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Utf8Parser.Guid.cs
256 lines (221 loc) · 8.75 KB
/
Utf8Parser.Guid.cs
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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.
namespace System.Buffers.Text
{
public static partial class Utf8Parser
{
/// <summary>
/// Parses a Guid 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:
/// D (default) nnnnnnnn-nnnn-nnnn-nnnn-nnnnnnnnnnnn
/// B {nnnnnnnn-nnnn-nnnn-nnnn-nnnnnnnnnnnn}
/// P (nnnnnnnn-nnnn-nnnn-nnnn-nnnnnnnnnnnn)
/// N nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn
/// </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 Guid value, out int bytesConsumed, char standardFormat = default)
{
FastPath:
if (standardFormat == default)
{
return TryParseGuidCore(source, out value, out bytesConsumed, ends: 0);
}
switch (standardFormat)
{
case 'D':
standardFormat = default;
goto FastPath;
case 'B':
return TryParseGuidCore(source, out value, out bytesConsumed, ends: '{' | ('}' << 8));
case 'P':
return TryParseGuidCore(source, out value, out bytesConsumed, ends: '(' | (')' << 8));
case 'N':
return TryParseGuidN(source, out value, out bytesConsumed);
default:
return ParserHelpers.TryParseThrowFormatException(source, out value, out bytesConsumed);
}
}
// nnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnn (not very Guid-like, but the format is what it is...)
private static bool TryParseGuidN(ReadOnlySpan<byte> text, out Guid value, out int bytesConsumed)
{
if (text.Length < 32)
{
value = default;
bytesConsumed = 0;
return false;
}
if (!TryParseUInt32X(text.Slice(0, 8), out uint i1, out int justConsumed) || justConsumed != 8)
{
value = default;
bytesConsumed = 0;
return false; // 8 digits
}
if (!TryParseUInt16X(text.Slice(8, 4), out ushort i2, out justConsumed) || justConsumed != 4)
{
value = default;
bytesConsumed = 0;
return false; // next 4 digits
}
if (!TryParseUInt16X(text.Slice(12, 4), out ushort i3, out justConsumed) || justConsumed != 4)
{
value = default;
bytesConsumed = 0;
return false; // next 4 digits
}
if (!TryParseUInt16X(text.Slice(16, 4), out ushort i4, out justConsumed) || justConsumed != 4)
{
value = default;
bytesConsumed = 0;
return false; // next 4 digits
}
if (!TryParseUInt64X(text.Slice(20), out ulong i5, out justConsumed) || justConsumed != 12)
{
value = default;
bytesConsumed = 0;
return false; // next 4 digits
}
bytesConsumed = 32;
value = new Guid((int)i1, (short)i2, (short)i3, (byte)(i4 >> 8), (byte)i4,
(byte)(i5 >> 40), (byte)(i5 >> 32), (byte)(i5 >> 24), (byte)(i5 >> 16), (byte)(i5 >> 8), (byte)i5);
return true;
}
// {8-4-4-4-12}, where number is the number of hex digits, and {/} are ends.
private static bool TryParseGuidCore(ReadOnlySpan<byte> source, out Guid value, out int bytesConsumed, int ends)
{
int expectedCodingUnits = 36 + ((ends != 0) ? 2 : 0); // 32 hex digits + 4 delimiters + 2 optional ends
if (source.Length < expectedCodingUnits)
{
value = default;
bytesConsumed = 0;
return false;
}
// The 'ends' parameter is a 16-bit value where the byte denoting the starting
// brace is at byte position 0 and the byte denoting the closing brace is at
// byte position 1. If no braces are expected, has value 0.
// Default: ends = 0
// Braces: ends = "}{"
// Parens: ends = ")("
if (ends != 0)
{
if (source[0] != (byte)ends)
{
value = default;
bytesConsumed = 0;
return false;
}
source = source.Slice(1); // skip beginning
ends >>= 8; // shift the closing brace to byte position 0
}
if (!TryParseUInt32X(source, out uint i1, out int justConsumed))
{
value = default;
bytesConsumed = 0;
return false;
}
if (justConsumed != 8)
{
value = default;
bytesConsumed = 0;
return false; // 8 digits
}
if (source[justConsumed] != '-')
{
value = default;
bytesConsumed = 0;
return false;
}
source = source.Slice(9); // justConsumed + 1 for delimiter
if (!TryParseUInt16X(source, out ushort i2, out justConsumed))
{
value = default;
bytesConsumed = 0;
return false;
}
if (justConsumed != 4)
{
value = default;
bytesConsumed = 0;
return false; // 4 digits
}
if (source[justConsumed] != '-')
{
value = default;
bytesConsumed = 0;
return false;
}
source = source.Slice(5); // justConsumed + 1 for delimiter
if (!TryParseUInt16X(source, out ushort i3, out justConsumed))
{
value = default;
bytesConsumed = 0;
return false;
}
if (justConsumed != 4)
{
value = default;
bytesConsumed = 0;
return false; // 4 digits
}
if (source[justConsumed] != '-')
{
value = default;
bytesConsumed = 0;
return false;
}
source = source.Slice(5); // justConsumed + 1 for delimiter
if (!TryParseUInt16X(source, out ushort i4, out justConsumed))
{
value = default;
bytesConsumed = 0;
return false;
}
if (justConsumed != 4)
{
value = default;
bytesConsumed = 0;
return false; // 4 digits
}
if (source[justConsumed] != '-')
{
value = default;
bytesConsumed = 0;
return false;
}
source = source.Slice(5); // justConsumed + 1 for delimiter
if (!TryParseUInt64X(source, out ulong i5, out justConsumed))
{
value = default;
bytesConsumed = 0;
return false;
}
if (justConsumed != 12)
{
value = default;
bytesConsumed = 0;
return false; // 12 digits
}
if (ends != 0 && source[justConsumed] != (byte)ends)
{
value = default;
bytesConsumed = 0;
return false;
}
bytesConsumed = expectedCodingUnits;
value = new Guid((int)i1, (short)i2, (short)i3, (byte)(i4 >> 8), (byte)i4,
(byte)(i5 >> 40), (byte)(i5 >> 32), (byte)(i5 >> 24), (byte)(i5 >> 16), (byte)(i5 >> 8), (byte)i5);
return true;
}
}
}