org.logicalcobwebs.asm
Class ClassReader

java.lang.Object
  org.logicalcobwebs.asm.ClassReader

public class ClassReader
extends java.lang.Object

A Java class parser to make a ClassVisitor visit an existing class. This class parses a byte array conforming to the Java class file format and calls the appropriate visit methods of a given class visitor for each field, method and bytecode instruction encountered.

Field Summary

protected byte[]	b The class to be parsed.
private int	header Start index of the class header information (access, name...) in b.
private int[]	items The start index of each constant pool item in b, plus one.
private int	maxStringLength Maximum length of the strings contained in the constant pool of the class.
private java.lang.String[]	strings The String objects corresponding to the CONSTANT_Utf8 items.

Constructor Summary

ClassReader(byte[] b)
Constructs a new ClassReader object.

ClassReader(byte[] b, int off, int len)
Constructs a new ClassReader object.

ClassReader(java.io.InputStream is)
Constructs a new ClassReader object.

ClassReader(java.lang.String name)
Constructs a new ClassReader object.

Method Summary

void	accept(ClassVisitor classVisitor, boolean skipDebug) Makes the given visitor visit the Java class of this ClassReader.
protected Attribute	readAttribute(java.lang.String type, int off, int len, char[] buf) Reads an attribute in b.
private static byte[]	readClass(java.io.InputStream is) Reads the bytecode of a class.
protected java.lang.String	readClass(int index, char[] buf) Reads a class constant pool item in b.
protected java.lang.Object	readConst(int item, char[] buf) Reads a numeric or string constant pool item in b.
protected int	readInt(int index) Reads a signed int value in b.
protected long	readLong(int index) Reads a signed long value in b.
protected short	readShort(int index) Reads a signed short value in b.
protected int	readUnsignedShort(int index) Reads an unsigned short value in b.
protected java.lang.String	readUTF8(int index, char[] buf) Reads an UTF8 constant pool item in b.

Methods inherited from class java.lang.Object

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

Field Detail

b

protected final byte[] b

The class to be parsed. The content of this array must not be modified.

items

private int[] items

The start index of each constant pool item in b, plus one. The one byte offset skips the constant pool item tag that indicates its type.

strings

private java.lang.String[] strings

The String objects corresponding to the CONSTANT_Utf8 items. This cache avoids multiple parsing of a given CONSTANT_Utf8 constant pool item, which GREATLY improves performances (by a factor 2 to 3). This caching strategy could be extended to all constant pool items, but its benefit would not be so great for these items (because they are much less expensive to parse than CONSTANT_Utf8 items).

maxStringLength

private int maxStringLength

Maximum length of the strings contained in the constant pool of the class.

header

private int header

Start index of the class header information (access, name...) in b.

Constructor Detail

ClassReader

public ClassReader(byte[] b)

Constructs a new ClassReader object.

Parameters:

b - the bytecode of the class to be read.

ClassReader

public ClassReader(byte[] b,
                   int off,
                   int len)

Constructs a new ClassReader object.

Parameters:

b - the bytecode of the class to be read.

off - the start offset of the class data.

len - the length of the class data.

ClassReader

public ClassReader(java.io.InputStream is)
            throws java.io.IOException

Constructs a new ClassReader object.

Parameters:

is - an input stream from which to read the class.

Throws:

java.io.IOException - if a problem occurs during reading.

ClassReader

public ClassReader(java.lang.String name)
            throws java.io.IOException

Constructs a new ClassReader object.

Parameters:

name - the fully qualified name of the class to be read.

Throws:

java.io.IOException - if an exception occurs during reading.

Method Detail

readClass

private static byte[] readClass(java.io.InputStream is)
                         throws java.io.IOException

Reads the bytecode of a class.

Parameters:

is - an input stream from which to read the class.

Returns:

the bytecode read from the given input stream.

Throws:

java.io.IOException - if a problem occurs during reading.

accept

public void accept(ClassVisitor classVisitor,
                   boolean skipDebug)

Makes the given visitor visit the Java class of this ClassReader. This class is the one specified in the constructor (see ClassReader).

Parameters:

classVisitor - the visitor that must visit this class.

skipDebug - true if the debug information of the class must not be visited. In this case the visitLocalVariable and visitLineNumber methods will not be called.

readUnsignedShort

protected int readUnsignedShort(int index)

Reads an unsigned short value in b.

Parameters:

index - the start index of the value to be read in b.

Returns:

the read value.

readShort

protected short readShort(int index)

Reads a signed short value in b.

Parameters:

index - the start index of the value to be read in b.

Returns:

the read value.

readInt

protected int readInt(int index)

Reads a signed int value in b.

Parameters:

index - the start index of the value to be read in b.

Returns:

the read value.

readLong

protected long readLong(int index)

Reads a signed long value in b.

Parameters:

index - the start index of the value to be read in b.

Returns:

the read value.

readUTF8

protected java.lang.String readUTF8(int index,
                                    char[] buf)

Reads an UTF8 constant pool item in b.

Parameters:

index - the start index of an unsigned short value in b, whose value is the index of an UTF8 constant pool item.

buf - buffer to be used to read the item. This buffer must be sufficiently large. It is not automatically resized.

Returns:

the String corresponding to the specified UTF8 item.

readClass

protected java.lang.String readClass(int index,
                                     char[] buf)

Reads a class constant pool item in b.

Parameters:

index - the start index of an unsigned short value in b, whose value is the index of a class constant pool item.

buf - buffer to be used to read the item. This buffer must be sufficiently large. It is not automatically resized.

Returns:

the String corresponding to the specified class item.

readConst

protected java.lang.Object readConst(int item,
                                     char[] buf)

Reads a numeric or string constant pool item in b.

Parameters:

item - the index of a constant pool item.

buf - buffer to be used to read the item. This buffer must be sufficiently large. It is not automatically resized.

Returns:

the Integer, Float, Long, Double or String corresponding to the given constant pool item.

readAttribute

protected Attribute readAttribute(java.lang.String type,
                                  int off,
                                  int len,
                                  char[] buf)

Reads an attribute in b. The default implementation of this method returns instances of the Attribute class for all attributes.

Parameters:

type - the type of the attribute.

off - the first byte of the attribute's content in b. The 6 attribute header bytes, containing the type and the length of the attribute, are not taken into account here (they have already been read).

len - the length of the attribute's content.

buf - buffer to be used to call readUTF8, readClass or readConst.

Returns:

the attribute that has been read.