Package org.objectweb.asm
Class Attribute
java.lang.Object
org.objectweb.asm.Attribute
- Direct Known Subclasses:
ModuleHashesAttribute
,ModuleResolutionAttribute
,ModuleTargetAttribute
A non standard class, field, method or Code attribute, as defined in the Java Virtual Machine
Specification (JVMS).
- See Also:
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Nested Class Summary
Nested ClassesModifier and TypeClassDescription(package private) static final class
A set of attribute prototypes (attributes with the same type are considered equal). -
Field Summary
FieldsModifier and TypeFieldDescriptionprivate ByteVector
The raw content of this attribute, as returned bywrite(ClassWriter,byte[],int,int,int)
.(package private) Attribute
The next attribute in this attribute list (Attribute instances can be linked via this field to store a list of class, field, method or Code attributes).final String
The type of this attribute, also called its name in the JVMS. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescription(package private) final int
computeAttributesSize
(SymbolTable symbolTable) Returns the total size in bytes of all the attributes in the attribute list that begins with this attribute.(package private) final int
computeAttributesSize
(SymbolTable symbolTable, byte[] code, int codeLength, int maxStack, int maxLocals) Returns the total size in bytes of all the attributes in the attribute list that begins with this attribute.(package private) static int
computeAttributesSize
(SymbolTable symbolTable, int accessFlags, int signatureIndex) Returns the total size in bytes of all the attributes that correspond to the given field, method or class access flags and signature.(package private) final int
Returns the number of attributes of the attribute list that begins with this attribute.protected Label[]
Deprecated.no longer used by ASM.boolean
Returns true if this type of attribute is a Code attribute.boolean
Returns true if this type of attribute is unknown.private ByteVector
maybeWrite
(ClassWriter classWriter, byte[] code, int codeLength, int maxStack, int maxLocals) Callswrite(ClassWriter,byte[],int,int,int)
if it has not already been called and returns its result or its (cached) previous result.(package private) final void
putAttributes
(SymbolTable symbolTable, byte[] code, int codeLength, int maxStack, int maxLocals, ByteVector output) Puts all the attributes of the attribute list that begins with this attribute, in the given byte vector.(package private) static void
putAttributes
(SymbolTable symbolTable, int accessFlags, int signatureIndex, ByteVector output) Puts all the attributes that correspond to the given field, method or class access flags and signature, in the given byte vector.(package private) final void
putAttributes
(SymbolTable symbolTable, ByteVector output) Puts all the attributes of the attribute list that begins with this attribute, in the given byte vector.static Attribute
read
(Attribute attribute, ClassReader classReader, int offset, int length, char[] charBuffer, int codeAttributeOffset, Label[] labels) Reads an attribute with the sametype
as the given attribute.protected Attribute
read
(ClassReader classReader, int offset, int length, char[] charBuffer, int codeAttributeOffset, Label[] labels) Reads atype
attribute.static Label
readLabel
(ClassReader classReader, int bytecodeOffset, Label[] labels) Returns the label corresponding to the given bytecode offset by callingClassReader.readLabel(int, org.objectweb.asm.Label[])
.static byte[]
write
(Attribute attribute, ClassWriter classWriter, byte[] code, int codeLength, int maxStack, int maxLocals) Returns the byte array form of the content of the given attribute.protected ByteVector
write
(ClassWriter classWriter, byte[] code, int codeLength, int maxStack, int maxLocals) Returns the byte array form of the content of this attribute.
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Field Details
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type
The type of this attribute, also called its name in the JVMS. -
cachedContent
The raw content of this attribute, as returned bywrite(ClassWriter,byte[],int,int,int)
. The 6 header bytes of the attribute (attribute_name_index and attribute_length) are not included. -
nextAttribute
Attribute nextAttributeThe next attribute in this attribute list (Attribute instances can be linked via this field to store a list of class, field, method or Code attributes). May be null.
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Constructor Details
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Attribute
Constructs a new empty attribute.- Parameters:
type
- the type of the attribute.
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Method Details
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isUnknown
public boolean isUnknown()Returns true if this type of attribute is unknown. This means that the attribute content can't be parsed to extract constant pool references, labels, etc. Instead, the attribute content is read as an opaque byte array, and written back as is. This can lead to invalid attributes, if the content actually contains constant pool references, labels, or other symbolic references that need to be updated when there are changes to the constant pool, the method bytecode, etc. The default implementation of this method always returns true.- Returns:
- true if this type of attribute is unknown.
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isCodeAttribute
public boolean isCodeAttribute()Returns true if this type of attribute is a Code attribute.- Returns:
- true if this type of attribute is a Code attribute.
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getLabels
Deprecated.no longer used by ASM.Returns the labels corresponding to this attribute.- Returns:
- the labels corresponding to this attribute, or null if this attribute is not a Code attribute that contains labels.
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read
protected Attribute read(ClassReader classReader, int offset, int length, char[] charBuffer, int codeAttributeOffset, Label[] labels) Reads atype
attribute. This method must return a newAttribute
object, of typetype
, corresponding to the 'length' bytes starting at 'offset', in the given ClassReader.- Parameters:
classReader
- the class that contains the attribute to be read.offset
- index of the first byte of the attribute's content inClassReader
. The 6 attribute header bytes (attribute_name_index and attribute_length) are not taken into account here.length
- the length of the attribute's content (excluding the 6 attribute header bytes).charBuffer
- the buffer to be used to call the ClassReader methods requiring a 'charBuffer' parameter.codeAttributeOffset
- index of the first byte of content of the enclosing Code attribute inClassReader
, or -1 if the attribute to be read is not a Code attribute. The 6 attribute header bytes (attribute_name_index and attribute_length) are not taken into account here.labels
- the labels of the method's code, or null if the attribute to be read is not a Code attribute. Labels defined in the attribute must be created and added to this array, if not already present, by calling thereadLabel(org.objectweb.asm.ClassReader, int, org.objectweb.asm.Label[])
method (do not createLabel
instances directly).- Returns:
- a new
Attribute
object corresponding to the specified bytes.
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read
public static Attribute read(Attribute attribute, ClassReader classReader, int offset, int length, char[] charBuffer, int codeAttributeOffset, Label[] labels) Reads an attribute with the sametype
as the given attribute. This method returns a newAttribute
object, corresponding to the 'length' bytes starting at 'offset', in the given ClassReader.- Parameters:
attribute
- The attribute prototype that is used for reading.classReader
- the class that contains the attribute to be read.offset
- index of the first byte of the attribute's content inClassReader
. The 6 attribute header bytes (attribute_name_index and attribute_length) are not taken into account here.length
- the length of the attribute's content (excluding the 6 attribute header bytes).charBuffer
- the buffer to be used to call the ClassReader methods requiring a 'charBuffer' parameter.codeAttributeOffset
- index of the first byte of content of the enclosing Code attribute inClassReader
, or -1 if the attribute to be read is not a Code attribute. The 6 attribute header bytes (attribute_name_index and attribute_length) are not taken into account here.labels
- the labels of the method's code, or null if the attribute to be read is not a Code attribute. Labels defined in the attribute are added to this array, if not already present.- Returns:
- a new
Attribute
object corresponding to the specified bytes.
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readLabel
Returns the label corresponding to the given bytecode offset by callingClassReader.readLabel(int, org.objectweb.asm.Label[])
. This creates and adds the label to the given array if it is not already present. Note that this created label may be aLabel
subclass instance, if the given ClassReader overridesClassReader.readLabel(int, org.objectweb.asm.Label[])
. Henceread(ClassReader, int, int, char[], int, Label[])
must not manually createLabel
instances.- 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 does not create a new one. Otherwise it stores the new label in this array.- Returns:
- a label for the given bytecode offset.
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maybeWrite
private ByteVector maybeWrite(ClassWriter classWriter, byte[] code, int codeLength, int maxStack, int maxLocals) Callswrite(ClassWriter,byte[],int,int,int)
if it has not already been called and returns its result or its (cached) previous result.- Parameters:
classWriter
- the class to which this attribute must be added. This parameter can be used to add the items that corresponds to this attribute to the constant pool of this class.code
- the bytecode of the method corresponding to this Code attribute, or null if this attribute is not a Code attribute. Corresponds to the 'code' field of the Code attribute.codeLength
- the length of the bytecode of the method corresponding to this code attribute, or 0 if this attribute is not a Code attribute. Corresponds to the 'code_length' field of the Code attribute.maxStack
- the maximum stack size of the method corresponding to this Code attribute, or -1 if this attribute is not a Code attribute.maxLocals
- the maximum number of local variables of the method corresponding to this code attribute, or -1 if this attribute is not a Code attribute.- Returns:
- the byte array form of this attribute.
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write
protected ByteVector write(ClassWriter classWriter, byte[] code, int codeLength, int maxStack, int maxLocals) Returns the byte array form of the content of this attribute. The 6 header bytes (attribute_name_index and attribute_length) must not be added in the returned ByteVector.This method is only invoked once to compute the binary form of this attribute. Subsequent changes to the attribute after it was written for the first time will not be considered.
- Parameters:
classWriter
- the class to which this attribute must be added. This parameter can be used to add the items that corresponds to this attribute to the constant pool of this class.code
- the bytecode of the method corresponding to this Code attribute, or null if this attribute is not a Code attribute. Corresponds to the 'code' field of the Code attribute.codeLength
- the length of the bytecode of the method corresponding to this code attribute, or 0 if this attribute is not a Code attribute. Corresponds to the 'code_length' field of the Code attribute.maxStack
- the maximum stack size of the method corresponding to this Code attribute, or -1 if this attribute is not a Code attribute.maxLocals
- the maximum number of local variables of the method corresponding to this code attribute, or -1 if this attribute is not a Code attribute.- Returns:
- the byte array form of this attribute.
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write
public static byte[] write(Attribute attribute, ClassWriter classWriter, byte[] code, int codeLength, int maxStack, int maxLocals) Returns the byte array form of the content of the given attribute. The 6 header bytes (attribute_name_index and attribute_length) are not added in the returned byte array.- Parameters:
attribute
- The attribute that should be written.classWriter
- the class to which this attribute must be added. This parameter can be used to add the items that corresponds to this attribute to the constant pool of this class.code
- the bytecode of the method corresponding to this Code attribute, or null if this attribute is not a Code attribute. Corresponds to the 'code' field of the Code attribute.codeLength
- the length of the bytecode of the method corresponding to this code attribute, or 0 if this attribute is not a Code attribute. Corresponds to the 'code_length' field of the Code attribute.maxStack
- the maximum stack size of the method corresponding to this Code attribute, or -1 if this attribute is not a Code attribute.maxLocals
- the maximum number of local variables of the method corresponding to this code attribute, or -1 if this attribute is not a Code attribute.- Returns:
- the byte array form of this attribute.
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getAttributeCount
final int getAttributeCount()Returns the number of attributes of the attribute list that begins with this attribute.- Returns:
- the number of attributes of the attribute list that begins with this attribute.
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computeAttributesSize
Returns the total size in bytes of all the attributes in the attribute list that begins with this attribute. This size includes the 6 header bytes (attribute_name_index and attribute_length) per attribute. Also adds the attribute type names to the constant pool.- Parameters:
symbolTable
- where the constants used in the attributes must be stored.- Returns:
- the size of all the attributes in this attribute list. This size includes the size of the attribute headers.
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computeAttributesSize
final int computeAttributesSize(SymbolTable symbolTable, byte[] code, int codeLength, int maxStack, int maxLocals) Returns the total size in bytes of all the attributes in the attribute list that begins with this attribute. This size includes the 6 header bytes (attribute_name_index and attribute_length) per attribute. Also adds the attribute type names to the constant pool.- Parameters:
symbolTable
- where the constants used in the attributes must be stored.code
- the bytecode of the method corresponding to these Code attributes, or null if they are not Code attributes. Corresponds to the 'code' field of the Code attribute.codeLength
- the length of the bytecode of the method corresponding to these code attributes, or 0 if they are not Code attributes. Corresponds to the 'code_length' field of the Code attribute.maxStack
- the maximum stack size of the method corresponding to these Code attributes, or -1 if they are not Code attributes.maxLocals
- the maximum number of local variables of the method corresponding to these Code attributes, or -1 if they are not Code attribute.- Returns:
- the size of all the attributes in this attribute list. This size includes the size of the attribute headers.
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computeAttributesSize
Returns the total size in bytes of all the attributes that correspond to the given field, method or class access flags and signature. This size includes the 6 header bytes (attribute_name_index and attribute_length) per attribute. Also adds the attribute type names to the constant pool.- Parameters:
symbolTable
- where the constants used in the attributes must be stored.accessFlags
- some field, method or class access flags.signatureIndex
- the constant pool index of a field, method of class signature.- Returns:
- the size of all the attributes in bytes. This size includes the size of the attribute headers.
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putAttributes
Puts all the attributes of the attribute list that begins with this attribute, in the given byte vector. This includes the 6 header bytes (attribute_name_index and attribute_length) per attribute.- Parameters:
symbolTable
- where the constants used in the attributes must be stored.output
- where the attributes must be written.
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putAttributes
final void putAttributes(SymbolTable symbolTable, byte[] code, int codeLength, int maxStack, int maxLocals, ByteVector output) Puts all the attributes of the attribute list that begins with this attribute, in the given byte vector. This includes the 6 header bytes (attribute_name_index and attribute_length) per attribute.- Parameters:
symbolTable
- where the constants used in the attributes must be stored.code
- the bytecode of the method corresponding to these Code attributes, or null if they are not Code attributes. Corresponds to the 'code' field of the Code attribute.codeLength
- the length of the bytecode of the method corresponding to these code attributes, or 0 if they are not Code attributes. Corresponds to the 'code_length' field of the Code attribute.maxStack
- the maximum stack size of the method corresponding to these Code attributes, or -1 if they are not Code attributes.maxLocals
- the maximum number of local variables of the method corresponding to these Code attributes, or -1 if they are not Code attribute.output
- where the attributes must be written.
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putAttributes
static void putAttributes(SymbolTable symbolTable, int accessFlags, int signatureIndex, ByteVector output) Puts all the attributes that correspond to the given field, method or class access flags and signature, in the given byte vector. This includes the 6 header bytes (attribute_name_index and attribute_length) per attribute.- Parameters:
symbolTable
- where the constants used in the attributes must be stored.accessFlags
- some field, method or class access flags.signatureIndex
- the constant pool index of a field, method of class signature.output
- where the attributes must be written.
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