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Fix redundant iteration while splitting lines #14720

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hez2010 wants to merge 1 commit into from
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Fix redundant iteration while splitting lines #14720

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16 changes: 9 additions & 7 deletions src/System.Management.Automation/FormatAndOutput/common/ComplexWriter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -416,10 +416,12 @@ private static StringCollection GenerateLinesWithoutWordWrap(DisplayCells displa

for (int k = 0; k < lines.Length; k++)
{
if (lines[k] == null || displayCells.Length(lines[k]) <= firstLineLen)
var currentLine = lines[k];
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@xtqqczze xtqqczze Feb 13, 2021

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Suggested change
var currentLine = lines[k];
string currentLine = lines[k];

We should respect EditorConfig setting: csharp_style_var_for_built_in_types = false.


if (currentLine == null || displayCells.Length(currentLine) <= firstLineLen)
{
// we do not need to split further, just add
retVal.Add(lines[k]);
retVal.Add(currentLine);
continue;
}

Expand All @@ -432,15 +434,15 @@ private static StringCollection GenerateLinesWithoutWordWrap(DisplayCells displa

int offset = 0; // offset into the line we are splitting

while (true)
while (currentLine.Length > offset)
{
// acquire the current active display line length (it can very from call to call)
int currentDisplayLen = accumulator.ActiveLen;

// determine if the current tail would fit or not

// for the remaining part of the string, determine its display cell count
int currentCellsToFit = displayCells.Length(lines[k], offset);
int currentCellsToFit = displayCells.Length(currentLine, offset);

// determine if we fit into the line
int excessCells = currentCellsToFit - currentDisplayLen;
Expand All @@ -449,7 +451,7 @@ private static StringCollection GenerateLinesWithoutWordWrap(DisplayCells displa
{
// we are not at the end of the string, select a sub string
// that would fit in the remaining display length
int charactersToAdd = displayCells.GetHeadSplitLength(lines[k], offset, currentDisplayLen);
int charactersToAdd = displayCells.GetHeadSplitLength(currentLine, offset, currentDisplayLen);

if (charactersToAdd <= 0)
{
Expand All @@ -463,7 +465,7 @@ private static StringCollection GenerateLinesWithoutWordWrap(DisplayCells displa
else
{
// of the given length, add it to the accumulator
accumulator.AddLine(lines[k].Substring(offset, charactersToAdd));
accumulator.AddLine(currentLine.Substring(offset, charactersToAdd));
}

// increase the offset by the # of characters added
Expand All @@ -472,7 +474,7 @@ private static StringCollection GenerateLinesWithoutWordWrap(DisplayCells displa
else
{
// we reached the last (partial) line, we add it all
accumulator.AddLine(lines[k].Substring(offset));
accumulator.AddLine(currentLine.Substring(offset));
break;
}
}
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13 changes: 10 additions & 3 deletions src/System.Management.Automation/FormatAndOutput/out-console/ConsoleLineOutput.cs
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Expand Up @@ -87,8 +87,15 @@ internal DisplayCellsPSHost(PSHostRawUserInterface rawUserInterface)

internal override int Length(string str, int offset)
{
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@xtqqczze xtqqczze Feb 14, 2021

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Are the changes to this method necessary to fix the issue?

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@hez2010 hez2010 Feb 14, 2021

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No. But it's a refactor to Length to reduce ops while str is empty.

Dbg.Assert(offset >= 0, "offset >= 0");
Dbg.Assert(string.IsNullOrEmpty(str) || (offset < str.Length), "offset < str.Length");
if (string.IsNullOrEmpty(str))
{
return 0;
}

if (offset < 0 || offset >= str.Length)
{
throw PSTraceSource.NewArgumentException(nameof(offset));
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@xtqqczze xtqqczze Feb 14, 2021

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In particular this exception.

}

try
{
Expand All @@ -100,7 +107,7 @@ internal override int Length(string str, int offset)
// we will fallback to the default value.
}

return string.IsNullOrEmpty(str) ? 0 : str.Length - offset;
return str.Length - offset;
}

internal override int Length(string str)
Expand Down