Class: Diff::GDiff::Operations::Copy

Inherits:
Object
  • Object
show all
Defined in:
lib/gdiff.rb

Overview

A Copy operation copies part of the source file to the target file.

The #pack operation may create multiple copy operations if neccessary.

Constant Summary collapse

TYPES =

Codes and maximum sizes

[ [249, USHORT, UBYTE],
[250, USHORT, USHORT],
[251, USHORT, INT],
[252, INT, UBYTE],
[253, INT, USHORT],
[254, INT, INT],
[255, LONG, INT] ]

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(position, length) ⇒ Copy

Create a new Copy object that copies length bytes from the source string at position.



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# File 'lib/gdiff.rb', line 104

def initialize(position, length)
  @position = position
  @length = length
end

Instance Attribute Details

#length ⇒ Object (readonly)

Returns the value of attribute length.



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# File 'lib/gdiff.rb', line 92

def length
  @length
end

#position ⇒ Object (readonly)

Returns the value of attribute position.



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# File 'lib/gdiff.rb', line 92

def position
  @position
end

Class Method Details

.unpack_if_match(string, position) ⇒ Object

Takes a string and a position and returns the position after this operation and a new operation object if the operation starting at the position is a Copy operation. Otherwise returns nil.



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# File 'lib/gdiff.rb', line 138

def self.unpack_if_match(string, position)
  TYPES.each do | (c, (p_pack, _, p_size), (l_pack, _, l_size)) |
    if c == string[position]
      operation = self.new(*string[position+1, p_size + l_size].unpack("" << p_pack << l_pack))
      position += p_size + l_size + 1
      return position, operation
    end
  end
  nil
end

Instance Method Details

#pack ⇒ Object

Create a binary representation in gdiff format.



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# File 'lib/gdiff.rb', line 110

def pack
  result = ""
  l = @length
  p = @position
  while l > 0
    raise "Can't express position" if p > LONG[1]

    matched = TYPES.inject(nil) { | r, (c, (p_pack, p_max), (l_pack, l_max)) |
      next r if r
    if l <= l_max and p <= p_max
      result << [c, p, l].pack("C" << p_pack << l_pack)
      p += l
      l = 0
    end
    }

    unless matched
      result << [255, p, INT[1]].pack("C" << LONG[0] << INT[0])
      p += INT[1]
      l -= INT[1]
    end
  end
  result
end

#to_s ⇒ Object

Return a readable representation of the operation



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# File 'lib/gdiff.rb', line 150

def to_s
  "Copy: #{position}, #{length}"
end