org.objectweb.asm

Class ClassReader


public class ClassReader
extends 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.

Authors:
Eric Bruneton
Eugene Kuleshov

Field Summary

byte[]
b
The class to be parsed.

Constructor Summary

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

Method Summary

void
accept(ClassVisitor classVisitor, boolean skipDebug)
Makes the given visitor visit the Java class of this ClassReader.
void
accept(ClassVisitor classVisitor, Attribute[] attrs, boolean skipDebug)
Makes the given visitor visit the Java class of this ClassReader.
int
getItem(int item)
Returns the start index of the constant pool item in b, plus one.
int
readByte(int index)
Reads a byte value in b.
String
readClass(int index, char[] buf)
Reads a class constant pool item in b.
Object
readConst(int item, char[] buf)
Reads a numeric or string constant pool item in b.
int
readInt(int index)
Reads a signed int value in b.
long
readLong(int index)
Reads a signed long value in b.
short
readShort(int index)
Reads a signed short value in b.
String
readUTF8(int index, char[] buf)
Reads an UTF8 string constant pool item in b.
int
readUnsignedShort(int index)
Reads an unsigned short value in b.

Field Details

b

public final byte[] b
The class to be parsed. The content of this array must not be modified. This field is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

Constructor Details

ClassReader

public ClassReader(InputStream is)
            throws IOException

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


ClassReader

public ClassReader(String name)
            throws IOException

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


ClassReader

public ClassReader(byte[] b)

Parameters:
b - the bytecode of the class to be read.


ClassReader

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

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.

Method Details

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). visitLocalVariable and visitLineNumber methods will not be called.

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


accept

public void accept(ClassVisitor classVisitor,
                   Attribute[] attrs,
                   boolean skipDebug)
Makes the given visitor visit the Java class of this ClassReader. This class is the one specified in the constructor (see ClassReader). visitLocalVariable and visitLineNumber methods will not be called.

Parameters:
classVisitor - the visitor that must visit this class.
attrs - prototypes of the attributes that must be parsed during the visit of the class. Any attribute whose type is not equal to the type of one the prototypes will be ignored.
skipDebug - true if the debug information of the class must not be visited. In this case the


getItem

public int getItem(int item)
Returns the start index of the constant pool item in b, plus one. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

Parameters:
item - the index a constant pool item.

Returns:
the start index of the constant pool item in b, plus one.


readByte

public int readByte(int index)
Reads a byte value in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

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

Returns:
the read value.


readClass

public String readClass(int index,
                        char[] buf)
Reads a class constant pool item in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

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

public Object readConst(int item,
                        char[] buf)
Reads a numeric or string constant pool item in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters. String or Type corresponding to the given constant pool item.

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,


readInt

public int readInt(int index)
Reads a signed int value in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

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

Returns:
the read value.


readLong

public long readLong(int index)
Reads a signed long value in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

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

Returns:
the read value.


readShort

public short readShort(int index)
Reads a signed short value in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

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

Returns:
the read value.


readUTF8

public String readUTF8(int index,
                       char[] buf)
Reads an UTF8 string constant pool item in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

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.


readUnsignedShort

public int readUnsignedShort(int index)
Reads an unsigned short value in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.

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

Returns:
the read value.