Added wiki diff.

Diff can be viewed from the page history, or directly from the project activity page for each edit.
Uses Lars Christensen's diff library.

git-svn-id: http://redmine.rubyforge.org/svn/trunk@583 e93f8b46-1217-0410-a6f0-8f06a7374b81

1 files changed, 280 insertions, 0 deletions

diff --git a/lib/diff.rb b/lib/diff.rb
new file mode 100644
index 000000000..646f91bae
--- /dev/null
+++ b/lib/diff.rb
@@ -0,0 +1,280 @@
+class Diff
+
+  VERSION = 0.3
+
+  def Diff.lcs(a, b)
+    astart = 0
+    bstart = 0
+    afinish = a.length-1
+    bfinish = b.length-1
+    mvector = []
+    
+    # First we prune off any common elements at the beginning
+    while (astart <= afinish && bstart <= afinish && a[astart] == b[bstart])
+      mvector[astart] = bstart
+      astart += 1
+      bstart += 1
+    end
+    
+    # now the end
+    while (astart <= afinish && bstart <= bfinish && a[afinish] == b[bfinish])
+      mvector[afinish] = bfinish
+      afinish -= 1
+      bfinish -= 1
+    end
+
+    bmatches = b.reverse_hash(bstart..bfinish)
+    thresh = []
+    links = []
+    
+    (astart..afinish).each { |aindex|
+      aelem = a[aindex]
+      next unless bmatches.has_key? aelem
+      k = nil
+      bmatches[aelem].reverse.each { |bindex|
+	if k && (thresh[k] > bindex) && (thresh[k-1] < bindex)
+	  thresh[k] = bindex
+	else
+	  k = thresh.replacenextlarger(bindex, k)
+	end
+	links[k] = [ (k==0) ? nil : links[k-1], aindex, bindex ] if k
+      }
+    }
+
+    if !thresh.empty?
+      link = links[thresh.length-1]
+      while link
+	mvector[link[1]] = link[2]
+	link = link[0]
+      end
+    end
+
+    return mvector
+  end
+
+  def makediff(a, b)
+    mvector = Diff.lcs(a, b)
+    ai = bi = 0
+    while ai < mvector.length
+      bline = mvector[ai]
+      if bline
+	while bi < bline
+	  discardb(bi, b[bi])
+	  bi += 1
+	end
+	match(ai, bi)
+	bi += 1
+      else
+	discarda(ai, a[ai])
+      end
+      ai += 1
+    end
+    while ai < a.length
+      discarda(ai, a[ai])
+      ai += 1
+    end
+    while bi < b.length
+      discardb(bi, b[bi])
+      bi += 1
+    end
+    match(ai, bi)
+    1
+  end
+
+  def compactdiffs
+    diffs = []
+    @diffs.each { |df|
+      i = 0
+      curdiff = []
+      while i < df.length
+	whot = df[i][0]
+	s = @isstring ? df[i][2].chr : [df[i][2]]
+	p = df[i][1]
+	last = df[i][1]
+	i += 1
+	while df[i] && df[i][0] == whot && df[i][1] == last+1
+	  s << df[i][2]
+	  last  = df[i][1]
+	  i += 1
+	end
+	curdiff.push [whot, p, s]
+      end
+      diffs.push curdiff
+    }
+    return diffs
+  end
+
+  attr_reader :diffs, :difftype
+
+  def initialize(diffs_or_a, b = nil, isstring = nil)
+    if b.nil?
+      @diffs = diffs_or_a
+      @isstring = isstring
+    else
+      @diffs = []
+      @curdiffs = []
+      makediff(diffs_or_a, b)
+      @difftype = diffs_or_a.class
+    end
+  end
+  
+  def match(ai, bi)
+    @diffs.push @curdiffs unless @curdiffs.empty?
+    @curdiffs = []
+  end
+
+  def discarda(i, elem)
+    @curdiffs.push ['-', i, elem]
+  end
+
+  def discardb(i, elem)
+    @curdiffs.push ['+', i, elem]
+  end
+
+  def compact
+    return Diff.new(compactdiffs)
+  end
+
+  def compact!
+    @diffs = compactdiffs
+  end
+
+  def inspect
+    @diffs.inspect
+  end
+
+end
+
+module Diffable
+  def diff(b)
+    Diff.new(self, b)
+  end
+
+  # Create a hash that maps elements of the array to arrays of indices
+  # where the elements are found.
+
+  def reverse_hash(range = (0...self.length))
+    revmap = {}
+    range.each { |i|
+      elem = self[i]
+      if revmap.has_key? elem
+	revmap[elem].push i
+      else
+	revmap[elem] = [i]
+      end
+    }
+    return revmap
+  end
+
+  def replacenextlarger(value, high = nil)
+    high ||= self.length
+    if self.empty? || value > self[-1]
+      push value
+      return high
+    end
+    # binary search for replacement point
+    low = 0
+    while low < high
+      index = (high+low)/2
+      found = self[index]
+      return nil if value == found
+      if value > found
+	low = index + 1
+      else
+	high = index
+      end
+    end
+
+    self[low] = value
+    # $stderr << "replace #{value} : 0/#{low}/#{init_high} (#{steps} steps) (#{init_high-low} off )\n"
+    # $stderr.puts self.inspect
+    #gets
+    #p length - low
+    return low
+  end
+
+  def patch(diff)
+    newary = nil
+    if diff.difftype == String
+      newary = diff.difftype.new('')
+    else
+      newary = diff.difftype.new
+    end
+    ai = 0
+    bi = 0
+    diff.diffs.each { |d|
+      d.each { |mod|
+	case mod[0]
+	when '-'
+	  while ai < mod[1]
+	    newary << self[ai]
+	    ai += 1
+	    bi += 1
+	  end
+	  ai += 1
+	when '+'
+	  while bi < mod[1]
+	    newary << self[ai]
+	    ai += 1
+	    bi += 1
+	  end
+	  newary << mod[2]
+	  bi += 1
+	else
+	  raise "Unknown diff action"
+	end
+      }
+    }
+    while ai < self.length
+      newary << self[ai]
+      ai += 1
+      bi += 1
+    end
+    return newary
+  end
+end
+
+class Array
+  include Diffable
+end
+
+class String
+  include Diffable
+end
+
+=begin
+= Diff
+(({diff.rb})) - computes the differences between two arrays or
+strings. Copyright (C) 2001 Lars Christensen
+
+== Synopsis
+
+    diff = Diff.new(a, b)
+    b = a.patch(diff)
+
+== Class Diff
+=== Class Methods
+--- Diff.new(a, b)
+--- a.diff(b)
+      Creates a Diff object which represent the differences between
+      ((|a|)) and ((|b|)). ((|a|)) and ((|b|)) can be either be arrays
+      of any objects, strings, or object of any class that include
+      module ((|Diffable|))
+
+== Module Diffable
+The module ((|Diffable|)) is intended to be included in any class for
+which differences are to be computed. Diffable is included into String
+and Array when (({diff.rb})) is (({require}))'d.
+
+Classes including Diffable should implement (({[]})) to get element at
+integer indices, (({<<})) to append elements to the object and
+(({ClassName#new})) should accept 0 arguments to create a new empty
+object.
+
+=== Instance Methods
+--- Diffable#patch(diff)
+      Applies the differences from ((|diff|)) to the object ((|obj|))
+      and return the result. ((|obj|)) is not changed. ((|obj|)) and
+      can be either an array or a string, but must match the object
+      from which the ((|diff|)) was created.
+=end