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Use string.Create instead of concatenation in PdhHelper #13425

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xtqqczze wants to merge 6 commits into from
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Use string.Create instead of concatenation in PdhHelper #13425

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0d76ecc
Use StringBuilder in loop
xtqqczze Aug 12, 2020
e267df2
Use List<string> instead of StringCollection
xtqqczze Aug 14, 2020
b3de861
Calculate StringBuilder capacity upfront
xtqqczze Aug 16, 2020
5ba99b7
Use Span<char>
xtqqczze Aug 16, 2020
0e363ee
Use string.Create
xtqqczze Aug 28, 2020
38b1c06
Merge branch 'master' into StringBuilder-ConnectToDataSource
xtqqczze Jun 27, 2021
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30 changes: 24 additions & 6 deletions src/Microsoft.PowerShell.Commands.Diagnostics/PdhHelper.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,7 @@
using System.Diagnostics;
using System.Globalization;
using System.Runtime.InteropServices;

using System.Text;
using Microsoft.PowerShell.Commands.GetCounter;
using Microsoft.Win32;

Expand Down Expand Up @@ -531,20 +531,38 @@ public uint ConnectToDataSource(string dataSourceName)
return res;
}

public uint ConnectToDataSource(StringCollection blgFileNames)
public uint ConnectToDataSource(List<string> blgFileNames)
{
if (blgFileNames.Count == 1)
{
return ConnectToDataSource(blgFileNames[0]);
}

string doubleNullTerminated = string.Empty;
foreach (string fileName in blgFileNames)
int length = blgFileNames.Count + 1;
for (int i = 0; i < blgFileNames.Count; i++)
{
doubleNullTerminated += fileName + '\0';
length += blgFileNames[i].Length;
}

doubleNullTerminated += '\0';
string doubleNullTerminated = string.Create(length, blgFileNames, (buf, fileNames) =>
{
int pos = 0;
for (int i = 0; i < fileNames.Count; i++)
{
string fileName = fileNames[i];
int fileNameLength = fileName.Length;
fileName.AsSpan().CopyTo(
buf.Slice(pos, fileNameLength));
pos += fileNameLength;
buf[pos] = '\0';
pos++;
}

buf[pos] = '\0';
pos++;

Debug.Assert(pos == length, "Error constructing double null terminated string.");
});

return ConnectToDataSource(doubleNullTerminated);
}
Expand Down