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Simplify KnownHeaders lookup in SocketsHttpHandler (dotnet#34974)
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* Simplify KnownHeaders lookup

* Update src/libraries/System.Net.Http/src/System/Net/Http/Headers/KnownHeaders.cs

Co-Authored-By: David Shulman <[email protected]>

Co-authored-by: David Shulman <[email protected]>
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@stephentoub @davidsh
stephentoub and davidsh authored Apr 15, 2020
1 parent 1cfccd2 commit cd024d4
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Showing 3 changed files with 255 additions and 112 deletions.
227 changes: 115 additions & 112 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 @@ -141,204 +141,207 @@ public BytePtrAccessor(byte* p, int length)
public char this[int index] => (char)_p[index];
}

// Find possible known header match via lookup on length and a distinguishing char for that length.
// Matching is case-insenstive.
// NOTE: 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.
/// <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>(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.

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

case 3:
switch (key[0])
switch (key[0] | 0x20)
{
case 'A': case 'a': return Age; // [A]ge
case 'P': case 'p': return P3P; // [P]3P
case 'T': case 't': return TSV; // [T]SV
case 'V': case 'v': return Via; // [V]ia
case 'a': return Age; // [A]ge
case 'p': return P3P; // [P]3P
case 't': return TSV; // [T]SV
case 'v': return Via; // [V]ia
}
break;

case 4:
switch (key[0])
switch (key[0] | 0x20)
{
case 'D': case 'd': return Date; // [D]ate
case 'E': case 'e': return ETag; // [E]Tag
case 'F': case 'f': return From; // [F]rom
case 'H': case 'h': return Host; // [H]ost
case 'L': case 'l': return Link; // [L]ink
case 'V': case 'v': return Vary; // [V]ary
case 'd': return Date; // [D]ate
case 'e': return ETag; // [E]Tag
case 'f': return From; // [F]rom
case 'h': return Host; // [H]ost
case 'l': return Link; // [L]ink
case 'v': return Vary; // [V]ary
}
break;

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

case 6:
switch (key[0])
switch (key[0] | 0x20)
{
case 'A': case 'a': return Accept; // [A]ccept
case 'C': case 'c': return Cookie; // [C]ookie
case 'E': case 'e': return Expect; // [E]xpect
case 'O': case 'o': return Origin; // [O]rigin
case 'P': case 'p': return Pragma; // [P]ragma
case 'S': case 's': return Server; // [S]erver
case 'a': return Accept; // [A]ccept
case 'c': return Cookie; // [C]ookie
case 'e': return Expect; // [E]xpect
case 'o': return Origin; // [O]rigin
case 'p': return Pragma; // [P]ragma
case 's': return Server; // [S]erver
}
break;

case 7:
switch (key[0])
switch (key[0] | 0x20)
{
case ':': return PseudoStatus; // [:]status
case 'A': case 'a': return AltSvc; // [A]lt-Svc
case 'C': case 'c': return Cookie2; // [C]ookie2
case 'E': case 'e': return Expires; // [E]xpires
case 'R': case 'r':
switch (key[3])
case 'a': return AltSvc; // [A]lt-Svc
case 'c': return Cookie2; // [C]ookie2
case 'e': return Expires; // [E]xpires
case 'r':
switch (key[3] | 0x20)
{
case 'E': case 'e': return Referer; // [R]ef[e]rer
case 'R': case 'r': return Refresh; // [R]ef[r]esh
case 'e': return Referer; // [R]ef[e]rer
case 'r': return Refresh; // [R]ef[r]esh
}
break;
case 'T': case 't': return Trailer; // [T]railer
case 'U': case 'u': return Upgrade; // [U]pgrade
case 'W': case 'w': return Warning; // [W]arning
case 'X': case 'x': return XCache; // [X]-Cache
case 't': return Trailer; // [T]railer
case 'u': return Upgrade; // [U]pgrade
case 'w': return Warning; // [W]arning
case 'x': return XCache; // [X]-Cache
}
break;

case 8:
switch (key[3])
switch (key[3] | 0x20)
{
case 'M': case 'm': return IfMatch; // If-[M]atch
case 'R': case 'r': return IfRange; // If-[R]ange
case 'A': case 'a': return Location; // Loc[a]tion
case '-': return AltUsed; // Alt[-]Used
case 'a': return Location; // Loc[a]tion
case 'm': return IfMatch; // If-[M]atch
case 'r': return IfRange; // If-[R]ange
}
break;

case 9:
switch (key[0])
{
case 'E': case 'e': return ExpectCT; // [E]xpect-CT
}
break;
return ExpectCT; // Expect-CT

case 10:
switch (key[0])
switch (key[0] | 0x20)
{
case 'C': case 'c': return Connection; // [C]onnection
case 'K': case 'k': return KeepAlive; // [K]eep-Alive
case 'S': case 's': return SetCookie; // [S]et-Cookie
case 'U': case 'u': return UserAgent; // [U]ser-Agent
case 'c': return Connection; // [C]onnection
case 'k': return KeepAlive; // [K]eep-Alive
case 's': return SetCookie; // [S]et-Cookie
case 'u': return UserAgent; // [U]ser-Agent
}
break;

case 11:
switch (key[0])
switch (key[0] | 0x20)
{
case 'C': case 'c': return ContentMD5; // [C]ontent-MD5
case 'R': case 'r': return RetryAfter; // [R]etry-After
case 'S': case 's': return SetCookie2; // [S]et-Cookie2
case 'c': return ContentMD5; // [C]ontent-MD5
case 'r': return RetryAfter; // [R]etry-After
case 's': return SetCookie2; // [S]et-Cookie2
}
break;

case 12:
switch (key[2])
switch (key[2] | 0x20)
{
case 'C': case 'c': return AcceptPatch; // Ac[c]ept-Patch
case 'N': case 'n': return ContentType; // Co[n]tent-Type
case 'X': case 'x': return MaxForwards; // Ma[x]-Forwards
case 'M': case 'm': return XMSEdgeRef; // X-[M]SEdge-Ref
case 'P': case 'p': return XPoweredBy; // X-[P]owered-By
case 'R': case 'r': return XRequestID; // X-[R]equest-ID
case 'c': return AcceptPatch; // Ac[c]ept-Patch
case 'm': return XMSEdgeRef; // X-[M]SEdge-Ref
case 'n': return ContentType; // Co[n]tent-Type
case 'p': return XPoweredBy; // X-[P]owered-By
case 'r': return XRequestID; // X-[R]equest-ID
case 'x': return MaxForwards; // Ma[x]-Forwards
}
break;

case 13:
switch (key[12])
switch (key[12] | 0x20)
{
case 'S': case 's': return AcceptRanges; // Accept-Range[s]
case 'N': case 'n': return Authorization; // Authorizatio[n]
case 'L': case 'l': return CacheControl; // Cache-Contro[l]
case 'E': case 'e': return ContentRange; // Content-Rang[e]
case 'H': case 'h': return IfNoneMatch; // If-None-Matc[h]
case 'D': case 'd': return LastModified; // Last-Modifie[d]
case 'T': case 't': return ProxySupport; // Proxy-Suppor[t]
case 'G': case 'g': return ServerTiming; // Server-Timin[g]
case 'd': return LastModified; // Last-Modifie[d]
case 'e': return ContentRange; // Content-Rang[e]
case 'g': return ServerTiming; // Server-Timin[g]
case 'h': return IfNoneMatch; // If-None-Matc[h]
case 'l': return CacheControl; // Cache-Contro[l]
case 'n': return Authorization; // Authorizatio[n]
case 's': return AcceptRanges; // Accept-Range[s]
case 't': return ProxySupport; // Proxy-Suppor[t]
}
break;

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

case 15:
switch (key[7])
switch (key[7] | 0x20)
{
case '-': return XFrameOptions; // X-Frame[-]Options
case 'M': case 'm': return XUACompatible; // X-UA-Co[m]patible
case 'E': case 'e': return AcceptEncoding; // Accept-[E]ncoding
case 'K': case 'k': return PublicKeyPins; // Public-[K]ey-Pins
case 'L': case 'l': return AcceptLanguage; // Accept-[L]anguage
case 'R': case 'r': return ReferrerPolicy; // Referre[r]-Policy
case 'e': return AcceptEncoding; // Accept-[E]ncoding
case 'k': return PublicKeyPins; // Public-[K]ey-Pins
case 'l': return AcceptLanguage; // Accept-[L]anguage
case 'm': return XUACompatible; // X-UA-Co[m]patible
case 'r': return ReferrerPolicy; // Referre[r]-Policy
}
break;

case 16:
switch (key[11])
switch (key[11] | 0x20)
{
case 'O': case 'o': return ContentEncoding; // Content-Enc[o]ding
case 'G': case 'g': return ContentLanguage; // Content-Lan[g]uage
case 'A': case 'a': return ContentLocation; // Content-Loc[a]tion
case 'C': case 'c':
switch (key[0])
case 'a': return ContentLocation; // Content-Loc[a]tion
case 'c':
switch (key[0] | 0x20)
{
case 'P': case 'p': return ProxyConnection; // [P]roxy-Conne[c]tion
case 'X': case 'x': return XXssProtection; // [X]-XSS-Prote[c]tion
case 'p': return ProxyConnection; // [P]roxy-Conne[c]tion
case 'x': return XXssProtection; // [X]-XSS-Prote[c]tion
}
break;
case 'I': case 'i': return WWWAuthenticate; // WWW-Authent[i]cate
case 'R': case 'r': return XAspNetVersion; // X-AspNet-Ve[r]sion
case 'g': return ContentLanguage; // Content-Lan[g]uage
case 'i': return WWWAuthenticate; // WWW-Authent[i]cate
case 'o': return ContentEncoding; // Content-Enc[o]ding
case 'r': return XAspNetVersion; // X-AspNet-Ve[r]sion
}
break;

case 17:
switch (key[0])
switch (key[0] | 0x20)
{
case 'I': case 'i': return IfModifiedSince; // [I]f-Modified-Since
case 'S': case 's': return SecWebSocketKey; // [S]ec-WebSocket-Key
case 'T': case 't': return TransferEncoding; // [T]ransfer-Encoding
case 'i': return IfModifiedSince; // [I]f-Modified-Since
case 's': return SecWebSocketKey; // [S]ec-WebSocket-Key
case 't': return TransferEncoding; // [T]ransfer-Encoding
}
break;

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

case 19:
switch (key[0])
switch (key[0] | 0x20)
{
case 'C': case 'c': return ContentDisposition; // [C]ontent-Disposition
case 'I': case 'i': return IfUnmodifiedSince; // [I]f-Unmodified-Since
case 'P': case 'p': return ProxyAuthorization; // [P]roxy-Authorization
case 'c': return ContentDisposition; // [C]ontent-Disposition
case 'i': return IfUnmodifiedSince; // [I]f-Unmodified-Since
case 'p': return ProxyAuthorization; // [P]roxy-Authorization
}
break;

Expand All @@ -349,11 +352,11 @@ public BytePtrAccessor(byte* p, int length)
return SecWebSocketVersion; // Sec-WebSocket-Version

case 22:
switch (key[0])
switch (key[0] | 0x20)
{
case 'A': case 'a': return AccessControlMaxAge; // [A]ccess-Control-Max-Age
case 'S': case 's': return SecWebSocketProtocol; // [S]ec-WebSocket-Protocol
case 'X': case 'x': return XContentTypeOptions; // [X]-Content-Type-Options
case 'a': return AccessControlMaxAge; // [A]ccess-Control-Max-Age
case 's': return SecWebSocketProtocol; // [S]ec-WebSocket-Protocol
case 'x': return XContentTypeOptions; // [X]-Content-Type-Options
}
break;

Expand All @@ -364,21 +367,21 @@ public BytePtrAccessor(byte* p, int length)
return SecWebSocketExtensions; // Sec-WebSocket-Extensions

case 25:
switch (key[0])
switch (key[0] | 0x20)
{
case 'S': case 's': return StrictTransportSecurity; // [S]trict-Transport-Security
case 'U': case 'u': return UpgradeInsecureRequests; // [U]pgrade-Insecure-Requests
case 's': return StrictTransportSecurity; // [S]trict-Transport-Security
case 'u': return UpgradeInsecureRequests; // [U]pgrade-Insecure-Requests
}
break;

case 27:
return AccessControlAllowOrigin; // Access-Control-Allow-Origin

case 28:
switch (key[21])
switch (key[21] | 0x20)
{
case 'H': case 'h': return AccessControlAllowHeaders; // Access-Control-Allow-[H]eaders
case 'M': case 'm': return AccessControlAllowMethods; // Access-Control-Allow-[M]ethods
case 'h': return AccessControlAllowHeaders; // Access-Control-Allow-[H]eaders
case 'm': return AccessControlAllowMethods; // Access-Control-Allow-[M]ethods
}
break;

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