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# scanf for Ruby
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#
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# $Release Version: 1.1.2 $
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# $Revision$
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# $Id$
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# $Author$
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# $Date$
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#
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# A product of the Austin Ruby Codefest (Austin, Texas, August 2002)
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=begin
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=scanf for Ruby
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==Description
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scanf for Ruby is an implementation of the C function scanf(3),
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modified as necessary for Ruby compatibility.
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The methods provided are String#scanf, IO#scanf, and
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Kernel#scanf. Kernel#scanf is a wrapper around STDIN.scanf. IO#scanf
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can be used on any IO stream, including file handles and sockets.
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scanf can be called either with or without a block.
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scanf for Ruby scans an input string or stream according to a
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<b>format</b>, as described below ("Conversions"), and returns an
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array of matches between the format and the input. The format is
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defined in a string, and is similar (though not identical) to the
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formats used in Kernel#printf and Kernel#sprintf.
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The format may contain <b>conversion specifiers</b>, which tell scanf
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what form (type) each particular matched substring should be converted
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to (e.g., decimal integer, floating point number, literal string,
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etc.) The matches and conversions take place from left to right, and
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the conversions themselves are returned as an array.
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The format string may also contain characters other than those in the
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conversion specifiers. White space (blanks, tabs, or newlines) in the
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format string matches any amount of white space, including none, in
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the input. Everything else matches only itself.
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Scanning stops, and scanf returns, when any input character fails to
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match the specifications in the format string, or when input is
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exhausted, or when everything in the format string has been
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matched. All matches found up to the stopping point are returned in
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the return array (or yielded to the block, if a block was given).
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==Basic usage
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require 'scanf.rb'
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# String#scanf and IO#scanf take a single argument (a format string)
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array = aString.scanf("%d%s")
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array = anIO.scanf("%d%s")
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# Kernel#scanf reads from STDIN
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array = scanf("%d%s")
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==Block usage
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When called with a block, scanf keeps scanning the input, cycling back
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to the beginning of the format string, and yields a new array of
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conversions to the block every time the format string is matched
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(including partial matches, but not including complete failures). The
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actual return value of scanf when called with a block is an array
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containing the results of all the executions of the block.
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str = "123 abc 456 def 789 ghi"
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str.scanf("%d%s") { |num,str| [ num * 2, str.upcase ] }
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# => [[246, "ABC"], [912, "DEF"], [1578, "GHI"]]
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==Conversions
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The single argument to scanf is a format string, which generally
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includes one or more conversion specifiers. Conversion specifiers
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begin with the percent character ('%') and include information about
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what scanf should next scan for (string, decimal number, single
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character, etc.).
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There may be an optional maximum field width, expressed as a decimal
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integer, between the % and the conversion. If no width is given, a
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default of `infinity' is used (with the exception of the %c specifier;
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see below). Otherwise, given a field width of <em>n</em> for a given
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conversion, at most <em>n</em> characters are scanned in processing
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that conversion. Before conversion begins, most conversions skip
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white space in the input string; this white space is not counted
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against the field width.
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The following conversions are available. (See the files EXAMPLES
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and <tt>tests/scanftests.rb</tt> for examples.)
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[%]
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Matches a literal `%'. That is, `%%' in the format string matches a
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single input `%' character. No conversion is done, and the resulting
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'%' is not included in the return array.
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[d]
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Matches an optionally signed decimal integer.
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[u]
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Same as d.
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[i]
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Matches an optionally signed integer. The integer is read in base
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16 if it begins with `0x' or `0X', in base 8 if it begins with `0',
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and in base 10 other- wise. Only characters that correspond to the
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base are recognized.
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[o]
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Matches an optionally signed octal integer.
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[x,X]
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Matches an optionally signed hexadecimal integer,
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[f,g,e,E]
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Matches an optionally signed floating-point number.
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[s]
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Matches a sequence of non-white-space character. The input string stops at
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white space or at the maximum field width, whichever occurs first.
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[c]
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Matches a single character, or a sequence of <em>n</em> characters if a
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field width of <em>n</em> is specified. The usual skip of leading white
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space is suppressed. To skip white space first, use an explicit space in
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the format.
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[<tt>[</tt>]
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Matches a nonempty sequence of characters from the specified set
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of accepted characters. The usual skip of leading white space is
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suppressed. This bracketed sub-expression is interpreted exactly like a
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character class in a Ruby regular expression. (In fact, it is placed as-is
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in a regular expression.) The matching against the input string ends with
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the appearance of a character not in (or, with a circumflex, in) the set,
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or when the field width runs out, whichever comes first.
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===Assignment suppression
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To require that a particular match occur, but without including the result
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in the return array, place the <b>assignment suppression flag</b>, which is
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the star character ('*'), immediately after the leading '%' of a format
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specifier (just before the field width, if any).
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==Examples
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See the files <tt>EXAMPLES</tt> and <tt>tests/scanftests.rb</tt>.
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==scanf for Ruby compared with scanf in C
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scanf for Ruby is based on the C function scanf(3), but with modifications,
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dictated mainly by the underlying differences between the languages.
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===Unimplemented flags and specifiers
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* The only flag implemented in scanf for Ruby is '<tt>*</tt>' (ignore
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upcoming conversion). Many of the flags available in C versions of scanf(4)
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have to do with the type of upcoming pointer arguments, and are literally
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meaningless in Ruby.
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* The <tt>n</tt> specifier (store number of characters consumed so far in
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next pointer) is not implemented.
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* The <tt>p</tt> specifier (match a pointer value) is not implemented.
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===Altered specifiers
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[o,u,x,X]
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In scanf for Ruby, all of these specifiers scan for an optionally signed
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integer, rather than for an unsigned integer like their C counterparts.
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===Return values
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scanf for Ruby returns an array of successful conversions, whereas
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scanf(3) returns the number of conversions successfully
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completed. (See below for more details on scanf for Ruby's return
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values.)
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==Return values
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Without a block, scanf returns an array containing all the conversions
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it has found. If none are found, scanf will return an empty array. An
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unsuccesful match is never ignored, but rather always signals the end
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of the scanning operation. If the first unsuccessful match takes place
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after one or more successful matches have already taken place, the
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returned array will contain the results of those successful matches.
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With a block scanf returns a 'map'-like array of transformations from
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the block -- that is, an array reflecting what the block did with each
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yielded result from the iterative scanf operation. (See "Block
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usage", above.)
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==Test suite
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scanf for Ruby includes a suite of unit tests (requiring the
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<tt>TestUnit</tt> package), which can be run with the command <tt>ruby
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tests/scanftests.rb</tt> or the command <tt>make test</tt>.
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==Current limitations and bugs
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When using IO#scanf under Windows, make sure you open your files in
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binary mode:
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File.open("filename", "rb")
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so that scanf can keep track of characters correctly.
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Support for character classes is reasonably complete (since it
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essentially piggy-backs on Ruby's regular expression handling of
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character classes), but users are advised that character class testing
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has not been exhaustive, and that they should exercise some caution
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in using any of the more complex and/or arcane character class
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idioms.
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==Technical notes
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===Rationale behind scanf for Ruby
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The impetus for a scanf implementation in Ruby comes chiefly from the fact
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that existing pattern matching operations, such as Regexp#match and
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String#scan, return all results as strings, which have to be converted to
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integers or floats explicitly in cases where what's ultimately wanted are
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integer or float values.
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===Design of scanf for Ruby
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scanf for Ruby is essentially a <format string>-to-<regular
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expression> converter.
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When scanf is called, a FormatString object is generated from the
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format string ("%d%s...") argument. The FormatString object breaks the
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format string down into atoms ("%d", "%5f", "blah", etc.), and from
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each atom it creates a FormatSpecifier object, which it
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saves.
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Each FormatSpecifier has a regular expression fragment and a "handler"
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associated with it. For example, the regular expression fragment
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associated with the format "%d" is "([-+]?\d+)", and the handler
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associated with it is a wrapper around String#to_i. scanf itself calls
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FormatString#match, passing in the input string. FormatString#match
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iterates through its FormatSpecifiers; for each one, it matches the
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corresponding regular expression fragment against the string. If
|
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there's a match, it sends the matched string to the handler associated
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with the FormatSpecifier.
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|
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Thus, to follow up the "%d" example: if "123" occurs in the input
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string when a FormatSpecifier consisting of "%d" is reached, the "123"
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will be matched against "([-+]?\d+)", and the matched string will be
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rendered into an integer by a call to to_i.
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The rendered match is then saved to an accumulator array, and the
|
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input string is reduced to the post-match substring. Thus the string
|
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is "eaten" from the left as the FormatSpecifiers are applied in
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sequence. (This is done to a duplicate string; the original string is
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not altered.)
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|
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As soon as a regular expression fragment fails to match the string, or
|
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when the FormatString object runs out of FormatSpecifiers, scanning
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stops and results accumulated so far are returned in an array.
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==License and copyright
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Copyright:: (c) 2002-2003 David Alan Black
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License:: Distributed on the same licensing terms as Ruby itself
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==Warranty disclaimer
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This software is provided "as is" and without any express or implied
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warranties, including, without limitation, the implied warranties of
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merchantibility and fitness for a particular purpose.
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==Credits and acknowledgements
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|
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scanf for Ruby was developed as the major activity of the Austin
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Ruby Codefest (Austin, Texas, August 2002).
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Principal author:: David Alan Black (mailto:dblack@superlink.net)
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Co-author:: Hal Fulton (mailto:hal9000@hypermetrics.com)
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Project contributors:: Nolan Darilek, Jason Johnston
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Thanks to Hal Fulton for hosting the Codefest.
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Thanks to Matz for suggestions about the class design.
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Thanks to Gavin Sinclair for some feedback on the documentation.
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The text for parts of this document, especially the Description and
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Conversions sections, above, were adapted from the Linux Programmer's
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Manual manpage for scanf(3), dated 1995-11-01.
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==Bugs and bug reports
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scanf for Ruby is based on something of an amalgam of C scanf
|
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implementations and documentation, rather than on a single canonical
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description. Suggestions for features and behaviors which appear in
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other scanfs, and would be meaningful in Ruby, are welcome, as are
|
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reports of suspicious behaviors and/or bugs. (Please see "Credits and
|
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acknowledgements", above, for email addresses.)
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=end
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module Scanf
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class FormatSpecifier
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attr_reader :re_string, :matched_string, :conversion
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attr_writer :i
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private
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def skip; /^\s*%\*/.match(@spec_string); end
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def extract_float(s); s.to_f if s &&! skip; end
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def extract_decimal(s); s.to_i if s &&! skip; end
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def extract_hex(s); s.hex if s &&! skip; end
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def extract_octal(s); s.oct if s &&! skip; end
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def extract_integer(s); Integer(s) if s &&! skip; end
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def extract_plain(s); s unless skip; end
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def nil_proc(s); nil; end
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public
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def to_s
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@spec_string
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end
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def count_space?
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/(?:\A|\S)%\*?\d*c|\[/.match(@spec_string)
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end
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def initialize(str)
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@spec_string = str
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h = '[A-Fa-f0-9]'
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@re_string, @handler =
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case @spec_string
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# %[[:...:]]
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when /%\*?(\[\[:[a-z]+:\]\])/
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[ "(#{$1}+)", :extract_plain ]
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|
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# %5[[:...:]]
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when /%\*?(\d+)(\[\[:[a-z]+:\]\])/
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[ "(#{$2}{1,#{$1}})", :extract_plain ]
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|
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# %[...]
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when /%\*?\[([^\]]*)\]/
|
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yes = $1
|
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if /^\^/.match(yes) then no = yes[1..-1] else no = '^' + yes end
|
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[ "([#{yes}]+)(?=[#{no}]|\\z)", :extract_plain ]
|
||||
|
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# %5[...]
|
||||
when /%\*?(\d+)\[([^\]]*)\]/
|
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yes = $2
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w = $1
|
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[ "([#{yes}]{1,#{w}})", :extract_plain ]
|
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|
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# %i
|
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when /%\*?i/
|
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[ "([-+]?(?:(?:0[0-7]+)|(?:0[Xx]#{h}+)|(?:[1-9]\\d+)))", :extract_integer ]
|
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|
||||
# %5i
|
||||
when /%\*?(\d+)i/
|
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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)
|
||||
s = str.dup
|
||||
s.sub!(/\A\s+/,'') unless count_space?
|
||||
res = to_re.match(s)
|
||||
if res
|
||||
@conversion = send(@handler, res[1])
|
||||
@matched_string = @matched_item.to_s
|
||||
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 || 0
|
||||
end
|
||||
|
||||
def mid_match?
|
||||
cc_no_width = letter == '[' && width.zero?
|
||||
c_or_cc_width = (letter == 'c' || letter == '[') &&! width.zero?
|
||||
c_or_cc_open = c_or_cc_width && (matched_string.size < width)
|
||||
|
||||
return c_or_cc_open || 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 = []
|
||||
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
|
||||
@spec_string
|
||||
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.
|
||||
#
|
||||
# Match succeeds (non-emptily)
|
||||
# and the last attempted spec/string sub-match succeeded:
|
||||
#
|
||||
# is the current matched spec a '%[...]' or '%c' with a width?
|
||||
# yes: is current.string.size < available width?
|
||||
# yes: save interim results
|
||||
# no: width is used up, so move on (next)
|
||||
# no: is it a '%[...]' with no width?
|
||||
# yes: evidently nothing violated it yet, so store
|
||||
# interim results and continue (next)
|
||||
#
|
||||
# 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
|
||||
matched_so_far = 0
|
||||
source_buffer = ""
|
||||
result_buffer = []
|
||||
final_result = []
|
||||
|
||||
fstr = Scanf::FormatString.new(str)
|
||||
|
||||
loop do
|
||||
if eof
|
||||
final_result.concat(result_buffer)
|
||||
break
|
||||
end
|
||||
|
||||
source_buffer << gets
|
||||
current_match = fstr.match(source_buffer)
|
||||
|
||||
spec = fstr.last_spec_tried
|
||||
|
||||
if fstr.last_match_tried
|
||||
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
|
||||
end
|
||||
|
||||
def block_scanf(str)
|
||||
final = []
|
||||
begin
|
||||
current = scanf(str)
|
||||
final.push(yield(current)) unless current.empty?
|
||||
end until current.empty? || eof
|
||||
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)
|
||||
STDIN.scanf(fs)
|
||||
end
|
||||
end
|
||||
Загрузка…
Ссылка в новой задаче