Package javassist.bytecode.analysis

Class ControlFlow

java.lang.Object

javassist.bytecode.analysis.ControlFlow

public class ControlFlow
extends Object

Represents the control flow graph of a given method.

To obtain the control flow graph, do the following:

CtMethod m = ...
 ControlFlow cf = new ControlFlow(m);
 Block[] blocks = cf.basicBlocks();
 

blocks is an array of basic blocks in that method body.

Since:

3.16

Author:

Shigeru Chiba

See Also:

• CtMethod
• ControlFlow.Block
• Frame
• Analyzer

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ControlFlow.Block	Basic block.
static class	ControlFlow.Catcher	Represents a catch clause.
static class	ControlFlow.Node	A node of (post) dominator trees.

Constructor Summary

Constructors

Constructor	Description
ControlFlow(CtClass ctclazz, MethodInfo minfo)	Constructs a control-flow analyzer.
ControlFlow(CtMethod method)	Constructs a control-flow analyzer for the given method.

Method Summary

Modifier and Type	Method	Description
ControlFlow.Block[]	basicBlocks()	Returns all the basic blocks in the method body.
ControlFlow.Node[]	dominatorTree()	Constructs a dominator tree.
Frame	frameAt(int pos)	Returns the types of the local variables and stack frame entries available at the given position.
ControlFlow.Node[]	postDominatorTree()	Constructs a post dominator tree.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

ControlFlow

public ControlFlow(CtMethod method)
            throws BadBytecode

Constructs a control-flow analyzer for the given method.

Throws:

BadBytecode

ControlFlow

public ControlFlow(CtClass ctclazz,
 MethodInfo minfo)
            throws BadBytecode

Constructs a control-flow analyzer.

Throws:

BadBytecode

Method Details

basicBlocks

public ControlFlow.Block[] basicBlocks()

Returns all the basic blocks in the method body.

Returns:

an array of basic blocks, the array has length 0 if the method doesn't have code.

frameAt

public Frame frameAt(int pos)
              throws BadBytecode

Returns the types of the local variables and stack frame entries available at the given position. If the byte at the position is not the first byte of an instruction, then this method returns null.

Parameters:

pos - the position.

Throws:

BadBytecode

dominatorTree

public ControlFlow.Node[] dominatorTree()

Constructs a dominator tree. This method returns an array of the tree nodes. The first element of the array is the root of the tree.

The order of the elements is the same as that of the elements in the Block array returned by the basicBlocks method. If a Block object is at the i-th position in the Block array, then the Node object referring to that Block object is at the i-th position in the array returned by this method. For every array element node, its index in the array is equivalent to node.block().index().

Returns:

an array of the tree nodes, or null if the method doesn't have code.

See Also:

• ControlFlow.Node.block()
• ControlFlow.Block.index()

postDominatorTree

public ControlFlow.Node[] postDominatorTree()

Constructs a post dominator tree. This method returns an array of the tree nodes. Note that the tree has multiple roots. The parent of the root nodes is null.

The order of the elements is the same as that of the elements in the Block array returned by the basicBlocks method. If a Block object is at the i-th position in the Block array, then the Node object referring to that Block object is at the i-th position in the array returned by this method. For every array element node, its index in the array is equivalent to node.block().index().

Returns:

an array of the tree nodes, or null if the method doesn't have code.

See Also:

• ControlFlow.Node.block()
• ControlFlow.Block.index()