qexprlex.l

TxQuery is an SQL engine implemented in a TDataSet descendant component, that can parse SQL syntax,

%{

{**************************************************}
{   Lexical analizer for Expression Parser         }
{   Copyright (c) 2002 by Ingenieria Construmap    }
{                      Developed by Alfonso Moreno }
{**************************************************}

unit QExprLex;

{$I XQ_FLAG.INC}
interface

uses
  SysUtils, QLexLib, QExprYacc;

type
    TExprLexer = Class(TCustomLexer)
    public
      // utility functions
      function IsKeyword(const id : String; var token : integer) : boolean;
      // Lexer main functions
      function yylex : Integer; override;
      procedure yyaction( yyruleno : integer);
      procedure commenteof;
    end;

//===============================================
// reserved words definition
//===============================================
  type
    TRWord = record
       rword: string[14];
       token: smallint;
    end;

  const
    rwords : array [1..26] of TRword = (
    (rword: 'AND';            token: RW_AND),
    (rword: 'OR';             token: RW_OR),
    (rword: 'XOR';            token: RW_XOR),
    (rword: 'NOT';            token: RW_NOT),
    (rword: 'MOD';            token: RW_MOD),
    (rword: 'TRUE';           token: RW_TRUE),
    (rword: 'FALSE';          token: RW_FALSE),
    (rword: 'LIKE';           token: RW_LIKE),
    (rword: 'STRING';         token: RW_STRING),
    (rword: 'FLOAT';          token: RW_FLOAT),
    (rword: 'INTEGER';        token: RW_INTEGER),
    (rword: 'BOOLEAN';        token: RW_BOOLEAN),
    (rword: 'SHL';            token: RW_SHL),
    (rword: 'SHR';            token: RW_SHR),
    (rword: 'IN';             token: RW_IN),
    (rword: 'BETWEEN';        token: RW_BETWEEN),
    (rword: 'DIV';            token: RW_DIV),
    (rword: 'CASE';           token: RW_CASE),
    (rword: 'WHEN';           token: RW_WHEN),
    (rword: 'THEN';           token: RW_THEN),
    (rword: 'ELSE';           token: RW_ELSE),
    (rword: 'IF';             token: RW_IF),
    (rword: 'CAST';           token: RW_CAST),
    (rword: 'ESCAPE';         token: RW_ESCAPE),
    (rword: 'AS';             token: RW_AS),
    (rword: 'END';            token: RW_END)
    );

implementation

resourcestring
  SDefaultDateFormat = 'm/d/yyyy';

function TExprLexer.IsKeyword(const id : string; var token : integer) : boolean;
(* returns corresponding token number in token *)

var
  k : integer;
begin
  Result:= false;
  for k:= Low(rwords) to High(rwords) do
    if AnsiCompareText(id, rwords[k].rword)=0 then
    begin
       Result:= True;
       token := rwords[k].token;
       Exit;
    end;
end;

procedure TExprLexer.commenteof;
begin
  writeln(yyErrorfile, 'unexpected EOF inside comment at line ' +intToStr( yylineno));
end;

%}

DIGIT     [0-9]
LOWER     [a-z]
UPPER     [A-Z]
EXTENDED  [\200-\377]
LETTER    ({UPPER}|{LOWER}|{EXTENDED})

UINT      {DIGIT}+
SINT      [+-]{DIGIT}+
HEXA      [$]({DIGIT}|[A-Fa-f])+
ENL       ([+-])?({UINT}"."{UINT})|({UINT}".")|("."{UINT})
ANL       {ENL}[Ee]{SINT}

%%

   var
      c: char;
      token, code, value: Integer;
      SaveDate: String;

{LETTER}("_"|{LETTER}|{DIGIT})*
  if IsKeyword(yylval.yystring, token) then
    returni(token)
  else
    returni(_IDENTIFIER);
\[[^\[\]]*\]
  begin
    // extended identifier for using in fields with same name as reserved word
    yylval.yystring := Copy(yylval.yystring, 2, yyTextLen - 2);
    returni( _IDENTIFIER );
  end;

({ENL})|({ANL})      returni( _NUMERIC );

{UINT}               returni( _UINTEGER );

{SINT}               returni( _SINTEGER );

{HEXA}
  begin
    Val(yylval.yystring, value, code);
    if code=0 then
    begin
      yylval.yystring:= IntToStr(value);
      returni(_NUMERIC);
    end else
      returni(_ILLEGAL);
  end;

\'[^\']*\'
  begin
    c := get_char;
    if c = #39 then
      yymore
    else
    begin
      unget_char(c);
      returni( _STRING );
    end;
  end;
\"[^\"]*\"
  begin
    c := get_char;
    if c = #34 then
      yymore
    else
    begin
      unget_char(c);
      returni( _STRING );
    end;
  end;
\#[^\#]*\#
  if Length( yylval.yystring ) >= 10 then
  begin
    { section to handle dates in the format m/d/yyyy }
    SaveDate := ShortDateFormat;
    ShortDateFormat := SDefaultDateFormat;
    yylval.yystring := FloatToStr(StrToDate(Copy(yylval.yystring, 2, yyTextLen - 2)));
    ShortDateFormat := SaveDate;
    returni(_NUMERIC);
  end;
","  returni( _COMA );
"("  returni( _LPAREN );
")"  returni( _RPAREN );
">"  returni( _GT );
"<"  returni( _LT );
"="  returni( _EQ );
"<>" returni( _NEQ );
">=" returni( _GE );
"<=" returni( _LE );
"."  returni( _PERIOD );
":"  returni( _COLON );
"*"  returni( _MULT );
"+"  returni( _PLUS );
"-"  returni( _SUB );
"^"  returni( _EXP );
"/"  returni( _DIV );
"/*"[^\*]*"*/" returni( _COMMENT );
[ ]  returni( _BLANK );
[\n] returni( _NEWLINE );
[\t] returni( _TAB );
.    returni( _ILLEGAL );