IMPLEMENTATION MODULE Lexer;

FROM FIO IMPORT ReadNBytes, StdErr;
FROM SYSTEM IMPORT ADR, TSIZE;

FROM DynamicStrings IMPORT String, InitStringCharStar, KillString;
FROM StringConvert IMPORT StringToInteger;
FROM Storage IMPORT DEALLOCATE, ALLOCATE;
FROM Strings IMPORT Length;
FROM MemUtils IMPORT MemCopy, MemZero;
FROM StrCase IMPORT Lower;

CONST
  CHUNK_SIZE = 65536;

TYPE
  (*
   * Classification table assigns each possible character to a group (class). All
  * characters of the same group a handled equivalently.
  *
  * Classification:
  *)
  TransitionClass = (
    transitionClassInvalid,
    transitionClassDigit,
    transitionClassAlpha,
    transitionClassSpace,
    transitionClassColon,
    transitionClassEquals,
    transitionClassLeftParen,
    transitionClassRightParen,
    transitionClassAsterisk,
    transitionClassUnderscore,
    transitionClassSingle,
    transitionClassHex,
    transitionClassZero,
    transitionClassX,
    transitionClassEof,
    transitionClassDot,
    transitionClassMinus,
    transitionClassSingleQuote,
    transitionClassDoubleQuote,
    transitionClassGreater,
    transitionClassLess,
    transitionClassOther
  );
  TransitionState = (
    transitionStateStart,
    transitionStateColon,
    transitionStateIdentifier,
    transitionStateDecimal,
    transitionStateGreater,
    transitionStateMinus,
    transitionStateLeftParen,
    transitionStateLess,
    transitionStateDot,
    transitionStateComment,
    transitionStateClosingComment,
    transitionStateCharacter,
    transitionStateString,
    transitionStateLeadingZero,
    transitionStateDecimalSuffix,
    transitionStateEnd
  );
  TransitionAction = PROCEDURE(PLexer, PLexerToken);
  Transition = RECORD
    Action: TransitionAction;
    NextState: TransitionState
  END;
  TransitionClasses = ARRAY[1..22] OF Transition;

VAR
  classification: ARRAY[1..128] OF TransitionClass;
  transitions: ARRAY[1..16] OF TransitionClasses;

PROCEDURE initialize_classification();
VAR
  i: CARDINAL;
BEGIN
  classification[1] := transitionClassEof; (* NUL *)
  classification[2] := transitionClassInvalid; (* SOH *)
  classification[3] := transitionClassInvalid; (* STX *)
  classification[4] := transitionClassInvalid; (* ETX *)
  classification[5] := transitionClassInvalid; (* EOT *)
  classification[6] := transitionClassInvalid; (* EMQ *)
  classification[7] := transitionClassInvalid; (* ACK *)
  classification[8] := transitionClassInvalid; (* BEL *)
  classification[9] := transitionClassInvalid; (* BS *)
  classification[10] := transitionClassSpace; (* HT *)
  classification[11] := transitionClassSpace; (* LF *)
  classification[12] := transitionClassInvalid; (* VT *)
  classification[13] := transitionClassInvalid; (* FF *)
  classification[14] := transitionClassSpace; (* CR *)
  classification[15] := transitionClassInvalid; (* SO *)
  classification[16] := transitionClassInvalid; (* SI *)
  classification[17] := transitionClassInvalid; (* DLE *)
  classification[18] := transitionClassInvalid; (* DC1 *)
  classification[19] := transitionClassInvalid; (* DC2 *)
  classification[20] := transitionClassInvalid; (* DC3 *)
  classification[21] := transitionClassInvalid; (* DC4 *)
  classification[22] := transitionClassInvalid; (* NAK *)
  classification[23] := transitionClassInvalid; (* SYN *)
  classification[24] := transitionClassInvalid; (* ETB *)
  classification[25] := transitionClassInvalid; (* CAN *)
  classification[26] := transitionClassInvalid; (* EM *)
  classification[27] := transitionClassInvalid; (* SUB *)
  classification[28] := transitionClassInvalid; (* ESC *)
  classification[29] := transitionClassInvalid; (* FS *)
  classification[30] := transitionClassInvalid; (* GS *)
  classification[31] := transitionClassInvalid; (* RS *)
  classification[32] := transitionClassInvalid; (* US *)
  classification[33] := transitionClassSpace; (* Space *)
  classification[34] := transitionClassSingle; (* ! *)
  classification[35] := transitionClassDoubleQuote; (* " *)
  classification[36] := transitionClassOther; (* # *)
  classification[37] := transitionClassOther; (* $ *)
  classification[38] := transitionClassSingle; (* % *)
  classification[39] := transitionClassSingle; (* AND *)
  classification[40] := transitionClassSingleQuote; (* ' *)
  classification[41] := transitionClassLeftParen; (* ( *)
  classification[42] := transitionClassRightParen; (* ) *)
  classification[43] := transitionClassAsterisk; (* * *)
  classification[44] := transitionClassSingle; (* + *)
  classification[45] := transitionClassSingle; (* , *)
  classification[46] := transitionClassMinus; (* - *)
  classification[47] := transitionClassDot; (* . *)
  classification[48] := transitionClassSingle; (* / *)
  classification[49] := transitionClassZero; (* 0 *)
  classification[50] := transitionClassDigit; (* 1 *)
  classification[51] := transitionClassDigit; (* 2 *)
  classification[52] := transitionClassDigit; (* 3 *)
  classification[53] := transitionClassDigit; (* 4 *)
  classification[54] := transitionClassDigit; (* 5 *)
  classification[55] := transitionClassDigit; (* 6 *)
  classification[56] := transitionClassDigit; (* 7 *)
  classification[57] := transitionClassDigit; (* 8 *)
  classification[58] := transitionClassDigit; (* 9 *)
  classification[59] := transitionClassColon; (* : *)
  classification[60] := transitionClassSingle; (* ; *)
  classification[61] := transitionClassLess; (* < *)
  classification[62] := transitionClassEquals; (* = *)
  classification[63] := transitionClassGreater; (* > *)
  classification[64] := transitionClassOther; (* ? *)
  classification[65] := transitionClassSingle; (* @ *)
  classification[66] := transitionClassAlpha; (* A *)
  classification[67] := transitionClassAlpha; (* B *)
  classification[68] := transitionClassAlpha; (* C *)
  classification[69] := transitionClassAlpha; (* D *)
  classification[70] := transitionClassAlpha; (* E *)
  classification[71] := transitionClassAlpha; (* F *)
  classification[72] := transitionClassAlpha; (* G *)
  classification[73] := transitionClassAlpha; (* H *)
  classification[74] := transitionClassAlpha; (* I *)
  classification[75] := transitionClassAlpha; (* J *)
  classification[76] := transitionClassAlpha; (* K *)
  classification[77] := transitionClassAlpha; (* L *)
  classification[78] := transitionClassAlpha; (* M *)
  classification[79] := transitionClassAlpha; (* N *)
  classification[80] := transitionClassAlpha; (* O *)
  classification[81] := transitionClassAlpha; (* P *)
  classification[82] := transitionClassAlpha; (* Q *)
  classification[83] := transitionClassAlpha; (* R *)
  classification[84] := transitionClassAlpha; (* S *)
  classification[85] := transitionClassAlpha; (* T *)
  classification[86] := transitionClassAlpha; (* U *)
  classification[87] := transitionClassAlpha; (* V *)
  classification[88] := transitionClassAlpha; (* W *)
  classification[89] := transitionClassAlpha; (* X *)
  classification[90] := transitionClassAlpha; (* Y *)
  classification[91] := transitionClassAlpha; (* Z *)
  classification[92] := transitionClassSingle; (* [ *)
  classification[93] := transitionClassOther; (* \ *)
  classification[94] := transitionClassSingle; (* ] *)
  classification[95] := transitionClassSingle; (* ^ *)
  classification[96] := transitionClassUnderscore; (* _ *)
  classification[97] := transitionClassOther; (* ` *)
  classification[98] := transitionClassHex; (* a *)
  classification[99] := transitionClassHex; (* b *)
  classification[100] := transitionClassHex; (* c *)
  classification[101] := transitionClassHex; (* d *)
  classification[102] := transitionClassHex; (* e *)
  classification[103] := transitionClassHex; (* f *)
  classification[104] := transitionClassAlpha; (* g *)
  classification[105] := transitionClassAlpha; (* h *)
  classification[106] := transitionClassAlpha; (* i *)
  classification[107] := transitionClassAlpha; (* j *)
  classification[108] := transitionClassAlpha; (* k *)
  classification[109] := transitionClassAlpha; (* l *)
  classification[110] := transitionClassAlpha; (* m *)
  classification[111] := transitionClassAlpha; (* n *)
  classification[112] := transitionClassAlpha; (* o *)
  classification[113] := transitionClassAlpha; (* p *)
  classification[114] := transitionClassAlpha; (* q *)
  classification[115] := transitionClassAlpha; (* r *)
  classification[116] := transitionClassAlpha; (* s *)
  classification[117] := transitionClassAlpha; (* t *)
  classification[118] := transitionClassAlpha; (* u *)
  classification[119] := transitionClassAlpha; (* v *)
  classification[120] := transitionClassAlpha; (* w *)
  classification[121] := transitionClassX; (* x *)
  classification[122] := transitionClassAlpha; (* y *)
  classification[123] := transitionClassAlpha; (* z *)
  classification[124] := transitionClassOther; (* { *)
  classification[125] := transitionClassSingle; (* | *)
  classification[126] := transitionClassOther; (* } *)
  classification[127] := transitionClassSingle; (* ~ *)
  classification[128] := transitionClassInvalid; (* DEL *)

  i := 129;
  WHILE i <= 256 DO
    classification[i] := transitionClassOther;
    i := i + 1
  END
END initialize_classification;
PROCEDURE compare_keyword(Keyword: ARRAY OF CHAR; TokenStart: PLexerBuffer; TokenEnd: PLexerBuffer): BOOLEAN;
VAR
  result: BOOLEAN;
  index: CARDINAL;
BEGIN
  index := 0;
  result := TRUE;

  WHILE (index < Length(Keyword)) AND (TokenStart <> TokenEnd) AND result DO
    result := (Keyword[index] = TokenStart^) OR (Lower(Keyword[index]) = TokenStart^);
    INC(TokenStart);
    INC(index)
  END;
  result := (index = Length(Keyword)) AND (TokenStart = TokenEnd) AND result;
  RETURN result
END compare_keyword;
(* Reached the end of file. *)
PROCEDURE transition_action_eof(lexer: PLexer; token: PLexerToken);
BEGIN
  token^.kind := lexerKindEof
END transition_action_eof;
(* Add the character to the token currently read and advance to the next character. *)
PROCEDURE transition_action_accumulate(lexer: PLexer; token: PLexerToken);
BEGIN
  INC(lexer^.Current)
END transition_action_accumulate;
(* The current character is not a part of the token. Finish the token already
 * read. Don't advance to the next character. *)
PROCEDURE transition_action_finalize(lexer: PLexer; token: PLexerToken);
BEGIN
  IF lexer^.Start^ = ':' THEN
    token^.kind := lexerKindColon
  END;
  IF lexer^.Start^ = '>' THEN
    token^.kind := lexerKindGreaterThan
  END;
  IF lexer^.Start^ = '<' THEN
    token^.kind := lexerKindLessThan
  END;
  IF lexer^.Start^ = '(' THEN
    token^.kind := lexerKindLeftParen
  END;
  IF lexer^.Start^ = '-' THEN
    token^.kind := lexerKindLeftParen
  END;
  IF lexer^.Start^ = '.' THEN
    token^.kind := lexerKindDot
  END
END transition_action_finalize;
(* An action for tokens containing multiple characters. *)
PROCEDURE transition_action_composite(lexer: PLexer; token: PLexerToken);
BEGIN
  IF lexer^.Start^ = '<' THEN
    IF lexer^.Current^ = '>' THEN
      token^.kind := lexerKindNotEqual
    END;
    IF lexer^.Current^ = '=' THEN
      token^.kind := lexerKindLessEqual
    END
  END;
  IF (lexer^.Start^ = '>') AND (lexer^.Current^ = '=') THEN
    token^.kind := lexerKindGreaterEqual
  END;
  IF (lexer^.Start^ = '.') AND (lexer^.Current^ = '.') THEN
    token^.kind := lexerKindRange
  END;
  IF (lexer^.Start^ = ':') AND (lexer^.Current^ = '=') THEN
    token^.kind := lexerKindAssignment
  END;
  IF (lexer^.Start^ = '-') AND (lexer^.Current^ = '>') THEN
    token^.kind := lexerKindArrow
  END;
  INC(lexer^.Current)
END transition_action_composite;
(* Skip a space. *)
PROCEDURE transition_action_skip(lexer: PLexer; token: PLexerToken);
BEGIN
  INC(lexer^.Current);
  INC(lexer^.Start)
END transition_action_skip;
(* Delimited string action. *)
PROCEDURE transition_action_delimited(lexer: PLexer; token: PLexerToken);
BEGIN
  IF lexer^.Start^ = '(' THEN
    token^.kind := lexerKindComment
  END;
  IF lexer^.Start^ = '"' THEN
    token^.kind := lexerKindCharacter
  END;
  IF lexer^.Start^ = "'" THEN
    token^.kind := lexerKindString
  END;
  INC(lexer^.Current)
END transition_action_delimited;
(* Finalize keyword OR identifier. *)
PROCEDURE transition_action_key_id(lexer: PLexer; token: PLexerToken);
BEGIN
  token^.kind := lexerKindIdentifier;

  token^.identifierKind[1] := lexer^.Current - lexer^.Start;
  MemCopy(lexer^.Start, ORD(token^.identifierKind[1]), ADR(token^.identifierKind[2]));

  IF compare_keyword('PROGRAM', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindProgram
  END;
  IF compare_keyword('IMPORT', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindImport
  END;
  IF compare_keyword('CONST', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindConst
  END;
  IF compare_keyword('VAR', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindVar
  END;
  IF compare_keyword('IF', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindIf
  END;
  IF compare_keyword('THEN', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindThen
  END;
  IF compare_keyword('ELSIF', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindElsif
  END;
  IF compare_keyword('ELSE', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindElse
  END;
  IF compare_keyword('WHILE', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindWhile
  END;
  IF compare_keyword('DO', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindDo
  END;
  IF compare_keyword('proc', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindProc
  END;
  IF compare_keyword('BEGIN', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindBegin
  END;
  IF compare_keyword('END', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindEnd
  END;
  IF compare_keyword('TYPE', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindType
  END;
  IF compare_keyword('RECORD', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindRecord
  END;
  IF compare_keyword('UNION', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindUnion
  END;
  IF compare_keyword('NIL', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindNull
  END;
  IF compare_keyword('AND', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindAnd
  END;
  IF compare_keyword('OR', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindOr
  END;
  IF compare_keyword('RETURN', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindReturn
  END;
  IF compare_keyword('DEFINITION', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindDefinition
  END;
  IF compare_keyword('TO', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindTo
  END;
  IF compare_keyword('CASE', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindCase
  END;
  IF compare_keyword('OF', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindOf
  END;
  IF compare_keyword('FROM', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindFrom
  END;
  IF compare_keyword('MODULE', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindModule
  END;
  IF compare_keyword('IMPLEMENTATION', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindImplementation
  END;
  IF compare_keyword('POINTER', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindPointer
  END;
  IF compare_keyword('ARRAY', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindArray
  END;
  IF compare_keyword('TRUE', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindBoolean;
    token^.booleanKind := TRUE
  END;
  IF compare_keyword('FALSE', lexer^.Start, lexer^.Current) THEN
    token^.kind := lexerKindBoolean;
    token^.booleanKind := FALSE
  END
END transition_action_key_id;
(* Action for tokens containing only one character. The character cannot be
 * followed by other characters forming a composite token. *)
PROCEDURE transition_action_single(lexer: PLexer; token: PLexerToken);
BEGIN
  IF lexer^.Current^ = '&' THEN
    token^.kind := lexerKindAnd
  END;
  IF lexer^.Current^ = ';' THEN
    token^.kind := lexerKindSemicolon
  END;
  IF lexer^.Current^ = ',' THEN
    token^.kind := lexerKindComma
  END;
  IF lexer^.Current^ = ',' THEN
    token^.kind := lexerKindComma
  END;
  IF lexer^.Current^ = ')' THEN
    token^.kind := lexerKindRightParen
  END;
  IF lexer^.Current^ = '[' THEN
    token^.kind := lexerKindLeftSquare
  END;
  IF lexer^.Current^ = ']' THEN
    token^.kind := lexerKindRightSquare
  END;
  IF lexer^.Current^ = '^' THEN
    token^.kind := lexerKindHat
  END;
  IF lexer^.Current^ = '=' THEN
    token^.kind := lexerKindEqual
  END;
  IF lexer^.Current^ = '+' THEN
    token^.kind := lexerKindPlus
  END;
  IF lexer^.Current^ = '/' THEN
    token^.kind := lexerKindDivision
  END;
  IF lexer^.Current^ = '%' THEN
    token^.kind := lexerKindRemainder
  END;
  IF lexer^.Current^ = '@' THEN
    token^.kind := lexerKindAt
  END;
  IF lexer^.Current^ = '|' THEN
    token^.kind := lexerKindPipe
  END;
  INC(lexer^.Current)
END transition_action_single;
(* Handle an integer literal. *)
PROCEDURE transition_action_integer(lexer: PLexer; token: PLexerToken);
VAR
  buffer: String;
  integer_length: CARDINAL;
  found: BOOLEAN;
BEGIN
  token^.kind := lexerKindInteger;

  integer_length := lexer^.Current - lexer^.Start;
  MemZero(ADR(token^.identifierKind), TSIZE(Identifier));
  MemCopy(lexer^.Start, integer_length, ADR(token^.identifierKind[1]));

  buffer := InitStringCharStar(ADR(token^.identifierKind[1]));
  token^.integerKind := StringToInteger(buffer, 10, found);
  buffer := KillString(buffer)
END transition_action_integer;
PROCEDURE set_default_transition(CurrentState: TransitionState; DefaultAction: TransitionAction; NextState: TransitionState);
VAR
  DefaultTransition: Transition;
BEGIN
  DefaultTransition.Action := DefaultAction;
  DefaultTransition.NextState := NextState;

  transitions[ORD(CurrentState) + 1][ORD(transitionClassInvalid) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassDigit) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassAlpha) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassSpace) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassColon) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassEquals) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassLeftParen) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassRightParen) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassAsterisk) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassUnderscore) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassSingle) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassHex) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassZero) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassX) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassEof) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassDot) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassMinus) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassSingleQuote) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassDoubleQuote) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassGreater) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassLess) + 1] := DefaultTransition;
  transitions[ORD(CurrentState) + 1][ORD(transitionClassOther) + 1] := DefaultTransition
END set_default_transition;
(*
 * The transition table describes transitions from one state to another, given
 * a symbol (character class).
 *
 * The table has m rows and n columns, where m is the amount of states and n is
 * the amount of classes. So given the current state and a classified character
 * the table can be used to look up the next state.
 *
 * Each cell is a word long.
 * - The least significant byte of the word is a row number (beginning with 0).
 *   It specifies the target state. "ff" means that this is an end state and no
 *   transition is possible.
 * - The next byte is the action that should be performed when transitioning.
 *   For the meaning of actions see labels in the lex_next function, which
 *   handles each action.
 *)
PROCEDURE initialize_transitions();
BEGIN
  (* Start state. *)
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassInvalid) + 1].Action := NIL;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassInvalid) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassDigit) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassDigit) + 1].NextState := transitionStateDecimal;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassAlpha) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassAlpha) + 1].NextState := transitionStateIdentifier;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassSpace) + 1].Action := transition_action_skip;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassSpace) + 1].NextState := transitionStateStart;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassColon) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassColon) + 1].NextState := transitionStateColon;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassEquals) + 1].Action := transition_action_single;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassEquals) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassLeftParen) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassLeftParen) + 1].NextState := transitionStateLeftParen;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassRightParen) + 1].Action := transition_action_single;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassRightParen) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassAsterisk) + 1].Action := transition_action_single;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassAsterisk) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassUnderscore) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassUnderscore) + 1].NextState := transitionStateIdentifier;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassSingle) + 1].Action := transition_action_single;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassSingle) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassHex) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassHex) + 1].NextState := transitionStateIdentifier;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassZero) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassZero) + 1].NextState := transitionStateLeadingZero;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassX) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassX) + 1].NextState := transitionStateIdentifier;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassEof) + 1].Action := transition_action_eof;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassEof) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassDot) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassDot) + 1].NextState := transitionStateDot;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassMinus) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassMinus) + 1].NextState := transitionStateMinus;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassSingleQuote) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassSingleQuote) + 1].NextState := transitionStateCharacter;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassDoubleQuote) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassDoubleQuote) + 1].NextState := transitionStateString;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassGreater) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassGreater) + 1].NextState := transitionStateGreater;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassLess) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassLess) + 1].NextState := transitionStateLess;

  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassOther) + 1].Action := NIL;
  transitions[ORD(transitionStateStart) + 1][ORD(transitionClassOther) + 1].NextState := transitionStateEnd;

  (* Colon state. *)
  set_default_transition(transitionStateColon, transition_action_finalize, transitionStateEnd);

  transitions[ORD(transitionStateColon) + 1][ORD(transitionClassEquals) + 1].Action := transition_action_composite;
  transitions[ORD(transitionStateColon) + 1][ORD(transitionClassEquals) + 1].NextState := transitionStateEnd;

  (* Identifier state. *)
  set_default_transition(transitionStateIdentifier, transition_action_key_id, transitionStateEnd);

  transitions[ORD(transitionStateIdentifier) + 1][ORD(transitionClassDigit) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateIdentifier) + 1][ORD(transitionClassDigit) + 1].NextState := transitionStateIdentifier;

  transitions[ORD(transitionStateIdentifier) + 1][ORD(transitionClassAlpha) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateIdentifier) + 1][ORD(transitionClassAlpha) + 1].NextState := transitionStateIdentifier;

  transitions[ORD(transitionStateIdentifier) + 1][ORD(transitionClassUnderscore) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateIdentifier) + 1][ORD(transitionClassUnderscore) + 1].NextState := transitionStateIdentifier;

  transitions[ORD(transitionStateIdentifier) + 1][ORD(transitionClassHex) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateIdentifier) + 1][ORD(transitionClassHex) + 1].NextState := transitionStateIdentifier;

  transitions[ORD(transitionStateIdentifier) + 1][ORD(transitionClassZero) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateIdentifier) + 1][ORD(transitionClassZero) + 1].NextState := transitionStateIdentifier;

  transitions[ORD(transitionStateIdentifier) + 1][ORD(transitionClassX) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateIdentifier) + 1][ORD(transitionClassX) + 1].NextState := transitionStateIdentifier;

  (* Decimal state. *)
  set_default_transition(transitionStateDecimal, transition_action_integer, transitionStateEnd);

  transitions[ORD(transitionStateDecimal) + 1][ORD(transitionClassDigit) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateDecimal) + 1][ORD(transitionClassDigit) + 1].NextState := transitionStateDecimal;

  transitions[ORD(transitionStateDecimal) + 1][ORD(transitionClassAlpha) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateDecimal) + 1][ORD(transitionClassAlpha) + 1].NextState := transitionStateDecimalSuffix;

  transitions[ORD(transitionStateDecimal) + 1][ORD(transitionClassUnderscore) + 1].Action := NIL;
  transitions[ORD(transitionStateDecimal) + 1][ORD(transitionClassUnderscore) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateDecimal) + 1][ORD(transitionClassHex) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateDecimal) + 1][ORD(transitionClassHex) + 1].NextState := transitionStateDecimalSuffix;

  transitions[ORD(transitionStateDecimal) + 1][ORD(transitionClassZero) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateDecimal) + 1][ORD(transitionClassZero) + 1].NextState := transitionStateDecimal;

  transitions[ORD(transitionStateDecimal) + 1][ORD(transitionClassX) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateDecimal) + 1][ORD(transitionClassX) + 1].NextState := transitionStateDecimalSuffix;

  (* Greater state. *)
  set_default_transition(transitionStateGreater, transition_action_finalize, transitionStateEnd);

  transitions[ORD(transitionStateGreater) + 1][ORD(transitionClassEquals) + 1].Action := transition_action_composite;
  transitions[ORD(transitionStateGreater) + 1][ORD(transitionClassEquals) + 1].NextState := transitionStateEnd;

  (* Minus state. *)
  set_default_transition(transitionStateMinus, transition_action_finalize, transitionStateEnd);

  transitions[ORD(transitionStateMinus) + 1][ORD(transitionClassGreater) + 1].Action := transition_action_composite;
  transitions[ORD(transitionStateMinus) + 1][ORD(transitionClassGreater) + 1].NextState := transitionStateEnd;

  (* Left paren state. *)
  set_default_transition(transitionStateLeftParen, transition_action_finalize, transitionStateEnd);

  transitions[ORD(transitionStateLeftParen) + 1][ORD(transitionClassAsterisk) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateLeftParen) + 1][ORD(transitionClassAsterisk) + 1].NextState := transitionStateComment;

  (* Less state. *)
  set_default_transition(transitionStateLess, transition_action_finalize, transitionStateEnd);

  transitions[ORD(transitionStateLess) + 1][ORD(transitionClassEquals) + 1].Action := transition_action_composite;
  transitions[ORD(transitionStateLess) + 1][ORD(transitionClassEquals) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateLess) + 1][ORD(transitionClassGreater) + 1].Action := transition_action_composite;
  transitions[ORD(transitionStateLess) + 1][ORD(transitionClassGreater) + 1].NextState := transitionStateEnd;

  (* Hexadecimal after 0x. *)
  set_default_transition(transitionStateDot, transition_action_finalize, transitionStateEnd);

  transitions[ORD(transitionStateDot) + 1][ORD(transitionClassDot) + 1].Action := transition_action_composite;
  transitions[ORD(transitionStateDot) + 1][ORD(transitionClassDot) + 1].NextState := transitionStateEnd;

  (* Comment. *)
  set_default_transition(transitionStateComment, transition_action_accumulate, transitionStateComment);

  transitions[ORD(transitionStateComment) + 1][ORD(transitionClassAsterisk) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateComment) + 1][ORD(transitionClassAsterisk) + 1].NextState := transitionStateClosingComment;

  transitions[ORD(transitionStateComment) + 1][ORD(transitionClassEof) + 1].Action := NIL;
  transitions[ORD(transitionStateComment) + 1][ORD(transitionClassEof) + 1].NextState := transitionStateEnd;

  (* Closing comment. *)
  set_default_transition(transitionStateClosingComment, transition_action_accumulate, transitionStateComment);

  transitions[ORD(transitionStateClosingComment) + 1][ORD(transitionClassInvalid) + 1].Action := NIL;
  transitions[ORD(transitionStateClosingComment) + 1][ORD(transitionClassInvalid) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateClosingComment) + 1][ORD(transitionClassRightParen) + 1].Action := transition_action_delimited;
  transitions[ORD(transitionStateClosingComment) + 1][ORD(transitionClassRightParen) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateClosingComment) + 1][ORD(transitionClassAsterisk) + 1].Action := transition_action_accumulate;
  transitions[ORD(transitionStateClosingComment) + 1][ORD(transitionClassAsterisk) + 1].NextState := transitionStateClosingComment;

  transitions[ORD(transitionStateClosingComment) + 1][ORD(transitionClassEof) + 1].Action := NIL;
  transitions[ORD(transitionStateClosingComment) + 1][ORD(transitionClassEof) + 1].NextState := transitionStateEnd;

  (* Character. *)
  set_default_transition(transitionStateCharacter, transition_action_accumulate, transitionStateCharacter);

  transitions[ORD(transitionStateCharacter) + 1][ORD(transitionClassInvalid) + 1].Action := NIL;
  transitions[ORD(transitionStateCharacter) + 1][ORD(transitionClassInvalid) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateCharacter) + 1][ORD(transitionClassEof) + 1].Action := NIL;
  transitions[ORD(transitionStateCharacter) + 1][ORD(transitionClassEof) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateCharacter) + 1][ORD(transitionClassSingleQuote) + 1].Action := transition_action_delimited;
  transitions[ORD(transitionStateCharacter) + 1][ORD(transitionClassSingleQuote) + 1].NextState := transitionStateEnd;

  (* String. *)
  set_default_transition(transitionStateString, transition_action_accumulate, transitionStateString);

  transitions[ORD(transitionStateString) + 1][ORD(transitionClassInvalid) + 1].Action := NIL;
  transitions[ORD(transitionStateString) + 1][ORD(transitionClassInvalid) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateString) + 1][ORD(transitionClassEof) + 1].Action := NIL;
  transitions[ORD(transitionStateString) + 1][ORD(transitionClassEof) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateString) + 1][ORD(transitionClassDoubleQuote) + 1].Action := transition_action_delimited;
  transitions[ORD(transitionStateString) + 1][ORD(transitionClassDoubleQuote) + 1].NextState := transitionStateEnd;

  (* Leading zero. *)
  set_default_transition(transitionStateLeadingZero, transition_action_integer, transitionStateEnd);

  transitions[ORD(transitionStateLeadingZero) + 1][ORD(transitionClassDigit) + 1].Action := NIL;
  transitions[ORD(transitionStateLeadingZero) + 1][ORD(transitionClassDigit) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateLeadingZero) + 1][ORD(transitionClassAlpha) + 1].Action := NIL;
  transitions[ORD(transitionStateLeadingZero) + 1][ORD(transitionClassAlpha) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateLeadingZero) + 1][ORD(transitionClassUnderscore) + 1].Action := NIL;
  transitions[ORD(transitionStateLeadingZero) + 1][ORD(transitionClassUnderscore) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateLeadingZero) + 1][ORD(transitionClassHex) + 1].Action := NIL;
  transitions[ORD(transitionStateLeadingZero) + 1][ORD(transitionClassHex) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateLeadingZero) + 1][ORD(transitionClassZero) + 1].Action := NIL;
  transitions[ORD(transitionStateLeadingZero) + 1][ORD(transitionClassZero) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateLeadingZero) + 1][ORD(transitionClassX) + 1].Action := NIL;
  transitions[ORD(transitionStateLeadingZero) + 1][ORD(transitionClassX) + 1].NextState := transitionStateEnd;

  (* Digit with a character suffix. *)
  set_default_transition(transitionStateDecimalSuffix, transition_action_integer, transitionStateEnd);

  transitions[ORD(transitionStateDecimalSuffix) + 1][ORD(transitionClassAlpha) + 1].Action := NIL;
  transitions[ORD(transitionStateDecimalSuffix) + 1][ORD(transitionClassAlpha) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateDecimalSuffix) + 1][ORD(transitionClassDigit) + 1].Action := NIL;
  transitions[ORD(transitionStateDecimalSuffix) + 1][ORD(transitionClassDigit) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateDecimalSuffix) + 1][ORD(transitionClassHex) + 1].Action := NIL;
  transitions[ORD(transitionStateDecimalSuffix) + 1][ORD(transitionClassHex) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateDecimalSuffix) + 1][ORD(transitionClassZero) + 1].Action := NIL;
  transitions[ORD(transitionStateDecimalSuffix) + 1][ORD(transitionClassZero) + 1].NextState := transitionStateEnd;

  transitions[ORD(transitionStateDecimalSuffix) + 1][ORD(transitionClassX) + 1].Action := NIL;
  transitions[ORD(transitionStateDecimalSuffix) + 1][ORD(transitionClassX) + 1].NextState := transitionStateEnd
END initialize_transitions;
PROCEDURE lexer_initialize(lexer: PLexer; Input: File);
BEGIN
  lexer^.Input := Input;
  lexer^.Length := 0;

  ALLOCATE(lexer^.Buffer, CHUNK_SIZE);
  MemZero(lexer^.Buffer, CHUNK_SIZE);
  lexer^.Size := CHUNK_SIZE
END lexer_initialize;
PROCEDURE lexer_current(lexer: PLexer): LexerToken;
VAR
  CurrentClass: TransitionClass;
  CurrentState: TransitionState;
  CurrentTransition: Transition;
  result: LexerToken;
BEGIN
  lexer^.Current := lexer^.Start;
  CurrentState := transitionStateStart;

  WHILE CurrentState <> transitionStateEnd DO
    CurrentClass := classification[ORD(lexer^.Current^) + 1];

    CurrentTransition := transitions[ORD(CurrentState) + 1][ORD(CurrentClass) + 1];
    IF CurrentTransition.Action <> NIL THEN
      CurrentTransition.Action(lexer, ADR(result))
    END;
    CurrentState := CurrentTransition.NextState
  END;
  RETURN result
END lexer_current;
PROCEDURE lexer_lex(lexer: PLexer): LexerToken;
VAR
  result: LexerToken;
BEGIN
  IF lexer^.Length = 0 THEN
    lexer^.Length := ReadNBytes(lexer^.Input, CHUNK_SIZE, lexer^.Buffer);
    lexer^.Current := lexer^.Buffer
  END;
  lexer^.Start := lexer^.Current;

  result := lexer_current(lexer);
  RETURN result
END lexer_lex;
PROCEDURE lexer_destroy(lexer: PLexer);
BEGIN
  DEALLOCATE(lexer^.Buffer, lexer^.Size)
END lexer_destroy;
BEGIN
  initialize_classification();
  initialize_transitions()
END Lexer.