#
#
#      c2nim - C to Nimrod source converter
#        (c) Copyright 2010 Andreas Rumpf
#
#    See the file "copying.txt", included in this
#    distribution, for details about the copyright.
#

# This module implements an Ansi C scanner. This is an adaption from
# the scanner module. Keywords are not handled here, but in the parser to make
# it more flexible.


import 
  options, msgs, strutils, platform, lexbase, llstream

const 
  MaxLineLength* = 80         # lines longer than this lead to a warning
  numChars*: TCharSet = {'0'..'9', 'a'..'z', 'A'..'Z'} 
  SymChars*: TCharSet = {'a'..'z', 'A'..'Z', '0'..'9', '_', '\x80'..'\xFF'}
  SymStartChars*: TCharSet = {'a'..'z', 'A'..'Z', '_', '\x80'..'\xFF'}

type
  TTokKind* = enum 
    pxInvalid, pxEof,         
    pxMacroParam,             # fake token: macro parameter (with its index)
    pxStarComment,            # /* */ comment
    pxLineComment,            # // comment
    pxDirective,              # #define, etc.
    pxDirectiveParLe,         # #define m( with parle (yes, C is that ugly!)
    pxDirConc,                # ##
    pxNewLine,                # newline: end of directive
    pxAmp,                    # &
    pxAmpAmp,                 # && 
    pxAmpAsgn,                # &=
    pxAmpAmpAsgn,             # &&=
    pxBar,                    # |
    pxBarBar,                 # ||
    pxBarAsgn,                # |=
    pxBarBarAsgn,             # ||=
    pxNot,                    # !
    pxPlusPlus,               # ++
    pxMinusMinus,             # --
    pxPlus,                   # +
    pxPlusAsgn,               # +=
    pxMinus,                  # -
    pxMinusAsgn,              # -=
    pxMod,                    # %
    pxModAsgn,                # %=
    pxSlash,                  # /
    pxSlashAsgn,              # /=
    pxStar,                   # *
    pxStarAsgn,               # *=
    pxHat,                    # ^
    pxHatAsgn,                # ^=
    pxAsgn,                   # =
    pxEquals,                 # ==
    pxDot,                    # .
    pxDotDotDot,              # ...
    pxLe,                     # <=
    pxLt,                     # <
    pxGe,                     # >=
    pxGt,                     # >
    pxNeq,                    # != 
    pxConditional,            # ?
    pxShl,                    # <<
    pxShlAsgn,                # <<=
    pxShr,                    # >>
    pxShrAsgn,                # >>=
    pxTilde,                  # ~
    pxTildeAsgn,              # ~=
    pxArrow,                  # ->
    pxScope,                  # ::

    pxStrLit, 
    pxCharLit,
    pxSymbol,                 # a symbol
    pxIntLit, 
    pxInt64Lit, # long constant like 0x70fffffff or out of int range
    pxFloatLit, 
    pxParLe, pxBracketLe, pxCurlyLe, # this order is important 
    pxParRi, pxBracketRi, pxCurlyRi, # for macro argument parsing!
    pxComma, pxSemiColon, pxColon,
  TTokKinds* = set[TTokKind]

type
  TNumericalBase* = enum base10, base2, base8, base16
  TToken* = object
    xkind*: TTokKind          # the type of the token
    s*: string                # parsed symbol, char or string literal
    iNumber*: BiggestInt      # the parsed integer literal;
                              # if xkind == pxMacroParam: parameter's position
    fNumber*: BiggestFloat    # the parsed floating point literal
    base*: TNumericalBase     # the numerical base; only valid for int
                              # or float literals
    next*: ref TToken         # for C we need arbitrary look-ahead :-(
  
  TLexer* = object of TBaseLexer
    filename*: string
    inDirective: bool
  
proc getTok*(L: var TLexer, tok: var TToken)
proc PrintTok*(tok: TToken)
proc `$`*(tok: TToken): string
# implementation

var
  gLinesCompiled*: int

proc fillToken(L: var TToken) = 
  L.xkind = pxInvalid
  L.iNumber = 0
  L.s = ""
  L.fNumber = 0.0
  L.base = base10
  
proc openLexer*(lex: var TLexer, filename: string, inputstream: PLLStream) = 
  openBaseLexer(lex, inputstream)
  lex.filename = filename

proc closeLexer*(lex: var TLexer) = 
  inc(gLinesCompiled, lex.LineNumber)
  closeBaseLexer(lex)

proc getColumn*(L: TLexer): int = 
  result = getColNumber(L, L.bufPos)

proc getLineInfo*(L: TLexer): TLineInfo = 
  result = newLineInfo(L.filename, L.linenumber, getColNumber(L, L.bufpos))

proc lexMessage*(L: TLexer, msg: TMsgKind, arg = "") = 
  msgs.liMessage(getLineInfo(L), msg, arg)

proc lexMessagePos(L: var TLexer, msg: TMsgKind, pos: int, arg = "") = 
  var info = newLineInfo(L.filename, L.linenumber, pos - L.lineStart)
  msgs.liMessage(info, msg, arg)

proc TokKindToStr*(k: TTokKind): string =
  case k
  of pxEof: result = "[EOF]"
  of pxInvalid: result = "[invalid]"
  of pxMacroParam: result = "[macro param]"
  of pxStarComment, pxLineComment: result = "[comment]" 
  of pxStrLit: result = "[string literal]"
  of pxCharLit: result = "[char literal]"

  of pxDirective, pxDirectiveParLe: result = "#"             # #define, etc.
  of pxDirConc: result = "##"
  of pxNewLine: result = "[NewLine]"
  of pxAmp: result = "&"                   # &
  of pxAmpAmp: result = "&&"                # && 
  of pxAmpAsgn: result = "&="                # &=
  of pxAmpAmpAsgn: result = "&&="            # &&=
  of pxBar: result = "|"                   # |
  of pxBarBar: result = "||"                # ||
  of pxBarAsgn: result = "|="               # |=
  of pxBarBarAsgn: result = "||="            # ||=
  of pxNot: result = "!"                   # !
  of pxPlusPlus: result = "++"             # ++
  of pxMinusMinus: result = "--"            # --
  of pxPlus: result = "+"                  # +
  of pxPlusAsgn: result = "+="              # +=
  of pxMinus: result = "-"                 # -
  of pxMinusAsgn: result = "-="             # -=
  of pxMod: result = "%"                   # %
  of pxModAsgn: result = "%="               # %=
  of pxSlash: result = "/"                 # /
  of pxSlashAsgn: result = "/="             # /=
  of pxStar: result = "*"                  # *
  of pxStarAsgn: result = "*="              # *=
  of pxHat: result = "^"                   # ^
  of pxHatAsgn: result = "^="               # ^=
  of pxAsgn: result = "="                  # =
  of pxEquals: result = "=="                # ==
  of pxDot: result = "."                   # .
  of pxDotDotDot: result = "..."             # ...
  of pxLe: result = "<="                    # <=
  of pxLt: result = "<"                    # <
  of pxGe: result = ">="                    # >=
  of pxGt: result = ">"                    # >
  of pxNeq: result = "!="                   # != 
  of pxConditional: result = "?"
  of pxShl: result = "<<"
  of pxShlAsgn: result = "<<="
  of pxShr: result = ">>"
  of pxShrAsgn: result = ">>="
  of pxTilde: result = "~"
  of pxTildeAsgn: result = "~="
  of pxArrow: result = "->"
  of pxScope: result = "::"

  of pxSymbol: result = "[identifier]"
  of pxIntLit, pxInt64Lit: result = "[integer literal]"
  of pxFloatLit: result = "[floating point literal]"
  of pxParLe: result = "("
  of pxParRi: result = ")"
  of pxBracketLe: result = "["
  of pxBracketRi: result = "]"
  of pxComma: result = ","
  of pxSemiColon: result = ";"
  of pxColon: result = ":"
  of pxCurlyLe: result = "{"
  of pxCurlyRi: result = "}"

proc `$`(tok: TToken): string = 
  case tok.xkind
  of pxSymbol, pxInvalid, pxStarComment, pxLineComment, pxStrLit: result = tok.s
  of pxIntLit, pxInt64Lit: result = $tok.iNumber
  of pxFloatLit: result = $tok.fNumber
  else: result = TokKindToStr(tok.xkind)
  
proc PrintTok(tok: TToken) = 
  writeln(stdout, $tok)
  
proc matchUnderscoreChars(L: var TLexer, tok: var TToken, chars: TCharSet) = 
  # matches ([chars]_)*
  var pos = L.bufpos              # use registers for pos, buf
  var buf = L.buf
  while true: 
    if buf[pos] in chars: 
      add(tok.s, buf[pos])
      Inc(pos)
    else: 
      break 
    if buf[pos] == '_': 
      add(tok.s, '_')
      Inc(pos)
  L.bufPos = pos

proc isFloatLiteral(s: string): bool = 
  for i in countup(0, len(s)-1): 
    if s[i] in {'.', 'e', 'E'}: 
      return true

proc getNumber2(L: var TLexer, tok: var TToken) = 
  var pos = L.bufpos + 2 # skip 0b
  tok.base = base2
  var xi: biggestInt = 0
  var bits = 0
  while true: 
    case L.buf[pos]
    of 'A'..'Z', 'a'..'z':
      # ignore type suffix:
      inc(pos)
    of '2'..'9', '.': 
      lexMessage(L, errInvalidNumber)
      inc(pos)
    of '_': 
      inc(pos)
    of '0', '1': 
      xi = `shl`(xi, 1) or (ord(L.buf[pos]) - ord('0'))
      inc(pos)
      inc(bits)
    else: break 
  tok.iNumber = xi
  if (bits > 32): tok.xkind = pxInt64Lit
  else: tok.xkind = pxIntLit
  L.bufpos = pos

proc getNumber8(L: var TLexer, tok: var TToken) = 
  var pos = L.bufpos + 2 # skip 0b
  tok.base = base8
  var xi: biggestInt = 0
  var bits = 0
  while true: 
    case L.buf[pos]
    of 'A'..'Z', 'a'..'z':
      # ignore type suffix:
      inc(pos)
    of '8'..'9', '.': 
      lexMessage(L, errInvalidNumber)
      inc(pos)
    of '_': 
      inc(pos)
    of '0'..'7': 
      xi = `shl`(xi, 3) or (ord(L.buf[pos]) - ord('0'))
      inc(pos)
      inc(bits)
    else: break 
  tok.iNumber = xi
  if (bits > 12): tok.xkind = pxInt64Lit
  else: tok.xkind = pxIntLit
  L.bufpos = pos

proc getNumber16(L: var TLexer, tok: var TToken) = 
  var pos = L.bufpos + 2          # skip 0x
  tok.base = base16
  var xi: biggestInt = 0
  var bits = 0
  while true: 
    case L.buf[pos]
    of 'G'..'Z', 'g'..'z': 
      # ignore type suffix:
      inc(pos)
    of '_': inc(pos)
    of '0'..'9': 
      xi = `shl`(xi, 4) or (ord(L.buf[pos]) - ord('0'))
      inc(pos)
      inc(bits, 4)
    of 'a'..'f': 
      xi = `shl`(xi, 4) or (ord(L.buf[pos]) - ord('a') + 10)
      inc(pos)
      inc(bits, 4)
    of 'A'..'F': 
      xi = `shl`(xi, 4) or (ord(L.buf[pos]) - ord('A') + 10)
      inc(pos)
      inc(bits, 4)
    else: break 
  tok.iNumber = xi
  if bits > 32: tok.xkind = pxInt64Lit
  else: tok.xkind = pxIntLit
  L.bufpos = pos

proc getNumber(L: var TLexer, tok: var TToken) = 
  tok.base = base10
  matchUnderscoreChars(L, tok, {'0'..'9'})
  if (L.buf[L.bufpos] == '.') and (L.buf[L.bufpos + 1] in {'0'..'9'}): 
    add(tok.s, '.')
    inc(L.bufpos)
    matchUnderscoreChars(L, tok, {'e', 'E', '+', '-', '0'..'9'})
  try: 
    if isFloatLiteral(tok.s): 
      tok.fnumber = parseFloat(tok.s)
      tok.xkind = pxFloatLit
    else: 
      tok.iNumber = ParseInt(tok.s)
      if (tok.iNumber < low(int32)) or (tok.iNumber > high(int32)): 
        tok.xkind = pxInt64Lit
      else: 
        tok.xkind = pxIntLit
  except EInvalidValue: 
    lexMessage(L, errInvalidNumber, tok.s)
  except EOverflow: 
    lexMessage(L, errNumberOutOfRange, tok.s)
  # ignore type suffix:
  while L.buf[L.bufpos] in {'A'..'Z', 'a'..'z'}: inc(L.bufpos)
  
proc HandleCRLF(L: var TLexer, pos: int): int = 
  case L.buf[pos]
  of CR: result = lexbase.HandleCR(L, pos)
  of LF: result = lexbase.HandleLF(L, pos)
  else: result = pos
  
proc escape(L: var TLexer, tok: var TToken, allowEmpty=false) = 
  inc(L.bufpos) # skip \ 
  case L.buf[L.bufpos]
  of 'b', 'B':
    add(tok.s, '\b')
    inc(L.bufpos)
  of 't', 'T':
    add(tok.s, '\t')
    inc(L.bufpos)
  of 'n', 'N':
    add(tok.s, '\L')
    inc(L.bufpos)
  of 'f', 'F':
    add(tok.s, '\f')
    inc(L.bufpos)
  of 'r', 'R':
    add(tok.s, '\r')
    inc(L.bufpos)
  of '\'':
    add(tok.s, '\'')
    inc(L.bufpos)
  of '"':
    add(tok.s, '"')
    inc(L.bufpos)
  of '\\':
    add(tok.s, '\b')
    inc(L.bufpos)  
  of '0'..'7':
    var xi = ord(L.buf[L.bufpos]) - ord('0')
    inc(L.bufpos)
    if L.buf[L.bufpos] in {'0'..'7'}:
      xi = (xi shl 3) or (ord(L.buf[L.bufpos]) - ord('0'))
      inc(L.bufpos)
      if L.buf[L.bufpos] in {'0'..'7'}:
        xi = (xi shl 3) or (ord(L.buf[L.bufpos]) - ord('0'))
        inc(L.bufpos)
    add(tok.s, chr(xi))
  elif not allowEmpty:
    lexMessage(L, errInvalidCharacterConstant)
  
proc getCharLit(L: var TLexer, tok: var TToken) = 
  inc(L.bufpos) # skip '
  if L.buf[L.bufpos] == '\\':
    escape(L, tok)
  else:
    add(tok.s, L.buf[L.bufpos])
    inc(L.bufpos)
  if L.buf[L.bufpos] == '\'':
    inc(L.bufpos)
  else:
    lexMessage(L, errMissingFinalQuote)
  tok.xkind = pxCharLit

proc getString(L: var TLexer, tok: var TToken) = 
  var pos = L.bufPos + 1          # skip "
  var buf = L.buf                 # put `buf` in a register
  var line = L.linenumber         # save linenumber for better error message
  while true: 
    case buf[pos]
    of '\"': 
      Inc(pos)
      break
    of CR: 
      pos = lexbase.HandleCR(L, pos)
      buf = L.buf
    of LF: 
      pos = lexbase.HandleLF(L, pos)
      buf = L.buf
    of lexbase.EndOfFile: 
      var line2 = L.linenumber
      L.LineNumber = line
      lexMessagePos(L, errClosingQuoteExpected, L.lineStart)
      L.LineNumber = line2
      break 
    of '\\': 
      # we allow an empty \ for line concatenation, but we don't require it
      # for line concatenation
      L.bufpos = pos
      escape(L, tok, allowEmpty=true)
      pos = L.bufpos
    else: 
      add(tok.s, buf[pos])
      Inc(pos)
  L.bufpos = pos
  tok.xkind = pxStrLit

proc getSymbol(L: var TLexer, tok: var TToken) = 
  var pos = L.bufpos
  var buf = L.buf
  while true: 
    var c = buf[pos]
    if c notin SymChars: break
    add(tok.s, c)
    Inc(pos)
  L.bufpos = pos
  tok.xkind = pxSymbol

proc scanLineComment(L: var TLexer, tok: var TToken) = 
  var pos = L.bufpos
  var buf = L.buf 
  # a comment ends if the next line does not start with the // on the same
  # column after only whitespace
  tok.xkind = pxLineComment
  var col = getColNumber(L, pos)
  while true: 
    inc(pos, 2)               # skip //
    add(tok.s, '#')
    while not (buf[pos] in {CR, LF, lexbase.EndOfFile}): 
      add(tok.s, buf[pos])
      inc(pos)
    pos = handleCRLF(L, pos)
    buf = L.buf
    var indent = 0
    while buf[pos] == ' ': 
      inc(pos)
      inc(indent)
    if (col == indent) and (buf[pos] == '/') and (buf[pos + 1] == '/'): 
      add(tok.s, "\n")
    else: 
      break 
  L.bufpos = pos

proc scanStarComment(L: var TLexer, tok: var TToken) = 
  var pos = L.bufpos
  var buf = L.buf
  tok.s = "#"
  tok.xkind = pxStarComment
  while true: 
    case buf[pos]
    of CR, LF: 
      pos = HandleCRLF(L, pos)
      buf = L.buf
      add(tok.s, "\n#")
      # skip annoying stars as line prefix: (eg.
      # /*
      #  * ugly comment <-- this star
      #  */
      while buf[pos] in {' ', '\t'}:
        add(tok.s, ' ')
        inc(pos)
      if buf[pos] == '*' and buf[pos+1] != '/': inc(pos)
    of '*': 
      inc(pos)
      if buf[pos] == '/': 
        inc(pos)
        break 
      else: 
        add(tok.s, '*')
    of lexbase.EndOfFile: 
      lexMessage(L, errTokenExpected, "*/")
    else: 
      add(tok.s, buf[pos])
      inc(pos)
  L.bufpos = pos

proc skip(L: var TLexer, tok: var TToken) = 
  var pos = L.bufpos
  var buf = L.buf
  while true: 
    case buf[pos]
    of '\\': 
      # Ignore \ line continuation characters when not inDirective
      inc(pos)
      if L.inDirective:
        while buf[pos] in {' ', '\t'}: inc(pos)
        if buf[pos] in {CR, LF}:
          pos = HandleCRLF(L, pos)
          buf = L.buf
    of ' ', Tabulator: 
      Inc(pos)                # newline is special:
    of CR, LF: 
      pos = HandleCRLF(L, pos)
      buf = L.buf
      if L.inDirective:
        tok.xkind = pxNewLine
        L.inDirective = false
    else: 
      break                   # EndOfFile also leaves the loop
  L.bufpos = pos

proc getDirective(L: var TLexer, tok: var TToken) = 
  var pos = L.bufpos + 1
  var buf = L.buf
  while buf[pos] in {' ', '\t'}: inc(pos)
  while buf[pos] in SymChars: 
    add(tok.s, buf[pos])
    inc(pos)
  # a HACK: we need to distinguish 
  # #define x (...)
  # from:
  # #define x(...)
  # 
  L.bufpos = pos
  # look ahead:
  while buf[pos] in {' ', '\t'}: inc(pos)
  while buf[pos] in SymChars: inc(pos)
  if buf[pos] == '(': tok.xkind = pxDirectiveParLe
  else: tok.xkind = pxDirective
  L.inDirective = true

proc getTok(L: var TLexer, tok: var TToken) = 
  tok.xkind = pxInvalid
  fillToken(tok)
  skip(L, tok)
  if tok.xkind == pxNewLine: return
  var c = L.buf[L.bufpos]
  if c in SymStartChars: 
    getSymbol(L, tok)
  elif c == '0':
    case L.buf[L.bufpos+1]
    of 'x', 'X': getNumber16(L, tok)
    of 'b', 'B': getNumber2(L, tok)
    of '1'..'7': getNumber8(L, tok)
    else: getNumber(L, tok)
  elif c in {'1'..'9'}: 
    getNumber(L, tok)
  else: 
    case c
    of ';': 
      tok.xkind = pxSemicolon
      Inc(L.bufpos)
    of '/': 
      if L.buf[L.bufpos + 1] == '/': 
        scanLineComment(L, tok)
      elif L.buf[L.bufpos+1] == '*':
        inc(L.bufpos, 2)
        scanStarComment(L, tok)
      elif L.buf[L.bufpos+1] == '=':
        inc(L.bufpos, 2)
        tok.xkind = pxSlashAsgn
      else: 
        tok.xkind = pxSlash
        inc(L.bufpos)
    of ',': 
      tok.xkind = pxComma
      Inc(L.bufpos)
    of '(': 
      Inc(L.bufpos)
      tok.xkind = pxParLe
    of '*': 
      inc(L.bufpos)
      if L.buf[L.bufpos] == '=':
        inc(L.bufpos)
        tok.xkind = pxStarAsgn
      else:
        tok.xkind = pxStar
    of ')': 
      Inc(L.bufpos)
      tok.xkind = pxParRi
    of '[': 
      Inc(L.bufpos)
      tok.xkind = pxBracketLe
    of ']': 
      Inc(L.bufpos)
      tok.xkind = pxBracketRi
    of '.': 
      inc(L.bufpos)
      if L.buf[L.bufpos] == '.' and L.buf[L.bufpos+1] == '.': 
        tok.xkind = pxDotDotDot
        inc(L.bufpos, 2)
      else: 
        tok.xkind = pxDot
    of '{': 
      Inc(L.bufpos)
      tok.xkind = pxCurlyLe
    of '}': 
      Inc(L.bufpos)
      tok.xkind = pxCurlyRi
    of '+': 
      inc(L.bufpos)
      if L.buf[L.bufpos] == '=':
        tok.xkind = pxPlusAsgn
        inc(L.bufpos)
      elif L.buf[L.bufpos] == '+': 
        tok.xkind = pxPlusPlus
        inc(L.bufpos)
      else: 
        tok.xkind = pxPlus
    of '-': 
      inc(L.bufpos)
      case L.buf[L.bufpos] 
      of '>':
        tok.xkind = pxArrow
        inc(L.bufpos)
      of '=':
        tok.xkind = pxMinusAsgn
        inc(L.bufpos)
      of '-': 
        tok.xkind = pxMinusMinus
        inc(L.bufpos)
      else: 
        tok.xkind = pxMinus
    of '?':
      inc(L.bufpos)
      tok.xkind = pxConditional
    of ':': 
      inc(L.bufpos)
      if L.buf[L.bufpos] == ':':
        tok.xkind = pxScope
        inc(L.bufpos)
      else:
        tok.xkind = pxColon
    of '!':
      inc(L.bufpos)
      if L.buf[L.bufpos] == '=':
        tok.xkind = pxNeq
        inc(L.bufpos)
      else: 
        tok.xkind = pxNot
    of '<': 
      inc(L.bufpos)
      if L.buf[L.bufpos] == '=': 
        inc(L.bufpos)
        tok.xkind = pxLe
      elif L.buf[L.bufpos] == '<':
        inc(L.bufpos)
        if L.buf[L.bufpos] == '=': 
          inc(L.bufpos)
          tok.xkind = pxShlAsgn
        else:
          tok.xkind = pxShl
      else: 
        tok.xkind = pxLt
    of '>': 
      inc(L.bufpos)
      if L.buf[L.bufpos] == '=': 
        inc(L.bufpos)
        tok.xkind = pxGe
      elif L.buf[L.bufpos] == '>':
        inc(L.bufpos)
        if L.buf[L.bufpos] == '=': 
          inc(L.bufpos)
          tok.xkind = pxShrAsgn
        else:
          tok.xkind = pxShr
      else: 
        tok.xkind = pxGt
    of '=': 
      inc(L.bufpos)
      if L.buf[L.bufpos] == '=':
        tok.xkind = pxEquals
        inc(L.bufpos)
      else: 
        tok.xkind = pxAsgn
    of '&': 
      inc(L.bufpos)
      if L.buf[L.bufpos] == '=':
        tok.xkind = pxAmpAsgn
        inc(L.bufpos)
      elif L.buf[L.bufpos] == '&':
        inc(L.bufpos)
        if L.buf[L.bufpos] == '=':
          inc(L.bufpos)
          tok.xkind = pxAmpAmpAsgn
        else:
          tok.xkind = pxAmpAmp
      else: 
        tok.xkind = pxAmp
    of '|': 
      inc(L.bufpos)
      if L.buf[L.bufpos] == '=':
        tok.xkind = pxBarAsgn
        inc(L.bufpos)
      elif L.buf[L.bufpos] == '|':
        inc(L.bufpos)
        if L.buf[L.bufpos] == '=':
          inc(L.bufpos)
          tok.xkind = pxBarBarAsgn
        else:
          tok.xkind = pxBarBar
      else: 
        tok.xkind = pxBar
    of '^': 
      inc(L.bufpos)
      if L.buf[L.bufpos] == '=':
        tok.xkind = pxHatAsgn
        inc(L.bufpos)
      else: 
        tok.xkind = pxHat
    of '%': 
      inc(L.bufpos)
      if L.buf[L.bufpos] == '=':
        tok.xkind = pxModAsgn
        inc(L.bufpos)
      else: 
        tok.xkind = pxMod
    of '~':
      inc(L.bufpos)
      if L.buf[L.bufpos] == '=':
        tok.xkind = pxTildeAsgn
        inc(L.bufpos)
      else: 
        tok.xkind = pxTilde
    of '#': 
      if L.buf[L.bufpos+1] == '#':
        inc(L.bufpos, 2)
        tok.xkind = pxDirConc
      else:
        getDirective(L, tok)
    of '"': getString(L, tok)
    of '\'': getCharLit(L, tok)
    of lexbase.EndOfFile: 
      tok.xkind = pxEof
    else: 
      tok.s = $c
      tok.xkind = pxInvalid
      lexMessage(L, errInvalidToken, c & " (\\" & $(ord(c)) & ')')
      Inc(L.bufpos)