dx/src/com/android/dx/cf/code/ExecutionStack.java - platform/dalvik - Git at Google

 /*
  * Copyright (C) 2007 The Android Open Source Project
  *
  * Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */

 package com.android.dx.cf.code;

 import com.android.dx.rop.type.Type;
 import com.android.dx.rop.type.TypeBearer;
 import com.android.dx.util.ExceptionWithContext;
 import com.android.dx.util.Hex;
 import com.android.dx.util.MutabilityControl;

 /**
  * Representation of a Java method execution stack.
  *
  * <p><b>Note:</b> For the most part, the documentation for this class
  * ignores the distinction between {@link Type} and {@link
  * TypeBearer}.</p>
  */
 public final class ExecutionStack extends MutabilityControl {
     /** non-null; array of stack contents */
     private final TypeBearer[] stack;

     /**
      * &gt;= 0; stack pointer (points one past the end) / current stack
      * size
      */
     private int stackPtr;

     /**
      * Constructs an instance.
      *
      * @param maxStack &gt;= 0; the maximum size of the stack for this
      * instance
      */
     public ExecutionStack(int maxStack) {
         super(maxStack != 0);
         stack = new TypeBearer[maxStack];
         stackPtr = 0;
     }

     /**
      * Makes and returns a mutable copy of this instance.
      *
      * @return non-null; the copy
      */
     public ExecutionStack copy() {
         ExecutionStack result = new ExecutionStack(stack.length);

         System.arraycopy(stack, 0, result.stack, 0, stack.length);
         result.stackPtr = stackPtr;

         return result;
     }

     /**
      * Annotates (adds context to) the given exception with information
      * about this instance.
      *
      * @param ex non-null; the exception to annotate
      */
     public void annotate(ExceptionWithContext ex) {
         int limit = stackPtr - 1;

         for (int i = 0; i <= limit; i++) {
             String idx = (i == limit) ? "top0" : Hex.u2(limit - i);

             ex.addContext("stack[" + idx + "]: " +
                           stackElementString(stack[i]));
         }
     }

     /**
      * Replaces all the occurrences of the given uninitialized type in
      * this stack with its initialized equivalent.
      *
      * @param type non-null; type to replace
      */
     public void makeInitialized(Type type) {
         if (stackPtr == 0) {
             // We have to check for this before checking for immutability.
             return;
         }

         throwIfImmutable();

         Type initializedType = type.getInitializedType();

         for (int i = 0; i < stackPtr; i++) {
             if (stack[i] == type) {
                 stack[i] = initializedType;
             }
         }
     }

     /**
      * Gets the maximum stack size for this instance.
      *
      * @return &gt;= 0; the max stack size
      */
     public int getMaxStack() {
         return stack.length;
     }

     /**
      * Gets the current stack size.
      *
      * @return &gt;= 0, &lt; getMaxStack(); the current stack size
      */
     public int size() {
         return stackPtr;
     }

     /**
      * Clears the stack. (That is, this method pops everything off.)
      */
     public void clear() {
         throwIfImmutable();

         for (int i = 0; i < stackPtr; i++) {
             stack[i] = null;
         }

         stackPtr = 0;
     }

     /**
      * Pushes a value of the given type onto the stack.
      *
      * @param type non-null; type of the value
      * @throws SimException thrown if there is insufficient room on the
      * stack for the value
      */
     public void push(TypeBearer type) {
         throwIfImmutable();

         int category;

         try {
             type = type.getFrameType();
             category = type.getType().getCategory();
         } catch (NullPointerException ex) {
             // Elucidate the exception.
             throw new NullPointerException("type == null");
         }

         if ((stackPtr + category) > stack.length) {
             throwSimException("overflow");
             return;
         }

         if (category == 2) {
             stack[stackPtr] = null;
             stackPtr++;
         }

         stack[stackPtr] = type;
         stackPtr++;
     }

     /**
      * Peeks at the <code>n</code>th element down from the top of the stack.
      * <code>n == 0</code> means to peek at the top of the stack. Note that
      * this will return <code>null</code> if the indicated element is the
      * deeper half of a category-2 value.
      *
      * @param n &gt;= 0; which element to peek at
      * @return null-ok; the type of value stored at that element
      * @throws SimException thrown if <code>n &gt;= size()</code>
      */
     public TypeBearer peek(int n) {
         if (n < 0) {
             throw new IllegalArgumentException("n < 0");
         }

         if (n >= stackPtr) {
             return throwSimException("underflow");
         }

         return stack[stackPtr - n - 1];
     }

     /**
      * Peeks at the <code>n</code>th element down from the top of the
      * stack, returning the type per se, as opposed to the
      * <i>type-bearer</i>.  This method is just a convenient shorthand
      * for <code>peek(n).getType()</code>.
      *
      * @see #peek
      */
     public Type peekType(int n) {
         return peek(n).getType();
     }

     /**
      * Pops the top element off of the stack.
      *
      * @return non-null; the type formerly on the top of the stack
      * @throws SimException thrown if the stack is empty
      */
     public TypeBearer pop() {
         throwIfImmutable();

         TypeBearer result = peek(0);

         stack[stackPtr - 1] = null;
         stackPtr -= result.getType().getCategory();

         return result;
     }

     /**
      * Changes an element already on a stack. This method is useful in limited
      * contexts, particularly when merging two instances. As such, it places
      * the following restriction on its behavior: You may only replace
      * values with other values of the same category.
      *
      * @param n &gt;= 0; which element to change, where <code>0</code> is
      * the top element of the stack
      * @param type non-null; type of the new value
      * @throws SimException thrown if <code>n &gt;= size()</code> or
      * the action is otherwise prohibited
      */
     public void change(int n, TypeBearer type) {
         throwIfImmutable();

         try {
             type = type.getFrameType();
         } catch (NullPointerException ex) {
             // Elucidate the exception.
             throw new NullPointerException("type == null");
         }

         int idx = stackPtr - n - 1;
         TypeBearer orig = stack[idx];

         if ((orig == null) ||
             (orig.getType().getCategory() != type.getType().getCategory())) {
             throwSimException("incompatible substitution: " +
                               stackElementString(orig) + " -> " +
                               stackElementString(type));
         }

         stack[idx] = type;
     }

     /**
      * Merges this stack with another stack. A new instance is returned if
      * this merge results in a change. If no change results, this instance is
      * returned.  See {@link Merger#mergeStack(ExecutionStack,ExecutionStack)
      * Merger.mergeStack()}
      *
      * @param other non-null; a stack to merge with
      * @return non-null; the result of the merge
      */
     public ExecutionStack merge(ExecutionStack other) {
         try {
             return Merger.mergeStack(this, other);
         } catch (SimException ex) {
             ex.addContext("underlay stack:");
             this.annotate(ex);
             ex.addContext("overlay stack:");
             other.annotate(ex);
             throw ex;
         }
     }

     /**
      * Gets the string form for a stack element. This is the same as
      * <code>toString()</code> except that <code>null</code> is converted
      * to <code>"&lt;invalid&gt;"</code>.
      *
      * @param type null-ok; the stack element
      * @return non-null; the string form
      */
     private static String stackElementString(TypeBearer type) {
         if (type == null) {
             return "<invalid>";
         }

         return type.toString();
     }

     /**
      * Throws a properly-formatted exception.
      *
      * @param msg non-null; useful message
      * @return never (keeps compiler happy)
      */
     private static TypeBearer throwSimException(String msg) {
         throw new SimException("stack: " + msg);
     }
 }
	/*
	* Copyright (C) 2007 The Android Open Source Project
	*
	* Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/

	package com.android.dx.cf.code;

	import com.android.dx.rop.type.Type;
	import com.android.dx.rop.type.TypeBearer;
	import com.android.dx.util.ExceptionWithContext;
	import com.android.dx.util.Hex;
	import com.android.dx.util.MutabilityControl;

	/**
	* Representation of a Java method execution stack.
	*
	* <p><b>Note:</b> For the most part, the documentation for this class
	* ignores the distinction between {@link Type} and {@link
	* TypeBearer}.</p>
	*/
	public final class ExecutionStack extends MutabilityControl {
	/** non-null; array of stack contents */
	private final TypeBearer[] stack;

	/**
	* >= 0; stack pointer (points one past the end) / current stack
	* size
	*/
	private int stackPtr;

	/**
	* Constructs an instance.
	*
	* @param maxStack >= 0; the maximum size of the stack for this
	* instance
	*/
	public ExecutionStack(int maxStack) {
	super(maxStack != 0);
	stack = new TypeBearer[maxStack];
	stackPtr = 0;
	}

	/**
	* Makes and returns a mutable copy of this instance.
	*
	* @return non-null; the copy
	*/
	public ExecutionStack copy() {
	ExecutionStack result = new ExecutionStack(stack.length);

	System.arraycopy(stack, 0, result.stack, 0, stack.length);
	result.stackPtr = stackPtr;

	return result;
	}

	/**
	* Annotates (adds context to) the given exception with information
	* about this instance.
	*
	* @param ex non-null; the exception to annotate
	*/
	public void annotate(ExceptionWithContext ex) {
	int limit = stackPtr - 1;

	for (int i = 0; i <= limit; i++) {
	String idx = (i == limit) ? "top0" : Hex.u2(limit - i);

	ex.addContext("stack[" + idx + "]: " +
	stackElementString(stack[i]));
	}
	}

	/**
	* Replaces all the occurrences of the given uninitialized type in
	* this stack with its initialized equivalent.
	*
	* @param type non-null; type to replace
	*/
	public void makeInitialized(Type type) {
	if (stackPtr == 0) {
	// We have to check for this before checking for immutability.
	return;
	}

	throwIfImmutable();

	Type initializedType = type.getInitializedType();

	for (int i = 0; i < stackPtr; i++) {
	if (stack[i] == type) {
	stack[i] = initializedType;
	}
	}
	}

	/**
	* Gets the maximum stack size for this instance.
	*
	* @return >= 0; the max stack size
	*/
	public int getMaxStack() {
	return stack.length;
	}

	/**
	* Gets the current stack size.
	*
	* @return >= 0, < getMaxStack(); the current stack size
	*/
	public int size() {
	return stackPtr;
	}

	/**
	* Clears the stack. (That is, this method pops everything off.)
	*/
	public void clear() {
	throwIfImmutable();

	for (int i = 0; i < stackPtr; i++) {
	stack[i] = null;
	}

	stackPtr = 0;
	}

	/**
	* Pushes a value of the given type onto the stack.
	*
	* @param type non-null; type of the value
	* @throws SimException thrown if there is insufficient room on the
	* stack for the value
	*/
	public void push(TypeBearer type) {
	throwIfImmutable();

	int category;

	try {
	type = type.getFrameType();
	category = type.getType().getCategory();
	} catch (NullPointerException ex) {
	// Elucidate the exception.
	throw new NullPointerException("type == null");
	}

	if ((stackPtr + category) > stack.length) {
	throwSimException("overflow");
	return;
	}

	if (category == 2) {
	stack[stackPtr] = null;
	stackPtr++;
	}

	stack[stackPtr] = type;
	stackPtr++;
	}

	/**
	* Peeks at the <code>n</code>th element down from the top of the stack.
	* <code>n == 0</code> means to peek at the top of the stack. Note that
	* this will return <code>null</code> if the indicated element is the
	* deeper half of a category-2 value.
	*
	* @param n >= 0; which element to peek at
	* @return null-ok; the type of value stored at that element
	* @throws SimException thrown if <code>n >= size()</code>
	*/
	public TypeBearer peek(int n) {
	if (n < 0) {
	throw new IllegalArgumentException("n < 0");
	}

	if (n >= stackPtr) {
	return throwSimException("underflow");
	}

	return stack[stackPtr - n - 1];
	}

	/**
	* Peeks at the <code>n</code>th element down from the top of the
	* stack, returning the type per se, as opposed to the
	* <i>type-bearer</i>. This method is just a convenient shorthand
	* for <code>peek(n).getType()</code>.
	*
	* @see #peek
	*/
	public Type peekType(int n) {
	return peek(n).getType();
	}

	/**
	* Pops the top element off of the stack.
	*
	* @return non-null; the type formerly on the top of the stack
	* @throws SimException thrown if the stack is empty
	*/
	public TypeBearer pop() {
	throwIfImmutable();

	TypeBearer result = peek(0);

	stack[stackPtr - 1] = null;
	stackPtr -= result.getType().getCategory();

	return result;
	}

	/**
	* Changes an element already on a stack. This method is useful in limited
	* contexts, particularly when merging two instances. As such, it places
	* the following restriction on its behavior: You may only replace
	* values with other values of the same category.
	*
	* @param n >= 0; which element to change, where <code>0</code> is
	* the top element of the stack
	* @param type non-null; type of the new value
	* @throws SimException thrown if <code>n >= size()</code> or
	* the action is otherwise prohibited
	*/
	public void change(int n, TypeBearer type) {
	throwIfImmutable();

	try {
	type = type.getFrameType();
	} catch (NullPointerException ex) {
	// Elucidate the exception.
	throw new NullPointerException("type == null");
	}

	int idx = stackPtr - n - 1;
	TypeBearer orig = stack[idx];

	if ((orig == null) \|\|
	(orig.getType().getCategory() != type.getType().getCategory())) {
	throwSimException("incompatible substitution: " +
	stackElementString(orig) + " -> " +
	stackElementString(type));
	}

	stack[idx] = type;
	}

	/**
	* Merges this stack with another stack. A new instance is returned if
	* this merge results in a change. If no change results, this instance is
	* returned. See {@link Merger#mergeStack(ExecutionStack,ExecutionStack)
	* Merger.mergeStack()}
	*
	* @param other non-null; a stack to merge with
	* @return non-null; the result of the merge
	*/
	public ExecutionStack merge(ExecutionStack other) {
	try {
	return Merger.mergeStack(this, other);
	} catch (SimException ex) {
	ex.addContext("underlay stack:");
	this.annotate(ex);
	ex.addContext("overlay stack:");
	other.annotate(ex);
	throw ex;
	}
	}

	/**
	* Gets the string form for a stack element. This is the same as
	* <code>toString()</code> except that <code>null</code> is converted
	* to <code>"<invalid>"</code>.
	*
	* @param type null-ok; the stack element
	* @return non-null; the string form
	*/
	private static String stackElementString(TypeBearer type) {
	if (type == null) {
	return "<invalid>";
	}

	return type.toString();
	}

	/**
	* Throws a properly-formatted exception.
	*
	* @param msg non-null; useful message
	* @return never (keeps compiler happy)
	*/
	private static TypeBearer throwSimException(String msg) {
	throw new SimException("stack: " + msg);
	}
	}