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[no-merge] Revert "Remove unsafe code from Http KnownHeaders (#114757)" #120680

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[no-merge] Revert "Remove unsafe code from Http KnownHeaders (#114757)" #120680

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108 changes: 72 additions & 36 deletions src/libraries/System.Net.Http/src/System/Net/Http/Headers/KnownHeaders.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,7 @@

using System.Net.Http.HPack;
using System.Net.Http.QPack;
using System.Numerics;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Text;

namespace System.Net.Http.Headers
Expand Down Expand Up @@ -118,29 +117,63 @@ internal static class KnownHeaders
private static AltSvcHeaderParser? GetAltSvcHeaderParser() => AltSvcHeaderParser.Parser;
#endif

// Helper interface for making GetCandidate generic over strings, utf8, etc
private interface IHeaderNameAccessor
{
int Length { get; }
char this[int index] { get; }
}

private readonly struct StringAccessor : IHeaderNameAccessor
{
private readonly string _string;

public StringAccessor(string s)
{
_string = s;
}

public int Length => _string.Length;
public char this[int index] => _string[index];
}

// Can't use Span here as it's unsupported.
private readonly unsafe struct BytePtrAccessor : IHeaderNameAccessor
{
private readonly byte* _p;
private readonly int _length;

public BytePtrAccessor(byte* p, int length)
{
_p = p;
_length = length;
}

public int Length => _length;
public char this[int index] => (char)_p[index];
}

/// <summary>
/// Find possible known header match via lookup on length and a distinguishing char for that length.
/// </summary>
/// <remarks>
/// Matching is case-insensitive. Because of this, we do not preserve the case of the original header,
/// whether from the wire or from the user explicitly setting a known header using a header name string.
/// </remarks>
private static KnownHeader? GetCandidate<T>(ReadOnlySpan<T> key)
where T : struct, INumberBase<T>
private static KnownHeader? GetCandidate<T>(T key)
where T : struct, IHeaderNameAccessor // Enforce struct for performance
{
// Lookup is performed by first switching on the header name's length, and then switching
// on the most unique position in that length's string.

[MethodImpl(MethodImplOptions.AggressiveInlining)]
static int GetLower(T value) => int.CreateTruncating(value) | 0x20;

switch (key.Length)
int length = key.Length;
switch (length)
{
case 2:
return TE; // TE

case 3:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 'a': return Age; // [A]ge
case 'p': return P3P; // [P]3P
Expand All @@ -150,7 +183,7 @@ internal static class KnownHeaders
break;

case 4:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 'd': return Date; // [D]ate
case 'e': return ETag; // [E]Tag
Expand All @@ -162,15 +195,15 @@ internal static class KnownHeaders
break;

case 5:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 'a': return Allow; // [A]llow
case 'r': return Range; // [R]ange
}
break;

case 6:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 'a': return Accept; // [A]ccept
case 'c': return Cookie; // [C]ookie
Expand All @@ -182,14 +215,14 @@ internal static class KnownHeaders
break;

case 7:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case ':': return PseudoStatus; // [:]status
case 'a': return AltSvc; // [A]lt-Svc
case 'c': return Cookie2; // [C]ookie2
case 'e': return Expires; // [E]xpires
case 'r':
switch (GetLower(key[3]))
switch (key[3] | 0x20)
{
case 'e': return Referer; // [R]ef[e]rer
case 'r': return Refresh; // [R]ef[r]esh
Expand All @@ -203,7 +236,7 @@ internal static class KnownHeaders
break;

case 8:
switch (GetLower(key[3]))
switch (key[3] | 0x20)
{
case '-': return AltUsed; // Alt[-]Used
case 'a': return Location; // Loc[a]tion
Expand All @@ -216,7 +249,7 @@ internal static class KnownHeaders
return ExpectCT; // Expect-CT

case 10:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 'c': return Connection; // [C]onnection
case 'k': return KeepAlive; // [K]eep-Alive
Expand All @@ -226,7 +259,7 @@ internal static class KnownHeaders
break;

case 11:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 'c': return ContentMD5; // [C]ontent-MD5
case 'g': return GrpcStatus; // [g]rpc-status
Expand All @@ -237,7 +270,7 @@ internal static class KnownHeaders
break;

case 12:
switch (GetLower(key[5]))
switch (key[5] | 0x20)
{
case 'd': return XMSEdgeRef; // X-MSE[d]ge-Ref
case 'e': return XPoweredBy; // X-Pow[e]red-By
Expand All @@ -250,12 +283,12 @@ internal static class KnownHeaders
break;

case 13:
switch (GetLower(key[12]))
switch (key[12] | 0x20)
{
case 'd': return LastModified; // Last-Modifie[d]
case 'e': return ContentRange; // Content-Rang[e]
case 'g':
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 's': return ServerTiming; // [S]erver-Timin[g]
case 'g': return GrpcEncoding; // [g]rpc-encodin[g]
Expand All @@ -270,15 +303,15 @@ internal static class KnownHeaders
break;

case 14:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 'a': return AcceptCharset; // [A]ccept-Charset
case 'c': return ContentLength; // [C]ontent-Length
}
break;

case 15:
switch (GetLower(key[7]))
switch (key[7] | 0x20)
{
case '-': return XFrameOptions; // X-Frame[-]Options
case 'e': return AcceptEncoding; // Accept-[E]ncoding
Expand All @@ -290,11 +323,11 @@ internal static class KnownHeaders
break;

case 16:
switch (GetLower(key[11]))
switch (key[11] | 0x20)
{
case 'a': return ContentLocation; // Content-Loc[a]tion
case 'c':
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 'p': return ProxyConnection; // [P]roxy-Conne[c]tion
case 'x': return XXssProtection; // [X]-XSS-Prote[c]tion
Expand All @@ -308,7 +341,7 @@ internal static class KnownHeaders
break;

case 17:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 'i': return IfModifiedSince; // [I]f-Modified-Since
case 's': return SecWebSocketKey; // [S]ec-WebSocket-Key
Expand All @@ -317,15 +350,15 @@ internal static class KnownHeaders
break;

case 18:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 'p': return ProxyAuthenticate; // [P]roxy-Authenticate
case 'x': return XContentDuration; // [X]-Content-Duration
}
break;

case 19:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 'c': return ContentDisposition; // [C]ontent-Disposition
case 'i': return IfUnmodifiedSince; // [I]f-Unmodified-Since
Expand All @@ -341,7 +374,7 @@ internal static class KnownHeaders
return SecWebSocketVersion; // Sec-WebSocket-Version

case 22:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 'a': return AccessControlMaxAge; // [A]ccess-Control-Max-Age
case 's': return SecWebSocketProtocol; // [S]ec-WebSocket-Protocol
Expand All @@ -356,7 +389,7 @@ internal static class KnownHeaders
return SecWebSocketExtensions; // Sec-WebSocket-Extensions

case 25:
switch (GetLower(key[0]))
switch (key[0] | 0x20)
{
case 's': return StrictTransportSecurity; // [S]trict-Transport-Security
case 'u': return UpgradeInsecureRequests; // [U]pgrade-Insecure-Requests
Expand All @@ -367,7 +400,7 @@ internal static class KnownHeaders
return AccessControlAllowOrigin; // Access-Control-Allow-Origin

case 28:
switch (GetLower(key[21]))
switch (key[21] | 0x20)
{
case 'h': return AccessControlAllowHeaders; // Access-Control-Allow-[H]eaders
case 'm': return AccessControlAllowMethods; // Access-Control-Allow-[M]ethods
Expand All @@ -385,9 +418,9 @@ internal static class KnownHeaders
return null;
}

public static KnownHeader? TryGetKnownHeader(string name)
internal static KnownHeader? TryGetKnownHeader(string name)
{
KnownHeader? candidate = GetCandidate<char>(name);
KnownHeader? candidate = GetCandidate(new StringAccessor(name));
if (candidate != null && StringComparer.OrdinalIgnoreCase.Equals(name, candidate.Name))
{
return candidate;
Expand All @@ -396,12 +429,15 @@ internal static class KnownHeaders
return null;
}

public static KnownHeader? TryGetKnownHeader(ReadOnlySpan<byte> name)
internal static unsafe KnownHeader? TryGetKnownHeader(ReadOnlySpan<byte> name)
{
KnownHeader? candidate = GetCandidate(name);
if (candidate != null && Ascii.EqualsIgnoreCase(name, candidate.Name))
fixed (byte* p = &MemoryMarshal.GetReference(name))
{
return candidate;
KnownHeader? candidate = GetCandidate(new BytePtrAccessor(p, name.Length));
if (candidate != null && Ascii.EqualsIgnoreCase(name, candidate.Name))
{
return candidate;
}
}

return null;
Expand Down
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