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authorJari Vetoniemi <jari.vetoniemi@indooratlas.com>2020-03-16 18:49:26 +0900
committerJari Vetoniemi <jari.vetoniemi@indooratlas.com>2020-03-30 00:39:06 +0900
commitfcbf63e62c627deae76c1b8cb8c0876c536ed811 (patch)
tree64cb17de3f41a2b6fef2368028fbd00349946994 /jni/ruby/lib/prettyprint.rb
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+# This class implements a pretty printing algorithm. It finds line breaks and
+# nice indentations for grouped structure.
+#
+# By default, the class assumes that primitive elements are strings and each
+# byte in the strings have single column in width. But it can be used for
+# other situations by giving suitable arguments for some methods:
+# * newline object and space generation block for PrettyPrint.new
+# * optional width argument for PrettyPrint#text
+# * PrettyPrint#breakable
+#
+# There are several candidate uses:
+# * text formatting using proportional fonts
+# * multibyte characters which has columns different to number of bytes
+# * non-string formatting
+#
+# == Bugs
+# * Box based formatting?
+# * Other (better) model/algorithm?
+#
+# Report any bugs at http://bugs.ruby-lang.org
+#
+# == References
+# Christian Lindig, Strictly Pretty, March 2000,
+# http://www.st.cs.uni-sb.de/~lindig/papers/#pretty
+#
+# Philip Wadler, A prettier printer, March 1998,
+# http://homepages.inf.ed.ac.uk/wadler/topics/language-design.html#prettier
+#
+# == Author
+# Tanaka Akira <akr@fsij.org>
+#
+class PrettyPrint
+
+ # This is a convenience method which is same as follows:
+ #
+ # begin
+ # q = PrettyPrint.new(output, maxwidth, newline, &genspace)
+ # ...
+ # q.flush
+ # output
+ # end
+ #
+ def PrettyPrint.format(output='', maxwidth=79, newline="\n", genspace=lambda {|n| ' ' * n})
+ q = PrettyPrint.new(output, maxwidth, newline, &genspace)
+ yield q
+ q.flush
+ output
+ end
+
+ # This is similar to PrettyPrint::format but the result has no breaks.
+ #
+ # +maxwidth+, +newline+ and +genspace+ are ignored.
+ #
+ # The invocation of +breakable+ in the block doesn't break a line and is
+ # treated as just an invocation of +text+.
+ #
+ def PrettyPrint.singleline_format(output='', maxwidth=nil, newline=nil, genspace=nil)
+ q = SingleLine.new(output)
+ yield q
+ output
+ end
+
+ # Creates a buffer for pretty printing.
+ #
+ # +output+ is an output target. If it is not specified, '' is assumed. It
+ # should have a << method which accepts the first argument +obj+ of
+ # PrettyPrint#text, the first argument +sep+ of PrettyPrint#breakable, the
+ # first argument +newline+ of PrettyPrint.new, and the result of a given
+ # block for PrettyPrint.new.
+ #
+ # +maxwidth+ specifies maximum line length. If it is not specified, 79 is
+ # assumed. However actual outputs may overflow +maxwidth+ if long
+ # non-breakable texts are provided.
+ #
+ # +newline+ is used for line breaks. "\n" is used if it is not specified.
+ #
+ # The block is used to generate spaces. {|width| ' ' * width} is used if it
+ # is not given.
+ #
+ def initialize(output='', maxwidth=79, newline="\n", &genspace)
+ @output = output
+ @maxwidth = maxwidth
+ @newline = newline
+ @genspace = genspace || lambda {|n| ' ' * n}
+
+ @output_width = 0
+ @buffer_width = 0
+ @buffer = []
+
+ root_group = Group.new(0)
+ @group_stack = [root_group]
+ @group_queue = GroupQueue.new(root_group)
+ @indent = 0
+ end
+
+ # The output object.
+ #
+ # This defaults to '', and should accept the << method
+ attr_reader :output
+
+ # The maximum width of a line, before it is separated in to a newline
+ #
+ # This defaults to 79, and should be a Fixnum
+ attr_reader :maxwidth
+
+ # The value that is appended to +output+ to add a new line.
+ #
+ # This defaults to "\n", and should be String
+ attr_reader :newline
+
+ # A lambda or Proc, that takes one argument, of a Fixnum, and returns
+ # the corresponding number of spaces.
+ #
+ # By default this is:
+ # lambda {|n| ' ' * n}
+ attr_reader :genspace
+
+ # The number of spaces to be indented
+ attr_reader :indent
+
+ # The PrettyPrint::GroupQueue of groups in stack to be pretty printed
+ attr_reader :group_queue
+
+ # Returns the group most recently added to the stack.
+ #
+ # Contrived example:
+ # out = ""
+ # => ""
+ # q = PrettyPrint.new(out)
+ # => #<PrettyPrint:0x82f85c0 @output="", @maxwidth=79, @newline="\n", @genspace=#<Proc:0x82f8368@/home/vbatts/.rvm/rubies/ruby-head/lib/ruby/2.0.0/prettyprint.rb:82 (lambda)>, @output_width=0, @buffer_width=0, @buffer=[], @group_stack=[#<PrettyPrint::Group:0x82f8138 @depth=0, @breakables=[], @break=false>], @group_queue=#<PrettyPrint::GroupQueue:0x82fb7c0 @queue=[[#<PrettyPrint::Group:0x82f8138 @depth=0, @breakables=[], @break=false>]]>, @indent=0>
+ # q.group {
+ # q.text q.current_group.inspect
+ # q.text q.newline
+ # q.group(q.current_group.depth + 1) {
+ # q.text q.current_group.inspect
+ # q.text q.newline
+ # q.group(q.current_group.depth + 1) {
+ # q.text q.current_group.inspect
+ # q.text q.newline
+ # q.group(q.current_group.depth + 1) {
+ # q.text q.current_group.inspect
+ # q.text q.newline
+ # }
+ # }
+ # }
+ # }
+ # => 284
+ # puts out
+ # #<PrettyPrint::Group:0x8354758 @depth=1, @breakables=[], @break=false>
+ # #<PrettyPrint::Group:0x8354550 @depth=2, @breakables=[], @break=false>
+ # #<PrettyPrint::Group:0x83541cc @depth=3, @breakables=[], @break=false>
+ # #<PrettyPrint::Group:0x8347e54 @depth=4, @breakables=[], @break=false>
+ def current_group
+ @group_stack.last
+ end
+
+ # Breaks the buffer into lines that are shorter than #maxwidth
+ def break_outmost_groups
+ while @maxwidth < @output_width + @buffer_width
+ return unless group = @group_queue.deq
+ until group.breakables.empty?
+ data = @buffer.shift
+ @output_width = data.output(@output, @output_width)
+ @buffer_width -= data.width
+ end
+ while !@buffer.empty? && Text === @buffer.first
+ text = @buffer.shift
+ @output_width = text.output(@output, @output_width)
+ @buffer_width -= text.width
+ end
+ end
+ end
+
+ # This adds +obj+ as a text of +width+ columns in width.
+ #
+ # If +width+ is not specified, obj.length is used.
+ #
+ def text(obj, width=obj.length)
+ if @buffer.empty?
+ @output << obj
+ @output_width += width
+ else
+ text = @buffer.last
+ unless Text === text
+ text = Text.new
+ @buffer << text
+ end
+ text.add(obj, width)
+ @buffer_width += width
+ break_outmost_groups
+ end
+ end
+
+ # This is similar to #breakable except
+ # the decision to break or not is determined individually.
+ #
+ # Two #fill_breakable under a group may cause 4 results:
+ # (break,break), (break,non-break), (non-break,break), (non-break,non-break).
+ # This is different to #breakable because two #breakable under a group
+ # may cause 2 results:
+ # (break,break), (non-break,non-break).
+ #
+ # The text +sep+ is inserted if a line is not broken at this point.
+ #
+ # If +sep+ is not specified, " " is used.
+ #
+ # If +width+ is not specified, +sep.length+ is used. You will have to
+ # specify this when +sep+ is a multibyte character, for example.
+ #
+ def fill_breakable(sep=' ', width=sep.length)
+ group { breakable sep, width }
+ end
+
+ # This says "you can break a line here if necessary", and a +width+\-column
+ # text +sep+ is inserted if a line is not broken at the point.
+ #
+ # If +sep+ is not specified, " " is used.
+ #
+ # If +width+ is not specified, +sep.length+ is used. You will have to
+ # specify this when +sep+ is a multibyte character, for example.
+ #
+ def breakable(sep=' ', width=sep.length)
+ group = @group_stack.last
+ if group.break?
+ flush
+ @output << @newline
+ @output << @genspace.call(@indent)
+ @output_width = @indent
+ @buffer_width = 0
+ else
+ @buffer << Breakable.new(sep, width, self)
+ @buffer_width += width
+ break_outmost_groups
+ end
+ end
+
+ # Groups line break hints added in the block. The line break hints are all
+ # to be used or not.
+ #
+ # If +indent+ is specified, the method call is regarded as nested by
+ # nest(indent) { ... }.
+ #
+ # If +open_obj+ is specified, <tt>text open_obj, open_width</tt> is called
+ # before grouping. If +close_obj+ is specified, <tt>text close_obj,
+ # close_width</tt> is called after grouping.
+ #
+ def group(indent=0, open_obj='', close_obj='', open_width=open_obj.length, close_width=close_obj.length)
+ text open_obj, open_width
+ group_sub {
+ nest(indent) {
+ yield
+ }
+ }
+ text close_obj, close_width
+ end
+
+ # Takes a block and queues a new group that is indented 1 level further.
+ def group_sub
+ group = Group.new(@group_stack.last.depth + 1)
+ @group_stack.push group
+ @group_queue.enq group
+ begin
+ yield
+ ensure
+ @group_stack.pop
+ if group.breakables.empty?
+ @group_queue.delete group
+ end
+ end
+ end
+
+ # Increases left margin after newline with +indent+ for line breaks added in
+ # the block.
+ #
+ def nest(indent)
+ @indent += indent
+ begin
+ yield
+ ensure
+ @indent -= indent
+ end
+ end
+
+ # outputs buffered data.
+ #
+ def flush
+ @buffer.each {|data|
+ @output_width = data.output(@output, @output_width)
+ }
+ @buffer.clear
+ @buffer_width = 0
+ end
+
+ # The Text class is the means by which to collect strings from objects.
+ #
+ # This class is intended for internal use of the PrettyPrint buffers.
+ class Text # :nodoc:
+
+ # Creates a new text object.
+ #
+ # This constructor takes no arguments.
+ #
+ # The workflow is to append a PrettyPrint::Text object to the buffer, and
+ # being able to call the buffer.last() to reference it.
+ #
+ # As there are objects, use PrettyPrint::Text#add to include the objects
+ # and the width to utilized by the String version of this object.
+ def initialize
+ @objs = []
+ @width = 0
+ end
+
+ # The total width of the objects included in this Text object.
+ attr_reader :width
+
+ # Render the String text of the objects that have been added to this Text object.
+ #
+ # Output the text to +out+, and increment the width to +output_width+
+ def output(out, output_width)
+ @objs.each {|obj| out << obj}
+ output_width + @width
+ end
+
+ # Include +obj+ in the objects to be pretty printed, and increment
+ # this Text object's total width by +width+
+ def add(obj, width)
+ @objs << obj
+ @width += width
+ end
+ end
+
+ # The Breakable class is used for breaking up object information
+ #
+ # This class is intended for internal use of the PrettyPrint buffers.
+ class Breakable # :nodoc:
+
+ # Create a new Breakable object.
+ #
+ # Arguments:
+ # * +sep+ String of the separator
+ # * +width+ Fixnum width of the +sep+
+ # * +q+ parent PrettyPrint object, to base from
+ def initialize(sep, width, q)
+ @obj = sep
+ @width = width
+ @pp = q
+ @indent = q.indent
+ @group = q.current_group
+ @group.breakables.push self
+ end
+
+ # Holds the separator String
+ #
+ # The +sep+ argument from ::new
+ attr_reader :obj
+
+ # The width of +obj+ / +sep+
+ attr_reader :width
+
+ # The number of spaces to indent.
+ #
+ # This is inferred from +q+ within PrettyPrint, passed in ::new
+ attr_reader :indent
+
+ # Render the String text of the objects that have been added to this
+ # Breakable object.
+ #
+ # Output the text to +out+, and increment the width to +output_width+
+ def output(out, output_width)
+ @group.breakables.shift
+ if @group.break?
+ out << @pp.newline
+ out << @pp.genspace.call(@indent)
+ @indent
+ else
+ @pp.group_queue.delete @group if @group.breakables.empty?
+ out << @obj
+ output_width + @width
+ end
+ end
+ end
+
+ # The Group class is used for making indentation easier.
+ #
+ # While this class does neither the breaking into newlines nor indentation,
+ # it is used in a stack (as well as a queue) within PrettyPrint, to group
+ # objects.
+ #
+ # For information on using groups, see PrettyPrint#group
+ #
+ # This class is intended for internal use of the PrettyPrint buffers.
+ class Group # :nodoc:
+ # Create a Group object
+ #
+ # Arguments:
+ # * +depth+ - this group's relation to previous groups
+ def initialize(depth)
+ @depth = depth
+ @breakables = []
+ @break = false
+ end
+
+ # This group's relation to previous groups
+ attr_reader :depth
+
+ # Array to hold the Breakable objects for this Group
+ attr_reader :breakables
+
+ # Makes a break for this Group, and returns true
+ def break
+ @break = true
+ end
+
+ # Boolean of whether this Group has made a break
+ def break?
+ @break
+ end
+
+ # Boolean of whether this Group has been queried for being first
+ #
+ # This is used as a predicate, and ought to be called first.
+ def first?
+ if defined? @first
+ false
+ else
+ @first = false
+ true
+ end
+ end
+ end
+
+ # The GroupQueue class is used for managing the queue of Group to be pretty
+ # printed.
+ #
+ # This queue groups the Group objects, based on their depth.
+ #
+ # This class is intended for internal use of the PrettyPrint buffers.
+ class GroupQueue # :nodoc:
+ # Create a GroupQueue object
+ #
+ # Arguments:
+ # * +groups+ - one or more PrettyPrint::Group objects
+ def initialize(*groups)
+ @queue = []
+ groups.each {|g| enq g}
+ end
+
+ # Enqueue +group+
+ #
+ # This does not strictly append the group to the end of the queue,
+ # but instead adds it in line, base on the +group.depth+
+ def enq(group)
+ depth = group.depth
+ @queue << [] until depth < @queue.length
+ @queue[depth] << group
+ end
+
+ # Returns the outer group of the queue
+ def deq
+ @queue.each {|gs|
+ (gs.length-1).downto(0) {|i|
+ unless gs[i].breakables.empty?
+ group = gs.slice!(i, 1).first
+ group.break
+ return group
+ end
+ }
+ gs.each {|group| group.break}
+ gs.clear
+ }
+ return nil
+ end
+
+ # Remote +group+ from this queue
+ def delete(group)
+ @queue[group.depth].delete(group)
+ end
+ end
+
+ # PrettyPrint::SingleLine is used by PrettyPrint.singleline_format
+ #
+ # It is passed to be similar to a PrettyPrint object itself, by responding to:
+ # * #text
+ # * #breakable
+ # * #nest
+ # * #group
+ # * #flush
+ # * #first?
+ #
+ # but instead, the output has no line breaks
+ #
+ class SingleLine
+ # Create a PrettyPrint::SingleLine object
+ #
+ # Arguments:
+ # * +output+ - String (or similar) to store rendered text. Needs to respond to '<<'
+ # * +maxwidth+ - Argument position expected to be here for compatibility.
+ # This argument is a noop.
+ # * +newline+ - Argument position expected to be here for compatibility.
+ # This argument is a noop.
+ def initialize(output, maxwidth=nil, newline=nil)
+ @output = output
+ @first = [true]
+ end
+
+ # Add +obj+ to the text to be output.
+ #
+ # +width+ argument is here for compatibility. It is a noop argument.
+ def text(obj, width=nil)
+ @output << obj
+ end
+
+ # Appends +sep+ to the text to be output. By default +sep+ is ' '
+ #
+ # +width+ argument is here for compatibility. It is a noop argument.
+ def breakable(sep=' ', width=nil)
+ @output << sep
+ end
+
+ # Takes +indent+ arg, but does nothing with it.
+ #
+ # Yields to a block.
+ def nest(indent) # :nodoc:
+ yield
+ end
+
+ # Opens a block for grouping objects to be pretty printed.
+ #
+ # Arguments:
+ # * +indent+ - noop argument. Present for compatibility.
+ # * +open_obj+ - text appended before the &blok. Default is ''
+ # * +close_obj+ - text appended after the &blok. Default is ''
+ # * +open_width+ - noop argument. Present for compatibility.
+ # * +close_width+ - noop argument. Present for compatibility.
+ def group(indent=nil, open_obj='', close_obj='', open_width=nil, close_width=nil)
+ @first.push true
+ @output << open_obj
+ yield
+ @output << close_obj
+ @first.pop
+ end
+
+ # Method present for compatibility, but is a noop
+ def flush # :nodoc:
+ end
+
+ # This is used as a predicate, and ought to be called first.
+ def first?
+ result = @first[-1]
+ @first[-1] = false
+ result
+ end
+ end
+end