Class: ABNF

Inherits:
Object
  • Object
show all
Defined in:
lib/abnftt/abnf-util.rb,
lib/abnftt/abnf-writer.rb,
lib/abnftt/abnf-visitor.rb,
lib/abnftt/abnf-squasher.rb,
lib/abnftt/abnf-flattener.rb,
lib/abnftt.rb

Constant Summary collapse

UNESCAPED_SQSTR_RANGES = 
[[0xA, 0xA], [0x20, 0x26],  # "'"
   # [0x28, 0x5b], [0x5d, 0x7e], [0xa0, 0xd7ff], -- but JSON allows 7F-9F
   [0x28, 0x5b], [0x5d, 0xd7ff], # \
   [0xe000, 0x10ffff]].map {|l, r|
  [l.chr(Encoding::UTF_8), r.chr(Encoding::UTF_8)]
}
ESCAPED_SQSTR_MAPPINGS = 
[
["\x08", "b"],
["\x09", "t"],
["\x0A", "n"],
["\x0C", "f"],
["\x0D", "r"],
["\x27", "'"],
["\x2F", "/"],
["\x5C", "\\"]]
FIXUP_NAMES = 
Hash.new {|h, k| k}
@@parser = 
ABNFGrammarParser.new
@@gensym = 
0

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(ast_ = nil, rules_ = {}) ⇒ ABNF

Returns a new instance of ABNF.



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# File 'lib/abnftt.rb', line 61

def initialize(ast_ = nil, rules_ = {})
  if ast_
    @ast = ast_
    @tree = ast.ast
  end
  @rules = rules_
  @tree.each do |x|
    op, name, val, rest = x
    fail rest if rest
    @rules[name] =
      if old = @rules[name]
        fail "duplicate rule for name #{name}" if op == "="
        if Array === old && old[0] == "alt"
          old.dup << val
        else
          ["alt", old, val]
        end
      else
        val
      end
  end if @tree
  # warn "** rules #{rules.inspect}"
end

Instance Attribute Details

#ast ⇒ Object

Returns the value of attribute ast.



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# File 'lib/abnftt.rb', line 60

def ast
  @ast
end

#parser ⇒ Object

Returns the value of attribute parser.



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# File 'lib/abnftt.rb', line 206

def parser
  @parser
end

#rules ⇒ Object

Returns the value of attribute rules.



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# File 'lib/abnftt.rb', line 60

def rules
  @rules
end

#tree ⇒ Object

Returns the value of attribute tree.



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# File 'lib/abnftt.rb', line 60

def tree
  @tree
end

Class Method Details

.from_abnf(s) ⇒ Object 



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# File 'lib/abnftt.rb', line 48

def self.from_abnf(s)
  ast = @@parser.parse s
  if !ast
    fail self.reason(@@parser, s)
  end
  ABNF.new(ast)
end

.from_rules(r) ⇒ Object 



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# File 'lib/abnftt.rb', line 56

def self.from_rules(r)
  ABNF.new(nil, r)
end

.reason(parser, s) ⇒ Object 



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# File 'lib/abnftt.rb', line 37

def self.reason(parser, s)
  reason = [parser.failure_reason]
  parser.failure_reason =~ /^(Expected .+) after/m
  reason << "#{$1.gsub("\n", '<<<NEWLINE>>>')}:" if $1
  if line = s.lines.to_a[parser.failure_line - 1]
    reason << line
    reason << "#{'~' * (parser.failure_column - 1)}^"
  end
  reason.join("\n")
end

Instance Method Details

#alt_ranges(l, r, step = 4, ndig = false) ⇒ Object

Support legacy JSON u/uu and u… hex unicode



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# File 'lib/abnftt/abnf-util.rb', line 105

def alt_ranges(l, r, step = 4, ndig = false)
  alt = []
  do_range(l.ord, r.ord, step) do |l, r, column|
    alt << hex_ranges(l, r, ndig)
  end
  wrap("alt", alt.reverse)    # work around prioritized choice
end

#alt_ranges_legacy(l, r) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 113

def alt_ranges_legacy(l, r)
  alt = []
  if l < 0x10000
    alt << ["alt", alt_ranges(l, [r, 0xFFFF].min, 4, 4)]
  end
  if r >= 0x10000
    l1 = [l, 0x10000].max - 0x10000
    r1 = r - 0x10000
    do_range(l1, r1, 10) do |l2, r2, column|
      alt << ["seq",
              alt_ranges((l2 >> 10) + 0xD800, (r2 >> 10) + 0xD800, 4, 4),
              expand_string("\\u"),
              alt_ranges((l2 & 0x3FF) + 0xDC00, (r2 & 0x3FF) + 0xDC00, 4, 4)]
    end
  end
  wrap_flat("alt", alt)
end

#alt_ranges_modern(l, r, step = 4) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 131

def alt_ranges_modern(l, r, step = 4)
  ["seq",
   expand_string("{"),
   ["rep", 0, true, ["cs","0"]],
   alt_ranges(l, r, 4, false),
   expand_string("}")]
end

#breaker(s, col = 69) ⇒ Object

primitively break down lines so they fit on a teletype



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# File 'lib/abnftt/abnf-writer.rb', line 90

def breaker(s, col = 69)
  ret = ""
  s.each_line do |*l|
    while l[-1].size > col
      breakpoint = l[-1][0...col].rindex(' ')
      break unless breakpoint && breakpoint > 4
      while (partial = l[-1][0...breakpoint]).count('"').odd?
        break1 = partial.rindex('"')
        breakpoint = l[-1][0...break1].rindex(' ')
        break unless breakpoint && breakpoint > 4
      end
      l[-1..-1] = [
        l[-1][0...breakpoint],
        "    " << l[-1][breakpoint+1..-1]
      ]
    end
    ret << l.join("\n")
  end
  ret
end

#char_range_to_string ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 245

def char_range_to_string
  rules.each do |name, prod|
    rules[name] = ci_cs_merge(detect_ci(char_range_to_string1(prod)))
  end
end

#char_range_to_string1(prod) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 225

def char_range_to_string1(prod)
  visit(prod) do |here|
      case here
      in ["seq", *rest]
        rest = expand_range_into(rest, "seq")
        i = rest.size
        while i > 1
          if (rest[i-1] in ["cs", s2]) && (rest[i-2] in ["cs", s1])
            rest[i-2..i-1] = [["cs", s1 + s2]]
          end
          i -= 1
        end
        [true, rest]
      in ["char-range", chr, ^chr] if chr.between?(" ", "!") || chr.between?("#", "~")
        [true, ["cs", chr]]
      else
        false
      end
  end
end

#ci_compat(prod) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 276

def ci_compat(prod)
  case prod
  in ["ci", s]
    s
  in ["cs", s] if s =~ /\A[^A-Za-z]*\z/
    s
  else
    nil
  end
end

#ci_cs_merge(prod) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 286

def ci_cs_merge(prod)
  visit(prod) do |here|
      case here
      in ["seq", *rest]
        rest = rest.map{|x| ci_cs_merge(x)}
        i = rest.size
        while i > 1
          if (s2 = ci_compat(rest[i-1])) && (s1 = ci_compat(rest[i-2]))
            rest[i-2..i-1] = [["ci", s1 + s2]]
          end
          i -= 1
        end
        [true, wrap_flat("seq", rest)]
      else
        false
      end
  end
end

#count_alt(counter, prod) ⇒ Object

sharing



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# File 'lib/abnftt/abnf-util.rb', line 332

def count_alt(counter, prod)
  visit(prod) do |here|
    case here
    in ["alt", *rest]
      rest.each {|pr| count_alt(counter, pr)}
      counter[here] += 1
    else
      false
    end
  end
end

#detect_ci(prod) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 251

def detect_ci(prod)
  visit(prod) do |here|
      case here
      in ["alt", ["cs", c1], ["cs", c2]] if c1.downcase == c2 && c2.upcase == c1
        [true, ["ci", c1]]
      in [*rest1, ["cs", c1], ["cs", c2], *rest2] if c1.downcase == c2 && c2.upcase == c1
        # warn [:PEEP, rest1, c1, c2, rest2].inspect
        if rest1[0] == "alt"
          [true, detect_ci([*rest1, ["ci", c1], *rest2])]
        else
          false
        end
      # This isn't complete...
      in [*rest1, ["cs", c0], ["cs", c1], ["cs", c2], *rest2] if c1.downcase == c2 && c2.upcase == c1
        # warn [:PEEP2, rest1, c0, c1, c2, rest2].inspect
        if rest1[0] == "alt"
          [true, detect_ci([*rest1, ["cs", c0], ["ci", c1], *rest2])]
        else
          false
        end
      else
        false
      end
  end
end

#do_range(l, r, step = 4) ⇒ Object

split range into passages that have the property needed for hex_ranges



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# File 'lib/abnftt/abnf-util.rb', line 79

def do_range(l, r, step = 4)
  column = 0
  while l <= r
    mask = (1 << step * (column + 1)) - 1
    new_r = l | mask
    if new_r > r # right hand side: come down from mountain
      while column >= 0
        mask >>= step
        new_r = (r + 1) & ~mask
        yield l, new_r - 1, column + 1 if l != new_r
        l = new_r
        column -= 1
      end
      return
    else
      column += 1
      if (l & mask) != 0
        yield l, new_r, column
        l = new_r + 1
      end
    end
  end
end

#do_ranges_outside(cr, l, r) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 35

def do_ranges_outside(cr, l, r)
  if cr[2] < l || cr[1] > r # outside
    yield cr[1].ord, cr[2].ord
  else
    if cr[1] < l
      yield cr[1].ord, l.ord - 1
    end
    if cr[2] > r
      yield r.ord + 1, cr[2].ord
    end
  end
end

#expand_op_into(s, op, out = [op]) ⇒ Object 



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# File 'lib/abnftt/abnf-flattener.rb', line 4

def expand_op_into(s, op, out = [op])
  s.each do |el|
    case el
    in [^op, *inner]
      expand_op_into(inner, op, out)
    else
      out << flatten_ops_1(el)
    end
  end
  out
end

#expand_range_into(s, op, out = [op]) ⇒ Object

Cleanup operations



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# File 'lib/abnftt/abnf-util.rb', line 214

def expand_range_into(s, op, out = [op])
  s.each do |el|
    case el
    in [^op, *inner]
      expand_range_into(inner, op, out)
    else
      out << char_range_to_string1(el)
    end
  end
  out
end

#expand_string(s, case_fold = false) ⇒ Object

flatten_strings: reduce all strings to char-range/seq/alt



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# File 'lib/abnftt/abnf-util.rb', line 141

def expand_string(s, case_fold = false)
  wrap("seq",
       s.chars.map do |ch|
         if case_fold &&
            (u = ch.upcase; d = ch.downcase; u != d)
           ["alt", expand_string(u), expand_string(d)]
         else
           ["char-range", ch, ch]
         end
       end)
end

#flatten_ops ⇒ Object 



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# File 'lib/abnftt/abnf-flattener.rb', line 27

def flatten_ops
  rules.each do |name, prod|
    rules[name] = flatten_ops_1(prod)
  end
end

#flatten_ops_1(prod) ⇒ Object 



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# File 'lib/abnftt/abnf-flattener.rb', line 15

def flatten_ops_1(prod)
  visit(prod) do |here|
      case here
      in ["seq", *rest]
        [true, expand_op_into(rest, "seq")]
      in ["alt", *rest]
        [true, expand_op_into(rest, "alt")]
      else
        false
      end
  end
end

#flatten_strings ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 206

def flatten_strings
  rules.each do |name, prod|
    rules[name] = flatten_strings_1(prod)
  end
end

#flatten_strings_1(prod) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 153

def flatten_strings_1(prod)
  f1 = visit(prod) do |here|
      case here
      in ["cs", string]
        [true, expand_string(string, false)]
      in ["ci", string]
        [true, expand_string(string, true)]
      else
        false
      end
  end
  merge_strings_1(flatten_ops_1(f1))
end

#generate ⇒ Object 



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# File 'lib/abnftt.rb', line 85

def generate
  generate1(rules.first.first)
end

#generate1(what) ⇒ Object 



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# File 'lib/abnftt.rb', line 89

def generate1(what)
  case what
  when String
    expansion = rules[what]
    fail "can't find rules #{what}" unless expansion
    generate1(expansion)
  when Array
    op, *args = what
    case op
    when "seq"
      args.map {|arg| generate1(arg)}.join
    when "alt"
      generate1(args.sample)
    when "rep"
      l, h, x, rest = args
      fail rest if rest
      h = l+3 if h == true
      n = rand(h-l+1)+l
      (0...n).map { generate1(x) }.join
    when "ci"
      s, rest = args
      fail rest if rest
      s.chars.map{|x|[x.upcase, x.downcase].sample}.join
    when "cs"
      s, rest = args
      fail rest if rest
      s
    when "char-range"
      l, r = args
      fail rest if rest
      (rand(r.ord-l.ord+1)+l.ord).chr(Encoding::UTF_8)
    when "prose" # ["prose", text]
      fail "prose not implemented #{what.inspect}"
    when "im"
      warn "abnftt-style inline module ignored #{what.inspect}"
      ''
    else
      fail [op, args].inspect
    end
  else
    fail
  end
end

#hex_ranges(l, r, ndig = false) ⇒ Object

This assumes l and r are preprocessed to have single or full ranges except in one place



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# File 'lib/abnftt/abnf-util.rb', line 67

def hex_ranges(l, r, ndig = false)
  ld = l.digits(16)
  rd = r.digits(16)
  ndig ||= rd.size
  seq = []
  (0...ndig).each do |dig|
    seq << hexdig_range(ld[dig] || 0, rd[dig] || 0)
  end
  wrap("seq", seq.reverse)
end

#hexdig_range(l, r) ⇒ Object

Utilities for creating hexadecimal rules from unsigned integers



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# File 'lib/abnftt/abnf-util.rb', line 50

def hexdig_range(l, r)
  alt = []
  if l < 10
    alt << ["char-range",
            (l+0x30).chr(Encoding::UTF_8),
            ([r, 9].min+0x30).chr(Encoding::UTF_8)]
  end
  if r >= 10
    alt << ["char-range", ([l, 10].max+0x41-0xA).chr(Encoding::UTF_8),
            (r+0x41-0xA).chr(Encoding::UTF_8)]
    alt << ["char-range", ([l, 10].max+0x61-0xA).chr(Encoding::UTF_8),
            (r+0x61-0xA).chr(Encoding::UTF_8)]
  end
  wrap("alt", alt)
end

#merge_strings_1(prod) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 168

def merge_strings_1(prod)
  visit(prod) do |here|
    case here
    in ["alt", *rest]
      ranges = []
      i = 0
      while i < rest.size
        case rest[i]
        in ["char-range", _ic1, _ic2]
          j = i
          while j+1 < rest.size && (rest[j+1] in ["char-range", _jc1, _jc2])
            j += 1
          end
          ranges << [i, j] if i != j # inclusive right
          i = j
        else
          here[i+1] = merge_strings_1(rest[i]) # XXX could be part of a range
        end
        i += 1
      end
      ranges.reverse.each do |i, j|
        sorted = here[i+1..j+1].sort
        l = sorted.length
        while l > 1
          l -= 1              # index to last item
          if sorted[l][1].ord == sorted[l-1][2].ord+1 # merge:
            sorted[l-1..l] = [["char-range", sorted[l-1][1], sorted[l][2]]]
          end
        end
        here[i+1..j+1] = sorted
      end
      [true, here]
    else
      false
    end
  end
end

#overlap(cr, l, r) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 29

def overlap(cr, l, r)
  if cr[2] >= l && cr[1] <= r
    ["char-range", [cr[1], l].max, [cr[2], r].min]
  end
end

#prec_check(inner, targetprec, prec) ⇒ Object

precedence: 1: / alt -> (type1) 2: »« seq 4: atomic



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# File 'lib/abnftt/abnf-writer.rb', line 19

def prec_check(inner, targetprec, prec)
  if targetprec >= prec
    "(#{inner})"
  else
    inner
  end
end

#seq_rep(prod) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 305

def seq_rep(prod)
  visit(prod) do |here|
      case here
      in ["seq", *rest]
        rest = rest.map{|x| seq_rep(x)}
        i = rest.size         # behind last element
        while i > 1
          j = i - 1           # end of range
          s_end = rest[j]
          k = j               # start of range
          while k > 0 && rest[k-1] == s_end
            k -= 1
          end
          if k != j
            n = j - k + 1
            rest[k..j] = [["rep", n, n, s_end]]
          end
          i = k               # skip element k
        end
        [true, wrap_flat("seq", rest)]
      else
        false
      end
  end
end

#share_alt(prefix) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 344

def share_alt(prefix)
  counter = Hash.new(0)
  rules.each do |name, prod|
    count_alt(counter, prod)
  end
  subs = {}
  counter.to_a.select{|k, v| v > 2}.sort_by{|k, v| -v}.each_with_index do |(el, _count), i|
    name = "#{prefix}-a#{i}"
    rules[name] = el
    subs[el] = name
  end
  rules.each do |name, prod|
    count_alt(counter, prod)
  end
  rules.replace(Hash[rules.map do |k, v|
                  [k, seq_rep(visit(v) do |prod|
                     if (s = subs[prod]) && k != s
                       [true, s]
                     end
                   end)]
                end])
  replacements = Hash[
    rules.map{|k, v|
      [v, k] if String === v && /^sq-a\d+$/ === v
    }.compact]
  # warn [:REPLA, replacements].inspect
  used = {}
  used[rules.first.first] = true
  rules.each do |k, v|
    visit(v) do |here|
      if String === here
        if r = replacements[here]
          used[r] = true
        else
          used[here] = true
        end
      end
    end
  end
  # TODO: Should not do a h-x09
  # warn [:USED, used].inspect
  rules.replace(Hash[rules.map {|k, v|
                       unless replacements[k] || !used[k]
                         if r = replacements[v]
                           v = rules[v]
                         end
                         v = visit(v) do |here|
                           if String === here && (r = replacements[here])
                             # warn [:R, v, r].inspect
                             [true, r]
                           end
                         end
                         [k, v]
                       end
                     }.compact])
end

#share_hex(_prefix) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 454

def share_hex(_prefix)
  newrules = {}
  rules.each do |name, prod|
    rules[name] = share_hex_1(prod, newrules)
  end
  rules.merge!(Hash[newrules.sort])
end

#share_hex_1(prod, rules) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 401

def share_hex_1(prod, rules)
  visit(prod) do |here|
    case here
    in ["alt",
        ["char-range", c3l, "9"],
        ["char-range", "A", c4r],
        ["char-range", "a", c6r]] if c4r == c6r.upcase && c3l >= "0" && c6r <= "f"
      name = "x#{c3l}#{c6r}"
      rules[name] ||= here
      [true, name]
    in ["alt",
        ["char-range", c4l, c4r],
        ["char-range", c6l, c6r]] if c4r == c6r.upcase &&
                                     c4l == c6l.upcase &&
                                     c6l.between?("a", "f") &&
                                     c6r.between?("a", "f")
      name = "x#{c6l}#{c6r}"
      rules[name] ||= here
      [true, name]
    # in ["char-range", l, r] if l >= "0" && r <= "9"
    #   name = "x#{l}#{r}"
    #   rules[name] ||= here
    #   [true, name]
    in ["seq", ["cs", "\\u"], *rest]
      suff = "0"
      rest = rest.map {|r| share_hex_1(r, rules) }
      case rest
      in [["alt", [/^c./, hex], *], *]
        name = "u-#{hex}"
        while rules[name] && rules[name] != here
          name = "u-#{hex}-#{suff.succ!}"
        end
      in [["alt", ["seq", [/^c./, hex], *], *], *]
        name = "u-#{hex}x"
        while rules[name] && rules[name] != here
          name = "u-#{hex}x-#{suff.succ!}"
        end
      else
        # require 'neatjson'
        # warn ::JSON.neat_generate(here)
        name = "u-#{suff.succ!}"
        while rules[name] && rules[name] != here
          name = "u-#{suff.succ!}"
        end
      end
      rules[name] ||= here
      [true, name]
    else
      false
    end
  end
end

#squash_edn_levels(**options) ⇒ Object 



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# File 'lib/abnftt/abnf-squasher.rb', line 59

def squash_edn_levels(**options)
  rules.each do |name, prod|
    rules[name] = squash_edn_levels_1(prod, **options)
  end
end

#squash_edn_levels_1(prod, **options) ⇒ Object 



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# File 'lib/abnftt/abnf-squasher.rb', line 27

def squash_edn_levels_1(prod, **options)
  f1 = visit(prod) do |here|
    case here
    in ["char-range", c1, c2]
      lit = UNESCAPED_SQSTR_RANGES.map { |u1, u2|
        overlap(here, u1, u2) }.compact
      esc = ESCAPED_SQSTR_MAPPINGS.map {|cv, ev|
        if cv >= c1 && cv <= c2
          ["seq", ["char-range", "\\", "\\"], ["char-range", ev, ev]]
        end
      }.compact
      u_escapes = []
      if options[:ascii]
        do_ranges_outside(here, " ", "~") do |l, r|
          u_escapes << alt_ranges_legacy(l, r) # old
          u_escapes << alt_ranges_modern(l, r) # new
        end
      else
        u_escapes << alt_ranges_legacy(c1.ord, c2.ord) # old
        u_escapes << alt_ranges_modern(c1.ord, c2.ord) # new
      end
      oldnew = ["seq",
                ["cs", "\\u"],
                wrap_flat("alt", u_escapes) ] if u_escapes != []
      [true, wrap_flat("alt", [*lit, *esc, oldnew].compact.sort)]
    else
      false
    end
  end
  flatten_ops_1(f1)
end

#stringify(s) ⇒ Object

return [precedence ((2 if seq needed)), string]



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# File 'lib/abnftt/abnf-writer.rb', line 5

def stringify(s)
  fail "Can't stringify #{s.inspect} yet" unless s =~ /\A[ !#-~]*\z/
  %{"#{s}"}
end

#to_s ⇒ Object 



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# File 'lib/abnftt/abnf-writer.rb', line 85

def to_s
  rules.map {|k, v| write_rule(k, v) }.join("\n").sub(/.\z/) {$& << "\n"}
end

#to_treetop(modname) ⇒ Object 



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# File 'lib/abnftt.rb', line 134

def to_treetop(modname)
  <<~EOS
  # Encoding: UTF-8
  grammar #{modname}
  #{rules.map {|k, v| to_treetop0(k, v)}.join}
  end
EOS
end

#to_treetop0(k, v) ⇒ Object 



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# File 'lib/abnftt.rb', line 142

def to_treetop0(k, v)
  <<~EOS
  rule #{to_treetop1(k)}
  #{to_treetop1(v)}
  end
EOS
end

#to_treetop1(ast) ⇒ Object 



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# File 'lib/abnftt.rb', line 154

def to_treetop1(ast)
  case ast
  when String
    FIXUP_NAMES[ast].gsub("-", "_")
  when Array
    case ast[0]
    when "alt" # ["alt", *a]
      "(#{ast[1..-1].map {|x| to_treetop1(x)}.join(" / ")})"
    when "seq" # ["seq", *a]
      "(#{ast[1..-1].map {|x| to_treetop1(x)}.join(" ")})"
    when "rep" # ["rep", s, e, a]
      t = to_treetop1(ast[3]) || "@@@"
      if ast[3][0] == "rep"
        t = "(#{t})"
      end
      case [ast[1], ast[2]]
      when [0, 1]
        t + "?"
      when [0, true]
        t + "*"
      when [1, true]
        t + "+"
      else
        t + " #{ast[1]}..#{ast[2] == true ? '' : ast[2]}"
      end
    when "prose" # ["prose", text]
      fail "prose not implemented #{ast.inspect}"
    when "ci" # ["ci", text]
      s = ast[1]
      if s =~ /\A[^A-Za-z]*\z/
        s.inspect
      else
        s.inspect << "i"        # could do this always, but reduce noise
      end
    when "cs" # ["cs", text]
      ast[1].inspect
    when "char-range" # ["char-range", c1, c2]
      c1 = Regexp.quote(ast[1])
      c2 = Regexp.quote(ast[2])
      "[#{c1}-#{c2}]"           # XXX does that always work
    when "im" # ["im", a, text]
      to_treetop1(ast[1]) + " " + ast[2]
    else
      fail "to_treetop(#{ast.inspect})"
    end
  else
    fail "to_treetop(#{ast.inspect})"
  end
end

#validate(s) ⇒ Object 



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# File 'lib/abnftt.rb', line 207

def validate(s)
  @parser ||= Treetop.load_from_string(to_treetop("ABNF_Mod" << (@@gensym += 1).to_s))
  parser_instance ||= @parser.new
  unless result1 = parser_instance.parse(s)
    fail self.class.reason(parser_instance, s)
  end
end

#visit(prod, &block) ⇒ Object 



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# File 'lib/abnftt/abnf-visitor.rb', line 7

def visit(prod, &block)
  done, ret = block.call(prod, &block)
  if done
    return ret
  end

  case prod
  in ["alt", *prods]
    ["alt", *visit_all(prods, &block)]
  in ["tadd", *prods]
    ["tadd", *visit_all(prods, &block)]
  in ["seq", *prods]
    ["seq", *visit_all(prods, &block)]
  in ["rep", s, e, prod]
    ["rep", s, e, visit(prod, &block)]
  else
    prod
  end
end

#visit_all(prod_array, &block) ⇒ Object 



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# File 'lib/abnftt/abnf-visitor.rb', line 4

def visit_all(prod_array, &block)
  prod_array.map {|prod| visit(prod, &block)}
end

#wrap(head, all) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 6

def wrap(head, all)
  if all.size == 1
    all.first
  else
    [head, *all]
  end
end

#wrap_flat(head, all) ⇒ Object 



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# File 'lib/abnftt/abnf-util.rb', line 14

def wrap_flat(head, all)
  if all.size == 1
    all.first
  else
    [head, *all.collect_concat {|el|
       case el
       in [^head, *rest]
         rest
       else
         [el]
       end
     }]
  end
end

#write_lhs(k) ⇒ Object 



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# File 'lib/abnftt/abnf-writer.rb', line 10

def write_lhs(k)
    k
end

#write_rhs(v, targetprec = 0) ⇒ Object 



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# File 'lib/abnftt/abnf-writer.rb', line 27

def write_rhs(v, targetprec = 0)
  prec, ret =
  case v
  in String                   # this should really be ["name", id]
    [4, v]
  in ["name", id]
    [4, id]
  in ["alt" | "tadd", *types]
    [1, types.map{write_rhs(_1, 1)}.join(" / ")]
  in ["seq", *groups]
    case groups.size
    when 0; [4, ""]           # XXX
    else
      [2, "#{groups.map{write_rhs(_1, 2)}.join(" ")}"]
    end
  in ["ci", s]
    [4, stringify(s)]
  in ["cs", s]
    if s =~ /\A[^A-Za-z]*\z/
      [4, stringify(s)]
    else
      [4, "%s" << stringify(s)]  # reduce noise if no alphabetics
    end
  in ["char-range", c1, c2]
    nc1 = "%02x" % c1.ord

    nc2 = "%02x" % c2.ord
    nc2add = "-#{nc2}" if nc2 != nc1
    [4, "%x#{nc1}#{nc2add}"]
  in ["rep", s, e, group]
    if s == 0 && e == 1
      [4, "[#{write_rhs(group)}]"]
    else
      occur = case [s, e]
              in [1, 1];    ""
              in [0, true]; "*"
              in [n, ^n]; n.to_s
              else
                "#{s}*#{e != true ? e : ""}"
              end
      [4, "#{occur}#{write_rhs(group, 4)}"]
    end
  else
    fail [:WRITE_NOMATCH, v].inspect
  end
  prec_check(ret, targetprec, prec)
end

#write_rule(k, v) ⇒ Object 



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# File 'lib/abnftt/abnf-writer.rb', line 75

def write_rule(k, v)
    case v
    in ["tadd", *_rest]
      assign = "=/"
    else
      assign = "="
    end
    "#{write_lhs(k)} #{assign} #{write_rhs(v, 0)}"
end