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+# scanf for Ruby
+#
+# $Revision$
+# $Id$
+# $Author$
+# $Date$
+#
+# A product of the Austin Ruby Codefest (Austin, Texas, August 2002)
+
+=begin
+
+=scanf for Ruby
+
+==Description
+
+scanf for Ruby is an implementation of the C function scanf(3),
+modified as necessary for Ruby compatibility.
+
+The methods provided are String#scanf, IO#scanf, and
+Kernel#scanf. Kernel#scanf is a wrapper around STDIN.scanf. IO#scanf
+can be used on any IO stream, including file handles and sockets.
+scanf can be called either with or without a block.
+
+scanf for Ruby scans an input string or stream according to a
+<b>format</b>, as described below ("Conversions"), and returns an
+array of matches between the format and the input. The format is
+defined in a string, and is similar (though not identical) to the
+formats used in Kernel#printf and Kernel#sprintf.
+
+The format may contain <b>conversion specifiers</b>, which tell scanf
+what form (type) each particular matched substring should be converted
+to (e.g., decimal integer, floating point number, literal string,
+etc.) The matches and conversions take place from left to right, and
+the conversions themselves are returned as an array.
+
+The format string may also contain characters other than those in the
+conversion specifiers. White space (blanks, tabs, or newlines) in the
+format string matches any amount of white space, including none, in
+the input. Everything else matches only itself.
+
+Scanning stops, and scanf returns, when any input character fails to
+match the specifications in the format string, or when input is
+exhausted, or when everything in the format string has been
+matched. All matches found up to the stopping point are returned in
+the return array (or yielded to the block, if a block was given).
+
+
+==Basic usage
+
+ require 'scanf.rb'
+
+ # String#scanf and IO#scanf take a single argument (a format string)
+ array = aString.scanf("%d%s")
+ array = anIO.scanf("%d%s")
+
+ # Kernel#scanf reads from STDIN
+ array = scanf("%d%s")
+
+==Block usage
+
+When called with a block, scanf keeps scanning the input, cycling back
+to the beginning of the format string, and yields a new array of
+conversions to the block every time the format string is matched
+(including partial matches, but not including complete failures). The
+actual return value of scanf when called with a block is an array
+containing the results of all the executions of the block.
+
+ str = "123 abc 456 def 789 ghi"
+ str.scanf("%d%s") { |num,str| [ num * 2, str.upcase ] }
+ # => [[246, "ABC"], [912, "DEF"], [1578, "GHI"]]
+
+==Conversions
+
+The single argument to scanf is a format string, which generally
+includes one or more conversion specifiers. Conversion specifiers
+begin with the percent character ('%') and include information about
+what scanf should next scan for (string, decimal number, single
+character, etc.).
+
+There may be an optional maximum field width, expressed as a decimal
+integer, between the % and the conversion. If no width is given, a
+default of `infinity' is used (with the exception of the %c specifier;
+see below). Otherwise, given a field width of <em>n</em> for a given
+conversion, at most <em>n</em> characters are scanned in processing
+that conversion. Before conversion begins, most conversions skip
+white space in the input string; this white space is not counted
+against the field width.
+
+The following conversions are available. (See the files EXAMPLES
+and <tt>tests/scanftests.rb</tt> for examples.)
+
+[%]
+ Matches a literal `%'. That is, `%%' in the format string matches a
+ single input `%' character. No conversion is done, and the resulting
+ '%' is not included in the return array.
+
+[d]
+ Matches an optionally signed decimal integer.
+
+[u]
+ Same as d.
+
+[i]
+ Matches an optionally signed integer. The integer is read in base
+ 16 if it begins with `0x' or `0X', in base 8 if it begins with `0',
+ and in base 10 other- wise. Only characters that correspond to the
+ base are recognized.
+
+[o]
+ Matches an optionally signed octal integer.
+
+[x,X]
+ Matches an optionally signed hexadecimal integer,
+
+[f,g,e,E]
+ Matches an optionally signed floating-point number.
+
+[s]
+ Matches a sequence of non-white-space character. The input string stops at
+ white space or at the maximum field width, whichever occurs first.
+
+[c]
+ Matches a single character, or a sequence of <em>n</em> characters if a
+ field width of <em>n</em> is specified. The usual skip of leading white
+ space is suppressed. To skip white space first, use an explicit space in
+ the format.
+
+[<tt>[</tt>]
+ Matches a nonempty sequence of characters from the specified set
+ of accepted characters. The usual skip of leading white space is
+ suppressed. This bracketed sub-expression is interpreted exactly like a
+ character class in a Ruby regular expression. (In fact, it is placed as-is
+ in a regular expression.) The matching against the input string ends with
+ the appearance of a character not in (or, with a circumflex, in) the set,
+ or when the field width runs out, whichever comes first.
+
+===Assignment suppression
+
+To require that a particular match occur, but without including the result
+in the return array, place the <b>assignment suppression flag</b>, which is
+the star character ('*'), immediately after the leading '%' of a format
+specifier (just before the field width, if any).
+
+==Examples
+
+See the files <tt>EXAMPLES</tt> and <tt>tests/scanftests.rb</tt>.
+
+==scanf for Ruby compared with scanf in C
+
+scanf for Ruby is based on the C function scanf(3), but with modifications,
+dictated mainly by the underlying differences between the languages.
+
+===Unimplemented flags and specifiers
+
+* The only flag implemented in scanf for Ruby is '<tt>*</tt>' (ignore
+ upcoming conversion). Many of the flags available in C versions of scanf(4)
+ have to do with the type of upcoming pointer arguments, and are literally
+ meaningless in Ruby.
+
+* The <tt>n</tt> specifier (store number of characters consumed so far in
+ next pointer) is not implemented.
+
+* The <tt>p</tt> specifier (match a pointer value) is not implemented.
+
+===Altered specifiers
+
+[o,u,x,X]
+ In scanf for Ruby, all of these specifiers scan for an optionally signed
+ integer, rather than for an unsigned integer like their C counterparts.
+
+===Return values
+
+scanf for Ruby returns an array of successful conversions, whereas
+scanf(3) returns the number of conversions successfully
+completed. (See below for more details on scanf for Ruby's return
+values.)
+
+==Return values
+
+Without a block, scanf returns an array containing all the conversions
+it has found. If none are found, scanf will return an empty array. An
+unsuccesful match is never ignored, but rather always signals the end
+of the scanning operation. If the first unsuccessful match takes place
+after one or more successful matches have already taken place, the
+returned array will contain the results of those successful matches.
+
+With a block scanf returns a 'map'-like array of transformations from
+the block -- that is, an array reflecting what the block did with each
+yielded result from the iterative scanf operation. (See "Block
+usage", above.)
+
+==Test suite
+
+scanf for Ruby includes a suite of unit tests (requiring the
+<tt>TestUnit</tt> package), which can be run with the command <tt>ruby
+tests/scanftests.rb</tt> or the command <tt>make test</tt>.
+
+==Current limitations and bugs
+
+When using IO#scanf under Windows, make sure you open your files in
+binary mode:
+
+ File.open("filename", "rb")
+
+so that scanf can keep track of characters correctly.
+
+Support for character classes is reasonably complete (since it
+essentially piggy-backs on Ruby's regular expression handling of
+character classes), but users are advised that character class testing
+has not been exhaustive, and that they should exercise some caution
+in using any of the more complex and/or arcane character class
+idioms.
+
+
+==Technical notes
+
+===Rationale behind scanf for Ruby
+
+The impetus for a scanf implementation in Ruby comes chiefly from the fact
+that existing pattern matching operations, such as Regexp#match and
+String#scan, return all results as strings, which have to be converted to
+integers or floats explicitly in cases where what's ultimately wanted are
+integer or float values.
+
+===Design of scanf for Ruby
+
+scanf for Ruby is essentially a <format string>-to-<regular
+expression> converter.
+
+When scanf is called, a FormatString object is generated from the
+format string ("%d%s...") argument. The FormatString object breaks the
+format string down into atoms ("%d", "%5f", "blah", etc.), and from
+each atom it creates a FormatSpecifier object, which it
+saves.
+
+Each FormatSpecifier has a regular expression fragment and a "handler"
+associated with it. For example, the regular expression fragment
+associated with the format "%d" is "([-+]?\d+)", and the handler
+associated with it is a wrapper around String#to_i. scanf itself calls
+FormatString#match, passing in the input string. FormatString#match
+iterates through its FormatSpecifiers; for each one, it matches the
+corresponding regular expression fragment against the string. If
+there's a match, it sends the matched string to the handler associated
+with the FormatSpecifier.
+
+Thus, to follow up the "%d" example: if "123" occurs in the input
+string when a FormatSpecifier consisting of "%d" is reached, the "123"
+will be matched against "([-+]?\d+)", and the matched string will be
+rendered into an integer by a call to to_i.
+
+The rendered match is then saved to an accumulator array, and the
+input string is reduced to the post-match substring. Thus the string
+is "eaten" from the left as the FormatSpecifiers are applied in
+sequence. (This is done to a duplicate string; the original string is
+not altered.)
+
+As soon as a regular expression fragment fails to match the string, or
+when the FormatString object runs out of FormatSpecifiers, scanning
+stops and results accumulated so far are returned in an array.
+
+==License and copyright
+
+Copyright:: (c) 2002-2003 David Alan Black
+License:: Distributed on the same licensing terms as Ruby itself
+
+==Warranty disclaimer
+
+This software is provided "as is" and without any express or implied
+warranties, including, without limitation, the implied warranties of
+merchantibility and fitness for a particular purpose.
+
+==Credits and acknowledgements
+
+scanf for Ruby was developed as the major activity of the Austin
+Ruby Codefest (Austin, Texas, August 2002).
+
+Principal author:: David Alan Black (mailto:dblack@superlink.net)
+Co-author:: Hal Fulton (mailto:hal9000@hypermetrics.com)
+Project contributors:: Nolan Darilek, Jason Johnston
+
+Thanks to Hal Fulton for hosting the Codefest.
+
+Thanks to Matz for suggestions about the class design.
+
+Thanks to Gavin Sinclair for some feedback on the documentation.
+
+The text for parts of this document, especially the Description and
+Conversions sections, above, were adapted from the Linux Programmer's
+Manual manpage for scanf(3), dated 1995-11-01.
+
+==Bugs and bug reports
+
+scanf for Ruby is based on something of an amalgam of C scanf
+implementations and documentation, rather than on a single canonical
+description. Suggestions for features and behaviors which appear in
+other scanfs, and would be meaningful in Ruby, are welcome, as are
+reports of suspicious behaviors and/or bugs. (Please see "Credits and
+acknowledgements", above, for email addresses.)
+
+=end
+
+module Scanf
+
+ class FormatSpecifier
+
+ attr_reader :re_string, :matched_string, :conversion, :matched
+
+ private
+
+ def skip; /^\s*%\*/.match(@spec_string); end
+
+ def extract_float(s); s.to_f if s &&! skip; end
+ def extract_decimal(s); s.to_i if s &&! skip; end
+ def extract_hex(s); s.hex if s &&! skip; end
+ def extract_octal(s); s.oct if s &&! skip; end
+ def extract_integer(s); Integer(s) if s &&! skip; end
+ def extract_plain(s); s unless skip; end
+
+ def nil_proc(s); nil; end
+
+ public
+
+ def to_s
+ @spec_string
+ end
+
+ def count_space?
+ /(?:\A|\S)%\*?\d*c|\[/.match(@spec_string)
+ end
+
+ def initialize(str)
+ @spec_string = str
+ h = '[A-Fa-f0-9]'
+
+ @re_string, @handler =
+ case @spec_string
+
+ # %[[:...:]]
+ when /%\*?(\[\[:[a-z]+:\]\])/
+ [ "(#{$1}+)", :extract_plain ]
+
+ # %5[[:...:]]
+ when /%\*?(\d+)(\[\[:[a-z]+:\]\])/
+ [ "(#{$2}{1,#{$1}})", :extract_plain ]
+
+ # %[...]
+ when /%\*?\[([^\]]*)\]/
+ yes = $1
+ if /^\^/.match(yes) then no = yes[1..-1] else no = '^' + yes end
+ [ "([#{yes}]+)(?=[#{no}]|\\z)", :extract_plain ]
+
+ # %5[...]
+ when /%\*?(\d+)\[([^\]]*)\]/
+ yes = $2
+ w = $1
+ [ "([#{yes}]{1,#{w}})", :extract_plain ]
+
+ # %i
+ when /%\*?i/
+ [ "([-+]?(?:(?:0[0-7]+)|(?:0[Xx]#{h}+)|(?:[1-9]\\d+)))", :extract_integer ]
+
+ # %5i
+ when /%\*?(\d+)i/
+ n = $1.to_i
+ s = "("
+ if n > 1 then s += "[1-9]\\d{1,#{n-1}}|" end
+ if n > 1 then s += "0[0-7]{1,#{n-1}}|" end
+ if n > 2 then s += "[-+]0[0-7]{1,#{n-2}}|" end
+ if n > 2 then s += "[-+][1-9]\\d{1,#{n-2}}|" end
+ if n > 2 then s += "0[Xx]#{h}{1,#{n-2}}|" end
+ if n > 3 then s += "[-+]0[Xx]#{h}{1,#{n-3}}|" end
+ s += "\\d"
+ s += ")"
+ [ s, :extract_integer ]
+
+ # %d, %u
+ when /%\*?[du]/
+ [ '([-+]?\d+)', :extract_decimal ]
+
+ # %5d, %5u
+ when /%\*?(\d+)[du]/
+ n = $1.to_i
+ s = "("
+ if n > 1 then s += "[-+]\\d{1,#{n-1}}|" end
+ s += "\\d{1,#{$1}})"
+ [ s, :extract_decimal ]
+
+ # %x
+ when /%\*?[Xx]/
+ [ "([-+]?(?:0[Xx])?#{h}+)", :extract_hex ]
+
+ # %5x
+ when /%\*?(\d+)[Xx]/
+ n = $1.to_i
+ s = "("
+ if n > 3 then s += "[-+]0[Xx]#{h}{1,#{n-3}}|" end
+ if n > 2 then s += "0[Xx]#{h}{1,#{n-2}}|" end
+ if n > 1 then s += "[-+]#{h}{1,#{n-1}}|" end
+ s += "#{h}{1,#{n}}"
+ s += ")"
+ [ s, :extract_hex ]
+
+ # %o
+ when /%\*?o/
+ [ '([-+]?[0-7]+)', :extract_octal ]
+
+ # %5o
+ when /%\*?(\d+)o/
+ [ "([-+][0-7]{1,#{$1.to_i-1}}|[0-7]{1,#{$1}})", :extract_octal ]
+
+ # %f
+ when /%\*?f/
+ [ '([-+]?((\d+(?>(?=[^\d.]|$)))|(\d*(\.(\d*([eE][-+]?\d+)?)))))', :extract_float ]
+
+ # %5f
+ when /%\*?(\d+)f/
+ [ "(\\S{1,#{$1}})", :extract_float ]
+
+ # %5s
+ when /%\*?(\d+)s/
+ [ "(\\S{1,#{$1}})", :extract_plain ]
+
+ # %s
+ when /%\*?s/
+ [ '(\S+)', :extract_plain ]
+
+ # %c
+ when /\s%\*?c/
+ [ "\\s*(.)", :extract_plain ]
+
+ # %c
+ when /%\*?c/
+ [ "(.)", :extract_plain ]
+
+ # %5c (whitespace issues are handled by the count_*_space? methods)
+ when /%\*?(\d+)c/
+ [ "(.{1,#{$1}})", :extract_plain ]
+
+ # %%
+ when /%%/
+ [ '(\s*%)', :nil_proc ]
+
+ # literal characters
+ else
+ [ "(#{Regexp.escape(@spec_string)})", :nil_proc ]
+ end
+
+ @re_string = '\A' + @re_string
+ end
+
+ def to_re
+ Regexp.new(@re_string,Regexp::MULTILINE)
+ end
+
+ def match(str)
+ @matched = false
+ s = str.dup
+ s.sub!(/\A\s+/,'') unless count_space?
+ res = to_re.match(s)
+ if res
+ @conversion = send(@handler, res[1])
+ @matched_string = @conversion.to_s
+ @matched = true
+ end
+ res
+ end
+
+ def letter
+ /%\*?\d*([a-z\[])/.match(@spec_string).to_a[1]
+ end
+
+ def width
+ w = /%\*?(\d+)/.match(@spec_string).to_a[1]
+ w && w.to_i
+ end
+
+ def mid_match?
+ return false unless @matched
+ cc_no_width = letter == '[' &&! width
+ c_or_cc_width = (letter == 'c' || letter == '[') && width
+ width_left = c_or_cc_width && (matched_string.size < width)
+
+ return width_left || cc_no_width
+ end
+
+ end
+
+ class FormatString
+
+ attr_reader :string_left, :last_spec_tried,
+ :last_match_tried, :matched_count, :space
+
+ SPECIFIERS = 'diuXxofeEgsc'
+ REGEX = /
+ # possible space, followed by...
+ (?:\s*
+ # percent sign, followed by...
+ %
+ # another percent sign, or...
+ (?:%|
+ # optional assignment suppression flag
+ \*?
+ # optional maximum field width
+ \d*
+ # named character class, ...
+ (?:\[\[:\w+:\]\]|
+ # traditional character class, or...
+ \[[^\]]*\]|
+ # specifier letter.
+ [#{SPECIFIERS}])))|
+ # or miscellaneous characters
+ [^%\s]+/ix
+
+ def initialize(str)
+ @specs = []
+ @i = 1
+ s = str.to_s
+ return unless /\S/.match(s)
+ @space = true if /\s\z/.match(s)
+ @specs.replace s.scan(REGEX).map {|spec| FormatSpecifier.new(spec) }
+ end
+
+ def to_s
+ @specs.join('')
+ end
+
+ def prune(n=matched_count)
+ n.times { @specs.shift }
+ end
+
+ def spec_count
+ @specs.size
+ end
+
+ def last_spec
+ @i == spec_count - 1
+ end
+
+ def match(str)
+ accum = []
+ @string_left = str
+ @matched_count = 0
+
+ @specs.each_with_index do |spec,@i|
+ @last_spec_tried = spec
+ @last_match_tried = spec.match(@string_left)
+ break unless @last_match_tried
+ @matched_count += 1
+
+ accum << spec.conversion
+
+ @string_left = @last_match_tried.post_match
+ break if @string_left.empty?
+ end
+ return accum.compact
+ end
+ end
+end
+
+class IO
+
+# The trick here is doing a match where you grab one *line*
+# of input at a time. The linebreak may or may not occur
+# at the boundary where the string matches a format specifier.
+# And if it does, some rule about whitespace may or may not
+# be in effect...
+#
+# That's why this is much more elaborate than the string
+# version.
+#
+# For each line:
+# Match succeeds (non-emptily)
+# and the last attempted spec/string sub-match succeeded:
+#
+# could the last spec keep matching?
+# yes: save interim results and continue (next line)
+#
+# The last attempted spec/string did not match:
+#
+# are we on the next-to-last spec in the string?
+# yes:
+# is fmt_string.string_left all spaces?
+# yes: does current spec care about input space?
+# yes: fatal failure
+# no: save interim results and continue
+# no: continue [this state could be analyzed further]
+#
+#
+
+ def scanf(str,&b)
+ return block_scanf(str,&b) if b
+ return [] unless str.size > 0
+
+ start_position = pos rescue 0
+ matched_so_far = 0
+ source_buffer = ""
+ result_buffer = []
+ final_result = []
+
+ fstr = Scanf::FormatString.new(str)
+
+ loop do
+ if eof || (tty? &&! fstr.match(source_buffer))
+ final_result.concat(result_buffer)
+ break
+ end
+
+ source_buffer << gets
+
+ current_match = fstr.match(source_buffer)
+
+ spec = fstr.last_spec_tried
+
+ if spec.matched
+ if spec.mid_match?
+ result_buffer.replace(current_match)
+ next
+ end
+
+ elsif (fstr.matched_count == fstr.spec_count - 1)
+ if /\A\s*\z/.match(fstr.string_left)
+ break if spec.count_space?
+ result_buffer.replace(current_match)
+ next
+ end
+ end
+
+ final_result.concat(current_match)
+
+ matched_so_far += source_buffer.size
+ source_buffer.replace(fstr.string_left)
+ matched_so_far -= source_buffer.size
+ break if fstr.last_spec
+ fstr.prune
+ end
+ seek(start_position + matched_so_far, IO::SEEK_SET) rescue Errno::ESPIPE
+ soak_up_spaces if fstr.last_spec && fstr.space
+
+ return final_result
+ end
+
+ private
+
+ def soak_up_spaces
+ c = getc
+ ungetc(c) if c
+ until eof ||! c || /\S/.match(c.chr)
+ c = getc
+ end
+ ungetc(c) if (c && /\S/.match(c.chr))
+ end
+
+ def block_scanf(str)
+ final = []
+# Sub-ideal, since another FS gets created in scanf.
+# But used here to determine the number of specifiers.
+ fstr = Scanf::FormatString.new(str)
+ last_spec = fstr.last_spec
+ begin
+ current = scanf(str)
+ break if current.empty?
+ final.push(yield(current))
+ end until eof || fstr.last_spec_tried == last_spec
+ return final
+ end
+end
+
+class String
+
+ def scanf(fstr,&b)
+ if b
+ block_scanf(fstr,&b)
+ else
+ fs =
+ if fstr.is_a? Scanf::FormatString
+ fstr
+ else
+ Scanf::FormatString.new(fstr)
+ end
+ fs.match(self)
+ end
+ end
+
+ def block_scanf(fstr,&b)
+ fs = Scanf::FormatString.new(fstr)
+ str = self.dup
+ final = []
+ begin
+ current = str.scanf(fs)
+ final.push(yield(current)) unless current.empty?
+ str = fs.string_left
+ end until current.empty? || str.empty?
+ return final
+ end
+end
+
+module Kernel
+ private
+ def scanf(fs,&b)
+ STDIN.scanf(fs,&b)
+ end
+end
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