/// <summary>
/// Formats a TimeSpan as a UTF8 string.
/// </summary>
/// <param name="value">Value to format</param>
/// <param name="destination">Buffer to write the UTF8-formatted value to</param>
/// <param name="bytesWritten">Receives the length of the formatted text in bytes</param>
/// <param name="format">The standard format to use</param>
/// <returns>
/// true for success. "bytesWritten" contains the length of the formatted text in bytes.
/// false if buffer was too short. Iteratively increase the size of the buffer and retry until it succeeds.
/// </returns>
/// <remarks>
/// Formats supported:
/// c/t/T (default) [-][d.]hh:mm:ss[.fffffff] (constant format)
/// G [-]d:hh:mm:ss.fffffff (general long)
/// g [-][d:][h]h:mm:ss[.f[f[f[f[f[f[f]]]]]] (general short)
/// </remarks>
/// <exceptions>
/// <cref>System.FormatException</cref> if the format is not valid for this data type.
/// </exceptions>
public static bool TryFormat(TimeSpan value, Span <byte> destination, out int bytesWritten, StandardFormat format = default)
{
char symbol = FormattingHelpers.GetSymbolOrDefault(format, 'c');
switch (symbol)
{
case 'c':
case 'G':
case 'g':
break;
case 't':
case 'T':
symbol = 'c';
break;
default:
return(FormattingHelpers.TryFormatThrowFormatException(out bytesWritten));
}
// First, calculate how large an output buffer is needed to hold the entire output.
int requiredOutputLength = 8; // start with "hh:mm:ss" and adjust as necessary
uint fraction;
ulong totalSecondsRemaining;
{
// Turn this into a non-negative TimeSpan if possible.
long ticks = value.Ticks;
if (ticks < 0)
{
ticks = -ticks;
if (ticks < 0)
{
Debug.Assert(ticks == long.MinValue /* -9223372036854775808 */);
// We computed these ahead of time; they're straight from the decimal representation of Int64.MinValue.
fraction = 4775808;
totalSecondsRemaining = 922337203685;
goto AfterComputeFraction;
}
}
ulong fraction64;
(totalSecondsRemaining, fraction64) = Math.DivRem((ulong)Math.Abs(value.Ticks), TimeSpan.TicksPerSecond);
fraction = (uint)fraction64;
}
AfterComputeFraction:
int fractionDigits = 0;
if (symbol == 'c')
{
// Only write out the fraction if it's non-zero, and in that
// case write out the entire fraction (all digits).
if (fraction != 0)
{
fractionDigits = Utf8Constants.DateTimeNumFractionDigits;
}
}
else if (symbol == 'G')
{
// Always write out the fraction, even if it's zero.
fractionDigits = Utf8Constants.DateTimeNumFractionDigits;
}
else
{
// Only write out the fraction if it's non-zero, and in that
// case write out only the most significant digits.
if (fraction != 0)
{
fractionDigits = Utf8Constants.DateTimeNumFractionDigits - FormattingHelpers.CountDecimalTrailingZeros(fraction, out fraction);
}
}
Debug.Assert(fraction < 10_000_000);
// If we're going to write out a fraction, also need to write the leading decimal.
if (fractionDigits != 0)
{
requiredOutputLength += fractionDigits + 1;
}
ulong totalMinutesRemaining = 0;
ulong seconds = 0;
if (totalSecondsRemaining > 0)
{
// Only compute minutes if the TimeSpan has an absolute value of >= 1 minute.
(totalMinutesRemaining, seconds) = Math.DivRem(totalSecondsRemaining, 60 /* seconds per minute */);
}
Debug.Assert(seconds < 60);
ulong totalHoursRemaining = 0;
ulong minutes = 0;
if (totalMinutesRemaining > 0)
{
// Only compute hours if the TimeSpan has an absolute value of >= 1 hour.
(totalHoursRemaining, minutes) = Math.DivRem(totalMinutesRemaining, 60 /* minutes per hour */);
}
Debug.Assert(minutes < 60);
// At this point, we can switch over to 32-bit divmod since the data has shrunk far enough.
Debug.Assert(totalHoursRemaining <= uint.MaxValue);
uint days = 0;
uint hours = 0;
if (totalHoursRemaining > 0)
{
// Only compute days if the TimeSpan has an absolute value of >= 1 day.
(days, hours) = Math.DivRem((uint)totalHoursRemaining, 24 /* hours per day */);
}
Debug.Assert(hours < 24);
int hourDigits = 2;
if (hours < 10 && symbol == 'g')
{
// Only writing a one-digit hour, not a two-digit hour
hourDigits--;
requiredOutputLength--;
}
int dayDigits = 0;
if (days == 0)
{
if (symbol == 'G')
{
requiredOutputLength += 2; // for the leading "0:"
dayDigits = 1;
}
}
else
{
dayDigits = FormattingHelpers.CountDigits(days);
requiredOutputLength += dayDigits + 1; // for the leading "d:" (or "d.")
}
if (value.Ticks < 0)
{
requiredOutputLength++; // for the leading '-' sign
}
if (destination.Length < requiredOutputLength)
{
bytesWritten = 0;
return(false);
}
bytesWritten = requiredOutputLength;
int idx = 0;
// Write leading '-' if necessary
if (value.Ticks < 0)
{
destination[idx++] = Utf8Constants.Minus;
}
// Write day (and separator) if necessary
if (dayDigits > 0)
{
FormattingHelpers.WriteDigits(days, destination.Slice(idx, dayDigits));
idx += dayDigits;
destination[idx++] = (symbol == 'c') ? Utf8Constants.Period : Utf8Constants.Colon;
}
// Write "[h]h:mm:ss"
FormattingHelpers.WriteDigits(hours, destination.Slice(idx, hourDigits));
idx += hourDigits;
destination[idx++] = Utf8Constants.Colon;
FormattingHelpers.WriteDigits((uint)minutes, destination.Slice(idx, 2));
idx += 2;
destination[idx++] = Utf8Constants.Colon;
FormattingHelpers.WriteDigits((uint)seconds, destination.Slice(idx, 2));
idx += 2;
// Write fraction (and separator) if necessary
if (fractionDigits > 0)
{
destination[idx++] = Utf8Constants.Period;
FormattingHelpers.WriteDigits(fraction, destination.Slice(idx, fractionDigits));
idx += fractionDigits;
}
// And we're done!
Debug.Assert(idx == requiredOutputLength);
return(true);
}
