ClassReader

java.lang.Object
- scala.tools.asm.ClassReader

```
public class ClassReader
extends java.lang.Object
```
A parser to make a ClassVisitor visit a ClassFile structure, as defined in the Java Virtual Machine Specification (JVMS). This class parses the ClassFile content and calls the appropriate visit methods of a given ClassVisitor for each field, method and bytecode instruction encountered.

See Also:

JVMS 4

Field Summary

Fields
Modifier and Type	Field	Description
`byte[]`	`b`	A byte array containing the JVMS ClassFile structure to be parsed.
`static int`	`EXPAND_FRAMES`	A flag to expand the stack map frames.
`int`	`header`	The offset in bytes, in `b`, of the ClassFile's access_flags field.
`static int`	`SKIP_CODE`	A flag to skip the Code attributes.
`static int`	`SKIP_DEBUG`	A flag to skip the SourceFile, SourceDebugExtension, LocalVariableTable, LocalVariableTypeTable and LineNumberTable attributes.
`static int`	`SKIP_FRAMES`	A flag to skip the StackMap and StackMapTable attributes.

Constructor Summary

Constructors
Constructor	Description
`ClassReader(byte[] classFile)`	Constructs a new `ClassReader` object.
`ClassReader(byte[] classFileBuffer, int classFileOffset, int classFileLength)`	Constructs a new `ClassReader` object.
`ClassReader(java.io.InputStream inputStream)`	Constructs a new `ClassReader` object.
`ClassReader(java.lang.String className)`	Constructs a new `ClassReader` object.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`accept(ClassVisitor classVisitor, int parsingOptions)`	Makes the given visitor visit the JVMS ClassFile structure passed to the constructor of this `ClassReader`.
`void`	`accept(ClassVisitor classVisitor, Attribute[] attributePrototypes, int parsingOptions)`	Makes the given visitor visit the JVMS ClassFile structure passed to the constructor of this `ClassReader`.
`int`	`getAccess()`	Returns the class's access flags (see `Opcodes`).
`java.lang.String`	`getClassName()`	Returns the internal name of the class (see `Type.getInternalName()`).
`java.lang.String[]`	`getInterfaces()`	Returns the internal names of the implemented interfaces (see `Type.getInternalName()`).
`int`	`getItem(int constantPoolEntryIndex)`	Returns the start offset in `b` of a JVMS 'cp_info' structure (i.e.
`int`	`getItemCount()`	Returns the number of entries in the class's constant pool table.
`int`	`getMaxStringLength()`	Returns a conservative estimate of the maximum length of the strings contained in the class's constant pool table.
`java.lang.String`	`getSuperName()`	Returns the internal of name of the super class (see `Type.getInternalName()`).
`int`	`readByte(int offset)`	Reads a byte value in `b`.
`java.lang.String`	`readClass(int offset, char[] charBuffer)`	Reads a CONSTANT_Class constant pool entry in `b`.
`java.lang.Object`	`readConst(int constantPoolEntryIndex, char[] charBuffer)`	Reads a numeric or string constant pool entry in `b`.
`int`	`readInt(int offset)`	Reads a signed int value in `b`.
`protected Label`	`readLabel(int bytecodeOffset, Label[] labels)`	Returns the label corresponding to the given bytecode offset.
`long`	`readLong(int offset)`	Reads a signed long value in `b`.
`java.lang.String`	`readModule(int offset, char[] charBuffer)`	Reads a CONSTANT_Module constant pool entry in `b`.
`java.lang.String`	`readPackage(int offset, char[] charBuffer)`	Reads a CONSTANT_Package constant pool entry in `b`.
`short`	`readShort(int offset)`	Reads a signed short value in `b`.
`int`	`readUnsignedShort(int offset)`	Reads an unsigned short value in `b`.
`java.lang.String`	`readUTF8(int offset, char[] charBuffer)`	Reads a CONSTANT_Utf8 constant pool entry in `b`.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - SKIP_CODE
```
public static final int SKIP_CODE
```
    A flag to skip the Code attributes. If this flag is set the Code attributes are neither parsed nor visited.
    
    See Also:
    
    Constant Field Values
  - SKIP_DEBUG
```
public static final int SKIP_DEBUG
```
    A flag to skip the SourceFile, SourceDebugExtension, LocalVariableTable, LocalVariableTypeTable and LineNumberTable attributes. If this flag is set these attributes are neither parsed nor visited (i.e. ClassVisitor.visitSource(java.lang.String, java.lang.String), MethodVisitor.visitLocalVariable(java.lang.String, java.lang.String, java.lang.String, scala.tools.asm.Label, scala.tools.asm.Label, int) and MethodVisitor.visitLineNumber(int, scala.tools.asm.Label) are not called).
    
    See Also:
    
    Constant Field Values
  - SKIP_FRAMES
```
public static final int SKIP_FRAMES
```
    A flag to skip the StackMap and StackMapTable attributes. If this flag is set these attributes are neither parsed nor visited (i.e. MethodVisitor.visitFrame(int, int, java.lang.Object[], int, java.lang.Object[]) is not called). This flag is useful when the ClassWriter.COMPUTE_FRAMES option is used: it avoids visiting frames that will be ignored and recomputed from scratch.
    
    See Also:
    
    Constant Field Values
  - EXPAND_FRAMES
```
public static final int EXPAND_FRAMES
```
    A 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/compression step in ClassReader and ClassWriter which degrades performance quite a lot).
    
    See Also:
    
    Constant Field Values
  - b
```
public final byte[] b
```
    A byte array containing the JVMS ClassFile structure 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 visitors.
    NOTE: the ClassFile structure can start at any offset within this array, i.e. it does not necessarily start at offset 0. Use getItem(int) and header to get correct ClassFile element offsets within this byte array.
  - header
```
public final int header
```
    The offset in bytes, in b, of the ClassFile's access_flags field.
- Constructor Detail
  - ClassReader
```
public ClassReader(byte[] classFile)
```
    Constructs a new ClassReader object.
    
    Parameters:
    
    classFile - the JVMS ClassFile structure to be read.
  - ClassReader
```
public ClassReader(byte[] classFileBuffer,
                   int classFileOffset,
                   int classFileLength)
```
    Constructs a new ClassReader object.
    
    Parameters:
    
    classFileBuffer - a byte array containing the JVMS ClassFile structure to be read.
    
    classFileOffset - the offset in byteBuffer of the first byte of the ClassFile to be read.
    
    classFileLength - the length in bytes of the ClassFile to be read.
  - ClassReader
```
public ClassReader(java.io.InputStream inputStream)
            throws java.io.IOException
```
    Constructs a new ClassReader object.
    
    Parameters:
    
    inputStream - an input stream of the JVMS ClassFile structure to be read. This input stream must contain nothing more than the ClassFile structure itself. It is read from its current position to its end.
    
    Throws:
    
    java.io.IOException - if a problem occurs during reading.
  - ClassReader
```
public ClassReader(java.lang.String className)
            throws java.io.IOException
```
    Constructs a new ClassReader object.
    
    Parameters:
    
    className - the fully qualified name of the class to be read. The ClassFile structure is retrieved with the current class loader's ClassLoader.getSystemResourceAsStream(java.lang.String).
    
    Throws:
    
    java.io.IOException - if an exception occurs during reading.
- Method Detail
  - getAccess
```
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:
    
    ClassVisitor.visit(int, int, String, String, String, String[])
  - getClassName
```
public java.lang.String getClassName()
```
    Returns the internal name of the class (see Type.getInternalName()).
    
    Returns:
    
    the internal class name.
    
    See Also:
    
    ClassVisitor.visit(int, int, String, String, String, String[])
  - getSuperName
```
public java.lang.String getSuperName()
```
    Returns the internal of name of the super class (see Type.getInternalName()). For interfaces, the super class is Object.
    
    Returns:
    
    the internal name of the super class, or null for Object class.
    
    See Also:
    
    ClassVisitor.visit(int, int, String, String, String, String[])
  - getInterfaces
```
public java.lang.String[] getInterfaces()
```
    Returns the internal names of the implemented interfaces (see Type.getInternalName()).
    
    Returns:
    
    the internal names of the directly implemented interfaces. Inherited implemented interfaces are not returned.
    
    See Also:
    
    ClassVisitor.visit(int, int, String, String, String, String[])
  - accept
```
public void accept(ClassVisitor classVisitor,
                   int parsingOptions)
```
    Makes the given visitor visit the JVMS ClassFile structure passed to the constructor of this ClassReader.
    
    Parameters:
    
    classVisitor - the visitor that must visit this class.
    
    parsingOptions - the options to use to parse this class. One or more of SKIP_CODE, SKIP_DEBUG, SKIP_FRAMES or EXPAND_FRAMES.
  - accept
```
public void accept(ClassVisitor classVisitor,
                   Attribute[] attributePrototypes,
                   int parsingOptions)
```
    Makes the given visitor visit the JVMS ClassFile structure passed to the constructor of this ClassReader.
    
    Parameters:
    
    classVisitor - the visitor that must visit this class.
    
    attributePrototypes - 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.
    
    parsingOptions - the options to use to parse this class. One or more of SKIP_CODE, SKIP_DEBUG, SKIP_FRAMES or EXPAND_FRAMES.
  - readLabel
```
protected Label readLabel(int bytecodeOffset,
                          Label[] labels)
```
    Returns the label corresponding to the given bytecode offset. The default implementation of this method creates a label for the given offset if it has not been already created.
    
    Parameters:
    
    bytecodeOffset - a bytecode offset in a method.
    
    labels - the already created labels, indexed by their offset. If a label already exists for bytecodeOffset 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[bytecodeOffset].
  - getItemCount
```
public int getItemCount()
```
    Returns the number of entries in the class's constant pool table.
    
    Returns:
    
    the number of entries in the class's constant pool table.
  - getItem
```
public int getItem(int constantPoolEntryIndex)
```
    Returns the start offset in b of a JVMS 'cp_info' structure (i.e. a constant pool entry), plus one. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
    
    Parameters:
    
    constantPoolEntryIndex - the index a constant pool entry in the class's constant pool table.
    
    Returns:
    
    the start offset in b of the corresponding JVMS 'cp_info' structure, plus one.
  - getMaxStringLength
```
public int getMaxStringLength()
```
    Returns a conservative estimate of the maximum length of the strings contained in the class's constant pool table.
    
    Returns:
    
    a conservative estimate of the maximum length of the strings contained in the class's constant pool table.
  - readByte
```
public int readByte(int offset)
```
    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:
    
    offset - the start offset of the value to be read in b.
    
    Returns:
    
    the read value.
  - readUnsignedShort
```
public int readUnsignedShort(int offset)
```
    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:
    
    offset - the start index of the value to be read in b.
    
    Returns:
    
    the read value.
  - readShort
```
public short readShort(int offset)
```
    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:
    
    offset - the start offset of the value to be read in b.
    
    Returns:
    
    the read value.
  - readInt
```
public int readInt(int offset)
```
    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:
    
    offset - the start offset of the value to be read in b.
    
    Returns:
    
    the read value.
  - readLong
```
public long readLong(int offset)
```
    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:
    
    offset - the start offset of the value to be read in b.
    
    Returns:
    
    the read value.
  - readUTF8
```
public java.lang.String readUTF8(int offset,
                                 char[] charBuffer)
```
    Reads a CONSTANT_Utf8 constant pool entry in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
    
    Parameters:
    
    offset - the start offset of an unsigned short value in b, whose value is the index of a CONSTANT_Utf8 entry in the class's constant pool table.
    
    charBuffer - the buffer to be used to read the string. This buffer must be sufficiently large. It is not automatically resized.
    
    Returns:
    
    the String corresponding to the specified CONSTANT_Utf8 entry.
  - readClass
```
public java.lang.String readClass(int offset,
                                  char[] charBuffer)
```
    Reads a CONSTANT_Class constant pool entry in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
    
    Parameters:
    
    offset - the start offset of an unsigned short value in b, whose value is the index of a CONSTANT_Class entry in class's constant pool table.
    
    charBuffer - the 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 CONSTANT_Class entry.
  - readModule
```
public java.lang.String readModule(int offset,
                                   char[] charBuffer)
```
    Reads a CONSTANT_Module constant pool entry in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
    
    Parameters:
    
    offset - the start offset of an unsigned short value in b, whose value is the index of a CONSTANT_Module entry in class's constant pool table.
    
    charBuffer - the 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 CONSTANT_Module entry.
  - readPackage
```
public java.lang.String readPackage(int offset,
                                    char[] charBuffer)
```
    Reads a CONSTANT_Package constant pool entry in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
    
    Parameters:
    
    offset - the start offset of an unsigned short value in b, whose value is the index of a CONSTANT_Package entry in class's constant pool table.
    
    charBuffer - the 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 CONSTANT_Package entry.
  - readConst
```
public java.lang.Object readConst(int constantPoolEntryIndex,
                                  char[] charBuffer)
```
    Reads a numeric or string constant pool entry in b. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
    
    Parameters:
    
    constantPoolEntryIndex - the index of a CONSTANT_Integer, CONSTANT_Float, CONSTANT_Long, CONSTANT_Double, CONSTANT_Class, CONSTANT_String, CONSTANT_MethodType, CONSTANT_MethodHandle or CONSTANT_Dynamic entry in the class's constant pool.
    
    charBuffer - the buffer to be used to read strings. This buffer must be sufficiently large. It is not automatically resized.
    
    Returns:
    
    the Integer, Float, Long, Double, String, Type, Handle or ConstantDynamic corresponding to the specified constant pool entry.

Class ClassReader

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

SKIP_CODE

SKIP_DEBUG

SKIP_FRAMES

EXPAND_FRAMES

b

header

Constructor Detail

ClassReader

ClassReader

ClassReader

ClassReader

Method Detail

getAccess

getClassName

getSuperName

getInterfaces

accept

accept

readLabel

getItemCount

getItem

getMaxStringLength

readByte

readUnsignedShort

readShort

readInt

readLong

readUTF8

readClass

readModule

readPackage

readConst