{
* This Source Code Form is subject to the terms of the Mozilla Public License,
* v. 2.0. If a copy of the MPL was not distributed with this file, You can
* obtain one at http://mozilla.org/MPL/2.0/
*
* Copyright (C) 2010-2012, Peter Johnson (www.delphidabbler.com).
*
* $Rev$
* $Date$
*
* Provides code for handling RFC2822 format dates. This version provides one
* function to convert a RFC2822 date into a TDateTime.
}
unit URFC2822Date;
interface
uses
// Project
UExceptions;
function RFC2822DateToGMTDateTime(DateStr: string): TDateTime;
{Converts a date in RFC2822 format into the corresponding TDateTime value in
GMT (UTC).
@param DateStr [in] RFC2822 date string to be converted.
@return Converted date in GMT (UTC).
@except ERFC2822Date raised if DateStr is malformed.
}
type
{
ERFC2822Date:
Type of exception raised when a RFC2822 date passed to
RFC2822DateToGMTDateTime is malformed.
}
ERFC2822Date = class(ECodeSnip);
implementation
uses
// Delphi
SysUtils, DateUtils,
// Project
UIStringList, UStructs, UStrUtils;
function StrToWordInRange(const S: string; const Range: TRange;
const ErrMsg: string): Word;
{Converts a string representation of a number into a word value, checking it
is in an expected range.
@param S [in] String value to convert.
@param Range [in] Range of valid values for the number.
@param ErrMasg [in] Error message to use for any exception.
@return Required number.
@except ERFC2822Date raised if S does not contain a valid number or number
is not in required range.
}
var
Value: Integer; // value of S as integer
begin
if not TryStrToInt(S, Value) or not Range.Contains(Value) then
raise ERFC2822Date.CreateFmt(ErrMsg, [S]);
Result := Value;
end;
procedure ValidateDOW(const ADOW: string);
{Validates text storing a day of the week as a valid day name. Returns if day
of week is valid or raises exception if not.
@param ADOW [in] Text to be checked.
@except ERFC2822Date raised if ADOW is not a valid day name.
}
resourcestring
sErrMsg = 'Invalid day of week: "%s"'; // error message
const
// Map of day numbers to day names
cDOWs: array[1..7] of string = (
'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun'
);
var
DOW: string; // reference each day of week
begin
for DOW in cDOWs do
if DOW = ADOW then
Exit;
raise ERFC2822Date.CreateFmt(sErrMsg, [ADOW]);
end;
function GetDay(const ADayStr: string): Word;
{Converts day of month from string to Word value, checking value is valid for
a day of month.
@param ADayStr [in] String containing day number.
@return Required day number.
@except ERFC2822Date raised if ADayStr is not a valid number or is out of
range for a day of month.
}
resourcestring
sErrMsg = 'Invalid day of month: "%s"'; // error message
begin
Result := StrToWordInRange(ADayStr, TRange.Create(1, 31), sErrMsg);
end;
function GetMonth(const AMonthName: string): Word;
{Converts month named in required RFC2822 format into a month number.
@param AMonthName [in] String containing month name in RFC2822 format.
@return Required month number.
@except ERFC2822Date raised if AMonthName is not a valid RFC2822 month name.
}
resourcestring
sErrMsg = 'Invalid month: "%s"'; // error message
const
// Map of month number to month names
cMonths: array[1..12] of string = (
'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun',
'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'
);
var
I: 1..12; // loops through all elements of months map
begin
for I := 1 to 12 do
begin
if cMonths[I] = AMonthName then
Exit(I);
end;
raise ERFC2822Date.CreateFmt(sErrMsg, [AMonthName]);
end;
function GetYear(const AYearStr: string): Word;
{Converts year from string to Word value, adjusting 2 and 3 digit years per
RFC2822 specifications.
@param AYearStr [in] String containing year.
@return Required and adjusted, year number.
@except ERFC2822Date raised if AYearStr is not a valid number or is out of
range.
}
resourcestring
sErrMsg = 'Invalid year: "%s"'; // error message
var
Value: Integer; // value of AYearStr as integer
begin
// Check for valid Word value
if not TryStrToInt(AYearStr, Value)
or (Value < 0)
or (Value > High(Word)) then
raise ERFC2822Date.CreateFmt(sErrMsg, [AYearStr]);
// Adjust for 2 and 3 digit years
if TRange.Create(0, 49).Contains(Value) then
Inc(Value, 2000)
else if TRange.Create(50, 999).Contains(Value) then
Inc(Value, 1900);
Result := Value;
end;
function GetHour(const AHourStr: string): Word;
{Converts hour from string to Word value, checking value is valid for an hour
in the 24 hour clock.
@param AHourStr [in] String containing hour.
@return Required hour number.
@except ERFC2822Date raised if AHourStr is not a valid number or is out of
range for an hour.
}
resourcestring
sErrMsg = 'Invalid hour: "%s"'; // error message
begin
Result := StrToWordInRange(AHourStr, TRange.Create(0, 23), sErrMsg);
end;
function GetMinute(const AMinStr: string): Word;
{Converts minute from string to Word value, checking value is valid for a
minute.
@param AMinStr [in] String containing minute.
@return Required minute number.
@except ERFC2822Date raised if AMinStr is not a valid number or is out of
range for a minute.
}
resourcestring
sErrMsg = 'Invalid minute: "%s"'; // error message
begin
Result := StrToWordInRange(AMinStr, TRange.Create(0, 59), sErrMsg);
end;
function GetSecond(const ASecStr: string): Word;
{Converts second from string to Word value, checking value is valid for a
second.
@param ASecStr [in] String containing second.
@return Required second number.
@except ERFC2822Date raised if ASecStr is not a valid number or is out of
range for a second.
}
resourcestring
sErrMsg = 'Invalid second: "%s"'; // error message
begin
Result := StrToWordInRange(ASecStr, TRange.Create(0, 59), sErrMsg)
end;
function GetTime(const TimeStr: string): TTime;
{Converts a time string in format HH:MM:SS or HH:MM into a TTime value.
@param TimeStr [in] Time string to converted.
@return Converted value.
@except ERFC2822Date raised if the time string is invalid.
}
resourcestring
sErrMsg = 'Invalid time: "%s"'; // error message
var
Parts: IStringList; // constituent parts of time: hr, min sec
Hour, Min, Sec: Word; // numeric values of hr, min, sec
const
// Indices of time components in Parts
HourPart = 0; // hour part (0..23)
MinPart = 1; // minute part (0..59)
SecPart = 2; // second part (0..59)
begin
// Split time string to component parts: must be 2 or 3 parts (secs optional)
Parts := TIStringList.Create(TimeStr, ':', True, False);
if (Parts.Count < 2) or (Parts.Count > 3) then
raise ERFC2822Date.CreateFmt(sErrMsg, [TimeStr]);
// Get hour, minute and seconds as numbers
Hour := GetHour(Parts[HourPart]);
Min := GetMinute(Parts[MinPart]);
if Parts.IsValidIndex(SecPart) then
Sec := GetSecond(Parts[SecPart])
else
Sec := 0; // if seconds no specified use 0
Result := EncodeTime(Hour, Min, Sec, 0);
end;
procedure GetOffset(const AOffsetStr: string; out AHours, AMins: Integer);
{Gets offset in minutes and seconds from GMT from an RFC2822 format offset
string. Supports +9999, -9999 and text offsets. Unrecognised text offsets are
parsed as -0000 per the RFC.
@param AOffsetStr [in] The offset string to parse.
@param AHours [out] Hours component of offset as signed number.
@param AMins [out] Mins component of offset as signed number.
@except ERFC2822Date raised if a malformed numeric offset is found.
}
resourcestring
// Error message
sErrMsg = 'Invalid date offset: "%s"';
var
Sign: Integer; // sign of offset: -1 or +1
I: Integer; // loops thru elements of cObsZones table
const
// Table of supported text time offsets
cObsZones: array[1..10] of record
Zone: string; // offset time zone code
Sign: Integer; // sign of offset: -1 or +1
Hour: Integer; // offset hour: minutes always zero
end = (
(Zone: 'UT'; Sign: +1; Hour: 0),
(Zone: 'GMT'; Sign: +1; Hour: 0),
(Zone: 'EST'; Sign: -1; Hour: 5),
(Zone: 'EDT'; Sign: -1; Hour: 4),
(Zone: 'CST'; Sign: -1; Hour: 6),
(Zone: 'CDT'; Sign: -1; Hour: 5),
(Zone: 'MST'; Sign: -1; Hour: 7),
(Zone: 'MDT'; Sign: -1; Hour: 6),
(Zone: 'PST'; Sign: -1; Hour: 8),
(Zone: 'PDT'; Sign: -1; Hour: 7)
);
begin
if (Length(AOffsetStr) = 5) and (CharInSet(AOffsetStr[1], ['+', '-'])) then
begin
// Offset in standard format ("+" | "-") 9999
if AOffsetStr[1] = '-' then
Sign := -1
else
Sign := 1;
if not TryStrToInt(Copy(AOffsetStr, 2, 2), AHours)
or not TryStrToInt(Copy(AOffsetStr, 4, 2), AMins) then
raise ERFC2822Date.CreateFmt(sErrMsg, [AOffsetStr]);
end
else
begin
// Non-standard format: assume -0000 unless recognised code
Sign := -1;
AHours := 0;
AMins := 0;
for I := Low(cObsZones) to High(cObsZones) do
begin
if cObsZones[I].Zone = AOffsetStr then
begin
Sign := cObsZones[I].Sign;
AHours := cObsZones[I].Hour;
end;
end;
end;
// Adjust offsets per sign
AHours := Sign * AHours;
AMins := Sign * AMins;
end;
function RFC2822DateToGMTDateTime(DateStr: string): TDateTime;
{Converts a date in RFC2822 format into the corresponding TDateTime value in
GMT (UTC).
@param DateStr [in] RFC2822 date string to be converted.
@return Converted date in GMT (UTC).
@except ERFC2822Date raised if DateStr is malformed.
}
resourcestring
// Error messages
sBadDate = 'Bad date format';
sBadDay = 'Invalid day of month: "%s"';
var
Parts: IStringList; // component parts of date string
Day, Month, Year: Word; // day, month and year
OffsetHours, OffsetMins: Integer; // offset hours and minutes
const
// Indices of date components in Parts
DOWPart = 0; // day of week part (<day-name> ",")
DayPart = 1; // day number part
MonthPart = 2; // month number part
YearPart = 3; // year number part
TimePart = 4; // time component part (HH:MM:SS format)
OffsetPart = 5; // offset from GMT part (+9999, -9999 or some valid text)
begin
// Sun, 29 Aug 2010 13:06:03 +0000
// Newlines allowed between fields: we compress to single white spaces
DateStr := StrCompressWhiteSpace(DateStr);
// Split date into constituent parts
Parts := TIStringList.Create(DateStr, ' ', False, True);
if Parts.Count <> 6 then
raise ERFC2822Date.Create(sBadDate);
// Check day has a valid name: we don't check if it is correct for date since
// not clear whether day should be correct before or after offset is applied.
ValidateDOW(Copy(Parts[DOWPart], 1, 3));
// Extract Day, Month and Year
Day := GetDay(Parts[DayPart]);
Month := GetMonth(Parts[MonthPart]);
Year := GetYear(Parts[YearPart]);
// Check date (Day, Month, Year) for validity
if not TryEncodeDate(Year, Month, Day, Result) then
raise ERFC2822Date.Create(sBadDate);
if DaysInMonth(Result) < Day then
raise ERFC2822Date.CreateFmt(sBadDay, [Day]);
// Get time component
Result := Result + GetTime(Parts[TimePart]);
// Get any offset and adjust date accordingly
GetOffset(Parts[OffsetPart], OffsetHours, OffsetMins);
if OffsetHours <> 0 then
Result := IncHour(Result, OffsetHours);
if OffsetMins <> 0 then
Result := IncMinute(Result, OffsetMins);
end;
end.
