Class JavaClass::ClassFile::JavaClassHeader
In: lib/javaclass/classfile/java_class_header.rb
lib/javaclass/classfile/java_class_header_as_java_name.rb
lib/javaclass/classfile/java_class_header_shortcuts.rb
Parent: Object

Parse and disassemble Java class files, similar to the javap command. Provides all information of a Java class file. This is just a container for all kind of specialised elements. The constuctor parses and creates all contained elements.

See:java.sun.com/docs/books/jvms/second_edition/html/ClassFile.doc.html
See:en.wikipedia.org/wiki/Class
Author:Peter Kofler

Methods

abstract_class?   dump   interface?   new   super_class   this_class   to_javaname   to_jvmname   to_s  

Attributes

access_flags  [R] 
constant_pool  [R] 
interfaces  [R] 
magic  [R] 
references  [R] 
version  [R] 

Public Class methods

new(data)

Create a header with the binary data from the class file.

[Source]

# File lib/javaclass/classfile/java_class_header.rb, line 35
      def initialize(data)

        #  ClassFile {
        #    u4 magic; 
        @magic = ClassMagic.new(data)

        #    u2 minor_version;
        #    u2 major_version;
        @version = ClassVersion.new(data)

        #    u2 constant_pool_count;
        #    cp_info constant_pool[constant_pool_count-1];
        @constant_pool = ConstantPool.new(data)
        pos = 8 + @constant_pool.size

        #    u2 access_flags;
        @access_flags = AccessFlags.new(data, pos)
        pos += 2

        #    u2 this_class;
        @this_class_idx = data.u2(pos)
        pos += 2

        #    u2 super_class;
        @super_class_idx = data.u2(pos)
        pos += 2

        #    u2 interfaces_count;
        #    u2 interfaces[interfaces_count];
        count = data.u2(pos)
        @interfaces = data.u2rep(count, pos + 2).collect { |i| @constant_pool.class_item(i) }
        pos += 2 + count*2

        # TODO Implement parsing of fields and methods of the JVM spec 
        #    u2 fields_count;
        #    field_info fields[fields_count];
        #        count = data.u2(pos)
        #        @fields = data.u2rep(count, pos + 2).collect { |i| @constant_pool.field_item(i) }
        #        pos += 2 + count*2

        #    u2 methods_count;
        #    method_info methods[methods_count];
        #        count = data.u2(pos)
        #        @methods = data.u2rep(count, pos + 2).collect { |i| @constant_pool.method_item(i) }
        #        pos += 2 + count*2

        #    u2 attributes_count;
        #    attribute_info attributes[attributes_count];
        #  }
        @references = References.new(@constant_pool, @this_class_idx)
        
        #  Body {
        # Class: add the byte code sequences to the methods so it can be analysed later (see JVM spec)
        #  }

      end

Public Instance methods

abstract_class?()

Is this class an abstract class (and not an interface)?

[Source]

# File lib/javaclass/classfile/java_class_header_shortcuts.rb, line 12
      def abstract_class?
        access_flags.abstract? && !access_flags.interface?
      end
dump()

Return a debug output of this class that looks similar to javap output.

[Source]

# File lib/javaclass/classfile/java_class_header.rb, line 110
      def dump
        d = []
        mod = @access_flags.public? ? 'public ' : ''
        ext = super_class ? " extends #{super_class.to_classname}" : ''
        int = !@interfaces.empty? ? " implements #{@interfaces.join(',')}" : ''
        d << "#{mod}class #{this_class.to_classname}#{ext}#{int}"
        # d << "  SourceFile: \"#{read from LineNumberTable?}\""
        d += @version.dump
        d += @constant_pool.dump
        d << ''
        d << '{'
        d << '}'
        d
      end
interface?()

Is this class an interface (and not an annotation)?

[Source]

# File lib/javaclass/classfile/java_class_header_shortcuts.rb, line 7
      def interface?
        access_flags.interface? && !access_flags.annotation?
      end
super_class()

Return the name of the superclass of this class or nil. Returns a JavaVMName.

[Source]

# File lib/javaclass/classfile/java_class_header.rb, line 99
      def super_class
        if @super_class_idx > 0
          # This is a ConstantClass entry in the constant pool.
          @constant_pool.class_item(@super_class_idx).class_name
        else
          # special case: java.lang.Object has no superclass 
          nil
        end
      end
this_class()

Return the name of this class. Returns a JavaVMName.

[Source]

# File lib/javaclass/classfile/java_class_header.rb, line 93
      def this_class
        # This is a ConstantClass entry in the constant pool.
        @jvmname ||= @constant_pool.class_item(@this_class_idx).class_name 
      end
to_javaname()

Extend JavaClassHeader to behave like a JavaName in delegating to this_class method which returns a JavaVMName.

[Source]

# File lib/javaclass/classfile/java_class_header_as_java_name.rb, line 10
      def to_javaname
        this_class
      end
to_jvmname()

[Source]

# File lib/javaclass/classfile/java_class_header_as_java_name.rb, line 14
      def to_jvmname
        this_class
      end
to_s()

[Source]

# File lib/javaclass/classfile/java_class_header_as_java_name.rb, line 30
      def to_s
        to_classname
      end

[Validate]