Class: CloudRCS::Binary

Inherits:
PrimitivePatch show all
Defined in:
lib/cloud_rcs/patch_types/binary.rb

Constant Summary

Constants inherited from PrimitivePatch

PrimitivePatch::PATH_PREFIX

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from PrimitivePatch

#apply!, escape_path, merge, #named_patch?, #new_path, #primitive_patch?, #to_a, unescape_path

Class Method Details

.binary_to_hex(bin) ⇒ Object 



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 222

def binary_to_hex(bin)
  bin.unpack("H*").first
end

.generate(orig_file, changed_file) ⇒ Object 



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 135

def generate(orig_file, changed_file)
  return if orig_file.nil? and changed_file.nil?
  return unless (orig_file and orig_file.contents.is_binary_data?) or 
    (changed_file and changed_file.contents.is_binary_data?)

  # Convert binary data to hexadecimal for storage in a text
  # file
  orig_hex = orig_file ? binary_to_hex(orig_file.contents).scan(/.{2}/) : []
  changed_hex = changed_file ? binary_to_hex(changed_file.contents).scan(/.{2}/) : []

  file_path = orig_file ? orig_file.path : changed_file.path

  diffs = Diff::LCS.diff(orig_hex, changed_hex)
  chunks = []
  offset = 0
  diffs.each do |d|

    # We need to recalculate positions for removals - just as in
    # hunk generation.
    unless chunks.empty?
      offset += chunks.last.lengthnew - chunks.last.lengthold
    end
    d.collect! do |l|
      if l.action == '-'
        Diff::LCS::Change.new(l.action, l.position + (offset / 2), l.element)
      else
        l
      end
    end

    position = d.first.position * 2

    removed = d.find_all { |l| l.action == '-' }.collect { |l| l.element }.join
    added = d.find_all { |l| l.action == '+' }.collect { |l| l.element }.join
    
    unless removed.blank? and added.blank?
      chunks << Binary.new(:contents => [removed, added],
                           :position => position,
                           :path => file_path)
    end
    
  end
  
  return chunks
end

.hex_to_binary(hex) ⇒ Object

We want to store the contents of a binary file encoded as a hexidecimal value. These two methods allow for translating between binary and hexidecimal.

Code borrowed from: 4thmouse.com/index.php/2008/02/18/converting-hex-to-binary-in-4-languages/



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 218

def hex_to_binary(hex)
  hex.to_a.pack("H*")
end

.parse(contents) ⇒ Object 



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 181

def parse(contents)
  unless contents =~ /^binary\s+(\S+)\s+(\d+)\s+(.*)$/m
    raise ParseException.new(true), "Failed to parse binary patch: \"#{contents}\""
  end
  file_path = unescape_path($1)
  starting_position = $2.to_i
  contents = $3

  removed, added = [], []
  removed_offset = 0
  added_offset = 0
  contents.split("\n").each do |line|
    if line =~ /^-([\S]*)\s*$/
      removed << $1
      removed_offset += 1
    elsif line =~ /^\+([\S]*)\s*$/
      added << $1
      added_offset += 1
    else
      raise "Failed to parse a line in binary patch: \"#{line}\""
    end
  end

  removed = removed.join
  added = added.join

  return Binary.new(:path => file_path, 
                    :position => starting_position, 
                    :contents => [removed, added])
end

.priority ⇒ Object

Use a low priority so that the binary patch generating method will be called before the hunk patch generating method



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 131

def priority
  20
end

Instance Method Details

#added ⇒ Object 



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 115

def added
  contents.last
end

#apply_to(file) ⇒ Object 



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 9

def apply_to(file)
  return file unless file.path == path

  hex_contents = Binary.binary_to_hex(file.contents)

  # Check that the patch matches the file contents
  unless hex_contents[position...position+lengthold] == removed
    raise ApplyException.new(true), "Portion of binary patch marked for removal does not match existing contents in file. Existing contents at position #{position}: '#{hex_contents[position...position+lengthold]}' ; marked for removal: '#{removed}'"
  end

  # Then, remove stuff
  unless removed.blank?
    hex_contents[position...position+lengthold] = ""
  end

  # Finally, add stuff
  unless added.blank?
    hex_contents.insert(position, added)
  end

  file.contents = Binary.hex_to_binary(hex_contents)
  return file
end

#commute(patch) ⇒ Object 



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 40

def commute(patch)
  if patch.is_a? Binary and patch.path == self.path

    # self is applied first and precedes patch in the file
    if self.position + self.lengthnew < patch.position
      patch1 = Binary.new(:path => patch.path,
                        :position => (patch.position - self.lengthnew + self.lengthold),
                        :contents => patch.contents)
      patch2 = Binary.new(:path => self.path, 
                          :position => self.position, 
                          :contents => self.contents)
      
    # self is applied first, but is preceded by patch in the file          
    elsif patch.position + patch.lengthold < self.position
      patch1 = Binary.new(:path => patch.path, 
                          :position => patch.position, 
                          :contents => patch.contents)
      patch2 = Binary.new(:path => self.path, 
                        :position => (self.position + patch.lengthnew - patch.lengthold),
                        :contents => self.contents)
      
    # patch precedes self in file, but bumps up against it
    elsif patch.position + patch.lengthnew == self.position and
        self.lengthold != 0 and patch.lengthold != 0 and 
        self.lengthnew != 0 and patch.lengthnew != 0
      patch1 = Binary.new(:path => patch.path, 
                          :position => patch.position, 
                          :contents => patch.contents)
      patch2 = Binary.new(:path => self.path, 
                          :position => (self.position - patch.lengthnew + patch.lengthold), 
                          :contents => self.contents)
      
    # self precedes patch in file, but bumps up against it
    elsif self.position + self.lengthold == patch.position and
        self.lengthold != 0 and patch.lengthold != 0 and 
        self.lengthnew != 0 and patch.lengthnew != 0
      patch1 = Binary.new(:path => patch.path,
                          :position => patch.position,
                          :contents => patch.contents)
      patch2 = Binary.new(:path => self.path, 
                          :position => (self.position + patch.lengthnew - patch.lengthold), 
                          :contents => self.contents)
      
    # Patches overlap. This is a conflict scenario
    else
      raise CommuteException.new(true), "Conflict: binary patches overlap."
    end
    
  elsif patch.is_a? Rmfile and patch.path == self.path
    raise CommuteException.new(true), "Conflict: cannot modify a file after it is removed."

  elsif patch.is_a? Move and self.path == patch.original_path
    patch1 = patch.clone
    patch2 = self.clone
    patch2.path = patch.new_path
    
  # Commutation is trivial
  else
    patch1, patch2 = patch, self
  end
  
  return patch1, patch2
end

#inverse ⇒ Object 



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 33

def inverse
  Binary.new(:path => path,
             :position => position,
             :contents => [added, removed],
             :inverted => true)
end

#lengthnew ⇒ Object 



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 123

def lengthnew
  added.length
end

#lengthold ⇒ Object 



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 119

def lengthold
  removed.length
end

#removed ⇒ Object 



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 111

def removed
  contents.first
end

#to_s ⇒ Object 



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# File 'lib/cloud_rcs/patch_types/binary.rb', line 104

def to_s
  header = "binary #{self.class.escape_path(path)} #{position}"
  old = removed.scan(/.{1,78}/).collect { |c| '-' + c }.join("\n")
  new = added.scan(/.{1,78}/).collect { |c| '+' + c }.join("\n")
  return [header, old, new].delete_if { |e| e.blank? }.join("\n")
end