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Use IndexOfAny in StreamReader ReadLine #75646

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Use IndexOfAny in StreamReader ReadLine #75646

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164 changes: 80 additions & 84 deletions src/libraries/System.Private.CoreLib/src/System/IO/StreamReader.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -780,53 +780,23 @@ private int ReadBuffer(Span<char> userBuffer, out bool readToUserBuffer)
ThrowIfDisposed();
CheckAsyncTaskInProgress();

if (_charPos == _charLen)
{
if (ReadBuffer() == 0)
{
return null;
}
}

StringBuilder? sb = null;
do
bool spilledLineFeed = false;
while (true)
{
int i = _charPos;
do
if (_charPos == _charLen)
{
char ch = _charBuffer[i];
// Note the following common line feed chars:
// \n - UNIX \r\n - DOS \r - Mac
if (ch == '\r' || ch == '\n')
if (ReadBuffer() == 0)
{
string s;
if (sb != null)
{
sb.Append(_charBuffer, _charPos, i - _charPos);
s = sb.ToString();
}
else
{
s = new string(_charBuffer, _charPos, i - _charPos);
}
_charPos = i + 1;
if (ch == '\r' && (_charPos < _charLen || ReadBuffer() > 0))
{
if (_charBuffer[_charPos] == '\n')
{
_charPos++;
}
}
return s;
return sb?.ToString();
}
i++;
} while (i < _charLen);
}

i = _charLen - _charPos;
sb ??= new StringBuilder(i + 80);
sb.Append(_charBuffer, _charPos, i);
} while (ReadBuffer() > 0);
return sb.ToString();
if (TryReadLine(ref sb, ref spilledLineFeed, out string? result))
{
return result;
}
}
}

public override Task<string?> ReadLineAsync() =>
Expand Down Expand Up @@ -881,63 +851,89 @@ private int ReadBuffer(Span<char> userBuffer, out bool readToUserBuffer)

private async Task<string?> ReadLineAsyncInternal(CancellationToken cancellationToken)
{
if (_charPos == _charLen && (await ReadBufferAsync(cancellationToken).ConfigureAwait(false)) == 0)
{
return null;
}

StringBuilder? sb = null;

do
bool spilledLineFeed = false;
while (true)
{
char[] tmpCharBuffer = _charBuffer;
int tmpCharLen = _charLen;
int tmpCharPos = _charPos;
int i = tmpCharPos;
if (_charPos == _charLen)
{
if ((await ReadBufferAsync(cancellationToken).ConfigureAwait(false)) == 0)
{
return sb?.ToString();
}
}

do
if (TryReadLine(ref sb, ref spilledLineFeed, out string? result))
{
char ch = tmpCharBuffer[i];
return result;
}
}
}

// Note the following common line feed chars:
// \n - UNIX \r\n - DOS \r - Mac
if (ch == '\r' || ch == '\n')
{
string s;
private bool TryReadLine(ref StringBuilder? sb, ref bool spilledLineFeed, [NotNullWhen(true)] out string? result)
{
// Special case if the buffer runs out of space between \r and (potentially) \n
if (spilledLineFeed)
{
if (_charBuffer[_charPos] == '\n')
{
_charPos++;
}

if (sb != null)
{
sb.Append(tmpCharBuffer, tmpCharPos, i - tmpCharPos);
s = sb.ToString();
}
else
{
s = new string(tmpCharBuffer, tmpCharPos, i - tmpCharPos);
}
// sb cannot be null here
result = sb!.ToString();
return true;
}

_charPos = tmpCharPos = i + 1;
ReadOnlySpan<char> segment = _charBuffer.AsSpan(_charPos, _charLen - _charPos);

if (ch == '\r' && (tmpCharPos < tmpCharLen || (await ReadBufferAsync(cancellationToken).ConfigureAwait(false)) > 0))
int newLineIndex = segment.IndexOfAny('\r', '\n');
if ((uint)newLineIndex < (uint)segment.Length)
{
_charPos += newLineIndex + 1;
if (segment[newLineIndex] == '\r')
{
int nextCharIndex = newLineIndex + 1;
if ((uint)nextCharIndex < (uint)segment.Length)
{
if (segment[nextCharIndex] == '\n')
{
tmpCharPos = _charPos;
if (_charBuffer[tmpCharPos] == '\n')
{
_charPos = ++tmpCharPos;
}
_charPos++;
}

return s;
}
else
{
Debug.Assert(_charPos == _charLen);
// At the end of buffer, but there might be another line feed.
// Stash the current string and consume the line feed next iteration
sb ??= new StringBuilder(newLineIndex);
sb.Append(segment.Slice(0, newLineIndex));
spilledLineFeed = true;

result = null;
return false;
}
}

i++;
} while (i < tmpCharLen);
segment = segment.Slice(0, newLineIndex);
if (sb != null)
{
sb.Append(segment);
result = sb.ToString();
}
else
{
result = new string(segment);
}
return true;
}

i = tmpCharLen - tmpCharPos;
sb ??= new StringBuilder(i + 80);
sb.Append(tmpCharBuffer, tmpCharPos, i);
} while (await ReadBufferAsync(cancellationToken).ConfigureAwait(false) > 0);
sb ??= new StringBuilder(segment.Length + 80);
sb.Append(segment);
_charPos = _charLen;

return sb.ToString();
result = null;
return false;
}

public override Task<string> ReadToEndAsync() => ReadToEndAsync(default);
Expand Down