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Reduce allocations in MakePath() method #10027

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Merged
adityapatwardhan merged 2 commits into from
Aug 9, 2019
Merged

Reduce allocations in MakePath() method #10027

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eebbb01
Reduce allocations in MakePath() method
iSazonov Jun 28, 2019
31df893
Fix if child is a slash and update commants
iSazonov Jul 1, 2019
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68 changes: 12 additions & 56 deletions src/System.Management.Automation/namespaces/NavigationProviderBase.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -308,7 +308,7 @@ protected virtual string MakePath(string parent, string child)
/// If the <paramref name="childIsLeaf"/> is True, then we don't normalize the child path, and would do
/// some checks to decide whether to normalize the parent path.
/// </remarks>
/// <returns></returns>
/// <returns>New path string.</returns>
protected string MakePath(string parent, string child, bool childIsLeaf)
{
using (PSTransactionManager.GetEngineProtectionScope())
Expand All @@ -318,33 +318,24 @@ protected string MakePath(string parent, string child, bool childIsLeaf)
if (parent == null &&
child == null)
{
// If both are null it is an error

throw PSTraceSource.NewArgumentException("parent");
throw PSTraceSource.NewArgumentException(nameof(parent));
}
else if (string.IsNullOrEmpty(parent) &&
string.IsNullOrEmpty(child))
{
// If both are empty, just return the empty string.

if (string.IsNullOrEmpty(parent) &&
string.IsNullOrEmpty(child))
{
result = string.Empty;
}
else if (string.IsNullOrEmpty(parent) &&
!string.IsNullOrEmpty(child))
{
// If the parent is empty but the child is not, return the
// child

result = NormalizePath(child);
}
else if (!string.IsNullOrEmpty(parent) &&
string.IsNullOrEmpty(child))
(string.IsNullOrEmpty(child) ||
child.Equals(StringLiterals.DefaultPathSeparatorString, StringComparison.Ordinal) ||
child.Equals(StringLiterals.AlternatePathSeparatorString, StringComparison.Ordinal)))
{
// If the child is empty but the parent is not, return the
// parent with the path separator appended.

// Append the default path separator

if (parent.EndsWith(StringLiterals.DefaultPathSeparator))
{
result = parent;
Expand All @@ -357,7 +348,6 @@ protected string MakePath(string parent, string child, bool childIsLeaf)
else
{
// Both parts are not empty so join them

// 'childIsLeaf == true' indicates that 'child' is actually the name of a child item and
// guaranteed to exist. In this case, we don't normalize the child path.
if (childIsLeaf)
Expand All @@ -368,51 +358,17 @@ protected string MakePath(string parent, string child, bool childIsLeaf)
{
// Normalize the path so that only the default path separator is used as a
// separator even if the user types the alternate slash.

parent = NormalizePath(parent);
child = NormalizePath(child);
}

// Joins the paths

StringBuilder builder = new StringBuilder(parent, parent.Length + child.Length + 1);

if (parent.EndsWith(StringLiterals.DefaultPathSeparator))
ReadOnlySpan<char> appendChild = child.AsSpan();
if (child.StartsWith(StringLiterals.DefaultPathSeparator))
{
if (child.StartsWith(StringLiterals.DefaultPathSeparator))
{
builder.Append(child, 1, child.Length - 1);
}
else
{
builder.Append(child);
}
}
else
{
if (child.StartsWith(StringLiterals.DefaultPathSeparator))
{
if (parent.Length == 0)
{
builder.Append(child, 1, child.Length - 1);
}
else
{
builder.Append(child);
}
}
else
{
if (parent.Length > 0 && child.Length > 0)
{
builder.Append(StringLiterals.DefaultPathSeparator);
}

builder.Append(child);
}
appendChild = appendChild.Slice(1);
}

result = builder.ToString();
result = IO.Path.Join(parent.AsSpan(), appendChild);
}

return result;
Expand Down