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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
#nullable enable
using System.Diagnostics;
namespace System.Buffers.Text
{
public static partial class Utf8Parser
{
/// <summary>
/// Parses a TimeSpan at the start of a Utf8 string.
/// </summary>
/// <param name="source">The Utf8 string to parse</param>
/// <param name="value">Receives the parsed value</param>
/// <param name="bytesConsumed">On a successful parse, receives the length in bytes of the substring that was parsed </param>
/// <param name="standardFormat">Expected format of the Utf8 string</param>
/// <returns>
/// true for success. "bytesConsumed" contains the length in bytes of the substring that was parsed.
/// false if the string was not syntactically valid or an overflow or underflow occurred. "bytesConsumed" is set to 0.
/// </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: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 TryParse(ReadOnlySpan<byte> source, out TimeSpan value, out int bytesConsumed, char standardFormat = default)
{
switch (standardFormat)
{
case default(char):
case 'c':
case 't':
case 'T':
return TryParseTimeSpanC(source, out value, out bytesConsumed);
case 'G':
return TryParseTimeSpanBigG(source, out value, out bytesConsumed);
case 'g':
return TryParseTimeSpanLittleG(source, out value, out bytesConsumed);
default:
return ParserHelpers.TryParseThrowFormatException(out value, out bytesConsumed);
}
}
/// <summary>
/// Parse the fraction portion of a TimeSpan. Must be 1..7 digits. If fewer than 7, zeroes are implied to the right. If more than 7, the TimeSpan
/// parser rejects the string (even if the extra digits are all zeroes.)
/// </summary>
private static bool TryParseTimeSpanFraction(ReadOnlySpan<byte> source, out uint value, out int bytesConsumed)
{
int srcIndex = 0;
if (srcIndex == source.Length)
{
value = default;
bytesConsumed = 0;
return false;
}
uint digit = source[srcIndex] - 48u; // '0'
if (digit > 9)
{
value = default;
bytesConsumed = 0;
return false;
}
srcIndex++;
uint fraction = digit;
int digitCount = 1;
while (srcIndex != source.Length)
{
digit = source[srcIndex] - 48u; // '0'
if (digit > 9)
break;
srcIndex++;
digitCount++;
if (digitCount > Utf8Constants.DateTimeNumFractionDigits)
{
// Yes, TimeSpan fraction parsing is that picky.
value = default;
bytesConsumed = 0;
return false;
}
fraction = 10 * fraction + digit;
}
switch (digitCount)
{
case 7:
break;
case 6:
fraction *= 10;
break;
case 5:
fraction *= 100;
break;
case 4:
fraction *= 1000;
break;
case 3:
fraction *= 10000;
break;
case 2:
fraction *= 100000;
break;
default:
Debug.Assert(digitCount == 1);
fraction *= 1000000;
break;
}
value = fraction;
bytesConsumed = srcIndex;
return true;
}
/// <summary>
/// Overflow-safe TryCreateTimeSpan
/// </summary>
private static bool TryCreateTimeSpan(bool isNegative, uint days, uint hours, uint minutes, uint seconds, uint fraction, out TimeSpan timeSpan)
{
const long MaxMilliSeconds = long.MaxValue / TimeSpan.TicksPerMillisecond;
const long MinMilliSeconds = long.MinValue / TimeSpan.TicksPerMillisecond;
Debug.Assert(days >= 0 && hours >= 0 && minutes >= 0 && seconds >= 00 && fraction >= 0);
if (hours > 23 || minutes > 59 || seconds > 59)
{
timeSpan = default;
return false;
}
Debug.Assert(fraction <= Utf8Constants.MaxDateTimeFraction); // This value comes from TryParseTimeSpanFraction() which already rejects any fraction string longer than 7 digits.
long millisecondsWithoutFraction = (((long)days) * 3600 * 24 + ((long)hours) * 3600 + ((long)minutes) * 60 + seconds) * 1000;
long ticks;
if (isNegative)
{
millisecondsWithoutFraction = -millisecondsWithoutFraction;
if (millisecondsWithoutFraction < MinMilliSeconds)
{
timeSpan = default;
return false;
}
long ticksWithoutFraction = millisecondsWithoutFraction * TimeSpan.TicksPerMillisecond;
if (ticksWithoutFraction < long.MinValue + fraction)
{
timeSpan = default;
return false;
}
ticks = ticksWithoutFraction - fraction;
}
else
{
if (millisecondsWithoutFraction > MaxMilliSeconds)
{
timeSpan = default;
return false;
}
long ticksWithoutFraction = millisecondsWithoutFraction * TimeSpan.TicksPerMillisecond;
if (ticksWithoutFraction > long.MaxValue - fraction)
{
timeSpan = default;
return false;
}
ticks = ticksWithoutFraction + fraction;
}
timeSpan = new TimeSpan(ticks);
return true;
}
}
}
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