public class

ClassReader

extends Object
java.lang.Object
   ↳ org.eclipse.sisu.space.asm.ClassReader

Class Overview

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.

Summary

Constants
int EXPAND_FRAMES Flag to expand the stack map frames.
int SKIP_CODE Flag to skip method code.
int SKIP_DEBUG Flag to skip the debug information in the class.
int SKIP_FRAMES Flag to skip the stack map frames in the class.
Fields
public final byte[] b The class to be parsed.
public final int header Start index of the class header information (access, name...) in b.
Public Constructors
ClassReader(byte[] b)
Constructs a new ClassReader object.
ClassReader(byte[] b, int off, int len)
Constructs a new ClassReader object.
ClassReader(InputStream is)
Constructs a new ClassReader object.
ClassReader(String name)
Constructs a new ClassReader object.
Public Methods
void accept(ClassVisitor classVisitor, Attribute[] attrs, int flags)
Makes the given visitor visit the Java class of this ClassReader.
void accept(ClassVisitor classVisitor, int flags)
Makes the given visitor visit the Java class of this ClassReader .
int getAccess()
Returns the class's access flags (see Opcodes).
String getClassName()
Returns the internal name of the class (see getInternalName).
String[] getInterfaces()
Returns the internal names of the class's interfaces (see getInternalName).
int getItem(int item)
Returns the start index of the constant pool item in b, plus one.
int getItemCount()
Returns the number of constant pool items in b.
int getMaxStringLength()
Returns the maximum length of the strings contained in the constant pool of the class.
String getSuperName()
Returns the internal of name of the super class (see getInternalName).
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.
Protected Methods
Label readLabel(int offset, Label[] labels)
Returns the label corresponding to the given offset.
[Expand]
Inherited Methods
From class java.lang.Object

Constants

public static final int EXPAND_FRAMES

Flag to expand the stack map frames. By default stack map frames are visited in their original format (i.e. "expanded" for classes whose version is less than V1_6, and "compressed" for the other classes). If this flag is set, stack map frames are always visited in expanded format (this option adds a decompression/recompression step in ClassReader and ClassWriter which degrades performances quite a lot).

Constant Value: 8 (0x00000008)

public static final int SKIP_CODE

Flag to skip method code. If this class is set CODE attribute won't be visited. This can be used, for example, to retrieve annotations for methods and method parameters.

Constant Value: 1 (0x00000001)

public static final int SKIP_DEBUG

Flag to skip the debug information in the class. If this flag is set the debug information of the class is not visited, i.e. the visitLocalVariable and visitLineNumber methods will not be called.

Constant Value: 2 (0x00000002)

public static final int SKIP_FRAMES

Flag to skip the stack map frames in the class. If this flag is set the stack map frames of the class is not visited, i.e. the visitFrame method will not be called. This flag is useful when the COMPUTE_FRAMES option is used: it avoids visiting frames that will be ignored and recomputed from scratch in the class writer.

Constant Value: 4 (0x00000004)

Fields

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.

public final int header

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

Public Constructors

public ClassReader (byte[] b)

Constructs a new ClassReader object.

Parameters
b the bytecode of the class to be read.

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.

public ClassReader (InputStream is)

Constructs a new ClassReader object.

Parameters
is an input stream from which to read the class.
Throws
IOException if a problem occurs during reading.

public ClassReader (String name)

Constructs a new ClassReader object.

Parameters
name the binary qualified name of the class to be read.
Throws
IOException if an exception occurs during reading.

Public Methods

public void accept (ClassVisitor classVisitor, Attribute[] attrs, int flags)

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.
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 not be parsed: its byte array value will be passed unchanged to the ClassWriter. This may corrupt it if this value contains references to the constant pool, or has syntactic or semantic links with a class element that has been transformed by a class adapter between the reader and the writer.
flags option flags that can be used to modify the default behavior of this class. See SKIP_DEBUG, EXPAND_FRAMES , SKIP_FRAMES, SKIP_CODE.

public void accept (ClassVisitor classVisitor, int flags)

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.
flags option flags that can be used to modify the default behavior of this class. See SKIP_DEBUG, EXPAND_FRAMES , SKIP_FRAMES, SKIP_CODE.

public int getAccess ()

Returns the class's access flags (see Opcodes). This value may not reflect Deprecated and Synthetic flags when bytecode is before 1.5 and those flags are represented by attributes.

Returns
  • the class access flags
See Also

public String getClassName ()

Returns the internal name of the class (see getInternalName).

Returns
  • the internal class name
See Also

public String[] getInterfaces ()

Returns the internal names of the class's interfaces (see getInternalName).

Returns
  • the array of internal names for all implemented interfaces or null.
See Also

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.

public int getItemCount ()

Returns the number of constant pool items in b.

Returns
  • the number of constant pool items in b.

public int getMaxStringLength ()

Returns the maximum length of the strings contained in the constant pool of the class.

Returns
  • the maximum length of the strings contained in the constant pool of the class.

public String getSuperName ()

Returns the internal of name of the super class (see getInternalName). For interfaces, the super class is Object.

Returns
  • the internal name of super class, or null for Object class.
See Also

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.

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.

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.

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

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.

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.

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.

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.

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.

Protected Methods

protected Label readLabel (int offset, Label[] labels)

Returns the label corresponding to the given offset. The default implementation of this method creates a label for the given offset if it has not been already created.

Parameters
offset a bytecode offset in a method.
labels the already created labels, indexed by their offset. If a label already exists for offset this method must not create a new one. Otherwise it must store the new label in this array.
Returns
  • a non null Label, which must be equal to labels[offset].