replace mock allocator with simple k&r malloc

src/gc.c

@@ -1,12 +1,80 @@
 #include <stdlib.h>
 
 #include "picrin.h"
+#include "picrin/gc.h"
+
+void
+init_heap_page(struct heap_page *heap)
+{
+  struct header *base, *freep;
+  void *p;
+
+  p = (struct header *)malloc(PIC_HEAP_SIZE);
+
+  heap->base = base = (struct header *)
+    (((unsigned long)p + sizeof(struct header) -1) & ~(sizeof(struct header) - 1));
+  base->ptr = base + 1;
+  base->size = 0;
+
+  heap->freep = freep = base->ptr;
+  freep->ptr = base;
+  freep->size = ((char *)p + PIC_HEAP_SIZE - (char *)freep) / sizeof(struct header);
+}
 
 void *
 pic_alloc(pic_state *pic, size_t size)
 {
-  /* mock */
-  return malloc(size);
+  struct header *freep, *p, *prevp;
+  size_t nunits;
+
+  nunits = (size + sizeof(struct header) - 1) / sizeof(struct header) + 1;
+
+  freep = pic->heap->freep;
+  prevp = freep;
+  for (p = prevp->ptr; ; prevp = p, p = p->ptr) {
+    if (p->size >= nunits)
+      break;
+    if (p == freep)
+      return 0;
+  }
+  if (p->size == nunits) {
+    prevp->ptr = p->ptr;
+  }
+  else {
+    p->size -= nunits;
+    p += p->size;
+    p->size = nunits;
+  }
+  pic->heap->freep = prevp;
+
+  return (void *)(p + 1);
+}
+
+void
+pic_free(pic_state *pic, void *ptr)
+{
+  struct header *bp, *p;
+
+  bp = (struct header *)ptr - 1;
+
+  for (p = pic->heap->freep; !(p < bp && bp < p->ptr); p = p->ptr) {
+    if (p >= p->ptr && (bp > p || bp < p->ptr))
+	break;
+  }
+  if (bp + bp->size == p->ptr) {
+    bp->size += p->ptr->size;
+    bp->ptr = p->ptr->ptr;
+  }
+  else {
+    bp->ptr = p->ptr;
+  }
+  if (p + p->size == bp) {
+    p->size += bp->size;
+    p->ptr = bp->ptr;
+  } else {
+    p->ptr  =  bp;
+  }
+  pic->heap->freep = p;
 }
 
 struct pic_object *
@@ -20,8 +88,3 @@ pic_gc_alloc(pic_state *pic, size_t size, enum pic_tt tt)
   return obj;
 }
 
-void
-pic_free(pic_state *pic, void *ptr)
-{
-  free(ptr);
-}

src/state.c

@@ -1,6 +1,7 @@
 #include <stdlib.h>
 
 #include "picrin.h"
+#include "picrin/gc.h"
 
 static struct pic_env *
 pic_new_empty_env()
@@ -25,6 +26,10 @@ pic_open()
   pic->stbase = pic->sp = (pic_value *)malloc(sizeof(pic_value) * 1024);
   pic->stend = pic->stbase + 1024;
 
+  /* memory heap */
+  pic->heap = (struct heap_page *)malloc(sizeof(struct heap_page));
+  init_heap_page(pic->heap);
+
   pic->global_env = pic_new_empty_env();
 
   return pic;