Add some more fiber functions.

Add fiber.current and fiber.lineage

src/compiler/boot.dst

@@ -904,7 +904,7 @@ onvalue."
       (res)
       (do
        (:= good false)
-       (onerr "compile" (get res :error))))) :de))
+       (onerr "compile" (get res :error))))) :dey))
   (def res (fiber.resume f))
   (if good
    (cond

src/core/fiber.c

@@ -268,11 +268,11 @@ static int cfun_new(DstArgs args) {
         const uint8_t *flags;
         int32_t len, i;
         dst_arg_bytes(flags, len, args, 1);
-        fiber->flags |= DST_FIBER_MASK_ERROR;
+        fiber->flags |= DST_FIBER_MASK_ERROR | DST_FIBER_MASK_YIELD;
         for (i = 0; i < len; i++) {
             switch (flags[i]) {
                 default:
-                    return dst_throw(args, "invalid flag, expected d or e");
+                    return dst_throw(args, "invalid flag, expected d, e, or y");
                 case ':':
                     break;
                 case 'd':
@@ -281,6 +281,9 @@ static int cfun_new(DstArgs args) {
                 case 'e':
                     fiber->flags &= ~DST_FIBER_MASK_ERROR;
                     break;
+                case 'y':
+                    fiber->flags &= ~DST_FIBER_MASK_YIELD;
+                    break;
             }
         }
     }
@@ -367,10 +370,31 @@ static int cfun_stack(DstArgs args) {
     return dst_return(args, dst_wrap_array(array));
 }
 
+static int cfun_current(DstArgs args) {
+    dst_fixarity(args, 0);
+    return dst_return(args, dst_wrap_fiber(dst_vm_fiber));
+}
+
+static int cfun_lineage(DstArgs args) {
+    DstFiber *fiber;
+    DstArray *array;
+    dst_fixarity(args, 1);
+    dst_check(args, 0, DST_FIBER);
+    fiber = dst_unwrap_fiber(args.v[0]);
+    array = dst_array(0);
+    while (fiber) {
+        dst_array_push(array, dst_wrap_fiber(fiber));
+        fiber = fiber->child;
+    }
+    return dst_return(args, dst_wrap_array(array));
+}
+
 static const DstReg cfuns[] = {
     {"fiber.new", cfun_new},
     {"fiber.status", cfun_status},
     {"fiber.stack", cfun_stack},
+    {"fiber.current", cfun_current},
+    {"fiber.lineage", cfun_lineage},
     {NULL, NULL}
 };
 

src/core/fiber.h

@@ -25,6 +25,8 @@
 
 #include <dst/dst.h>
 
+extern DST_THREAD_LOCAL DstFiber *dst_vm_fiber;
+
 #define dst_stack_frame(s) ((DstStackFrame *)((s) - DST_FRAME_SIZE))
 #define dst_fiber_frame(f) dst_stack_frame((f)->data + (f)->frame)
 DstFiber *dst_fiber_reset(DstFiber *fiber, DstFunction *callee);

src/core/vm.c

@@ -29,6 +29,7 @@
 
 /* VM state */
 DST_THREAD_LOCAL int dst_vm_stackn = 0;
+DST_THREAD_LOCAL DstFiber *dst_vm_fiber = NULL;
 
 /* Maybe collect garbage */
 #define dst_maybe_collect() do {\
@@ -37,6 +38,9 @@ DST_THREAD_LOCAL int dst_vm_stackn = 0;
 /* Start running the VM from where it left off. */
 Dst dst_run(DstFiber *fiber) {
 
+    /* Save old fiber to reset */
+    DstFiber *old_vm_fiber = dst_vm_fiber;
+
     /* VM state */
     register Dst *stack;
     register uint32_t *pc;
@@ -53,13 +57,14 @@ Dst dst_run(DstFiber *fiber) {
     }
     dst_vm_stackn++;
 
-    /* Reset fiber state */
+    /* Setup fiber state */
+    dst_vm_fiber = fiber;
+    dst_gcroot(dst_wrap_fiber(fiber));
     if (fiber->flags & DST_FIBER_FLAG_NEW) {
         dst_fiber_funcframe(fiber, fiber->root);
         fiber->flags &= ~DST_FIBER_FLAG_NEW;
     }
     fiber->status = DST_FIBER_ALIVE;
-    dst_gcroot(dst_wrap_fiber(fiber));
     stack = fiber->data + fiber->frame;
     pc = dst_stack_frame(stack)->pc;
     func = dst_stack_frame(stack)->func;
@@ -202,7 +207,7 @@ static void *op_lookup[255] = {
         vm_next();\
     }
 
-    /* Main interpreter loop. Sematically is a switch on
+    /* Main interpreter loop. Semantically is a switch on
      * (*pc & 0xFF) inside of an infinte loop. */
     VM_START();
 
@@ -739,6 +744,7 @@ static void *op_lookup[255] = {
         }
         fiber->child = nextfiber;
         retreg = dst_run(nextfiber);
+        dst_vm_fiber = fiber;
         switch (nextfiber->status) {
             case DST_FIBER_DEBUG:
                 if (nextfiber->flags & DST_FIBER_MASK_DEBUG) goto vm_debug;
@@ -748,6 +754,13 @@ static void *op_lookup[255] = {
                 if (nextfiber->flags & DST_FIBER_MASK_ERROR) goto vm_error;
                 fiber->child = NULL;
                 break;
+            case DST_FIBER_PENDING:
+                if (nextfiber->flags & DST_FIBER_MASK_YIELD) {
+                    fiber->status = DST_FIBER_PENDING;
+                    goto vm_exit;
+                }
+                fiber->child = NULL;
+                break;
             default:
                 fiber->child = NULL;
                 break;
@@ -853,6 +866,7 @@ static void *op_lookup[255] = {
         dst_stack_frame(stack)->pc = pc;
         dst_vm_stackn--;
         dst_gcunroot(dst_wrap_fiber(fiber));
+        dst_vm_fiber = old_vm_fiber;
         return retreg;
     }
 

src/include/dst/dsttypes.h

@@ -344,6 +344,7 @@ struct DstArgs {
 /* Fiber signal masks. Should not overlap any fiber flags. */
 #define DST_FIBER_MASK_ERROR 1
 #define DST_FIBER_MASK_DEBUG 2
+#define DST_FIBER_MASK_YIELD 4
 
 /* A lightweight green thread in dst. Does not correspond to
  * operating system threads. */