+  pic_code *ip;
+
+  pic_value results;
+};
+
+static int
+save_point(pic_state *pic, struct pic_escape *escape)
+{
+  escape->valid = true;
+
+  /* save runtime context */
+  escape->wind = pic->wind;
+  escape->sp_offset = pic->sp - pic->stbase;
+  escape->ci_offset = pic->ci - pic->cibase;
+  escape->xp_offset = pic->xp - pic->xpbase;
+  escape->arena_idx = pic->arena_idx;
+  escape->ip = pic->ip;
+
+  escape->results = pic_undef_value();
+
+  return setjmp(escape->jmp);
+}
+
+noreturn static void
+load_point(pic_state *pic, struct pic_escape *escape)
+{
+  if (! escape->valid) {
+    pic_errorf(pic, "calling dead escape continuation");
+  }
+
+  pic_wind(pic, pic->wind, escape->wind);
+
+  /* load runtime context */
+  pic->wind = escape->wind;
+  pic->sp = pic->stbase + escape->sp_offset;
+  pic->ci = pic->cibase + escape->ci_offset;
+  pic->xp = pic->xpbase + escape->xp_offset;
+  pic->arena_idx = escape->arena_idx;
+  pic->ip = escape->ip;
+
+  longjmp(escape->jmp, 1);
+}
+
+noreturn static pic_value
+escape_call(pic_state *pic)
+{
+  size_t argc;
+  pic_value *argv;
+  struct pic_data *e;
+
+  pic_get_args(pic, "*", &argc, &argv);
+
+  e = pic_data_ptr(pic_attr_ref(pic, pic_get_proc(pic), "@@escape"));
+
+  load_point(pic, e->data);
+}
+
+pic_value
+pic_escape(pic_state *pic, struct pic_proc *proc)
+{
+  static const pic_data_type escape_type = { "escape", pic_free, NULL };
+  struct pic_escape *escape;
+
+  escape = pic_alloc(pic, sizeof(struct pic_escape));
+
+  if (save_point(pic, escape)) {
+    return pic_values_by_list(pic, escape->results);
+  }
+  else {
+    struct pic_proc *c;
+    pic_value val;
+    struct pic_data *e;
+
+    c = pic_make_proc(pic, escape_call, "<escape-procedure>");
+
+    e = pic_data_alloc(pic, &escape_type, escape);
+
+    /* save the escape continuation in proc */
+    pic_attr_set(pic, c, "@@escape", pic_obj_value(e));
+
+    val = pic_apply1(pic, proc, pic_obj_value(c));
+
+    escape->valid = false;
+
+    return val;
+  }
+}
+
 pic_value
 pic_values0(pic_state *pic)
 {
diff --git a/error.c b/error.c
index 8023c0be..978ff962 100644
--- a/error.c
+++ b/error.c
@@ -115,7 +115,7 @@ pic_push_try(pic_state *pic)
 {
   pic_value val;
 
-  val = pic_callcc(pic, pic_make_proc(pic, native_push_try, "(native-push-try)"));
+  val = pic_escape(pic, pic_make_proc(pic, native_push_try, "(native-push-try)"));
 
   return pic_test(val);
 }
diff --git a/include/picrin/cont.h b/include/picrin/cont.h
index f389c0fb..10c6913e 100644
--- a/include/picrin/cont.h
+++ b/include/picrin/cont.h
@@ -23,6 +23,7 @@ pic_value pic_values_by_list(pic_state *, pic_value);
 size_t pic_receive(pic_state *, size_t, pic_value *);
 
 pic_value pic_callcc(pic_state *, struct pic_proc *);
+pic_value pic_escape(pic_state *, struct pic_proc *);
 
 #if defined(__cplusplus)
 }