Allow iterating over fibers with each and similar.

Makefile

@@ -1,4 +1,4 @@
-# Copyright (c) 2020 Calvin Rose
+# Copyright (c) 2021 Calvin Rose
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to
@@ -27,7 +27,7 @@ PREFIX?=/usr/local
 INCLUDEDIR?=$(PREFIX)/include
 BINDIR?=$(PREFIX)/bin
 LIBDIR?=$(PREFIX)/lib
-JANET_BUILD?="\"$(shell git log --pretty=format:'%h' -n &>2 /dev/null || echo local)\""
+JANET_BUILD?="\"$(shell git log --pretty=format:'%h' -n 2> /dev/null || echo local)\""
 CLIBS=-lm -lpthread
 JANET_TARGET=build/janet
 JANET_LIBRARY=build/libjanet.so

examples/iterate-fiber.janet

@@ -0,0 +1,28 @@
+(def f
+  (coro
+    (for i 0 10
+      (yield (string "yield " i))
+      (os/sleep 0))))
+
+(print "simple yielding")
+(each item f (print "got: " item ", now " (fiber/status f)))
+
+(def f
+  (coro
+    (for i 0 10
+      (yield (string "yield " i))
+      (ev/sleep 0))))
+
+(print "old style fiber iteration")
+(eachy item f (print "got: " item ", now " (fiber/status f)))
+
+(def f
+  (coro
+    (for i 0 10
+      (yield (string "yield " i))
+      (ev/sleep 0))))
+
+(print "complex yielding")
+(each item f (print "got: " item ", now " (fiber/status f)))
+
+(print (fiber/status f))

src/core/ev.c

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2020 Calvin Rose
+* Copyright (c) 2021 Calvin Rose
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to

src/core/fiber.c

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2020 Calvin Rose
+* Copyright (c) 2021 Calvin Rose
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
@@ -37,6 +37,7 @@ static void fiber_reset(JanetFiber *fiber) {
     fiber->child = NULL;
     fiber->flags = JANET_FIBER_MASK_YIELD | JANET_FIBER_RESUME_NO_USEVAL | JANET_FIBER_RESUME_NO_SKIP;
     fiber->env = NULL;
+    fiber->last_value = janet_wrap_nil();
 #ifdef JANET_EV
     fiber->waiting = NULL;
     fiber->sched_id = 0;
@@ -586,6 +587,12 @@ static Janet cfun_fiber_can_resume(int32_t argc, Janet *argv) {
     return janet_wrap_boolean(!isFinished);
 }
 
+static Janet cfun_fiber_last_value(int32_t argc, Janet *argv) {
+    janet_fixarity(argc, 1);
+    JanetFiber *fiber = janet_getfiber(argv, 0);
+    return fiber->last_value;
+}
+
 static const JanetReg fiber_cfuns[] = {
     {
         "fiber/new", cfun_fiber_new,
@@ -663,6 +670,11 @@ static const JanetReg fiber_cfuns[] = {
         JDOC("(fiber/can-resume? fiber)\n\n"
              "Check if a fiber is finished and cannot be resumed.")
     },
+    {
+        "fiber/last-value", cfun_fiber_last_value,
+        JDOC("(fiber/last-value\n\n"
+             "Get the last value returned or signaled from the fiber.")
+    },
     {NULL, NULL, NULL}
 };
 

src/core/gc.c

@@ -244,6 +244,8 @@ recur:
         return;
     janet_gc_mark(fiber);
 
+    janet_mark(fiber->last_value);
+
     /* Mark values on the argument stack */
     janet_mark_many(fiber->data + fiber->stackstart,
                     fiber->stacktop - fiber->stackstart);

src/core/util.h

@@ -91,6 +91,7 @@ void janet_buffer_format(
     int32_t argstart,
     int32_t argc,
     Janet *argv);
+Janet janet_next_impl(Janet ds, Janet key, int is_interpreter);
 
 /* Inside the janet core, defining globals is different
  * at bootstrap time and normal runtime */

src/core/value.c

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2020 Calvin Rose
+* Copyright (c) 2021 Calvin Rose
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
@@ -25,6 +25,7 @@
 #include "util.h"
 #include "state.h"
 #include "gc.h"
+#include "fiber.h"
 #include <janet.h>
 #endif
 
@@ -115,6 +116,10 @@ static int traversal_next(Janet *x, Janet *y) {
  */
 
 Janet janet_next(Janet ds, Janet key) {
+    return janet_next_impl(ds, key, 0);
+}
+
+Janet janet_next_impl(Janet ds, Janet key, int is_interpreter) {
     JanetType t = janet_type(ds);
     switch (t) {
         default:
@@ -177,6 +182,44 @@ Janet janet_next(Janet ds, Janet key) {
             if (NULL == at->next) break;
             return at->next(abst, key);
         }
+        case JANET_FIBER: {
+            JanetFiber *child = janet_unwrap_fiber(ds);
+            Janet retreg;
+            JanetFiberStatus status = janet_fiber_status(child);
+            if (status == JANET_STATUS_ALIVE ||
+                    status == JANET_STATUS_DEAD ||
+                    status == JANET_STATUS_ERROR ||
+                    status == JANET_STATUS_USER0 ||
+                    status == JANET_STATUS_USER1 ||
+                    status == JANET_STATUS_USER2 ||
+                    status == JANET_STATUS_USER3 ||
+                    status == JANET_STATUS_USER4) {
+                return janet_wrap_nil();
+            }
+            janet_vm_fiber->child = child;
+            JanetSignal sig = janet_continue(child, janet_wrap_nil(), &retreg);
+            if (sig != JANET_SIGNAL_OK && !(child->flags & (1 << sig))) {
+                if (is_interpreter) {
+                    janet_signalv(sig, retreg);
+                } else {
+                    janet_vm_fiber->child = NULL;
+                    janet_panicv(retreg);
+                }
+            }
+            janet_vm_fiber->child = NULL;
+            if (sig == JANET_SIGNAL_OK ||
+                    sig == JANET_SIGNAL_ERROR ||
+                    sig == JANET_SIGNAL_USER0 ||
+                    sig == JANET_SIGNAL_USER1 ||
+                    sig == JANET_SIGNAL_USER2 ||
+                    sig == JANET_SIGNAL_USER3 ||
+                    sig == JANET_SIGNAL_USER4) {
+                /* Fiber cannot be resumed, so discard last value. */
+                return janet_wrap_nil();
+            } else {
+                return janet_wrap_integer(0);
+            }
+        }
     }
     return janet_wrap_nil();
 }
@@ -434,6 +477,14 @@ Janet janet_in(Janet ds, Janet key) {
             }
             break;
         }
+        case JANET_FIBER: {
+            /* Bit of a hack to allow iterating over fibers. */
+            if (janet_equals(key, janet_wrap_integer(0))) {
+                return janet_unwrap_fiber(ds)->last_value;
+            } else {
+                janet_panicf("expected key 0, got %v", key);
+            }
+        }
     }
     return value;
 }
@@ -489,6 +540,14 @@ Janet janet_get(Janet ds, Janet key) {
             const JanetKV *st = janet_unwrap_struct(ds);
             return janet_struct_get(st, key);
         }
+        case JANET_FIBER: {
+            /* Bit of a hack to allow iterating over fibers. */
+            if (janet_equals(key, janet_wrap_integer(0))) {
+                return janet_unwrap_fiber(ds)->last_value;
+            } else {
+                return janet_wrap_nil();
+            }
+        }
     }
 }
 
@@ -545,6 +604,14 @@ Janet janet_getindex(Janet ds, int32_t index) {
             }
             break;
         }
+        case JANET_FIBER: {
+            if (index == 0) {
+                value = janet_unwrap_fiber(ds)->last_value;
+            } else {
+                value = janet_wrap_nil();
+            }
+            break;
+        }
     }
     return value;
 }

src/core/vm.c

@@ -1,5 +1,5 @@
 /*
-* Copyright (c) 2020 Calvin Rose
+* Copyright (c) 2021 Calvin Rose
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
@@ -815,7 +815,11 @@ static JanetSignal run_vm(JanetFiber *fiber, Janet in) {
 
     VM_OP(JOP_NEXT)
     vm_commit();
-    stack[A] = janet_next(stack[B], stack[C]);
+    {
+        Janet temp = janet_next_impl(stack[B], stack[C], 1);
+        vm_restore();
+        stack[A] = temp;
+    }
     vm_pcnext();
 
     VM_OP(JOP_LOAD_NIL)
@@ -1341,10 +1345,14 @@ static JanetSignal janet_continue_no_check(JanetFiber *fiber, Janet in, Janet *o
     janet_fiber_did_resume(fiber);
 #endif
 
+    /* Clear last value */
+    fiber->last_value = janet_wrap_nil();
+
     /* Continue child fiber if it exists */
     if (fiber->child) {
         if (janet_vm_root_fiber == NULL) janet_vm_root_fiber = fiber;
         JanetFiber *child = fiber->child;
+        uint32_t instr = (janet_stack_frame(fiber->data + fiber->frame)->pc)[0];
         janet_vm_stackn++;
         JanetSignal sig = janet_continue(child, in, &in);
         janet_vm_stackn--;
@@ -1353,6 +1361,25 @@ static JanetSignal janet_continue_no_check(JanetFiber *fiber, Janet in, Janet *o
             *out = in;
             return sig;
         }
+        /* Check if we need any special handling for certain opcodes */
+        switch (instr & 0x7F) {
+            default:
+                break;
+            case JOP_NEXT: {
+                if (sig == JANET_SIGNAL_OK ||
+                        sig == JANET_SIGNAL_ERROR ||
+                        sig == JANET_SIGNAL_USER0 ||
+                        sig == JANET_SIGNAL_USER1 ||
+                        sig == JANET_SIGNAL_USER2 ||
+                        sig == JANET_SIGNAL_USER3 ||
+                        sig == JANET_SIGNAL_USER4) {
+                    in = janet_wrap_nil();
+                } else {
+                    in = janet_wrap_integer(0);
+                }
+                break;
+            }
+        }
         fiber->child = NULL;
     }
 
@@ -1384,6 +1411,7 @@ static JanetSignal janet_continue_no_check(JanetFiber *fiber, Janet in, Janet *o
     if (janet_vm_root_fiber == fiber) janet_vm_root_fiber = NULL;
     janet_fiber_set_status(fiber, signal);
     janet_restore(&tstate);
+    fiber->last_value = tstate.payload;
     *out = tstate.payload;
 
     return signal;

src/include/janet.h

@@ -838,6 +838,7 @@ struct JanetFiber {
     JanetTable *env; /* Dynamic bindings table (usually current environment). */
     Janet *data; /* Dynamically resized stack memory */
     JanetFiber *child; /* Keep linked list of fibers for restarting pending fibers */
+    Janet last_value; /* Last returned value from a fiber */
 #ifdef JANET_EV
     JanetListenerState *waiting;
     uint32_t sched_id; /* Increment everytime fiber is scheduled by event loop */