Class: JavaClass::ClassFile::JavaClassHeader

Inherits:
Object
  • Object
show all
Extended by:
DelegateDirective
Defined in:
lib/javaclass/classfile/java_class_header.rb,
lib/javaclass/classfile/java_class_header_shortcuts.rb,
lib/javaclass/classfile/java_class_header_as_java_name.rb

Overview

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

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from DelegateDirective

delegate, delegate_field

Constructor Details

#initialize(data) ⇒ JavaClassHeader

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



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# 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

Instance Attribute Details

#access_flags ⇒ Object (readonly)

Returns the value of attribute access_flags.



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# File 'lib/javaclass/classfile/java_class_header.rb', line 30

def access_flags
  @access_flags
end

#constant_pool ⇒ Object (readonly)

Returns the value of attribute constant_pool.



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# File 'lib/javaclass/classfile/java_class_header.rb', line 29

def constant_pool
  @constant_pool
end

#interfaces ⇒ Object (readonly)

Returns the value of attribute interfaces.



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# File 'lib/javaclass/classfile/java_class_header.rb', line 32

def interfaces
  @interfaces
end

#magic ⇒ Object (readonly)

Returns the value of attribute magic.



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# File 'lib/javaclass/classfile/java_class_header.rb', line 27

def magic
  @magic
end

#references ⇒ Object (readonly)

Returns the value of attribute references.



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# File 'lib/javaclass/classfile/java_class_header.rb', line 31

def references
  @references
end

#version ⇒ Object (readonly)

Returns the value of attribute version.



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# File 'lib/javaclass/classfile/java_class_header.rb', line 28

def version
  @version
end

Instance Method Details

#abstract_class? ⇒ Boolean

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

Returns:

  • (Boolean) 


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# File 'lib/javaclass/classfile/java_class_header_shortcuts.rb', line 12

def abstract_class?
  access_flags.abstract? && !access_flags.interface?
end

#dump ⇒ Object

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



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# 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? ⇒ Boolean

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

Returns:

  • (Boolean) 


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# File 'lib/javaclass/classfile/java_class_header_shortcuts.rb', line 7

def interface?
  access_flags.interface? && !access_flags.annotation?
end

#super_class ⇒ Object

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



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# 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 ⇒ Object

Return the name of this class. Returns a JavaVMName.



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# 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 ⇒ Object

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



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# File 'lib/javaclass/classfile/java_class_header_as_java_name.rb', line 10

def to_javaname
  this_class
end

#to_jvmname ⇒ Object 



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# File 'lib/javaclass/classfile/java_class_header_as_java_name.rb', line 14

def to_jvmname
  this_class
end

#to_s ⇒ Object 



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# File 'lib/javaclass/classfile/java_class_header_as_java_name.rb', line 30

def to_s
  to_classname
end