===== 6.11 Reference Location Component =====

The Reference Location Component represents lists of offsets into the info item of the Method Component ([[6.9_Method Component| Section 6.9, Method Component]]) to items that contain indices into the **constant_pool[]** array of the Constant Pool Component ([[6.7_Constant Pool Component| Section 6.7, Constant Pool Component]]). This includes all constant pool index operands of instructions, and all non-zero ****catch_type_index**** items of the **exception_handlers** array. The ****catch_type_index**** items that have the value of 0 are not included since they represent finally blocks instead of particular exception classes. 

Some of the constant pool indices are represented in one-byte values while others are represented in two-byte values. Operands of **getfield_T** and **putfield_T** instructions are one-byte constant pool indices. All other indices in a Method Component are two-byte values. 

The Reference Location Component is not referenced by any other component in this CAP file. 

The Reference Location Component structure is defined as: 

The items of the **reference_location_component** structure are as follows: 

**tag** 

The tag item has the value **COMPONENT_ReferenceLocation** (9). 

**size** 

The ******size****** item indicates the number of bytes in the **reference_location_component** structure, excluding the **tag** and ******size****** items. The value of the ******size****** item must be greater than zero. 

**byte_index_count** 

The **byte_index_count** item represents the number of elements in the **offsets_to_byte_indices** array. 

**offsets_to_byte_indices[]** 

The **offsets_to_byte_indices** item represents an array of 1-byte jump offsets into the **info** item of the Method Component to each 1-byte **constant_pool[]** array index. Each entry represents the number of bytes (or distance) between the current index to the next. If the distance is greater than or equal to 255 then there are n entries equal to 255 in the array, where n is equal to the distance divided by 255. The nth entry of 255 is followed by an entry containing the value of the distance modulo 255. 

An example of the jump offsets in an **offsets_to_byte_indices** array is shown in the following table. 

Instruction 

Offset to Operand 

Jump Offset 

**getfield_a 0** 

**10** 

**10** 

**putfield_b 2** 

**65** 

**55** 

 

 

**255** 

 

 

**255** 

**getfield_s 1** 

**580** 

**5** 

 

 

**255** 

**putfield_a 0** 

**835** 

**0** 

**getfield_i 3** 

**843** 

**8** 

All 1-byte **constant_pool[]** array indices in the Method Component must be represented in **offsets_to_byte_indices** array. 

**byte2_index_count** 

The **byte2_index_count** item represents the number of elements in the **offsets_to_byte2_indices** array. 

**offsets_to_byte2_indices[]** 

The **offsets_to_byte2_indices** item represents an array of 1-byte jump offsets into the info item of the Method Component to each 2-byte **constant_pool[]** array index. Each entry represents the number of bytes (or distance) between the current index to the next. If the distance is greater than or equal to 255 then there are n entries equal to 255 in the array, where n is equal to the distance divided by 255. The nth entry of 255 is followed by an entry containing the value of the distance modulo 255. 

An example of the jump offsets in an **offsets_to_byte_indices** array is shown in [[6._The_CAP_File_Format| TABLE 6-17]]. The same example applies to the **offsets_to_byte2_indices** array if the instructions are changed to those with 2-byte **constant_pool[]** array indices. 

All 2-byte **constant_pool[]** array indices in the Method Component must be represented in **offsets_to_byte2_indices** array, including those represented in **catch_type_index** items of the **exception_handler_info** array.