source code analysis using bat

Reverse Engineering Reverse Engineering (Source Code Analysis)(Source Code Analysis) © SERG

Source Code Analysis

Using BAT


What is Static Analysis?

• Mining source code for information.

• Using that information to present abstractions of, and answer questions about, software structure.


What can we get from source code analysis?

• Type of information is model dependent– In almost any language, we can find out

information about variable usage: Who? Where? etc.

– In an OO environment, we can find out which classes use other classes, which are a base of an inheritance structure, etc.

– We can also find potential blocks of code that can never be executed in running the program (dead code).


BAT

• Is a tool that lets us perform static analysis on Java programs (class files).

– Builds an XML database of entities and relationships in a system.

– Can use several tools for querying and visualizing the data.


Entities

• ‘Entities’ are individuals that live in the system, and attributes associated with them.

Some examples:– Classes, along with information about their superclass, their scope,

and ‘where’ in the code they exists.

– Methods/functions and what their return type or parameter list is, etc.

– Variables and what their types are, and whether or not they are static, etc.


Relationships

• ‘Relationships’ are interactions between the entities in the system.

Relationships include:– Classes inheriting from one another.

– Methods in one class calling the methods of another class, and methods within the same class calling one another.

– One variable referencing another variable.


Creating BAT Databases

• BAT is really a library that can process JAR files• BATAnalyzer is a small app wrapped around BAT

to return a full XML database from BAT for later processing– Found at: BATROOT/analyzer/src

• To run:export PATH=/usr/remote/serg/jdk1.5.0_11/bin/:$PATHjava -Xmx2G -cp /usr/remote/serg/binbat2toxml.jar:/usr/remote/serg/bin/batanalyzer.jar

batanalyzer.Main <JAR> <OUTPUT>

Need to give Java a lot of Memory to

process large projects

Project to analyze

BAT APIXML output file

Call to analyzer


Provided Tools to deal with BAT

• bdef – A BASH wrapper around XSLT queries to get entity information

• bref – A BASH wrapper around XSLT queries to get relationship information

• dot – A visualization tool. Takes information from query and displays it as a graph.

• On TUX to get the scripts do: export PATH=$PATH:/usr/remote/serg/bin/


bdef Syntax

• bdef takes information from the entities database based on a query, and returns the results in an ascii-table.

bdef xml_file entity_kind entity_name [attr=val]

– xml_file is the xml file containing the extracted database– entity_kind is the ‘type’ of entity to retrieve.– entity_name is a pattern to match for names of entities.– attr=val are bindings to match for attributes of the entity


Entity Kinds

• Chava recognizes several types of entity ‘kinds’ for use in the bdef/bref commands.

• m is for Method

• c is for Class

• f is for Field

• - is a match for any entity_kind


Entity Names

• An entity name can assume many forms following regEX patterns

– Explicit name (e.g., ‘myTempStringVar’)

– Wild-card Pattern (e.g., ‘myTemp.*’)

– A complete wild-card, denoted with ‘.*’


Attribute=Value

• Attribute=Value settings are used to further restrict a query based on some condition specified as regEX.

• Any field is searchable

• The most common restriction is to restrict to a specific file, or to filter out a file. E.g.,bdef file.xml - - filename=FileIDoLike.java

bdef file.xml - - filename=[^(FileIDoNOTLike.java)]


Fields

• Class– name, filename, scope, deprecated, final, abstract

• Method– name, class, filename, scope, static, deprecated, final,

abstract, varargs, bridge, native, synchronized, return, parameters

• Field– Name, class, filename, type, scope, static, deprecated

final, transient, volatile, enum


Example Query• Assume that we want to find all the methods in a specific file (in

this case, World.java) that start with ‘get’. Our query would look like the following:

bdef sim.xml m "get.*" filename="World\.java”

World.java is a part of a Discrete Event Simulator that contains information about the simulation environment


Example Results (bdef)

bdef sim.xml m "get.*" filename="World\.java"

getWorldArray:World:World.java:public:false:false:false:false:false:false:false:false:getWorldString:World:World.java:public:false:false:false:false:false:false:false:false:getWorldString:World:World.java:public:false:false:false:false:false:false:false:false:getWorldMaskString:World:World.java:public:false:false:false:false:false:false:false:false:getEmpty:World:World.java:public:false:false:false:false:false:false:false:false:getWidth:World:World.java:public:false:false:false:false:false:false:false:false:getHeight:World:World.java:public:false:false:false:false:false:false:false:false:


Results Explained

• The bdef query resulted in a collection of : separated lists. The data in the columns mean the following:

– name is the name of the method– class is the class the method belongs too– filename the file containing this method– scope the scope of the method– static if the method is static– deprecated if the method is deprecated– final if the method is final– abstract if the method is abstract– varargs if the method uses variable arguments– bridge if the method is a bridge– native if the method is native– synchronized if the method is synchronized– return the method’s return type– parameters the types of parameters accepted


Exercise

• This exercise uses some Unix utilities along with our use of bdef. The exercise involves two things:

– Counting the number of methods of class World (in World.java).

– Printing out a list of methods in the form of their name, return type, and parameter list.


Using Unix(Part One)

• In order to count the number of lines of a document, one can use the command line tool wc.– The –l option makes it count lines.– Piping to it makes it count the lines of output

from a program.{bdef query} | wc –l

counts the number of lines in a bdef query.


The solution is …

• The solution to the first problem is:

bdef sim.xml m ".*" filename="World\.java" | wc -l


Using Unix(Part Two)

• For the second question, we will again use the unformatted output of bdef.– This time, we’ll take note of the format of the

unformatted output! We’ll keep this limited to the case of unformatted output for methods.

– Each field of the unformatted output is delimited by a colon. The fields we care about are the name, return-type, and parameter-list fields. These are fields 1, 13, and 14, respectively.



• The final piece in the puzzle of displaying the specific fields is getting the fields themselves out of the output.– The cut utility will do nicely. We can send it a

delimiter, and a list of field numbers for a file, and it will return those fields for each line.

– The delimiter flag for cut is –d. The field numbers delimiter is –f, followed by a series of comma separated numbers.


The solution is …

• Our target query is thus:

bdef sim.xml m ".*" class="World" | cut -d ":" -f 1,13,14


Output for Exercise

• Question One: 13

• Question Two:<init>::(int,int,)removeEntity::(Location,)moveEntity::(Location,Location,)addEntity::(Location,)checkBounds:boolean:(Location,)checkLocation:boolean:(Location,)getWorldArray:char[][]:()getWorldString:java.lang.String:(char[][],)getWorldString:java.lang.String:()getWorldMaskString:java.lang.String:(java.util.Vector,java.util.Vector,)setBox::(char[][],int,int,int,int,char,)getEmpty:char:()getWidth:int:()getHeight:int:()<clinit>::()

• Not very pretty, but useful (we hope…).


bref

• bref is a tool that displays relationship information by linking one entity to another


bref Syntax

bref xml kind1 name1 kind2 name2

– kind1 and kind2 are entity kinds– name1 and name2 are entity names– xml the XML file containing the database


Example Query

• Here’s a query to find all class-class relationships in the database.

bref sim.xml c “.*” c “.*”


Example Results (bref)

• bref sim.xml c “.*” c “.*"AutoCar" -> "Car”

"AutoControl" -> "java.lang.Object"

"Car" -> "Entity”

"CarControlException" -> "java.lang.Exception"

"CarCrashException" -> "java.lang.Exception"

"CarMoveController" -> "Entity"

"CarOutOfBounds" -> "java.lang.Exception"

"CarParkTrafficGenerator" -> "Entity"

………………………


Results Explained

• bref returned a list of classes.

• Each line represents a relationship between the entities

• The entity on the right is the first entity asked for

• The entity of the left is the second entity asked for


Exercise – bref

• In these exercises, we’ll examine various relations between the entities of a system.

• We’ll go over:– Inheritance relationships.– Method-Method relationships.– How to write a shell script using BAT tools


Exercise #1

• We’ve already seen how to find the entire inheritance tree from our example, so this exercise should be easy:

– Find all the classes that Entity inherits from, and all the classes that subclass it.


Inheritance Relation

• The relation between classes that we are interested in is subclassing.

• But which entity in the relation subclasses the other?– The answer is that the first entity subclasses the

second.


Inheritance Relation (Cont’d)

– The answer to the question “which class is Entity a subclass of” is:

bref sim.xml c “Entity” c “.*”

– We can analogously find which classes subclass Entity :

bref sim.xml c “.*” c “Entity “


Exercise #2

• This exercise concentrates on method-to-method relations.

• Our task is to find what the fan-in and fan-out of a function are.

• We’ll use World.addEntity function in the example


Definition: Fan-In/Fan-Out

• Fan-In– The fan-in of a function/method is the number

of functions/methods that invoke that method.

• Fan-Out– The fan-out of a function/method is the number

of functions/methods that it invokes.


Finding Fan-In, Fan-Out

• The fan-in of a method can be calculated thusly:bref sim.xml m ".*" m "World.addEntity" | wc -l

• The fan-out of a method can be calculated analogously:bref sim.xml m "World.addEntity" m ".*" | wc -l


Exercise #3

• In this Exercise, we’ll write a shell script to determine if one class is an ancestor or a descendent of another.


Descendent Relation

• A class X is an descendent of class Y if X subclasses Y, or X’s superclass is a descendent of Y.

• This sets up a nice recursion, which will make our job easy.


Shell Scripting

• Our first step is to come up with an exact specification of what we want:– Given two classes, D and A, our script should

report a 1 if D is an descendent of A, and 0 otherwise.


Shell Scripting…

• Our first coding step is to determine what shell to use. For this exercise, we’ll be using the C shell.

• This makes our shebang line like:#!/bin/csh


Shell Scripting

• To make this a little nicer to look at, we’ll make a few small helper-scripts…– One to return whether one class subclasses

another.– One to return the ‘name’ field from

unformatted BAT output.– One to return the names of all the classes that

inherit from a given class.


Helper Script (does_subclass)

• Our first script is pretty simple:

#!/bin/csh

@ z = `bref $1 c $2 c $3 | wc -l` != 0

echo ${z}


Helper Script (get_name)

• Our get_name script only has to return the value of one field. We’ll just make a small script to do it.

cut -d " " -f1


Helper Script (subclasses)

• A script to get all the subclasses is also relatively trivial:

bref $1 c ".*" c $2 |get_name


The Actual Script (ancestor)

• Since our relation is a recursive one, we have to start our code by taking care of the base case (which is that D is a subclass of A. Parent-Child relationship…).

#!/bin/csh

if (`bref $1 c $2 c $3 | wc -l ` != 0) then

echo 1

exit

endif


The Rest of the Script

• The rest of the script deals with the recursion. We have to check every subclass to see if it is an ancestor of the target class.

foreach child (`subclasses $1 $3`) if (`ancestor $1 $2 $child`) then echo 1 exit endifend


However…

• There’s a better way to do this, which would be to traverse up from the descendent.– There can be multiple subclasses to any class.

– In Java, there is only one superclass to a class.

• We’ll call this the ancestor relation, defined as:– X is an ancestor of Y if X is Y’s superclass,

– or X is an ancestor of Y’s superclass.

• We’ll write two little helper scripts to do the rewrite.


Helper Scripts, II (other_name)

• A script to get the name of the second entity of a relation could be useful.

cut -d " " -f3


Helcper Scripts, II (parent)

• A second script, to return the parent of a class, if it exists, would be:

#!/bin/csh

bref $1 c $2 c ".*" | other_name


Making the Finished Product

• First take care of the base case of the recursion:

#!/bin/cshif (`other_name $1 $2 $3`) then echo 1 exitendif


Last Bit o’ Code

• The rest of the code deals with recursing up the inheritance tree…

if (`parent $1 $2 | wc -l ` != 0) then

ancestor $1 `parent $1 $2` $3

else

echo 0

endif


Visualizing Relationships

• We will be using DOT and Graphviz to visualize BAT relationships

– dot: Used to draw a ‘directed graph.’

– Graphviz: Visualizes DOT format


Graphs (Definition)

• A graph G(V, E) is a set of vertices, V, and a set of edges, E.

• For each edge e in E, there are two vertices, (x, y), in V such that E is an edge between x and y.


Graph Details

• Edge Crossings

• Directed Graphs

• Parallel Edges


Graph Examples

• A road map of a large area is a graph. Cities are vertices, and roads are edges.

• An inheritance tree is a directed graph.

• A call tree is a graph.


DOT Format

digraph mdg { "First" -> "java.lang.Object" "First" -> "Second" "Second" -> "java.lang.Object" "Second" -> "java.lang.System" "Second" -> "java.io.PrintStream"}


Relationship to DOT

• The relationship queries already return in DOT format, minus the header.

• All we need to do is append the following to the head:– digraph mdg {

• And the following to the tail:– }


XSLT

• Both bdef and bref are wrappers around XSLT queries

• XSLT/XPATH – Used to query the database.– Firefox can render XSLT stylesheets over XML

datasets


XSLT/XPATH Tutorials/Tools

• References– http://www.w3schools.com/– http://www.zvon.org/xxl/XSLTreference/Output/index.html

– http://www.xml.com/pub/a/2000/08/holman/index.html

• Tools– xsltproc on *nix systems– Windows:

http://www.microsoft.com/downloads/details.aspx?familyid=2fb55371-c94e-4373-b0e9-db4816552e41&displaylang=en

– Firefox can apply XSLT stylesheets


Source Code Analysis

Using Chava


What is Static Analysis?

• Mining source code for information.

• Using that information to present abstractions of, and answer questions about, software structure.


What can we get from source code analysis?

• Type of information is model dependent– In almost any language, we can find out

information about variable usage: Who? Where? etc.

– In an OO environment, we can find out which classes use other classes, which are a base of an inheritance structure, etc.

– We can also find potential blocks of code that can never be executed in running the program (dead code).


Chava

• Is a tool that lets us perform static analysis on Java programs (source or class files).

– Builds a database of entities in a system.

– Builds a database of relationships in a system.

– Includes several tools for querying the databases for data, and some tools for visualizing results.


Entities

• ‘Entities’ are individuals that live in the system, and attributes associated with them.

Some examples:– Classes, along with information about their superclass, their scope,

and ‘where’ in the code they exists.

– Methods/functions and what their return type or parameter list is, etc.

– Variables and what their types are, and whether or not they are static, etc.


Relationships

• ‘Relationships’ are interactions between the entities in the system.

Relationships include:– Classes inheriting from one another.

– Methods in one class calling the methods of another class, and methods within the same class calling one another.

– One variable referencing another variable.


Creating Chava Databases

• Chava takes java/class files, and turns them into data files (.A ext) that can be integrated into a database– Create a .A file for a given Java file:

chava –c filename.java– Create .A files for all Java files in directory:

chava –c *.class


Pulling it all together…

• Chava then takes .A files and creates the databases.– Create databases out of two .A files:

chava –l f1.A f2.A– Create databases for all .A files in directory:

chava –l *.A


Chava Tools

• cdef/vdef – Used to query the entities database.

• cref/vref – Used to query the relationship database.

• dagger/dot – A visualization tool. Takes information from chava databases and displays it as a graph.


cdef/vdef

• cdef takes information from the entities database based on a query, and returns the results in an ascii-table.

• vdef actually shows the code of the entities from a query.


Syntax

• cdef and vdef share the same syntax:

{vdef|cdef} entity_kind entity_name [attr=val]..

– entity_kind is the ‘type’ of entity to retrieve.

– entity_name is a pattern to match for names of entities.

– attr=val are bindings to match for attributes of the entity


Entity Kinds

• Chava recognizes several types of entity ‘kinds’ for use in the cdef/vdef/cref/vref commands.

• p is for Package

• f is for File

• m is for Method

• c is for Class

• l is for Field

• s is for String

• i is for Interface

• - is a match for any entity_kind


Entity Names

• An entity name can assume many forms

– Explicit name (e.g., ‘myTempStringVar’)

– Wild-card Pattern (e.g., ‘myTemp*’)

– A complete wild-card, denoted with ‘-’


Attribute=Value

• Attribute=Value settings are used to further restrict a query based on some condition.

• The most common restriction is to restrict to a specific file, or to filter out a file. E.g.,

cdef - - file=FileIDoLike.java

cdef - - file!=FileIDoNOTLike.java


Example Query• Assume that we want to find all the methods in a specific file (in

this case, ANSIDisplay.java) that start with ‘get’. Our query would look like the following:

cdef m ‘get*’ file=./ANSIDisplay.java

• Or, to see the code…vdef m ‘get*’ file=./ANSIDisplay.java


Example Results (cdef)

• cdef m ‘get*’ file=ANSIDisplay.java

name scope file bline eline

====================== ======= ================= ===== =====

String getEscapeSequen public ANSIDisplay.java 76 82






Results Explained

• The cdef query resulted in a table with several columns. The data in the columns mean the following:

– name: The name of the entity.

– scope: The scope of the entity within its ‘parent’ entity (the entity it resides in).

– file: The name of the file that the entity is in.

– bline: The line that the entity begins on.

– eline: The line that the entity ends on.


Example Results (vdef)

• vdef m ‘get*’ file=ANSIDisplay.java(partial results)

public static String getEscapeSequence(int colour, boolean foreground)

{

colour = setColour(colour, foreground);

return (ESCAPE + Integer.toString(colour) + "m");

}

public static String getEscapeSequence(int value)

{

if (!ANSIDisplaySwitchCheck.validSwitch(value))

throw new IllegalArgumentException("Bad Switch");

return (ESCAPE + Integer.toString(value) + "m");

}


Results Explained

• vdef printed out the entities we asked about, exactly how they appear in the source code.


Finding all File Names

• Knowing all the file names could be important, so let’s see how to do that with chava.– We want to use cdef for this, and just have chava output a list of

file names.

– We also want to restrict the entity_kind to that of file. If you remember, ‘f’ is the type for file.

– We also want any file in the database to be listed, so we want to match against any entity_name. ‘-’ will do.

cdef f -


Exercise

• It would be nice to know how a class interacts with its superclass.

• We’ll take a peek at this with the classes ANSIColourPrinter and ANSIPrinter.


Class-Superclass

• This problem is a bit more than just one cdef/vdef command. First step…– We need to see how ANSIColourPrinter

calls its super-constructor.– We want to see the calls, so we’ll use vdef.– Constructors are methods in chava.


Class-Superclass(Step One)

• The query we need to see the constructors of ANSIColourPrinter is:

vdef m ANSIColourPrinter

This results in…


Class-Superclass Interaction(Step 1 – Results)

public ANSIColourPrinter(OutputStream out)

{

this(out, m_defaultColour);

}

public ANSIColourPrinter(OutputStream out,boolean doReset)

{

this(out, m_defaultColour,doReset);

}

public ANSIColourPrinter(OutputStream out, ANSICharacterColour colour)

{

this(out, colour, m_defaultReset);

}

publicANSIColourPrinter(OutputStream out,ANSICharacterColour colour, boolean doReset)

{

super(colour, out, doReset);

}


Class-Superclass Interaction(Step One – Analysis)

• We now know that ANSIColourPrinter accepts: – An OutputStream,– An ANSICharacterColour– A boolean.

• When not supplied with either of the last two parameters, the constructor uses some defaults.


Class-Superclass Interaction(Step Two)

• The next step is to examine what ANSIPrinter does in its constructor.

• This is basically the same thing as peeking at the ANSIColourPrinter constructors.

vdef m ANSIPrinter


public ANSIPrinter(OutputStream out, ANSIEscapeSequenceType sequence){

this(out, sequence, m_defaultReset);}public ANSIPrinter(OutputStream out, ANSIEscapeSequenceType sequence, boolean doReset){

this(sequence, out, doReset, true);}public ANSIPrinter(OutputStream out, ANSIEscapeSequenceType sequence, boolean doReset,

boolean resetOnLeave){

super(out);

m_escape = sequence;m_reset = doReset;m_resetOnFinalize = resetOnLeave;

m_showEscape = false;}

Class-Superclass Interaction(Step Two – Results)


Class-Superclass Interaction(Step Two – Analysis)

• Apparently, the constructor for ANSIPrinter accepts values for:– an OutputStream– an ANSIEscapeSequenceType– two booleans.

• From what we see the constructor of ANSIPrinter doing, we know that the constructor does nothing more than just set some variables to what we pass to it. Nothing really that special.


Another Exercise

• This exercise uses some Unix utilities along with our use of cdef/vdef. The exercise involves two things:

1. Counting the number of methods of ANSICharacterColour (in ANSICharacterColour.java).

2. Printing out a list of methods in the form of their name, return type, and parameter list.



• In order to count the number of lines of a document, one can use the command line tool wc.– The –l option makes it count lines.– Piping to it makes it count the lines of output

from a program.{cdef query} | wc –l

counts the number of lines in a cdef query.



• Problem with using wc–wc counts all lines, including the ones for

our formatted output table.– Passing the –u option to cdef gives

unformatted output, which is very useful for integrating chava with unix tools. The syntax is:

cdef [-u] kind name [attr=val]


The solution is …

• The solution to the first problem is:cdef –u m – file=./ANSICharacterColour.java | wc -l



• For the second question, we will again use the unformatted output of cdef.– This time, we’ll take note of the format of the

unformatted output! We’ll keep this limited to the case of unformatted output for methods.

– Each field of the unformatted output is delimited by a semicolon. The fields we care about are the name, return-type, and parameter-list fields. These are fields 2, 5, and 9, respectively.



• The final piece in the puzzle of displaying the specific fields is getting the fields themselves out of the output.– The cut utility will do nicely. We can send it a

delimiter, and a list of field numbers for a file, and it will return those fields for each line.

– The delimiter flag for cut is –d. The field numbers delimiter is –f, followed by a series of comma separated numbers.


The solution is …

• Our target query is thus:cdef –u m – file=./ANSICharacterColour.java | cut –d’;’ –f2,5,9


Output for Exercise

• Question One: 13

• Question Two:ANSICharacterColour;void;(acin.common.ansi.ANSIColour,acin.common.ansi.ANSIColour)

create;acin.common.ansi.ANSICharacterColour;(acin.common.ansi.ANSIColour,acin.common.ansi.ANSIColour)

create;acin.common.ansi.ANSICharacterColour;(acin.common.ansi.ANSIColour,int)

create;acin.common.ansi.ANSICharacterColour;(acin.common.ansi.ANSIColour,java.lang.String)

create;acin.common.ansi.ANSICharacterColour;(int,acin.common.ansi.ANSIColour)

create;acin.common.ansi.ANSICharacterColour;(int,int)

create;acin.common.ansi.ANSICharacterColour;(int,java.lang.String)

create;acin.common.ansi.ANSICharacterColour;(java.lang.String,acin.common.ansi.ANSIColour)

create;acin.common.ansi.ANSICharacterColour;(java.lang.String,int)

create;acin.common.ansi.ANSICharacterColour;(java.lang.String,java.lang.String)

getANSIString;java.lang.String;()

getBackground;acin.common.ansi.ANSIColour;()

getForeground;acin.common.ansi.ANSIColour;()

• Not very pretty, but useful (we hope…).


cref/vref

• cref is a tool that displays information from the Chava relationship database, returning the results in a table.

• vref displays the actual entities involved in a relationship.


Syntax

• cref and vref share the same syntax{cref|vref} kind1 name1 kind2 name2 [attr=val].

– kind1 and kind2 are entity kinds– name1 and name2 are entity names

– Attributes are a bit different…


cref/vref Attributes

• Attr=val pairs in cref/vref are different because they have to deal with two different entities. This is solved by appending a ‘1’ or a ‘2’ on the attribute.

E.g.,– file1=myFile.java– file2!=yourFile.java


Example Query

• Here’s a query to find all class-class relationships in the database.

cref c – c –

or, to see the results:

vref c – c –


Example Results (cref)

• cref c – c –kind1 name1 file1 kind2 name2 file2 rk

===== ======== ================ ===== ======== ================ ==

class ANSIChar ANSICharacterCol class ANSIEsca ANSIEscapeSequen su

class ANSIColo ANSIColour.java class ANSIEsca ANSIEscapeSequen su

class ANSIColo ANSIColourPrinte class ANSIPrin ANSIPrinter.java su

class ANSIColo ANSIColourPrinte class ANSIPrin ANSIPrinterMap.j su

class ANSICurs ANSICursorMove.j class Object su

class ANSICurs ANSICursorMoveSe class Object su

class ANSIDisp ANSIDisplay.java class Object su

class ANSIDisp ANSIDisplaySwitc class Object su

class ANSIEsca ANSIEscapeSequen class ANSIEsca ANSIEscapeSequen su

class ANSIEsca ANSIEscapeSequen class Object su

class ANSIPrin ANSIPrinter.java class PrintStream su

class ANSIPrin ANSIPrinterMap.j class Object su

class ANSIPrin ANSIPrinterOptio class Object su


Results Explained

• cref returned a table. The columns are just like cdef columns, except some have a ‘1’ and some have a ‘2’ appended.

• Columns with a ‘1’ appended refer to the first entity.

• Columns with a ‘2’ refer to the second entity.


That last column…

• The last column, rk, denotes the kind of relationship. Its values can be:

• Reference• Fieldread• Fieldwrite• Implements• Subclass


Example Results (vref)

• vref c – c – (partial results)RECORD NUMBER 0### ANSICharacterColour.java ###public class ANSICharacterColour extends ANSIEscapeSequenceType{ private ANSIColour m_foreground; private ANSIColour m_background;

/** * Method to create an <code>ANSICharacterColour</code> from two integers representing the

foreground and background colour, as defined in <code>ANSIColourConstants</code>. * * @param foreground The value representing the colour to be the foreground. * @param background The value representing the colour to be the background. * @exception java.lang.IllegalArgumentException Thrown if the foreground and background values

aren't valid ANSI colours. */

public static ANSICharacterColour create(int foreground, int background) { return new ANSICharacterColour(new ANSIColour(foreground, true), new ANSIColour(background,

false)); }


Exercise – cref/vref

• In these exercises, we’ll examine various relations between the entities of a system.

• We’ll go over:– Inheritance relationships.– Method-Method relationships.– How to write a shell script using Chava tools


Exercise #1

• We’ve already seen how to find the entire inheritance tree from our example, so this exercise should be easy:

– Find all the classes that ANSIEscapeSequenceType inherits from, and all the classes that subclass it.


Inheritance Relation

• The relation between classes that we are interested in is subclassing.

• But which entity in the relation subclasses the other?– The answer is that the first entity subclasses the

second.


Inheritance Relation (Cont’d)

– The answer to the question “which class is ANSIEscapeSequenceType a subclass of” is:

cref c ANSIEscapeSequenceType c -

– We can analogously find which classes subclass ANSIEscapeSequenceType:

cref c - c ANSIEscapeSequenceType


Exercise #2

• This exercise concentrates on method-to-method relations.

• Our task is to find what the fan-in and fan-out of a function are.


Definition: Fan-In/Fan-Out

• Fan-In– The fan-in of a function/method is the number

of functions/methods that invoke that method.

• Fan-Out– The fan-out of a function/method is the number

of functions/methods that it invokes.


Finding Fan-In, Fan-Out

• A key piece of information to know here is that the –u option from cdef works in cref.

• The fan-in of a method can be calculated thusly:cref –u m – m my_method | wc –l

• The fan-out of a method can be calculated analogously:cref –u m my_method m - | wc –l


Exercise #3

• In this Exercise, we’ll write a shell script to determine if one class is an ancestor or a descendent of another.


Descendent Relation

• A class X is an descendent of class Y if X subclasses Y, or X’s superclass is a descendent of Y.

• This sets up a nice recursion, which will make our job easy.


Shell Scripting

• Our first step is to come up with an exact specification of what we want:– Given two classes, D and A, our script should

report a 1 if D is an descendent of A, and 0 otherwise.


Shell Scripting…

• Our first coding step is to determine what shell to use. For this exercise, we’ll be using the C shell.

• This makes our shebang line like:#!/bin/csh


Shell Scripting

• To make this a little nicer to look at, we’ll make a few small helper-scripts…– One to return whether one class subclasses

another.– One to return the ‘name’ field from

unformatted chava output.– One to return the names of all the classes that

inherit from a given class.


Helper Script (does_subclass)

• Our first script is pretty simple:

#!/bin/csh

@ z = `cref –u c $1 c $2 | wc –l` != 0

echo ${z}


Helper Script (get_name)

• Our get_name script only has to return the value of one field. We’ll just make a small awk script to do it.

awk –F ‘;’ ‘{print $3}’


Helper Script (subclasses)

• A script to get all the subclasses is also relatively trivial:

cref –u c – c $1 | get_name


The Actual Script (ancestor)

• Since our relation is a recursive one, we have to start our code by taking care of the base case (which is that D is a subclass of A. Parent-Child relationship…).

if (`cref –u c $1 c $2 | wc -l` != 0) then

echo 1

exit

endif


The Rest of the Script

• The rest of the script deals with the recursion. We have to check every subclass to see if it is an ancestor of the target class.

foreach child (`subclasses $2`)if (`ancestor $1 $child`)

thenecho 1exit

endifend


However…

• There’s a better way to do this, which would be to traverse up from the descendent.– There can be multiple subclasses to any class.

– In Java, there is only one superclass to a class.

• We’ll call this the ancestor relation, defined as:– X is an ancestor of Y if X is Y’s superclass,

– or X is an ancestor of Y’s superclass.

• We’ll write two little helper scripts to do the rewrite.


Helper Scripts, II (other_name)

• A script to get the name of the second entity of a relation could be useful.

awk -F ';' '{print $17}'


Helper Scripts, II (parent)

• A second script, to return the parent of a class, if it exists, would be:

#!/bin/csh

cref -u c $1 c - | other_name


Making the Finished Product

• First take care of the base case of the recursion:

if (`does_subclass $1 $2`) then

echo 1

exit

endif


Last Bit o’ Code

• The rest of the code deals with recursing up the inheritance tree…

if (`parent $1 | wc –l` != 0) then

ancestor `parent $1` $2

else

echo 0

endif


Visualizing Chava

• There are two tools we’ll be using to visualize chava queries.– dagger: Lets us use a cref-esque query to

create a ‘directed graph.’– dot: Used to draw a ‘directed graph.’


Graphs (Definition)

• A graph G(V, E) is a set of vertices, V, and a set of edges, E.

• For each edge e in E, there are two vertices, (x, y), in V such that E is an edge between x and y.


Graph Details

• Edge Crossings

• Directed Graphs

• Parallel Edges


Graph Examples

• A road map of a large area is a graph. Cities are vertices, and roads are edges.

• An inheritance tree is a directed graph.

• A call tree is a graph.


The dagger Tool

• The dagger tool takes a cref-style query, and returns the results as a graph of the relationships.


Syntax

• dagger syntax is exactly like cref syntax (except for lack of options).

dagger kind1 name1 kind2 name2


dagger to dot

• dagger only creates a representation describing a graph.

• dot takes that representation and outputs something that can be visualized.– Can make dotty files.– Can also make postscript files.

dagger kind1 name1 kind2 name2 | dot -Tps


Example Query

• A sample query will show just how the output of dagger -> dot looks.

• A good thing to check is the class inheritance heirarchy.– We already know the cref query for this.– The dagger query is

dagger c – c – | dot –Tps > classes.ps


Viewing PostScript

• A good PostScript viewer is ghostview.– The command to use ghostview is

ggv <file>

• Use ghostview to look at the class heirarchy graph that you just created.


Does Chava have siblings?

• Chava is really a tool that uses the CIA system, from AT&T Labs - Research.

• The CIA system can be extended to any type of structured language.

• Other implementations exist for:– C/C++, HTML, ksh, etc.

source code analysis using bat

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