From e6523730a45bbc0ccc84c21c3edb7cc3ac5e867a Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Fri, 22 Nov 2013 07:12:03 -0800
Subject: [PATCH] pluggable heap pages

---
 include/config.h |  2 +-
 src/gc.c         | 45 ++++++++++++++++++++++++++++++---------------
 2 files changed, 31 insertions(+), 16 deletions(-)

diff --git a/include/config.h b/include/config.h
index 28bebc91..5b72b9be 100644
--- a/include/config.h
+++ b/include/config.h
@@ -12,7 +12,7 @@
 
 /* initial memory size (to be dynamically extended if necessary) */
 #define PIC_ARENA_SIZE 100
-#define PIC_HEAP_SIZE (20000 * 8)
+#define PIC_HEAP_PAGE_SIZE (8192 * 8)
 #define PIC_STACK_SIZE 1024
 #define PIC_RESCUE_SIZE 30
 #define PIC_IREP_SIZE 256
diff --git a/src/gc.c b/src/gc.c
index b88a03e4..fa8ca17d 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -16,28 +16,42 @@
 void
 init_heap_page(struct heap_page *heap)
 {
-  int nu;
-
-  nu = (PIC_HEAP_SIZE + sizeof(union header) - 1) / sizeof(union header) + 1;
-
-  heap->base.s.ptr = (union header *)calloc(nu, sizeof(union header));
+  heap->base.s.ptr = heap->freep = &heap->base;
   heap->base.s.size = 0;	/* not 1, since it must never be fused into other headers */
   heap->base.s.mark = PIC_GC_UNMARK;
 
-  heap->freep = heap->base.s.ptr;
-  heap->freep->s.size = nu - 1;
-  heap->freep->s.ptr = heap->freep + heap->freep->s.size;
-  heap->freep->s.mark = PIC_GC_UNMARK;
-
-  heap->freep->s.ptr->s.size = 0;
-  heap->freep->s.ptr->s.ptr = &heap->base;
-  heap->freep->s.ptr->s.mark = PIC_GC_UNMARK;
-
 #if GC_DEBUG
   printf("freep = %p\n", heap->freep);
 #endif
 }
 
+static void gc_free(pic_state *, union header *);
+
+static void *
+add_heap_page(pic_state *pic)
+{
+  int nu;
+  union header *p, *ep;
+
+#if DEBUG
+  puts("heap page added");
+#endif
+
+  nu = (PIC_HEAP_PAGE_SIZE + sizeof(union header) - 1) / sizeof(union header) + 1;
+  p = (union header *)calloc(nu, sizeof(union header));
+  p->s.size = nu - 1;
+  p->s.mark = PIC_GC_UNMARK;
+  gc_free(pic, p);
+
+  ep = p + p->s.size;		/* end of page */
+  ep->s.size = 0;
+  ep->s.mark = PIC_GC_UNMARK;
+  ep->s.ptr = p->s.ptr;
+  p->s.ptr = ep;
+
+  return pic->heap->freep;
+}
+
 void *
 pic_alloc(pic_state *pic, size_t size)
 {
@@ -125,7 +139,8 @@ gc_alloc(pic_state *pic, size_t size)
     if (p->s.size >= nunits)
       break;
     if (p == freep) {
-      return 0;
+      if ((p = add_heap_page(pic)) == NULL)
+	return NULL;
     }
   }
   if (p->s.size == nunits) {