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Some optimisations to async reading. (#1171)

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MoveToContentAsync is often called in states where it will immediately
return true without any reading. In this case return AsyncUtils.True
avoiding allocation or async state-machine.

DoReadAsync is a very heavily hit method, and can often be fulfilled
without creating another state machine, so do this.

The remaining looping async case is the only use of ParsePostValueAsync,
so inline it into the calling method, so there is one less task
allocation.

Return value of EatWhitespaceAsync is never used, returning void reduces
the number of locals an hence the size of the state-machine. Do the same
for EatWhitespace though the impact is less.
This commit is contained in:
Jon Hanna
2017-01-13 20:41:18 +13:00
committed by James Newton-King
parent ba04246a16
commit dcae8e220d
3 changed files with 141 additions and 145 deletions
Download Patch File Download Diff File Expand all files Collapse all files
Src/Newtonsoft.Json/JsonReader.Async.cs
+18 -7
View File
@@ -27,7 +27,6 @@
using System;
using System.Collections.Generic;
using System.Globalization;
using System.Threading;
using System.Threading.Tasks;
using Newtonsoft.Json.Utilities;
@@ -210,19 +209,31 @@ namespace Newtonsoft.Json
return await ReadAsync(cancellationToken).ConfigureAwait(false) && await MoveToContentAsync(cancellationToken).ConfigureAwait(false);
}
internal async Task<bool> MoveToContentAsync(CancellationToken cancellationToken)
internal Task<bool> MoveToContentAsync(CancellationToken cancellationToken)
{
switch (TokenType)
{
case JsonToken.None:
case JsonToken.Comment:
return MoveToContentFromNonContentAsync(cancellationToken);
default:
return AsyncUtils.True;
}
}
private async Task<bool> MoveToContentFromNonContentAsync(CancellationToken cancellationToken)
{
while (true)
{
if (!await ReadAsync(cancellationToken).ConfigureAwait(false))
{
return false;
}
switch (TokenType)
{
case JsonToken.None:
case JsonToken.Comment:
if (!await ReadAsync(cancellationToken).ConfigureAwait(false))
{
return false;
}
break;
default:
return true;
Src/Newtonsoft.Json/JsonTextReader.Async.cs
+114 -124
View File
@@ -58,59 +58,125 @@ namespace Newtonsoft.Json
return _safeAsync ? DoReadAsync(cancellationToken) : base.ReadAsync(cancellationToken);
}
internal async Task<bool> DoReadAsync(CancellationToken cancellationToken)
internal Task<bool> DoReadAsync(CancellationToken cancellationToken)
{
EnsureBuffer();
while (true)
switch (_currentState)
{
switch (_currentState)
{
case State.Start:
case State.Property:
case State.Array:
case State.ArrayStart:
case State.Constructor:
case State.ConstructorStart:
return await ParseValueAsync(cancellationToken).ConfigureAwait(false);
case State.Object:
case State.ObjectStart:
return await ParseObjectAsync(cancellationToken).ConfigureAwait(false);
case State.PostValue:
case State.Start:
case State.Property:
case State.Array:
case State.ArrayStart:
case State.Constructor:
case State.ConstructorStart:
return ParseValueAsync(cancellationToken);
case State.Object:
case State.ObjectStart:
return ParseObjectAsync(cancellationToken);
case State.PostValue:
return LoopReadAsync(cancellationToken);
case State.Finished:
return ReadFromFinishedAsync(cancellationToken);
default:
throw JsonReaderException.Create(this, "Unexpected state: {0}.".FormatWith(CultureInfo.InvariantCulture, CurrentState));
}
}
// returns true if it hits
// end of object or array
if (await ParsePostValueAsync(cancellationToken).ConfigureAwait(false))
private async Task<bool> LoopReadAsync(CancellationToken cancellationToken)
{
while (_currentState == State.PostValue)
{
char currentChar = _chars[_charPos];
switch (currentChar)
{
case '\0':
if (_charsUsed == _charPos)
{
return true;
if (await ReadDataAsync(false, cancellationToken).ConfigureAwait(false) == 0)
{
_currentState = State.Finished;
}
}
else
{
_charPos++;
}
break;
case State.Finished:
if (await EnsureCharsAsync(0, false, cancellationToken).ConfigureAwait(false))
case '}':
_charPos++;
SetToken(JsonToken.EndObject);
return true;
case ']':
_charPos++;
SetToken(JsonToken.EndArray);
return true;
case ')':
_charPos++;
SetToken(JsonToken.EndConstructor);
return true;
case '/':
await ParseCommentAsync(true, cancellationToken).ConfigureAwait(false);
return true;
case ',':
_charPos++;
// finished parsing
SetStateBasedOnCurrent();
break;
case ' ':
case StringUtils.Tab:
// eat
_charPos++;
break;
case StringUtils.CarriageReturn:
await ProcessCarriageReturnAsync(false, cancellationToken).ConfigureAwait(false);
break;
case StringUtils.LineFeed:
ProcessLineFeed();
break;
default:
if (char.IsWhiteSpace(currentChar))
{
await EatWhitespaceAsync(false, cancellationToken).ConfigureAwait(false);
if (_isEndOfFile)
{
SetToken(JsonToken.None);
return false;
}
if (_chars[_charPos] == '/')
{
await ParseCommentAsync(true, cancellationToken).ConfigureAwait(false);
return true;
}
throw JsonReaderException.Create(this, "Additional text encountered after finished reading JSON content: {0}.".FormatWith(CultureInfo.InvariantCulture, _chars[_charPos]));
// eat
_charPos++;
}
else
{
throw JsonReaderException.Create(this, "After parsing a value an unexpected character was encountered: {0}.".FormatWith(CultureInfo.InvariantCulture, currentChar));
}
SetToken(JsonToken.None);
return false;
default:
throw JsonReaderException.Create(this, "Unexpected state: {0}.".FormatWith(CultureInfo.InvariantCulture, CurrentState));
break;
}
}
return await DoReadAsync(cancellationToken).ConfigureAwait(false);
}
private async Task<bool> ReadFromFinishedAsync(CancellationToken cancellationToken)
{
if (await EnsureCharsAsync(0, false, cancellationToken).ConfigureAwait(false))
{
await EatWhitespaceAsync(cancellationToken).ConfigureAwait(false);
if (_isEndOfFile)
{
SetToken(JsonToken.None);
return false;
}
if (_chars[_charPos] == '/')
{
await ParseCommentAsync(true, cancellationToken).ConfigureAwait(false);
return true;
}
throw JsonReaderException.Create(this, "Additional text encountered after finished reading JSON content: {0}.".FormatWith(CultureInfo.InvariantCulture, _chars[_charPos]));
}
SetToken(JsonToken.None);
return false;
}
private Task<int> ReadDataAsync(bool append, CancellationToken cancellationToken)
@@ -631,7 +697,7 @@ namespace Newtonsoft.Json
}
}
private async Task<bool> ParsePostValueAsync(CancellationToken cancellationToken)
private async Task EatWhitespaceAsync(CancellationToken cancellationToken)
{
while (true)
{
@@ -644,81 +710,7 @@ namespace Newtonsoft.Json
{
if (await ReadDataAsync(false, cancellationToken).ConfigureAwait(false) == 0)
{
_currentState = State.Finished;
return false;
}
}
else
{
_charPos++;
}
break;
case '}':
_charPos++;
SetToken(JsonToken.EndObject);
return true;
case ']':
_charPos++;
SetToken(JsonToken.EndArray);
return true;
case ')':
_charPos++;
SetToken(JsonToken.EndConstructor);
return true;
case '/':
await ParseCommentAsync(true, cancellationToken).ConfigureAwait(false);
return true;
case ',':
_charPos++;
// finished parsing
SetStateBasedOnCurrent();
return false;
case ' ':
case StringUtils.Tab:
// eat
_charPos++;
break;
case StringUtils.CarriageReturn:
await ProcessCarriageReturnAsync(false, cancellationToken).ConfigureAwait(false);
break;
case StringUtils.LineFeed:
ProcessLineFeed();
break;
default:
if (char.IsWhiteSpace(currentChar))
{
// eat
_charPos++;
}
else
{
throw JsonReaderException.Create(this, "After parsing a value an unexpected character was encountered: {0}.".FormatWith(CultureInfo.InvariantCulture, currentChar));
}
break;
}
}
}
private async Task<bool> EatWhitespaceAsync(bool oneOrMore, CancellationToken cancellationToken)
{
bool finished = false;
bool ateWhitespace = false;
while (!finished)
{
char currentChar = _chars[_charPos];
switch (currentChar)
{
case '\0':
if (_charsUsed == _charPos)
{
if (await ReadDataAsync(false, cancellationToken).ConfigureAwait(false) == 0)
{
finished = true;
return;
}
}
else
@@ -735,18 +727,15 @@ namespace Newtonsoft.Json
default:
if (currentChar == ' ' || char.IsWhiteSpace(currentChar))
{
ateWhitespace = true;
_charPos++;
}
else
{
finished = true;
return;
}
break;
}
}
return !oneOrMore || ateWhitespace;
}
private async Task ParseStringAsync(char quote, ReadType readType, CancellationToken cancellationToken)
@@ -811,7 +800,7 @@ namespace Newtonsoft.Json
{
if (await MatchValueWithTrailingSeparatorAsync("new", cancellationToken).ConfigureAwait(false))
{
await EatWhitespaceAsync(false, cancellationToken).ConfigureAwait(false);
await EatWhitespaceAsync(cancellationToken).ConfigureAwait(false);
int initialPosition = _charPos;
int endPosition;
@@ -871,7 +860,7 @@ namespace Newtonsoft.Json
_stringReference = new StringReference(_chars, initialPosition, endPosition - initialPosition);
string constructorName = _stringReference.ToString();
EatWhitespace(false);
await EatWhitespaceAsync(cancellationToken).ConfigureAwait(false);
if (_chars[_charPos] != '(')
{
@@ -958,7 +947,7 @@ namespace Newtonsoft.Json
propertyName = _stringReference.ToString();
}
await EatWhitespaceAsync(false, cancellationToken).ConfigureAwait(false);
await EatWhitespaceAsync(cancellationToken).ConfigureAwait(false);
if (_chars[_charPos] != ':')
{
@@ -1079,9 +1068,10 @@ namespace Newtonsoft.Json
{
if (await EnsureCharsAsync(0, false, cancellationToken).ConfigureAwait(false))
{
await EatWhitespaceAsync(false, cancellationToken).ConfigureAwait(false);
await EatWhitespaceAsync(cancellationToken).ConfigureAwait(false);
if (_isEndOfFile)
{
SetToken(JsonToken.None);
return;
}
Src/Newtonsoft.Json/JsonTextReader.cs
+9 -14
View File
@@ -404,7 +404,7 @@ namespace Newtonsoft.Json
case State.Finished:
if (EnsureChars(0, false))
{
EatWhitespace(false);
EatWhitespace();
if (_isEndOfFile)
{
SetToken(JsonToken.None);
@@ -1018,7 +1018,7 @@ namespace Newtonsoft.Json
{
if (EnsureChars(0, false))
{
EatWhitespace(false);
EatWhitespace();
if (_isEndOfFile)
{
return;
@@ -1513,7 +1513,7 @@ namespace Newtonsoft.Json
propertyName = _stringReference.ToString();
}
EatWhitespace(false);
EatWhitespace();
if (_chars[_charPos] != ':')
{
@@ -1727,11 +1727,9 @@ namespace Newtonsoft.Json
OnNewLine(_charPos);
}
private bool EatWhitespace(bool oneOrMore)
private void EatWhitespace()
{
bool finished = false;
bool ateWhitespace = false;
while (!finished)
while (true)
{
char currentChar = _chars[_charPos];
@@ -1742,7 +1740,7 @@ namespace Newtonsoft.Json
{
if (ReadData(false) == 0)
{
finished = true;
return;
}
}
else
@@ -1759,25 +1757,22 @@ namespace Newtonsoft.Json
default:
if (currentChar == ' ' || char.IsWhiteSpace(currentChar))
{
ateWhitespace = true;
_charPos++;
}
else
{
finished = true;
return;
}
break;
}
}
return (!oneOrMore || ateWhitespace);
}
private void ParseConstructor()
{
if (MatchValueWithTrailingSeparator("new"))
{
EatWhitespace(false);
EatWhitespace();
int initialPosition = _charPos;
int endPosition;
@@ -1837,7 +1832,7 @@ namespace Newtonsoft.Json
_stringReference = new StringReference(_chars, initialPosition, endPosition - initialPosition);
string constructorName = _stringReference.ToString();
EatWhitespace(false);
EatWhitespace();
if (_chars[_charPos] != '(')
{