JCOD Syntax

This chapter describes JCOD syntax, and how to encode class files using JCOD. Jcoder is a low-level assembler that accepts text in the JCOD format and produces a .class file for use with a Java Virtual Machine. Jcoder's primary use is as a tool for producing specialized tests for testing a JVM implementation.

Jcoder is called a low-level assembler because it provides very few higher abstractions beyond the class file format. Typically, there is a 1-1 relationship between constructs in the class file, and constructs in the JCOD format. All Java Spec come from Chapter 4 of the Java Virtual Machine Specification.

This chapter contains the following sections:

Syntax

The source text file can be free form (newlines are considered blanks) and may contain Java-style commenting. The first line of a JCOD file represents the name of the resulting file in the destination directory. This name does not affect the content of the resulting file. This line has two forms:

file FILENAME

or

class CLASSNAME

In the latter case, extension .class will be added to form FILENAME. Jcod's -d option allows you to define the destination directory. A list of structured data items follows the class name. The length (in bytes) of each item is determined by its representation.

Primitive Types

Decimal Values

Decimal values may be followed by an optional size indicator. Default values (no indicator) are 2 bytes. Decimal numbers may start with `#' sign. The `#' sign does not have an affect on the number, but may simply be used to indicate decimal values.

Optional Size Indicators

b (1 byte)
s (2 bytes)
i (4 bytes)
l (8 bytes)

Examples

17
17s
#17

Hexadecimal Values

Size of hexadecimal values is determined by the number of places the number holds. Two places is equal to 1 byte. A hexadecimal number may not hold more than 16 places (8 bytes). Leading zeros should be used to where appropriate.

Examples

0x17 (1 byte)
0x0017 (2 bytes)

Unicode Values

Unicode strings use the same syntax as strings in the Java programming language.

Pure unicode strings are bounded with character \' instead of \". Unlike ordinary strings, they are not prepended with two-byte integer representing actual string's length. As a result, they may exceed 64Kbyte limit.

Constant Values

Each constant is 1 byte in size.

Constant Pool Tags:

Utf8 = 1;
int = 3;
float = 4;
long = 5;
double = 6;
class = 7;
String = 8;
Field = 9;
Method = 10;
InterfaceMethod = 11;
NameAndType = 12;

Types for StackMap attribute:

B = 0;
I = 1;
F = 2;
D = 3;
L = 4;
N = 5;
IO = 6;
O = 7;
NO = 8;

Types for access flags typically are encoded in 2 bytes:

Flag Name	Value	Interpretation
`ACC_PUBLIC`	`0x0001`	Declared `public`; may be accessed from outside its package.
`ACC_PRIVATE`	`0x0002`	Declared `private`; usable only within the defining class.
`ACC_PROTECTED`	`0x0004`	Declared `protected`; may be accessed within subclasses.

Note - access flags are defined separately for Class, Field, Methods etc. You should look

at the VM spec to see the flags that are applicable for a given entity.

Structured Data Types

Types:

Record
Open List
Closed List
Array
Byte Array
Attribute
Component

Record

A record is a sequence of simple data types separated by blanks or commas. Records may be limited by a semicolon or right curly brace `}'.

Example

class #5
1,2,3,4

Open List

An open list is sequence of records separated by semicolons.

Example

class #5; // #1
class #12; // #2 
Method #2 #0; // #3

Closed List

Open list enclosed in curly braces `{ }'.

Example

{ 
 0x0001;// access 
 #14; // name_cpx 
 #15; // sig_cpx 
}

Array

An integer in square brackets followed by a closed list. The integer represents the length of the array and occupies 2 bytes in the resulting class file. If omitted, the integer will represent the number of records in the following closed list. If the right square bracket is followed by letter "b", then the length occupies 1 byte. Such arrays are used in JavaCard .cap files.

Example

[] 
{ 
 // Constant Pool 
 ; // first element of constant pool is always empty 
 class #5; // #1
 class #12; // #2 
 Method #2 #0; // #3 
 NameAndType #14 #0; // #4 
 Utf8 "empty"; // #5 
}

In this example, Jcoder will set the length of the array to 6 because the first semicolon is counted as an element delimiter, even though the first element occupies 0 bytes.

Byte Array

A byte array is defined through the use of the "Byte" keyword followed by length of the array and the array itself. By default, the length of the array occupies 4 bytes in the resulting .class file. If the right square bracket is followed by letter "b", then the length occupies 1 byte, letter "s" sets the size of length to 2 bytes. If the length is omitted, the number of bytes in the following closed list is used.

Example

Bytes[5] 
{
 0x2AB70003B1; 
};

Attribute

An attribute is defined through the use of the "Attr" keyword. This keyword is followed by a 2 byte integer index in the constant pool and a 4 byte integer representing the length of the variable part of the attribute in bytes. These two values should be inclosed in parenthesis and separated by commas. If the second value is omitted (length), the actual number of bytes in the following closed list is used.

Example

Attr(#9, 2)
{ // SourceFile at 0x000000DE 
 #13; 
} // end SourceFile

Component

A Component is very similar to Attribute. The only difference is that first value in parenthesis (used to be index in attribute and tag in component) occupies 1 byte and the second value (length) occupies 2 bytes. Component are useful to represent JavaCard .cap files.

Example

Component(3, 17) { // Applet
 	[1]b { // applets
 			{ // applet 0
	 			Bytes[13]b {
 					0xA00000006203010A;
 					0x0103010681;
 				};
 				142; // install method offset
 			};
 		};
};

Structured Data Type Rules

It is possible to define a length of an array, byte array or attribute that differs from the actual length of array, byte array or attribute. In this case, a warning is generated but the your defined length will be used.

General Class Structure

Class File Spec

JCOD

ClassFile {
    u4 magic;
    u2 minor_version;
    u2 major_version;
    u2 constant_pool_count;
    cp_info constant_pool[constant_pool_count-1];
    u2 access_flags;
    u2 this_class;
    u2 super_class;
    u2 interfaces_count;
    u2 interfaces[interfaces_count];
    u2 fields_count;
    field_info fields[fields_count];
    u2 methods_count;
    method_info methods[methods_count];
    u2 attributes_count;
    attribute_info attributes[attributes_count];
}

[4.1]

class Foo {                                             
  0xCAFEBABE; // magic
  0; // minor version
  50; // major version
  [v] { // Constant Pool
    ; // first element is empty
    ...   
  } // Constant Pool

  0x0021; // access flags
  #5;// this_cpx
  #6;// super_cpx

  [w] { // Interfaces
    ...
  } // Interfaces

  [x] { // fields
    ...
  } // fields

  [y] { // methods
      ...
  } // methods

  [z] { // Attributes
     ...
  } // Attributes
} // end class Foo

Class Attributes

The following examples describe the attributes that may appear in a classes attributes list.

Class File Spec	JCOD
`SourceFile_attribute {` `//index to (UTF8): "SourceFile"` `u2 attribute_name_index;` `u4 attribute_length; //always 2` `//index to` `(UTF8): file name` `u2` `sourcefile_index;}` [4.7.10]	class Foo { ... [1] { // Attributes Attr(#9, 2){ // SourceFile at 0x000000DE #13; // index to UTF8: filename } // end SourceFile attr } // end Attributes ... } // class Foo
`Deprecated_attribute {` `//index to (UTF8): "Deprecated"` `u2 attribute_name_index;` `u4 attribute_length;//always 0}` [4.7.15]	class Foo { ... [1] { // Attributes Attr(#8, 0){ // Deprecated } // end Deprecated attr } // end Attributes ... } // class Foo
`Synthetic_attribute {` `//index to (UTF8): "Synthetic"` `u2 attribute_name_index;` `u4 attribute_length;//always 0}` [4.7.8]	class Foo { ... [1] { // Attributes Attr(#8, 0){ // Synthetic } // end Synthetic attr } // end Attributes ... } // class Foo
`Signature_attribute {` `//index to (UTF8): "Signature"` `u2 attribute_name_index;` `u4 attribute_length;` `//index to (UTF8): signature` `u2 signature_index;` `}` [4.7.9]	class Foo { ... [1] { // Attributes Attr(#8, 2){ // Signature #30; //cpx_signature } // end Signature attr } // end Attributes ... } // class Foo
BootstrapMethods_attribute { //index to (UTF8): "BootstrapMethods" u2 attribute_name_index; u4 attribute_length; u2 bootstrap_method_count; { //index to CONSTANT_MethodHandle u2 bootstrap_method_ref; //number of arguments in Method u2 bootstrap_argument_count; { // constant pool index u2 bootstrap_argument; } arguments[number_of_arguments]; } bootstrap_methods [number_of_bootstrap_methods]; } [4.7.23]	class Foo { ... [1] { // Attributes Attr(#8, 6){ // BootstrapMethods [1] { // BootstrapMethodEntries #12; //cpx_method_handle [1] { // Arguments #14; //cpx_arg1 } // end Arguments } // end BootstrapMethods entries } // end BootstrapMethods attr } // end Attributes ... } // class Foo
`InnerClasses_attribute {` `//index to (UTF8): "InnerClasses"` `u2 attribute_name_index;` `u4 attribute_length;` `u2 number_of_classes;` `{` `//index to (Class:) Class Reference u2 inner_class_info_index;` `//index to (Class:) Class Reference` `u2 outer_class_info_index;` `//index to (UTF8): name` `u2 inner_name_index;` `// Access Flags (Long)` `u2 inner_class_access_flags;` `} classes[number_of_classes];` `}` [4.7.6]	class Foo { ... [1] { // Attributes Attr(#8, 8){ // InnerClasses [1] { // InnerClassEntries #12; //cpx_inner_class_info #13; //cpx_outer_class_info #14; //cpx_inner_class_name 01L; //inner class access } // end InnerClass entries } // end InnerClass attr } // end Attributes ... } // class Foo
`EnclosingMethod_attribute {` `u2 attribute_name_index;` `u4 attribute_length;` `//index to (Class:) Class Reference` u2 class_index `//index to (NameAndType): // Method name/type ref` `u2 method_index; }` [4.7.7]	class Foo { ... [1] { // Attributes Attr(#8, 4){ // EnclosingMethod #10; //cpx_class #42; //cpx_method } // end EnclosingMethod attr } // end Attributes ... } // class Foo
`SourceDebugExtension_attribute {` `u2 attribute_name_index;` `u4 attribute_length;` `u1 debug_extension[attribute_length];` `}` [4.7.11]	class Foo { ... [1] { // Attributes Attr(#8, 2){ // SourceDebugExtension Bytes[5] { 0x2AB70003B1; }; } // end SourceDebugExtension attr } // end Attributes ... } // class Foo
RuntimeVisibleAnnotations_attribute { u2 attribute_name_index; u4 attribute_length; u2 num_annotations; annotation annotations[num_annotations]; } [4.7.16]	class Foo { ... [1] { // Attributes Attr(#8, X){ // RuntimeVisibleAnnotations [n] { // annotations annotation_1 annotation_2 ... annotation_n } // end annotations } // end RuntimeVisibleAnnotations attr } // end Attributes ... } // class Foo
RuntimeInvisibleAnnotations_attribute { u2 attribute_name_index; u4 attribute_length; u2 num_annotations; annotation annotations[num_annotations]; } [4.7.17]	class Foo { ... [1] { // Attributes Attr(#8, X){ // RuntimeInvisibleAnnotations [n] { // annotations annotation_1 annotation_2 ... annotation_n } // end annotations } // end RuntimeInvisibleAnnotations attr } // end Attributes ... } // class Foo

The Constant Pool and Constant Elements

A variety of information is stored in the constant pool of a class file.

Class File Spec

JCOD

ClassFile {
 ...
    u2 constant_pool_count;
    cp_info constant_pool[constant_pool_count-1];
 ...

  
}

[4.4]

class Foo {                                      
 ...
  [] { // Constant Pool
    ; // first element is empty
    cp_info_1; // #1   
    cp_info_2; // #2   
    cp_info_3; // #3   
     ...
    cp_info_n; // #n   
  } // Constant Pool

  ...
} // end class Foo

Constant Declarations

The following examples describe the various constant declarations that may appear in a constant pool.

Class File Spec	JCOD
... u2 constant_pool_count; cp_info constant_pool[constant_pool_count-1] { `cp_info {` `u1 tag;` `u1 info[];` `} ...` } ... [4.4]	... [] { // Constant Pool ; // first element is empty Method #6 #15; // #1 Field #16 #17; // #2 String #18; // #3 Method #19 #20; // #4 class #21; // #5 class #22; // #6 Utf8 ""; // #7 Utf8 "()V"; // #8 Utf8 "Code"; // #9 Utf8 "LineNumberTable"; // #10 Utf8 "main"; // #11 Utf8 "([Ljava/lang/String;)V"; // #12 Utf8 "SourceFile"; // #13 Utf8 "HelloWorld.java"; // #14 NameAndType #7 #8; // #15 class #23; // #16 NameAndType #24 #25; // #17 Utf8 "Hello, world!"; // #18 class #26; // #19 NameAndType #27 #28; // #20 Utf8 "HelloWorld"; // #21 Utf8 "java/lang/Object"; // #22 Utf8 "java/lang/System"; // #23 Utf8 "out"; // #24 Utf8 "Ljava/io/PrintStream;"; // #25 Utf8 "java/io/PrintStream"; // #26 Utf8 "println"; // #27 Utf8 "(Ljava/lang/String;)V"; // #28 } // Constant Pool ...
`CONSTANT_Class (Reference)` `[7] // tag value for ClassRef[cp_index] //index to (UTF8): // Class name` [4.4.1]	class #26; // Class ref, name = const #26 ... Utf8 "java/io/PrintStream"; // #26
`CONSTANT_Fieldref` `(Reference)` `[9] // tag value for FieldRef` `[cp_index] //index to (Class): Class reference` `[cp_index] //index to (NameAndType): // Field name/type ref` [4.4.2]	Field #16 #17; // #2 ... class #23; // #16 NameAndType #24 #25; // #17
`CONSTANT_Methodref` `(Reference)` `[10] // tag value for ClassRef` `[cp_index] //index to (Class): Class reference` `[cp_index] //index to (NameAndType): // Method name/signature ref` [4.4.2]	Method #19 #20; // #4 ... class #26; // #19 NameAndType #27 #28; // #20
`CONSTANT_InterfaceMethodref` `(Reference)` `[11] // tag value for ClassRef` `[cp_index] //index to (Class): Class reference` `[cp_index] //index to (NameAndType): // Method name/signature ref` [4.4.2]	Interface #19 #20; // #4 ... class #26; // #19 NameAndType #27 #28; // #20
`CONSTANT_String (Reference)` `[8] // tag value for StringRef` `[cp_index] //index to (UTF8)` [4.4.3]	String #18; // #3 ... Utf8 "Hello, world!"; // #18
`CONSTANT_Integer (Value)` `[3] // tag value for Integer` `[u4] //bytes (Integer)` [4.4.4]	Integer 31; // = 31
`CONSTANT_Float (Value)` `[4] // tag value for Integer` `[u4] //bytes (Integer)` [4.4.4]	Float 3.14; // = 3.14f
`CONSTANT_Long (Value)` `[5] // tag value for Long[u4] //high-bytes (Long)` `[u4] //low-bytes (Long)` [4.4.5]	Long 0x7FFL; // = `0x7ff0000000000000L`
`CONSTANT_Double (Value)` `[6] // tag value for Long[u4] //high-bytes (Long)` `[u4] //low-bytes (Long)` [4.4.5]	Double 3.14; // = 3.14D
`CONSTANT_NameAndType (Reference)` `[12] // tag value for NameAndTypeRef[cp_index] //index to (UTF8): Name[cp_index] //index to (UTF8): // Type or Signature` [4.4.6]	NameAndType #27 #28; // #20 ... Utf8 "println"; // #27 Utf8 "(Ljava/lang/String;)V"; // #28
`CONSTANT_UTF8 (Value)` `[1] // tag value for UTF8 [u2] //string length (in bytes) bytes[u2] // byte array` [4.4.7]	Utf8 "main"; // #11
`CONSTANT_MethodHandle (Value)` `[u1] // subtag value` `[u2] // index to: // (MethodRef\|InterfaceMethod\|Field)` [4.4.8]	... [] { // Constant Pool ; // first element is empty ... Utf8 "()V"; // #11 Method #17 #19; // #12 ... // #16 // reference with subtag=7b to // Method Test.methName:"()V" MethodHandle 7b #12; class #18; // #17 Utf8 "Test"; // #18 NameAndType #20 #11; // #19 Utf8 "methName"; // #20 ... } // Constant Pool
`CONSTANT_MethodType (Value)` `[cp_index] //index to (UTF8): // method type` [4.4.9]	MethodType "()V"; // #11
`CONSTANT_InvokeDynamic (Value)` `[u1] // offset value in // BootstrapMethods table [cp_index] //index to (NameAndType)` [4.4.10]	... [] { // Constant Pool ; // first element is empty ... // #1 // reference to record at // index 0 in BootstrapMethods attribute, // and to NameAndType #10 // (methName:"(I)I") InvokeDynamic 0s #10; Utf8 "methName"; // #6 ... NameAndType #6 #21; // #10 ... Utf8 "(I)I"; // #21 } // Constant Pool

Fields and Field Elements

Class File Spec JCOD

ClassFile {
    ...
    u2 fields_count;
    field_info fields[fields_count];
    ...
}

[4.5 ]

class Foo {                                 
  ...
  [n] { // fields
    field_info_1; // #1   
    field_info_2; // #2   
    field_info_3; // #3   
     ...
    field_info_n; // #n   
  } // fields
  ...
} // end class Foo

field_info {
    u2 access_flags;

 //index to (UTF*): field name
    u2 name_index;

 //index to (UTF8): field type
    u2 descriptor_index;

 //integer attribute_info
    u2 attributes_count; attributes[attributes_count];
}

[4.5 ]

 [n] { // fields
      ...
       { // field_info Bar
         0x0001; // access_flags
         #7; // name_cpx
         #8; // desc_cpx
         1   // Attribute_count
         [x] { // Attributes
            ...
         } // end Attributes
     } // end Field Bar
   ... 
  } // fields

Field Attributes

The following examples describe the various attributes that may exist in a field attributes list.

Class File Spec	JCOD
`ConstantValue_attribute {` `//index to (UTF8): "ConstantValue"` `u2 attribute_name_index;` `u4 attribute_length; //always 2` `//index to (String\|Integer\|Long\|Float\|Double)` `u2 constantvalue_index;}` [4.7.2]	... { // Field Bar ... [1] { // Attributes Attr(#7, 2){ // ConstantValue #8; // attr_value_cpx } // end ConstantValue attr } // end Attributes ... } // end Field Bar ...
`Synthetic_attribute {` `//index to (UTF8): "Synthetic"` `u2 attribute_name_index;` `u4 attribute_length;//always 0}` [4.7.8]	... { // Field Bar ... [1] { // Attributes Attr(#8, 0){ // Synthetic } // end Synthetic attr } // end Attributes ... } // end Field Bar ...
`Deprecated_attribute {//index to (UTF8): "deprecated"` `u2 attribute_name_index;` `u4 attribute_length;//always 0}` [4.7.15]	... { // Field Bar ... [1] { // Attributes Attr(#8, 0){ // Deprecated } // end Deprecated attr } // end Attributes } // end Field Bar ...
`Signature_attribute {` `//index to (UTF8): "Signature" u2 attribute_name_index;` `u4 attribute_length; //index to (UTF8): signature` `u2 signature_index;` `}` [4.7.9]	... { // Field Bar ... [1] { // Attributes Attr(#8, 2){ // Signature #32; //cpx_signature } // end Signature attr } // end Attributes ... } // end Field Bar ...
RuntimeVisibleAnnotations_attribute { u2 attribute_name_index; u4 attribute_length; u2 num_annotations; annotation annotations[num_annotations]; } [4.7.16]	... { // Field Bar ... [1] { // Attributes // RuntimeVisibleAnnotations Attr(#8, X){ [n] { // annotations annotation_1 annotation_2 ... annotation_n } // end annotations } // end RuntimeVisibleAnnotations attr } // end Attributes ... } // end Field Bar ...
RuntimeInvisibleAnnotations_attribute { u2 attribute_name_index; u4 attribute_length; u2 num_annotations; annotation annotations[num_annotations]; } [4.7.17]	... { // Field Bar ... [1] { // Attributes // RuntimeInvisibleAnnotations Attr(#8, X){ [n] { // annotations annotation_1 annotation_2 ... annotation_n } // end annotations } // end RuntimeInvisibleAnnotations attr } // end Attributes ... } // end Field Bar ...

Methods and Method Elements

Class File Spec JCOD

ClassFile {
    ...
    u2 methods_count;
    method_info methods[methods_count];
    ...
}

[4.6]

class Foo {                                            
  ...
  [n] { // methods
    method_info_1; // #1   
    method_info_2; // #2   
    method_info_3; // #3   
     ...
    method_info_n; // #n   
  } // end methods
  ...
} // end class Foo

method_info {
    u2 access_flags;

 //index to (UTF8): Name
    u2 name_index;

 //index to (UTF8): Method Signature
    u2 descriptor_index;

 //integer attribute_info
    u2 attributes_count; attributes[attributes_count];
}

[4.6]

class Foo {
  ...
  [n] { // methods
    ...   
       {  // method info Bar 
         0x0001; // access_flags
         #7; // name_cpx
         #8; // desc_cpx
         1   // Attribute_count
         [x] { // Attributes
         ...
         } // end Attributes
       } // end method Bar  
     ...
  } // end methods
  ...
} // end class Foo

Method Attributes

The following examples describe the various attributes that may exist in a method attributes list.

Class File Spec	JCOD
`Exceptions_attribute {` `//index to (UTF8): "Exceptions"` `u2 attribute_name_index;` `u4 attribute_length;//integer` `u2 number_of_exceptions;//integer` `u2 exception_index_table[number_of_exceptions]; //index to (ConstantClassInfo)}` `[4.7.5]`	... { // Method Bar ... [1] { // Attributes ... // Exceptions Attr Attr(#7, 6){ [2] { // numb exceptions #30; // exception 1 #31; // exception 2 } } ... } } // end Method Bar ...
`Synthetic_attribute {` `//index to (UTF8): "Synthetic"` `u2 attribute_name_index;` `u4 attribute_length;//always 0}` `[4.7.8]`	... { // Method Bar ... [1] { // Attributes Attr(#8, 0){ // Synthetic } // end Synthetic attr } // end Attributes ... } // end Method Bar ...
`Deprecated_attribute {` `//index to (UTF8): "deprecated"` `u2 attribute_name_index;` `u4 attribute_length;//always 0` `}` `[4.7.15]`	... { // Method Bar ... [1] { // Attributes Attr(#8, 0){ // Deprecated } // end Deprecated attr } // end Attributes ... } // end Method Bar ...
`Signature_attribute {` `//index to (UTF8): "Signature"` `u2 attribute_name_index;` `u4 attribute_length;` `//index to (UTF8): signature` `u2 signature_index;` `}` `[4.7.9]`	... { // Method Bar ... [] { // Attributes Attr(#8){ // Signature #32; //cpx_signature } // end Signature attr } // end Attributes ... } // end Method Bar ...
`Code_attribute {` `//index to (UTF8): "Code"` `u2 attribute_name_index;` `u4 attribute_length; //integer` `u2 max_stack; //integer` `u2 max_locals; //integer` `u4 code_length; //long integer` `u1 code[code_length]; //byte array` `u2 exception_table_length; //integer` `{ u2 start_pc; //integer` `u2 end_pc; //integer` `u2 handler_pc; //integer` `u2 catch_type; //index to (ConstantClass)` `} exception_table[exception_table_length];` `u2 attributes_count; //integer` `attribute_info attributes[attributes_count];}` `[4.7.3]`	... { // Method Bar ... [] { // Attributes ... Attr(#11) { //Code 1; // max_stack 1; // max_locals Bytes[5] { 0x2AB70003B1; }; [] { // Traps } // end Traps [] { // Attributes ... } // end Attributes } // end Code Attr ... } // end Attributes } // end Method Bar ...
RuntimeVisibleAnnotations_attribute { u2 attribute_name_index; u4 attribute_length; u2 num_annotations; annotation annotations[num_annotations]; } `[4.7.16]`	... { // Method Bar ... [1] { // Attributes // RuntimeVisibleAnnotations Attr(#13) { [] { // annotations { // annotation annotation_1 annotation_2 ... annotation_n } // annotation } } // end RuntimeVisibleAnnotations ... } // end Attributes ... } // end Method Bar ...
RuntimeInvisibleAnnotations_attribute { u2 attribute_name_index; u4 attribute_length; u2 num_annotations; annotation annotations[num_annotations]; } `[4.7.17]`	... { // Method Bar ... [1] { // Attributes // RuntimeInvisibleAnnotations Attr(#13) { [] { // annotations { // annotation annotation_1 annotation_2 ... annotation_n } // annotation } } // end RuntimeInvisibleAnnotations ... } // end Attributes ... } // end Method Bar ...
RuntimeVisibleParameterAnnotations_attribute { u2 attribute_name_index; u4 attribute_length; u1 num_parameters; { u2 num_annotations; annotation annotations[num_annotations]; } parameter_annotations[num_parameters]; } `[4.7.18]`	... { // Method Bar ... [1] { // Attributes // RuntimeInvisibleParameterAnnotations Attr(#8, X){ [n] { // annotations annotation_1 annotation_2 ... annotation_n } // end annotations } // end RuntimeVisibleParameterAnnotations attr } // end Attributes ... } // end Method Bar ...
RuntimeInvisibleParameterAnnotations_attribute { u2 attribute_name_index; u4 attribute_length; u1 num_parameters; { u2 num_annotations; annotation annotations[num_annotations]; } parameter_annotations[num_parameters]; } `[4.7.19]`	... { // Method Bar ... [1] { // Attributes // RuntimeInvisibleParameterAnnotations Attr(#8, X){ [n] { // annotations annotation_1 annotation_2 ... annotation_n } // end annotations } // end RuntimeInvisibleParameterAnnotations attr } // end Attributes ... } // end Method Bar ...
AnnotationDefault_attribute { u2 attribute_name_index; u4 attribute_length; element_value default_value; } `[4.7.22]`	... { // Method Bar ... [] { // Attributes Attr(#8){ // AnnotationDefault element_value } // end annotations } // end AnnotationDefault attr } // end Attributes ... } // end Method Bar ...

Code Attributes

The following examples describe the various attributes that may exist in a code attribute.

Class File Spec	JCOD
`LineNumberTable_attribute {` `u2 attribute_name_index;` `u4 attribute_length;` `u2 line_number_table_length;` `{ u2 start_pc;` `u2 line_number;` `} line_number_table[line_number_table_length];}` `[4.7.12]`	... { // Code Attribute (Method Bar) ... [] { // Attributes Attr(#11) { // LineNumberTable [] { // LineNumberTable 0 // start_pc 2; // line_number } } // end LineNumberTable } // Attributes ... } // end Code Attribute ...
`LocalVariableTable_attribute {` `u2 attribute_name_index;` `u4 attribute_length;` `u2 local_variable_table_length;` `{ u2 start_pc;` `u2 length;` `u2 name_index;` `u2 descriptor_index;` `u2 index;` `} local_variable_table[local_variable_table_length];}` `[4.7.13]`	... { // Code Attribute (Method Bar) ... [] { // Attributes // LocalVariableTable Attr(#8) { [] { // LocalVariableTableEntry 0 //start_pc 1 //length #1 //name_cpx 1 //index } } // end LocalVariableTable } // Attributes ... } // end Code Attribute ...
`LocalVariableTypeTable_attribute {` `u2 attribute_name_index;` `u4 attribute_length;` `u2 local_variable_type_table_length;` `{ u2 start_pc;` `u2 length;` `u2 name_index;` `u2 signature_index;` `u2 index;` `}` `local_variable_type_table[local_variable_type_table_length];` `}` `[4.7.14]`	... { // Code Attribute (Method Bar) ... [1] { // Attributes // LocalVariableTypeTable Attr(#9) { [] { //LocalVariableTypeTableEntry 0 //start_pc 1 //length #14 //name_cpx #17 //signature_cpx 4 //index } } // end LocalVariableTypeTable } // Attributes ... } // end Code Attribute ...
`StackMapTable_attribute {` `u2 attribute_name_index;` `u4 attribute_length;` `u2 number_of_entries;` `stack_map_frame entries[number_of_entries];` `}` `[4.7.4]`	... { // Code Attribute (Method Bar) ... [] { // Attributes Attr(#11) { // StackMapTable [] { // StackMapTable stack_map_info_1 ... stack_map_info_n } } // end StackMapTable } // Attributes ... } // end Code Attribute ...

StackMapInfo Frames

The following examples describe Stack Map Frames that may appear in a Stack Map Attribute.

Class File Spec	JCOD
union stack_map_frame { same_frame; same_locals_1_stack_item_frame; same_locals_1_stack_item_frame_extended; chop_frame; same_frame_extended; append_frame; full_frame; } `[4.7.4]`
same_frame { u1 frame_type = SAME; /* 0-63 */ } `[4.7.4]`	... { // Code Attribute (Method Bar) ... [] { // Attributes Attr(#11) { // StackMapTable [] { // StackMapTable ... 63; //same_frame (offset = 63) ... } } // end StackMapTable } // Attributes ... } // end Code Attribute ...
same_locals_1_stack_item_frame { u1 frame_type = SAME_LOCALS_1_STACK_ITEM;/* 64-127 */ verification_type_info stack[1]; } `[4.7.4]`	... { // Code Attribute (Method Bar) ... [] { // Attributes Attr(#11) { // StackMapTable [] { // StackMapTable ... //same_locals_1_stack_item_frame // (offset = 65 - 64 = 1) 65; // verification type info verification_info_1; ... } } // end StackMapTable } // Attributes ... } // end Code Attribute ...
same_locals_1_stack_item_frame_extended { u1 frame_type = SAME_LOCALS_1_STACK_ITEM_EXTENDED; /* 247 */ u2 offset_delta; verification_type_info stack[1]; } `[4.7.4]`	... { // Code Attribute (Method Bar) ... [] { // Attributes Attr(#11) { // StackMapTable [] { // StackMapTable ... //same_locals_1_stack_item_frame_extended 247; 43L; // (offset = 43) // verification type info verification_info_1; ... } } // end StackMapTable } // Attributes ... } // end Code Attribute ...
chop_frame { u1 frame_type = CHOP; /* 248-250 */ u2 offset_delta; } `[4.7.4]`	... { // Code Attribute (Method Bar) ... [] { // Attributes Attr(#11) { // StackMapTable [] { // StackMapTable ... //chop_frame (last 1 local absent) 249; 43L; // (offset = 43) ... } } // end StackMapTable } // Attributes ... } // end Code Attribute ...
same_frame_extended { u1 frame_type = SAME_FRAME_EXTENDED; /* 251 */ u2 offset_delta; } `[4.7.4]`	... { // Code Attribute (Method Bar) ... [] { // Attributes Attr(#11) { // StackMapTable [] { // StackMapTable ... //same_frame_extended 251; 43L; // (offset = 43) ... } } // end StackMapTable } // Attributes ... } // end Code Attribute ...
append_frame { u1 frame_type = APPEND; /* 252-254 */ u2 offset_delta; verification_type_info locals[frame_type - 251]; } `[4.7.4]`	... { // Code Attribute (Method Bar) ... [] { // Attributes Attr(#11) { // StackMapTable [] { // StackMapTable ... 252; //append_frame 43L; // (offset = 43) // verification type info // numb verif info = 252 - 251 = 1 verification_info_1; ... } } // end StackMapTable } // Attributes ... } // end Code Attribute ...
union verification_type_info { Top_variable_info; // = 0 Integer_variable_info; // = 1 Float_variable_info; // = 2 Long_variable_info; // = 3 Double_variable_info; // = 4 Null_variable_info; // = 5 UninitializedThis_variable_info; // = 6 Object_variable_info; // = 7 + cpx Uninitialized_variable_info; // = 8 + u2 offset } `[4.7.4]`

Annotations and Annotation Elements

The following examples describe Annotations and Annotation Elements that may appear in an Annotations Attribute.

Class File Spec JCOD

annotation {
    u2 type_index;
    u2 num_element_value_pairs;
    {	u2 element_name_index;
	element_value value;
    }	element_value_pairs[num_element_value_pairs]
}

[4.7.16]

element_value {
    u1 tag;
    union {
	u2 const_value_index;
	{	u2 type_name_index;
		u2 const_name_index;
	}	enum_const_value;
	u2 class_info_index;
	annotation annotation_value;
	{	u2 num_values;
		element_value values[num_values];
	}	array_value;
    }	value;
}

[4.7.16.1]

 ...
     { // Method Bar
      ...
        [1] { // Attributes 
            Attr(#13) { // RuntimeVisibleAnnotations
              [] { // annotations
                {  //  annotation
                  #14;
                  [] { // element_value_pairs
                  }  //  element_value_pairs
                }  //  annotation
              }
            } // end RuntimeVisibleAnnotations
           ...
           } // end Attributes
       ...
    } // Method Bar

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Appendix B

JCOD Syntax

Syntax

Primitive Types

Types:

Decimal Values

Hexadecimal Values

Unicode Values

Constant Values

Structured Data Types

Types:

Record

Open List

Closed List

Array

Byte Array

Attribute

Component

Structured Data Type Rules

General Class Structure

Class Attributes

The Constant Pool and Constant Elements

Constant Declarations

Fields and Field Elements

Field Attributes

Methods and Method Elements

Method Attributes

Code Attributes

StackMapInfo Frames

Annotations and Annotation Elements