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体验新版 GitCode,发现更多精彩内容 >>
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24f1acda
编写于
2月 22, 2021
作者:
S
Stephen Toub
提交者:
GitHub
2月 22, 2021
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电子邮件补丁
差异文件
Special-case Enumerable.SequenceEqual for byte[] (#48287)
上级
970d347a
变更
2
隐藏空白更改
内联
并排
Showing
2 changed file
with
50 addition
and
5 deletion
+50
-5
src/libraries/System.Linq/src/System/Linq/SequenceEqual.cs
src/libraries/System.Linq/src/System/Linq/SequenceEqual.cs
+18
-5
src/libraries/System.Linq/tests/SequenceEqualTests.cs
src/libraries/System.Linq/tests/SequenceEqualTests.cs
+32
-0
未找到文件。
src/libraries/System.Linq/src/System/Linq/SequenceEqual.cs
浏览文件 @
24f1acda
...
...
@@ -12,11 +12,6 @@ public static partial class Enumerable
public
static
bool
SequenceEqual
<
TSource
>(
this
IEnumerable
<
TSource
>
first
,
IEnumerable
<
TSource
>
second
,
IEqualityComparer
<
TSource
>?
comparer
)
{
if
(
comparer
==
null
)
{
comparer
=
EqualityComparer
<
TSource
>.
Default
;
}
if
(
first
==
null
)
{
ThrowHelper
.
ThrowArgumentNullException
(
ExceptionArgument
.
first
);
...
...
@@ -27,6 +22,24 @@ public static bool SequenceEqual<TSource>(this IEnumerable<TSource> first, IEnum
ThrowHelper
.
ThrowArgumentNullException
(
ExceptionArgument
.
second
);
}
if
(
comparer
==
null
)
{
// It's relatively common to see code (especially in tests and testing frameworks) that ends up
// using Enumerable.SequenceEqual to compare two byte arrays. Using ReadOnlySpan.SequenceEqual
// is significantly faster than accessing each byte via the array's IList<byte> interface
// implementation. So, we special-case byte[] here. It would be nice to be able to delegate
// to ReadOnlySpan.SequenceEqual for all TSource[] arrays where TSource is a value type and
// implements IEquatable<TSource>, but there's no good way without reflection to convince
// the C# compiler to let us delegate, as ReadOnlySpan.SequenceEqual requires an IEquatable<T>
// constraint on its type parameter, and Enumerable.SequenceEqual lacks one on its type parameter.
if
(
typeof
(
TSource
)
==
typeof
(
byte
)
&&
first
is
byte
[]
firstArr
&&
second
is
byte
[]
secondArr
)
{
return
((
ReadOnlySpan
<
byte
>)
firstArr
).
SequenceEqual
(
secondArr
);
}
comparer
=
EqualityComparer
<
TSource
>.
Default
;
}
if
(
first
is
ICollection
<
TSource
>
firstCol
&&
second
is
ICollection
<
TSource
>
secondCol
)
{
if
(
firstCol
.
Count
!=
secondCol
.
Count
)
...
...
src/libraries/System.Linq/tests/SequenceEqualTests.cs
浏览文件 @
24f1acda
...
...
@@ -214,5 +214,37 @@ public void SecondSourceNull()
AssertExtensions
.
Throws
<
ArgumentNullException
>(
"second"
,
()
=>
first
.
SequenceEqual
(
second
));
}
[
Fact
]
public
void
ByteArrays_SpecialCasedButExpectedBehavior
()
{
AssertExtensions
.
Throws
<
ArgumentNullException
>(
"first"
,
()
=>
((
byte
[])
null
).
SequenceEqual
(
new
byte
[
1
]));
AssertExtensions
.
Throws
<
ArgumentNullException
>(
"second"
,
()
=>
new
byte
[
1
].
SequenceEqual
(
null
));
Assert
.
False
(
new
byte
[
1
].
SequenceEqual
(
new
byte
[
0
]));
Assert
.
False
(
new
byte
[
0
].
SequenceEqual
(
new
byte
[
1
]));
var
r
=
new
Random
();
for
(
int
i
=
0
;
i
<
32
;
i
++)
{
byte
[]
arr
=
new
byte
[
i
];
r
.
NextBytes
(
arr
);
byte
[]
same
=
(
byte
[])
arr
.
Clone
();
Assert
.
True
(
arr
.
SequenceEqual
(
same
));
Assert
.
True
(
same
.
SequenceEqual
(
arr
));
Assert
.
True
(
same
.
SequenceEqual
(
arr
.
ToList
()));
Assert
.
True
(
same
.
ToList
().
SequenceEqual
(
arr
));
Assert
.
True
(
same
.
ToList
().
SequenceEqual
(
arr
.
ToList
()));
if
(
i
>
0
)
{
byte
[]
diff
=
(
byte
[])
arr
.
Clone
();
diff
[^
1
]++;
Assert
.
False
(
arr
.
SequenceEqual
(
diff
));
Assert
.
False
(
diff
.
SequenceEqual
(
arr
));
}
}
}
}
}
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