public static string ToString (DateTime dt, TimeSpan? utc_offset, string format, DateTimeFormatInfo dfi)
{
// the length of the format is usually a good guess of the number
// of chars in the result. Might save us a few bytes sometimes
// Add + 10 for cases like mmmm dddd
StringBuilder result = new StringBuilder (format.Length + 10);
int i = 0;
bool saw_day_specifier = false;
while (i < format.Length) {
int tokLen;
bool omitZeros = false;
char ch = format [i];
switch (ch) {
//
// Time Formats
//
case 'h':
// hour, [1, 12]
tokLen = DateTimeUtils.CountRepeat (format, i, ch);
int hr = dt.Hour % 12;
if (hr == 0)
hr = 12;
DateTimeUtils.ZeroPad (result, hr, tokLen == 1 ? 1 : 2);
break;
case 'H':
// hour, [0, 23]
tokLen = DateTimeUtils.CountRepeat (format, i, ch);
DateTimeUtils.ZeroPad (result, dt.Hour, tokLen == 1 ? 1 : 2);
break;
case 'm':
// minute, [0, 59]
tokLen = DateTimeUtils.CountRepeat (format, i, ch);
DateTimeUtils.ZeroPad (result, dt.Minute, tokLen == 1 ? 1 : 2);
break;
case 's':
// second [0, 29]
tokLen = DateTimeUtils.CountRepeat (format, i, ch);
DateTimeUtils.ZeroPad (result, dt.Second, tokLen == 1 ? 1 : 2);
break;
case 'F':
omitZeros = true;
goto case 'f';
case 'f':
// fraction of second, to same number of
// digits as there are f's
tokLen = DateTimeUtils.CountRepeat (format, i, ch);
if (tokLen > 7)
throw new FormatException ("Invalid Format String");
int dec = (int)((long)(dt.Ticks % TimeSpan.TicksPerSecond) / (long) Math.Pow (10, 7 - tokLen));
int startLen = result.Length;
DateTimeUtils.ZeroPad (result, dec, tokLen);
if (omitZeros) {
while (result.Length > startLen && result [result.Length - 1] == '0')
result.Length--;
// when the value was 0, then trim even preceding '.' (!) It is fixed character.
if (dec == 0 && startLen > 0 && result [startLen - 1] == '.')
result.Length--;
}
break;
case 't':
// AM/PM. t == first char, tt+ == full
tokLen = DateTimeUtils.CountRepeat (format, i, ch);
string desig = dt.Hour < 12 ? dfi.AMDesignator : dfi.PMDesignator;
if (tokLen == 1) {
if (desig.Length >= 1)
result.Append (desig [0]);
}
else
result.Append (desig);
break;
case 'z':
// timezone. t = +/-h; tt = +/-hh; ttt+=+/-hh:mm
tokLen = DateTimeUtils.CountRepeat (format, i, ch);
TimeSpan offset =
utc_offset ??
TimeZone.CurrentTimeZone.GetUtcOffset (dt);
if (offset.Ticks >= 0)
result.Append ('+');
else
result.Append ('-');
switch (tokLen) {
case 1:
result.Append (Math.Abs (offset.Hours));
break;
case 2:
result.Append (Math.Abs (offset.Hours).ToString ("00"));
break;
default:
result.Append (Math.Abs (offset.Hours).ToString ("00"));
result.Append (':');
result.Append (Math.Abs (offset.Minutes).ToString ("00"));
break;
}
break;
case 'K': // 'Z' (UTC) or zzz (Local)
tokLen = 1;
if (utc_offset != null || dt.Kind == DateTimeKind.Local) {
offset = utc_offset ?? TimeZone.CurrentTimeZone.GetUtcOffset (dt);
if (offset.Ticks >= 0)
result.Append ('+');
else
result.Append ('-');
result.Append (Math.Abs (offset.Hours).ToString ("00"));
result.Append (':');
result.Append (Math.Abs (offset.Minutes).ToString ("00"));
} else if (dt.Kind == DateTimeKind.Utc)
result.Append ('Z');
break;
//
// Date tokens
//
case 'd':
// day. d(d?) = day of month (leading 0 if two d's)
// ddd = three leter day of week
// dddd+ full day-of-week
tokLen = DateTimeUtils.CountRepeat (format, i, ch);
if (tokLen <= 2)
DateTimeUtils.ZeroPad (result, dfi.Calendar.GetDayOfMonth (dt), tokLen == 1 ? 1 : 2);
else if (tokLen == 3)
result.Append (dfi.GetAbbreviatedDayName (dfi.Calendar.GetDayOfWeek (dt)));
else
result.Append (dfi.GetDayName (dfi.Calendar.GetDayOfWeek (dt)));
saw_day_specifier = true;
break;
case 'M':
// Month.m(m?) = month # (with leading 0 if two mm)
// mmm = 3 letter name
// mmmm+ = full name
tokLen = DateTimeUtils.CountRepeat (format, i, ch);
int month = dfi.Calendar.GetMonth(dt);
if (tokLen <= 2)
DateTimeUtils.ZeroPad (result, month, tokLen);
else if (tokLen == 3)
result.Append (dfi.GetAbbreviatedMonthName (month));
else {
// Handles MMMM dd format
if (!saw_day_specifier) {
for (int ii = i + 1; ii < format.Length; ++ii) {
ch = format [ii];
if (ch == 'd') {
saw_day_specifier = true;
break;
}
if (ch == '\'' || ch == '"') {
ii += ParseQuotedString (format, ii, null) - 1;
}
}
}
// NOTE: .NET ignores quoted 'd' and reads it as day specifier but I think
// that's wrong
result.Append (saw_day_specifier ? dfi.GetMonthGenitiveName (month) : dfi.GetMonthName (month));
}
break;
case 'y':
// Year. y(y?) = two digit year, with leading 0 if yy
// yyy+ full year with leading zeros if needed.
tokLen = DateTimeUtils.CountRepeat (format, i, ch);
if (tokLen <= 2)
DateTimeUtils.ZeroPad (result, dfi.Calendar.GetYear (dt) % 100, tokLen);
else
DateTimeUtils.ZeroPad (result, dfi.Calendar.GetYear (dt), tokLen);
break;
case 'g':
// Era name
tokLen = DateTimeUtils.CountRepeat (format, i, ch);
result.Append (dfi.GetEraName (dfi.Calendar.GetEra (dt)));
break;
//
// Other
//
case ':':
result.Append (dfi.TimeSeparator);
tokLen = 1;
break;
case '/':
result.Append (dfi.DateSeparator);
tokLen = 1;
break;
case '\'': case '"':
tokLen = ParseQuotedString (format, i, result);
break;
case '%':
if (i >= format.Length - 1)
throw new FormatException ("% at end of date time string");
if (format [i + 1] == '%')
throw new FormatException ("%% in date string");
// Look for the next char
tokLen = 1;
break;
case '\\':
// C-Style escape
if (i >= format.Length - 1)
throw new FormatException ("\\ at end of date time string");
result.Append (format [i + 1]);
tokLen = 2;
break;
default:
// catch all
result.Append (ch);
tokLen = 1;
break;
}
i += tokLen;
}
return result.ToString ();
}
