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1 /*
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2 * Copyright (c) 2013 Oracle and/or its affiliates. All rights reserved. This
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3 * code is released under a tri EPL/GPL/LGPL license. You can use it,
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4 * redistribute it and/or modify it under the terms of the:
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5 *
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6 * Eclipse Public License version 1.0
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7 * GNU General Public License version 2
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8 * GNU Lesser General Public License version 2.1
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9 */
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10 package com.oracle.truffle.ruby.runtime.core;
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11
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12 import com.oracle.truffle.ruby.runtime.*;
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13 import com.oracle.truffle.ruby.runtime.control.*;
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14 import com.oracle.truffle.ruby.runtime.core.array.*;
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15
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16 /**
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17 * Represents the Ruby {@code Continuation} class. We only support continuations that just move up
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18 * the stack and are one-shot.
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19 */
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20 public class RubyContinuation extends RubyObject {
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21
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22 /*
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23 * A continuation is dead if we have already resumed it once. We will not be able to resume it
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24 * again due to the current implementation being an exception thrown to go back up the stack.
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25 */
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26 private boolean dead = false;
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27
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28 public RubyContinuation(RubyClass rubyClass) {
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29 super(rubyClass);
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30 }
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31
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32 /**
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33 * To enter a continuation means to remember the execution state at this point, reify that into
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34 * an object, and then call the passed block. For our implementation, the continuation will be
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35 * dead when this method resumes.
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36 */
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37 public Object enter(RubyProc block) {
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38 try {
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39 return block.call(null, this);
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40 } catch (ContinuationReturnException e) {
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41 // Thrown in call
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42
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43 // Check the exception is for this continuation
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44
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45 if (e.getContinuation() == this) {
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46 return e.getValue();
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47 } else {
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48 throw e;
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49 }
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50 } finally {
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51 dead = true;
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52 }
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53 }
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54
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55 /**
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56 * To call a continuation means to go back to the execution state when it was created. For our
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57 * implementation we can only do this once, and only if that means jumping back up the stack.
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58 */
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59 public void call(Object... args) {
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60 if (dead) {
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61 throw new UnsupportedOperationException("Only continuations that just move up the stack and are one-shot are supported");
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62 }
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63
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64 Object returnValue;
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65
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66 if (args.length == 0) {
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67 returnValue = NilPlaceholder.INSTANCE;
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68 } else if (args.length == 1) {
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69 returnValue = args[0];
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70 } else {
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71 returnValue = RubyArray.specializedFromObjects(getRubyClass().getContext().getCoreLibrary().getArrayClass(), args);
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72 }
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73
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74 // Caught in enter
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75
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76 throw new ContinuationReturnException(this, returnValue);
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77 }
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78
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79 }
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