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Replace comparer with a bespoke BinarySearch

This commit is contained in:
Ryan Nowak 2016-02-03 18:09:54 -08:00
parent 1a87f6d91a
commit 063bc1f8e8
3 changed files with 165 additions and 26 deletions
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76
src/Microsoft.AspNetCore.Mvc.Core/Internal/PrefixContainer.cs
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@ -41,19 +41,7 @@ namespace Microsoft.AspNetCore.Mvc.Internal
return _sortedValues.Length > 0; // only match empty string when we have some value
}
var prefixComparer = new PrefixComparer(prefix);
var containsPrefix = Array.BinarySearch(_sortedValues, prefix, prefixComparer) > -1;
if (!containsPrefix)
{
// If there's something in the search boundary that starts with the same name
// as the collection prefix that we're trying to find, the binary search would actually fail.
// For example, let's say we have foo.a, foo.bE and foo.b[0]. Calling Array.BinarySearch
// will fail to find foo.b because it will land on foo.bE, then look at foo.a and finally
// failing to find the prefix which is actually present in the container (foo.b[0]).
// Here we're doing another pass looking specifically for collection prefix.
containsPrefix = Array.BinarySearch(_sortedValues, prefix + "[", prefixComparer) > -1;
}
return containsPrefix;
return BinarySearch(prefix) > -1;
}
// Given "foo.bar", "foo.hello", "something.other", foo[abc].baz and asking for prefix "foo" will return:
@ -259,25 +247,63 @@ namespace Microsoft.AspNetCore.Mvc.Internal
}
}
private sealed class PrefixComparer : IComparer<string>
private int BinarySearch(string prefix)
{
private readonly string _prefix;
var start = 0;
var end = _sortedValues.Length - 1;
public PrefixComparer(string prefix)
while (start <= end)
{
_prefix = prefix;
}
public int Compare(string x, string y)
{
var testString = object.ReferenceEquals(x, _prefix) ? y : x;
if (IsPrefixMatch(_prefix, testString))
var pivot = start + ((end - start) / 2);
var candidate = _sortedValues[pivot];
var compare = string.Compare(
prefix,
0,
candidate,
0,
prefix.Length,
StringComparison.OrdinalIgnoreCase);
if (compare == 0)
{
return 0;
Debug.Assert(candidate.StartsWith(prefix, StringComparison.OrdinalIgnoreCase));
// Ok, so now we have a candiate that starts with the prefix. If the candidate is longer than
// the prefix, we need to look at the next character and see if it's a delimiter.
if (candidate.Length == prefix.Length)
{
// Exact match
return pivot;
}
var c = candidate[prefix.Length];
if (c == '.' || c == '[')
{
// Match, followed by delimiter
return pivot;
}
// Ok, so the candidate has some extra text. We need to keep searching, but we know
// the candidate string is considered "greater" than the prefix, so treat it as-if
// the comparer returned a negative number.
//
// Ex:
// prefix: product
// candidate: productId
//
compare = -1;
}
return StringComparer.OrdinalIgnoreCase.Compare(x, y);
if (compare > 0)
{
start = pivot + 1;
}
else
{
end = pivot - 1;
}
}
return ~start;
}
}
}

5
test/Microsoft.AspNetCore.Mvc.Core.Test/Internal/ModelBinderExtensions.cs
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@ -1,4 +1,7 @@
using System.Threading.Tasks;
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System.Threading.Tasks;
namespace Microsoft.AspNetCore.Mvc.ModelBinding
{

110
test/Microsoft.AspNetCore.Mvc.Core.Test/Internal/PrefixContainerTest.cs Normal file
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@ -0,0 +1,110 @@
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using Xunit;
namespace Microsoft.AspNetCore.Mvc.Internal
{
public class PrefixContainerTest
{
[Fact]
public void ContainsPrefix_EmptyCollection_EmptyString_False()
{
// Arrange
var keys = new string[] { };
var container = new PrefixContainer(keys);
// Act
var result = container.ContainsPrefix(string.Empty);
// Assert
Assert.False(result);
}
[Fact]
public void ContainsPrefix_HasEntries_EmptyString_True()
{
// Arrange
var keys = new string[] { "some.prefix" };
var container = new PrefixContainer(keys);
// Act
var result = container.ContainsPrefix(string.Empty);
// Assert
Assert.True(result);
}
[Theory]
[InlineData("a")]
[InlineData("b")]
[InlineData("c")]
[InlineData("d")]
public void ContainsPrefix_HasEntries_ExactMatch(string prefix)
{
// Arrange
var keys = new string[] { "a", "b", "c", "d" };
var container = new PrefixContainer(keys);
// Act
var result = container.ContainsPrefix(prefix);
// Assert
Assert.True(result);
}
[Theory]
[InlineData("a")]
[InlineData("b")]
[InlineData("c")]
[InlineData("d")]
public void ContainsPrefix_HasEntries_NoMatch(string prefix)
{
// Arrange
var keys = new string[] { "ax", "bx", "cx", "dx" };
var container = new PrefixContainer(keys);
// Act
var result = container.ContainsPrefix(prefix);
// Assert
Assert.False(result);
}
[Theory]
[InlineData("a")]
[InlineData("b")]
[InlineData("c")]
[InlineData("d")]
public void ContainsPrefix_HasEntries_PrefixMatch_WithDot(string prefix)
{
// Arrange
var keys = new string[] { "a.x", "b.x", "c.x", "d.x" };
var container = new PrefixContainer(keys);
// Act
var result = container.ContainsPrefix(prefix);
// Assert
Assert.True(result);
}
[Theory]
[InlineData("a")]
[InlineData("b")]
[InlineData("c")]
[InlineData("d")]
public void ContainsPrefix_HasEntries_PrefixMatch_WithSquareBrace(string prefix)
{
// Arrange
var keys = new string[] { "a[x", "b[x", "c[x", "d[x" };
var container = new PrefixContainer(keys);
// Act
var result = container.ContainsPrefix(prefix);
// Assert
Assert.True(result);
}
}
}