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Edit File: scanf.rb
# scanf for Ruby # #-- # $Release Version: 1.1.2 $ # $Revision$ # $Id$ # $Author$ #++ # # == Description # # scanf 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 scans an input string or stream according to a <b>format</b>, as # described below in 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' # # # String#scanf and IO#scanf take a single argument, the format string # array = a_string.scanf("%d%s") # array = an_io.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. # # [%] # 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, # # [a, e, f, g, A, E, F, G] # 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. # # [[] # 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). # # == 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(3) have to do with the type of upcoming pointer arguments, and are # 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 # unsuccessful 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.) # # == 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. # # == 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 # merchantability and fitness for a particular purpose. # # == Credits and acknowledgements # # scanf 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.) module Scanf # :stopdoc: # ==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. class FormatSpecifier attr_reader :re_string, :matched_string, :conversion, :matched private def skip; /^\s*%\*/.match(@spec_string); end def extract_float(s) return nil unless s &&! skip if /\A(?<sign>[-+]?)0[xX](?<frac>\.\h+|\h+(?:\.\h*)?)[pP](?<exp>[-+]\d+)/ =~ s f1, f2 = frac.split('.') f = f1.hex if f2 len = f2.length if len > 0 f += f2.hex / (16.0 ** len) end end (sign == ?- ? -1 : 1) * Math.ldexp(f, exp.to_i) elsif /\A([-+]?\d+)\.([eE][-+]\d+)/ =~ s ($1 << $2).to_f else s.to_f end 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|%\d*\[/.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 /%\*?[aefgAEFG]/ [ '([-+]?(?:0[xX](?:\.\h+|\h+(?:\.\h*)?)[pP][-+]\d+|\d+(?![\d.])|\d*\.\d*(?:[eE][-+]?\d+)?))', :extract_float ] # %5f when /%\*?(\d+)[aefgAEFG]/ [ '(?=[-+]?(?:0[xX](?:\.\h+|\h+(?:\.\h*)?)[pP][-+]\d+|\d+(?![\d.])|\d*\.\d*(?:[eE][-+]?\d+)?))' + "(\\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 @spec_string[/%\*?\d*([a-z\[])/, 1] end def width w = @spec_string[/%\*?(\d+)/, 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 = 'diuXxofFeEgGscaA' 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| @i=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 # :startdoc: end class IO #:stopdoc: # 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] # #:startdoc: # Scans the current string until the match is exhausted, # yielding each match as it is encountered in the string. # A block is not necessary though, as the results will simply # be aggregated into the final array. # # "123 456".block_scanf("%d") # # => [123, 456] # # If a block is given, the value from that is returned from # the yield is added to an output array. # # "123 456".block_scanf("%d) do |digit,| # the ',' unpacks the Array # digit + 100 # end # # => [223, 556] # # See Scanf for details on creating a format string. # # You will need to require 'scanf' to use use IO#scanf. def scanf(str,&b) #:yield: current_match 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 begin seek(start_position + matched_so_far, IO::SEEK_SET) rescue Errno::ESPIPE end 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 # :section: scanf # # You will need to require 'scanf' to use these methods # Scans the current string. If a block is given, it # functions exactly like block_scanf. # # arr = "123 456".scanf("%d%d") # # => [123, 456] # # require 'pp' # # "this 123 read that 456 other".scanf("%s%d%s") {|m| pp m} # # # ["this", 123, "read"] # # ["that", 456, "other"] # # => [["this", 123, "read"], ["that", 456, "other"]] # # See Scanf for details on creating a format string. # # You will need to require 'scanf' to use String#scanf def scanf(fstr,&b) #:yield: current_match 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 # Scans the current string until the match is exhausted # yielding each match as it is encountered in the string. # A block is not necessary as the results will simply # be aggregated into the final array. # # "123 456".block_scanf("%d") # # => [123, 456] # # If a block is given, the value from that is returned from # the yield is added to an output array. # # "123 456".block_scanf("%d) do |digit,| # the ',' unpacks the Array # digit + 100 # end # # => [223, 556] # # See Scanf for details on creating a format string. # # You will need to require 'scanf' to use String#block_scanf def block_scanf(fstr) #:yield: current_match 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 # Scans STDIN for data matching +format+. See IO#scanf for details. # # See Scanf for details on creating a format string. # # You will need to require 'scanf' to use Kernel#scanf. def scanf(format, &b) #:doc: STDIN.scanf(format ,&b) end end