delphi 关于时间源代码

function TryEncodeTime(Hour, Min, Sec, MSec: Word; out Time: TDateTime): Boolean;
begin
  Result := False;
  if (Hour < HoursPerDay) and (Min < MinsPerHour) and (Sec < SecsPerMin) and (MSec < MSecsPerSec) then
  begin
    Time := (Hour * (MinsPerHour * SecsPerMin * MSecsPerSec) +
             Min * (SecsPerMin * MSecsPerSec) +
             Sec * MSecsPerSec +
             MSec) / MSecsPerDay;
    Result := True;
  end;
end;

 

function TryEncodeDate(Year, Month, Day: Word; out Date: TDateTime): Boolean;
var
  I: Integer;
  DayTable: PDayTable;
begin
  Result := False;
  DayTable := @MonthDays[IsLeapYear(Year)];
  if (Year >= 1) and (Year <= 9999) and (Month >= 1) and (Month <= 12) and
    (Day >= 1) and (Day <= DayTable^[Month]) then
  begin
    for I := 1 to Month - 1 do Inc(Day, DayTable^[I]);
    I := Year - 1;
    Date := I * 365 + I div 4 - I div 100 + I div 400 + Day - DateDelta;
    Result := True;
  end;
end;

非常简单的2个函数，说明了Delphi TDateTime的本质。

 

Function XXXNow(): TDateTime;
var
  t: TSystemTime;
Begin
  GetLocalTime(t);
  Result := EncodeDate(t.wYear, t.wMonth, t.wDay) + EnCodeTime(t.wHour, t.wMinute, t.wSecond, t.wMilliseconds);
end;

 

 

function IsValidIdent(const Ident: string): Boolean;
const
  Alpha = ['A'..'Z', 'a'..'z', '_'];
  AlphaNumeric = Alpha + ['0'..'9'];
var
  I: Integer;
begin
  Result := False;
  if (Length(Ident) = 0) or not (Ident[1] in Alpha) then Exit;
  for I := 2 to Length(Ident) do if not (Ident[I] in AlphaNumeric) then Exit;
  Result := True;
end;

 

function XXXUpCase(ch: Char): Char;
Begin
  Result := ch;
  case Result of
    'a'..'z': dec(Result, Ord('a') - Ord('A'));
  end;
end;