Java Doc for StackMapAttribute.java in  » Rule-Engine » drolls-Rule-Engine » org » drools » asm » attrs » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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,

• if the length of the method's byte code1 is 65535 or less, then uoffset represents the type u2; otherwise uoffset represents the type u4.
• If the maximum number of local variables for the method is 65535 or less, then ulocalvar represents the type u2; otherwise ulocalvar represents the type u4.
• If the maximum size of the operand stack is 65535 or less, then ustack represents the type u2; otherwise ustack represents the type u4.

 stack_map { // attribute StackMap
 u2 attribute_name_index;
 u4 attribute_length
 uoffset number_of_entries;
 stack_map_frame entries[number_of_entries];
 }
 

 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];
 }
 

 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;
 }