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Block.java

/***** BEGIN LICENSE BLOCK *****
 * Version: CPL 1.0/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Common Public
 * License Version 1.0 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.eclipse.org/legal/cpl-v10.html
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * Copyright (C) 2002-2004 Anders Bengtsson <ndrsbngtssn@yahoo.se>
 * Copyright (C) 2001-2004 Jan Arne Petersen <jpetersen@uni-bonn.de>
 * Copyright (C) 2002 Benoit Cerrina <b.cerrina@wanadoo.fr>
 * Copyright (C) 2004-2007 Thomas E Enebo <enebo@acm.org>
 * Copyright (C) 2004 Stefan Matthias Aust <sma@3plus4.de>
 * 
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
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 * use your version of this file under the terms of the CPL, indicate your
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 * and other provisions required by the GPL or the LGPL. If you do not delete
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package org.jruby.runtime;

import org.jruby.Ruby;
import org.jruby.RubyArray;
import org.jruby.RubyModule;
import org.jruby.RubyProc;
import org.jruby.ast.MultipleAsgnNode;
import org.jruby.ast.Node;
import org.jruby.ast.NodeTypes;
import org.jruby.ast.util.ArgsUtil;
import org.jruby.evaluator.AssignmentVisitor;
import org.jruby.exceptions.JumpException;
import org.jruby.parser.BlockStaticScope;
import org.jruby.runtime.builtin.IRubyObject;
import org.jruby.internal.runtime.methods.EvaluateCallable;
import org.jruby.util.collections.SinglyLinkedList;

/**
 *  Internal live representation of a block ({...} or do ... end).
 */
00052 public class Block {
    /**
     * All Block variables should either refer to a real block or this NULL_BLOCK.
     */
00056     public static final Block NULL_BLOCK = new Block() {
        public boolean isGiven() {
            return false;
        }
        
        public IRubyObject yield(ThreadContext context, IRubyObject value, IRubyObject self, 
                RubyModule klass, boolean aValue) {
            throw context.getRuntime().newLocalJumpError("yield called out of block");
        }
        
        public Block cloneBlock() {
            return this;
        }
    };

    /**
     * 'self' at point when the block is defined
     */
00074     private IRubyObject self;

    /**
     * body of the block (wrapped in an ICallable)
     */
00079     private ICallable method;

    /**
     * AST Node representing the parameter (VARiable) list to the block.
     */
00084     private Node varNode;
    
    /**
     * frame of method which defined this block
     */
00089     private Frame frame;
    private SinglyLinkedList cref;
    private Visibility visibility;
    private RubyModule klass;
    
    /**
     * A reference to all variable values (and names) that are in-scope for this block.
     */
00097     private DynamicScope dynamicScope;
    
    /**
     * The Proc that this block is associated with.  When we reference blocks via variable
     * reference they are converted to Proc objects.  We store a reference of the associated
     * Proc object for easy conversion.  
     */
00104     private RubyProc proc = null;
    
    public boolean isLambda = false;

    public static Block createBlock(ThreadContext context, Node varNode, DynamicScope dynamicScope,
            ICallable method, IRubyObject self) {
        return new Block(varNode,
                         method,
                         self,
                         context.getCurrentFrame(),
                         context.peekCRef(),
                         context.getCurrentFrame().getVisibility(),
                         context.getRubyClass(),
                         dynamicScope);
    }
    
    protected Block() {
        this(null, null, null, null, null, null, null, null);
    }

    public Block(Node varNode, ICallable method, IRubyObject self, Frame frame,
        SinglyLinkedList cref, Visibility visibility, RubyModule klass,
        DynamicScope dynamicScope) {
      
        //assert method != null;

        this.varNode = varNode;
        this.method = method;
        this.self = self;
        this.frame = frame;
        this.visibility = visibility;
        this.klass = klass;
        this.cref = cref;
        this.dynamicScope = dynamicScope;
    }
    
    public static Block createBinding(Frame frame, DynamicScope dynamicScope) {
        ThreadContext context = frame.getSelf().getRuntime().getCurrentContext();
        
        // We create one extra dynamicScope on a binding so that when we 'eval "b=1", binding' the
        // 'b' will get put into this new dynamic scope.  The original scope does not see the new
        // 'b' and successive evals with this binding will.  I take it having the ability to have 
        // succesive binding evals be able to share same scope makes sense from a programmers 
        // perspective.   One crappy outcome of this design is it requires Dynamic and Static 
        // scopes to be mutable for this one case.
        
        // Note: In Ruby 1.9 all of this logic can go away since they will require explicit
        // bindings for evals.
        
        // We only define one special dynamic scope per 'logical' binding.  So all bindings for
        // the same scope should share the same dynamic scope.  This allows multiple evals with
        // different different bindings in the same scope to see the same stuff.
        DynamicScope extraScope = dynamicScope.getBindingScope();
        
        // No binding scope so we should create one
        if (extraScope == null) {
            // If the next scope out has the same binding scope as this scope it means
            // we are evaling within an eval and in that case we should be sharing the same
            // binding scope.
            DynamicScope parent = dynamicScope.getNextCapturedScope(); 
            if (parent != null && parent.getBindingScope() == dynamicScope) {
                extraScope = dynamicScope;
            } else {
                extraScope = new DynamicScope(new BlockStaticScope(dynamicScope.getStaticScope()), dynamicScope);
                dynamicScope.setBindingScope(extraScope);
            }
        } 
        
        // FIXME: Ruby also saves wrapper, which we do not
        return new Block(null, null, frame.getSelf(), frame, context.peekCRef(), frame.getVisibility(), 
                context.getBindingRubyClass(), extraScope);
    }

    public IRubyObject call(ThreadContext context, IRubyObject[] args) {
        return yield(context, context.getRuntime().newArrayNoCopy(args), null, null, true);
    }
    
    protected void pre(ThreadContext context, RubyModule klass) {
        context.preYieldSpecificBlock(this, klass);
    }
    
    protected void post(ThreadContext context) {
        context.postYield();
    }
    
    public IRubyObject yield(ThreadContext context, IRubyObject value) {
        return yield(context, value, null, null, false);
    }

    /**
     * Yield to this block, usually passed to the current call.
     * 
     * @param context represents the current thread-specific data
     * @param value The value to yield, either a single value or an array of values
     * @param self The current self
     * @param klass
     * @param aValue Should value be arrayified or not?
     * @return
     */
00203     public IRubyObject yield(ThreadContext context, IRubyObject value, IRubyObject self, 
            RubyModule klass, boolean aValue) {
        if (klass == null) {
            self = this.self;
            frame.setSelf(self);
        }
        
        pre(context, klass);

        try {
            IRubyObject[] args = (method instanceof EvaluateCallable) ? getBlockArgsEvaluate(context, value, self, aValue) : getBlockArgs(context, value, self, aValue);
            // This while loop is for restarting the block call in case a 'redo' fires.
            while (true) {
                try {
                    return method.call(context, self, args, NULL_BLOCK);
                } catch (JumpException je) {
                    if (je.getJumpType() == JumpException.JumpType.RedoJump) {
                        context.pollThreadEvents();
                        // do nothing, allow loop to redo
                    } else {
                        if (je.getJumpType() == JumpException.JumpType.BreakJump && je.getTarget() == null) {
                            je.setTarget(this);                            
                        }                        
                        throw je;
                    }
                }
            }
            
        } catch (JumpException je) {
            // A 'next' is like a local return from the block, ending this call or yield.
            if (je.getJumpType() == JumpException.JumpType.NextJump) return (IRubyObject) je.getValue();

            throw je;
        } finally {
            post(context);
        }
    }

    private IRubyObject[] getBlockArgs(ThreadContext context, IRubyObject value, IRubyObject self, boolean valueIsArray) {
        //FIXME: block arg handling is mucked up in strange ways and NEED to
        // be fixed. Especially with regard to Enumerable. See RubyEnumerable#eachToList too.
        if (varNode == null) {
            return new IRubyObject[]{value};
        }
        
        Ruby runtime = self.getRuntime();
        
        switch (varNode.nodeId) {
            case NodeTypes.ZEROARGNODE:
                break;
            case NodeTypes.MULTIPLEASGNNODE:
                if (!valueIsArray) {
                    value = ArgsUtil.convertToRubyArray(runtime, value, ((MultipleAsgnNode)varNode).getHeadNode() != null);
                }

                value = AssignmentVisitor.multiAssign(runtime, context, self, (MultipleAsgnNode)varNode, (RubyArray)value, false);
                break;
            default:
                if (valueIsArray) {
                    int length = arrayLength(value);

                    switch (length) {
                        case 0:
                            value = runtime.getNil();
                            break;
                        case 1:
                            value = ((RubyArray)value).eltInternal(0);
                            break;
                        default:
                            runtime.getWarnings().warn("multiple values for a block parameter (" + length + " for 1)");
                    }
                } else if (value == null) { 
                    runtime.getWarnings().warn("multiple values for a block parameter (0 for 1)");
                }

                AssignmentVisitor.assign(runtime, context, self, varNode, value, Block.NULL_BLOCK, false);
        }
        return ArgsUtil.convertToJavaArray(value);
    }

    private IRubyObject[] getBlockArgsEvaluate(ThreadContext context, IRubyObject value, IRubyObject self, boolean valueIsArray) {
        //FIXME: block arg handling is mucked up in strange ways and NEED to
        // be fixed. Especially with regard to Enumerable. See RubyEnumerable#eachToList too.
        if (varNode == null) {
            return IRubyObject.NULL_ARRAY;
        }
        
        Ruby runtime = self.getRuntime();


        if(valueIsArray) {
            switch (varNode.nodeId) {
            case NodeTypes.ZEROARGNODE:
                break;
            case NodeTypes.MULTIPLEASGNNODE:
                value = AssignmentVisitor.multiAssign(runtime, context, self, (MultipleAsgnNode)varNode, (RubyArray)value, false);
                break;
            default:
                int length = arrayLength(value);
                switch (length) {
                case 0:
                    value = runtime.getNil();
                    break;
                case 1:
                    value = ((RubyArray)value).eltInternal(0);
                    break;
                default:
                    runtime.getWarnings().warn("multiple values for a block parameter (" + length + " for 1)");
                }
                AssignmentVisitor.assign(runtime, context, self, varNode, value, Block.NULL_BLOCK, false);
            }
        } else {
            switch (varNode.nodeId) {
            case NodeTypes.ZEROARGNODE:
                return IRubyObject.NULL_ARRAY;
            case NodeTypes.MULTIPLEASGNNODE:
                value = AssignmentVisitor.multiAssign(runtime, context, self, (MultipleAsgnNode)varNode,
                                                      ArgsUtil.convertToRubyArray(runtime, value, ((MultipleAsgnNode)varNode).getHeadNode() != null)
                                                      , false);
                break;
            default:
                if (value == null) { 
                    runtime.getWarnings().warn("multiple values for a block parameter (0 for 1)");
                }
                AssignmentVisitor.assign(runtime, context, self, varNode, value, Block.NULL_BLOCK, false);
            }
        }
        return IRubyObject.NULL_ARRAY;
    }
    
    private int arrayLength(IRubyObject node) {
        return node instanceof RubyArray ? ((RubyArray)node).getLength() : 0;
    }

    public Block cloneBlock() {
        // We clone dynamic scope because this will be a new instance of a block.  Any previously
        // captured instances of this block may still be around and we do not want to start
        // overwriting those values when we create a new one.
        // ENEBO: Once we make self, lastClass, and lastMethod immutable we can remove duplicate
        Block newBlock = new Block(varNode, method, self, frame.duplicate(), cref, visibility, klass, 
                dynamicScope.cloneScope());
        
        newBlock.isLambda = isLambda;

        return newBlock;
    }

    /**
     * What is the arity of this block?
     * 
     * @return the arity
     */
00355     public Arity arity() {
        return method.getArity();
    }

    public Visibility getVisibility() {
        return visibility;
    }

    public void setVisibility(Visibility visibility) {
        this.visibility = visibility;
    }
    
    public void setSelf(IRubyObject self) {
        this.self = self;
    }

    public SinglyLinkedList getCRef() {
        return cref;
    }

    /**
     * Retrieve the proc object associated with this block
     * 
     * @return the proc or null if this has no proc associated with it
     */
00380     public RubyProc getProcObject() {
      return proc;
    }
    
    /**
     * Set the proc object associated with this block
     * 
     * @param procObject
     */
00389     public void setProcObject(RubyProc procObject) {
      this.proc = procObject;
    }

    /**
     * Gets the dynamicVariables that are local to this block.   Parent dynamic scopes are also
     * accessible via the current dynamic scope.
     * 
     * @return Returns all relevent variable scoping information
     */
00399     public DynamicScope getDynamicScope() {
        return dynamicScope;
    }

    /**
     * Gets the frame.
     * 
     * @return Returns a RubyFrame
     */
00408     public Frame getFrame() {
        return frame;
    }

    /**
     * Gets the klass.
     * @return Returns a RubyModule
     */
00416     public RubyModule getKlass() {
        return klass;
    }
    
    /**
     * Is the current block a real yield'able block instead a null one
     * 
     * @return true if this is a valid block or false otherwise
     */
00425     public boolean isGiven() {
        return true;
    }
}

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