Class: JavaClass::ClassFile::ConstantPool

Inherits:
Object
  • Object
show all
Defined in:
lib/javaclass/classfile/constant_pool.rb

Overview

Container of the constant pool’s constants.

Author

Peter Kofler

Constant Summary collapse

CONSTANT_TYPE_TAGS =

Types of constants by their tag.

{
  CLASS_TAG     = 7 => Constants::ConstantClass, 
  FIELD_TAG     = 9 => Constants::ConstantField, 
  METHOD_TAG    = 10 => Constants::ConstantMethod, 
  INTERFACE_METHOD_TAG = 11 => Constants::ConstantInterfaceMethod, 
  STRING_TAG    = 8 => Constants::ConstantString, 
  INT_TAG       = 3 => Constants::ConstantInt, 
  FLOAT_TAG     = 4 => Constants::ConstantFloat, 
  LONG_TAG      = 5 => Constants::ConstantLong, 
  DOUBLE_TAG    = 6 => Constants::ConstantDouble, 
  NAME_AND_TYPE_TAG = 12 => Constants::ConstantNameAndType, 
  ASCIZ_TAG     = 1 => Constants::ConstantAsciz,
}

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(data, start = 8) ⇒ ConstantPool

Parse the constant pool from the bytes data beginning at position start (which is usually 8).



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

def initialize(data, start=8)
  @pool = {} # cnt (fixnum) => constant
  
  # parsing
  @item_count = data.u2(start)
  pos = start + 2
  cnt = 1
  while cnt <= @item_count-1
    
    type = CONSTANT_TYPE_TAGS[data.u1(pos)]
    unless type
      #puts dump.join("\n") 
      raise "const ##{cnt} = unknown constant pool tag #{data[pos]} at pos #{pos} in class"
    end
    
    constant = type.new(@pool, data, pos)
    @pool[cnt] = constant
    pos += constant.size
    cnt += constant.slots
    
  end
  
  @size = pos - start
end

Instance Attribute Details

#size ⇒ Object (readonly)

Size of the whole constant pool in bytes.



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

def size
  @size
end

Instance Method Details

#[](index) ⇒ Object

Return the index’th pool item. index is the real index in the pool which may skip numbers.



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# File 'lib/javaclass/classfile/constant_pool.rb', line 64

def[](index)
  @pool[index]
end

#dump ⇒ Object

Return a debug output of the whole pool.



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# File 'lib/javaclass/classfile/constant_pool.rb', line 84

def dump
  ["  Constant pool:"] + @pool.keys.sort.collect { |k| "const ##{k} = #{self[k].dump}"}
end

#find(*tags) ⇒ Object

Return an array of all constants of the given tags types.



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# File 'lib/javaclass/classfile/constant_pool.rb', line 74

def find(*tags)
  items.find_all { |item| tags.include? item.tag }
end

#item_count ⇒ Object

Return the number of pool items. This number might be larger than items available, because long and double constants take two slots.



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# File 'lib/javaclass/classfile/constant_pool.rb', line 59

def item_count
  @item_count-1
end

#items ⇒ Object

Return an array of the ordered list of constants.



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# File 'lib/javaclass/classfile/constant_pool.rb', line 69

def items
  @pool.keys.sort.collect { |k| self[k] }
end

#strings ⇒ Object

Return all string constants.



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# File 'lib/javaclass/classfile/constant_pool.rb', line 79

def strings
  find(STRING_TAG)
end