class LCS::Hunk
A Hunk
is a group of Blocks which overlap because of the context surrounding each block. (So if we’re not using context, every hunk will contain one block.) Used in the diff program (bin/ldiff).
Attributes
Change the “start” and “end” fields to note that context should be added to this hunk.
Public Class Methods
Create a hunk using references to both the old and new data, as well as the piece of data.
# File lib/diff/lcs/hunk.rb, line 16 def initialize(data_old, data_new, piece, flag_context, file_length_difference) # At first, a hunk will have just one Block in it @blocks = [Diff::LCS::Block.new(piece)] if @blocks[0].remove.empty? && @blocks[0].insert.empty? fail "Cannot build a hunk from #{piece.inspect}; has no add or remove actions" end if String.method_defined?(:encoding) @preferred_data_encoding = data_old.fetch(0) { data_new.fetch(0, "") }.encoding end @data_old = data_old @data_new = data_new before = after = file_length_difference after += @blocks[0].diff_size @file_length_difference = after # The caller must get this manually @max_diff_size = @blocks.map { |e| e.diff_size.abs }.max # Save the start & end of each array. If the array doesn't exist (e.g., # we're only adding items in this block), then figure out the line number # based on the line number of the other file and the current difference in # file lengths. if @blocks[0].remove.empty? a1 = a2 = nil else a1 = @blocks[0].remove[0].position a2 = @blocks[0].remove[-1].position end if @blocks[0].insert.empty? b1 = b2 = nil else b1 = @blocks[0].insert[0].position b2 = @blocks[0].insert[-1].position end @start_old = a1 || (b1 - before) @start_new = b1 || (a1 + before) @end_old = a2 || (b2 - after) @end_new = b2 || (a2 + after) self.flag_context = flag_context end
Public Instance Methods
Returns a diff string based on a format.
# File lib/diff/lcs/hunk.rb, line 115 def diff(format, last = false) case format when :old old_diff(last) when :unified unified_diff(last) when :context context_diff(last) when :ed self when :reverse_ed, :ed_finish ed_diff(format, last) else fail "Unknown diff format #{format}." end end
Merges this hunk and the provided hunk together if they overlap. Returns a truthy value so that if there is no overlap, you can know the merge was skipped.
# File lib/diff/lcs/hunk.rb, line 97 def merge(hunk) return unless overlaps?(hunk) @start_old = hunk.start_old @start_new = hunk.start_new blocks.unshift(*hunk.blocks) end
# File lib/diff/lcs/hunk.rb, line 331 def missing_last_newline?(data) newline = encode("\n") if data[-2] data[-2].end_with?(newline) && !data[-1].end_with?(newline) elsif data[-1] !data[-1].end_with?(newline) else true end end
Determines whether there is an overlap between this hunk and the provided hunk. This will be true if the difference between the two hunks start or end positions is within one position of each other.
# File lib/diff/lcs/hunk.rb, line 109 def overlaps?(hunk) hunk and (((@start_old - hunk.end_old) <= 1) or ((@start_new - hunk.end_new) <= 1)) end
Private Instance Methods
# File lib/diff/lcs/hunk.rb, line 214 def context_diff(last = false) s = encode("***************\n") s << encode("*** #{context_range(:old, ",", last)} ****\n") r = context_range(:new, ",", last) if last old_missing_newline = missing_last_newline?(@data_old) new_missing_newline = missing_last_newline?(@data_new) end # Print out file 1 part for each block in context diff format if there # are any blocks that remove items lo, hi = @start_old, @end_old removes = @blocks.reject { |e| e.remove.empty? } unless removes.empty? # standard:disable Performance/UnfreezeString outlist = @data_old[lo..hi].map { |e| String.new("#{encode(" ")}#{e.chomp}") } # standard:enable Performance/UnfreezeString last_block = removes[-1] removes.each do |block| block.remove.each do |item| outlist[item.position - lo][0, 1] = encode(block.op) # - or ! end if last && block == last_block && old_missing_newline outlist << encode('\\ No newline at end of file') end end s << outlist.join(encode("\n")) << encode("\n") end s << encode("--- #{r} ----\n") lo, hi = @start_new, @end_new inserts = @blocks.reject { |e| e.insert.empty? } unless inserts.empty? # standard:disable Performance/UnfreezeString outlist = @data_new[lo..hi].map { |e| String.new("#{encode(" ")}#{e.chomp}") } # standard:enable Performance/UnfreezeString last_block = inserts[-1] inserts.each do |block| block.insert.each do |item| outlist[item.position - lo][0, 1] = encode(block.op) # + or ! end if last && block == last_block && new_missing_newline outlist << encode('\\ No newline at end of file') end end s << outlist.join(encode("\n")) end s end
Generate a range of item numbers to print. Only print 1 number if the range has only one item in it. Otherwise, it’s ‘start,end’
# File lib/diff/lcs/hunk.rb, line 298 def context_range(mode, op, last = false) case mode when :old s, e = (@start_old + 1), (@end_old + 1) when :new s, e = (@start_new + 1), (@end_new + 1) end e -= 1 if last e = 1 if e.zero? (s < e) ? "#{s}#{op}#{e}" : e.to_s end
# File lib/diff/lcs/hunk.rb, line 276 def ed_diff(format, _last = false) warn "Expecting only one block in an old diff hunk!" if @blocks.size > 1 s = if format == :reverse_ed encode("#{ED_DIFF_OP_ACTION[@blocks[0].op]}#{context_range(:old, ",")}\n") else encode("#{context_range(:old, " ")}#{ED_DIFF_OP_ACTION[@blocks[0].op]}\n") end unless @blocks[0].insert.empty? @data_new[@start_new..@end_new].each do |e| s << e.chomp + encode("\n") end s << encode(".\n") end s end
# File lib/diff/lcs/hunk.rb, line 344 def encode(literal, target_encoding = @preferred_data_encoding) literal.encode target_encoding end
# File lib/diff/lcs/hunk.rb, line 348 def encode_as(string, *args) args.map { |arg| arg.encode(string.encoding) } end
Note that an old diff can’t have any context. Therefore, we know that there’s only one block in the hunk.
# File lib/diff/lcs/hunk.rb, line 134 def old_diff(_last = false) warn "Expecting only one block in an old diff hunk!" if @blocks.size > 1 block = @blocks[0] # Calculate item number range. Old diff range is just like a context # diff range, except the ranges are on one line with the action between # them. s = encode("#{context_range(:old, ",")}#{OLD_DIFF_OP_ACTION[block.op]}#{context_range(:new, ",")}\n") # If removing anything, just print out all the remove lines in the hunk # which is just all the remove lines in the block. unless block.remove.empty? @data_old[@start_old..@end_old].each { |e| s << encode("< ") + e.chomp + encode("\n") } end s << encode("---\n") if block.op == "!" unless block.insert.empty? @data_new[@start_new..@end_new].each { |e| s << encode("> ") + e.chomp + encode("\n") } end s end
# File lib/diff/lcs/hunk.rb, line 159 def unified_diff(last = false) # Calculate item number range. s = encode("@@ -#{unified_range(:old, last)} +#{unified_range(:new, last)} @@\n") # Outlist starts containing the hunk of the old file. Removing an item # just means putting a '-' in front of it. Inserting an item requires # getting it from the new file and splicing it in. We splice in # +num_added+ items. Remove blocks use +num_added+ because splicing # changed the length of outlist. # # We remove +num_removed+ items. Insert blocks use +num_removed+ # because their item numbers -- corresponding to positions in the NEW # file -- don't take removed items into account. lo, hi, num_added, num_removed = @start_old, @end_old, 0, 0 # standard:disable Performance/UnfreezeString outlist = @data_old[lo..hi].map { |e| String.new("#{encode(" ")}#{e.chomp}") } # standard:enable Performance/UnfreezeString last_block = blocks[-1] if last old_missing_newline = missing_last_newline?(@data_old) new_missing_newline = missing_last_newline?(@data_new) end @blocks.each do |block| block.remove.each do |item| op = item.action.to_s # - offset = item.position - lo + num_added outlist[offset][0, 1] = encode(op) num_removed += 1 end if last && block == last_block && old_missing_newline && !new_missing_newline outlist << encode('\\ No newline at end of file') num_removed += 1 end block.insert.each do |item| op = item.action.to_s # + offset = item.position - @start_new + num_removed outlist[offset, 0] = encode(op) + @data_new[item.position].chomp num_added += 1 end end outlist << encode('\\ No newline at end of file') if last && new_missing_newline s << outlist.join(encode("\n")) s end
Generate a range of item numbers to print for unified diff. Print number where block starts, followed by number of lines in the block (don’t print number of lines if it’s 1)
# File lib/diff/lcs/hunk.rb, line 316 def unified_range(mode, last) case mode when :old s, e = (@start_old + 1), (@end_old + 1) when :new s, e = (@start_new + 1), (@end_new + 1) end length = e - s + (last ? 0 : 1) first = (length < 2) ? e : s # "strange, but correct" (length <= 1) ? first.to_s : "#{first},#{length}" end