public class StackMapAttribute extends Attribute
Note that this implementation does not calculate StackMapFrame structures from the method bytecode. If method code is changed or generated from scratch, then developer is responsible to prepare a correct StackMapFrame structures.
The format of the stack map in the class file is given below. In the following,
stack_map { // attribute StackMap u2 attribute_name_index; u4 attribute_length uoffset number_of_entries; stack_map_frame entries[number_of_entries]; }Each stack map frame has the following format:
stack_map_frame { uoffset offset; ulocalvar number_of_locals; verification_type_info locals[number_of_locals]; ustack number_of_stack_items; verification_type_info stack[number_of_stack_items]; }The verification_type_info structure consists of a one-byte tag followed by zero or more bytes, giving more information about the tag. Each verification_type_info structure specifies the verification type of one or two locations.
union verification_type_info { Top_variable_info; Integer_variable_info; Float_variable_info; Long_variable_info; Double_variable_info; Null_variable_info; UninitializedThis_variable_info; Object_variable_info; Uninitialized_variable_info; } Top_variable_info { u1 tag = ITEM_Top; // 0 } Integer_variable_info { u1 tag = ITEM_Integer; // 1 } Float_variable_info { u1 tag = ITEM_Float; // 2 } Long_variable_info { u1 tag = ITEM_Long; // 4 } Double_variable_info { u1 tag = ITEM_Double; // 3 } Null_variable_info { u1 tag = ITEM_Null; // 5 } UninitializedThis_variable_info { u1 tag = ITEM_UninitializedThis; // 6 } Object_variable_info { u1 tag = ITEM_Object; // 7 u2 cpool_index; } Uninitialized_variable_info { u1 tag = ITEM_Uninitialized // 8 uoffset offset; }
Constructor and Description |
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StackMapAttribute() |
Modifier and Type | Method and Description |
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StackMapFrame |
getFrame(Label label) |
protected Label[] |
getLabels()
Returns the labels corresponding to this attribute.
|
protected Attribute |
read(ClassReader cr,
int off,
int len,
char[] buf,
int codeOff,
Label[] labels)
Reads a
type attribute. |
String |
toString() |
protected ByteVector |
write(ClassWriter cw,
byte[] code,
int len,
int maxStack,
int maxLocals)
Returns the byte array form of this attribute.
|
public ArrayList frames
public StackMapFrame getFrame(Label label)
protected Attribute read(ClassReader cr, int off, int len, char[] buf, int codeOff, Label[] labels)
Attribute
type
attribute. This method must return a new
Attribute
object, of type type
, corresponding to the
len bytes starting at the given offset, in the given class reader.read
in class Attribute
cr
- the class that contains the attribute to be read.off
- index of the first byte of the attribute's content in cr.b
. The 6 attribute header bytes, containing the type
and the length of the attribute, are not taken into account here.len
- the length of the attribute's content.buf
- buffer to be used to call readUTF8
,
readClass
or readConst
.codeOff
- index of the first byte of code's attribute content in
cr.b
, or -1 if the attribute to be read is not a
code attribute. The 6 attribute header bytes, containing the type and
the length of the attribute, 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.Attribute
object corresponding to the given
bytes.protected ByteVector write(ClassWriter cw, byte[] code, int len, int maxStack, int maxLocals)
Attribute
write
in class Attribute
cw
- the class to which this attribute must be added. This parameter
can be used to add to the constant pool of this class the items that
corresponds to this attribute.code
- the bytecode of the method corresponding to this code
attribute, or null if this attribute is not a code
attributes.len
- the length of the bytecode of the method corresponding to this
code attribute, or null if this attribute is not a 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.protected Label[] getLabels()
Attribute
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