com.android.tools.lint.checks
Class ControlFlowGraph

java.lang.Object
  com.android.tools.lint.checks.ControlFlowGraph

public class ControlFlowGraph
extends java.lang.Object

A ControlFlowGraph is a graph containing a node for each instruction in a method, and an edge for each possible control flow; usually just "next" for the instruction following the current instruction, but in the case of a branch such as an "if", multiple edges to each successive location, or with a "goto", a single edge to the jumped-to instruction.

It also adds edges for abnormal control flow, such as the possibility of a method call throwing a runtime exception.

Nested Class Summary

static class

ControlFlowGraph.Node A ControlFlowGraph.Node is a node in the control flow graph for a method, pointing to the instruction and its possible successors

Constructor Summary

ControlFlowGraph()

Method Summary

protected void	add(org.objectweb.asm.tree.AbstractInsnNode from, org.objectweb.asm.tree.AbstractInsnNode to) Adds an exception flow to this graph
static ControlFlowGraph	create(ControlFlowGraph initial, org.objectweb.asm.tree.ClassNode classNode, org.objectweb.asm.tree.MethodNode method) Creates a new ControlFlowGraph and populates it with the flow control for the given method.
protected void	exception(org.objectweb.asm.tree.AbstractInsnNode from, org.objectweb.asm.tree.AbstractInsnNode to) Adds an exception flow to this graph
protected void	exception(org.objectweb.asm.tree.AbstractInsnNode from, org.objectweb.asm.tree.TryCatchBlockNode tcb) Adds an exception try block node to this graph
ControlFlowGraph.Node	getNode(org.objectweb.asm.tree.AbstractInsnNode instruction) Looks up (and if necessary) creates a graph node for the given instruction
boolean	isConnected(org.objectweb.asm.tree.AbstractInsnNode from, org.objectweb.asm.tree.AbstractInsnNode to) Checks whether there is a path from the given instruction to the given instruction node
boolean	isConnected(ControlFlowGraph.Node from, ControlFlowGraph.Node to) Checks whether there is a path from the given source node to the given destination node
java.lang.String	toDot(java.util.Set<ControlFlowGraph.Node> highlight) Generates dot output of the graph.
java.lang.String	toString()
java.lang.String	toString(ControlFlowGraph.Node start) Creates a human readable version of the graph

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

ControlFlowGraph

public ControlFlowGraph()

Method Detail

create

@NonNull
public static ControlFlowGraph create(@Nullable
                                              ControlFlowGraph initial,
                                              @NonNull
                                              org.objectweb.asm.tree.ClassNode classNode,
                                              @NonNull
                                              org.objectweb.asm.tree.MethodNode method)
                               throws org.objectweb.asm.tree.analysis.AnalyzerException

Creates a new ControlFlowGraph and populates it with the flow control for the given method. If the optional initial parameter is provided with an existing graph, then the graph is simply populated, not created. This allows subclassing of the graph instance, if necessary.

Parameters:

initial - usually null, but can point to an existing instance of a ControlFlowGraph in which that graph is reused (but populated with new edges)

classNode - the class containing the method to be analyzed

method - the method to be analyzed

Returns:

a ControlFlowGraph with nodes for the control flow in the given method

Throws:

org.objectweb.asm.tree.analysis.AnalyzerException - if the underlying bytecode library is unable to analyze the method bytecode

isConnected

public boolean isConnected(@NonNull
                           ControlFlowGraph.Node from,
                           @NonNull
                           ControlFlowGraph.Node to)

Checks whether there is a path from the given source node to the given destination node

isConnected

public boolean isConnected(@NonNull
                           org.objectweb.asm.tree.AbstractInsnNode from,
                           @NonNull
                           org.objectweb.asm.tree.AbstractInsnNode to)

Checks whether there is a path from the given instruction to the given instruction node

add

protected void add(@NonNull
                   org.objectweb.asm.tree.AbstractInsnNode from,
                   @NonNull
                   org.objectweb.asm.tree.AbstractInsnNode to)

Adds an exception flow to this graph

exception

protected void exception(@NonNull
                         org.objectweb.asm.tree.AbstractInsnNode from,
                         @NonNull
                         org.objectweb.asm.tree.AbstractInsnNode to)

Adds an exception flow to this graph

exception

protected void exception(@NonNull
                         org.objectweb.asm.tree.AbstractInsnNode from,
                         @NonNull
                         org.objectweb.asm.tree.TryCatchBlockNode tcb)

Adds an exception try block node to this graph

getNode

@NonNull
public ControlFlowGraph.Node getNode(@NonNull
                                             org.objectweb.asm.tree.AbstractInsnNode instruction)

Looks up (and if necessary) creates a graph node for the given instruction

Parameters:

instruction - the instruction

Returns:

the control flow graph node corresponding to the given instruction

toString

@NonNull
public java.lang.String toString(@Nullable
                                         ControlFlowGraph.Node start)

Creates a human readable version of the graph

Parameters:

start - the starting instruction, or null if not known or to use the first instruction

Returns:

a string version of the graph

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

toDot

public java.lang.String toDot(@Nullable
                              java.util.Set<ControlFlowGraph.Node> highlight)

Generates dot output of the graph. This can be used with graphwiz to visualize the graph. For example, if you save the output as graph1.gv you can run

 $ dot -Tps graph1.gv -o graph1.ps
 

to generate a postscript file, which you can then view with "gv graph1.ps". (There are also some online web sites where you can paste in dot graphs and see the visualization right there in the browser.)

Returns:

a dot description of this control flow graph, useful for debugging