我优化了一个扩展方法来比较两个流是否相等(byte-for-byte) - 知道这是一个热门的方法,我试图尽可能优化它(流可以达到几兆字节的长度)。我基本上是想出了以下方法:If Condition True Block当条件为False
[StructLayout(LayoutKind.Explicit)]
struct Converter
{
[FieldOffset(0)]
public Byte[] Byte;
[FieldOffset(0)]
public UInt64[] UInt64;
}
/// <summary>
/// Compares two streams for byte-by-byte equality.
/// </summary>
/// <param name="target">The target stream.</param>
/// <param name="compareTo">The stream to compare the target to.</param>
/// <returns>A value indicating whether the two streams are identical.</returns>
public static bool CompareBytes(this Stream target, Stream compareTo)
{
if (target == null && compareTo == null)
return true;
if (target == null || compareTo == null)
return false;
if (target.Length != compareTo.Length)
return false;
if (object.ReferenceEquals(target, compareTo))
return true;
if (!target.CanRead || !target.CanSeek)
throw new ArgumentOutOfRangeException("target");
if (!compareTo.CanRead || !compareTo.CanSeek)
throw new ArgumentOutOfRangeException("target");
lock (target)
{
lock (compareTo)
{
var origa = target.Position;
var origb = compareTo.Position;
try
{
target.Position = compareTo.Position = 0;
// Shrink the number of comparisons.
var arr1 = new byte[4096];
var convert1 = new Converter() { Byte = arr1 };
var arr2 = new byte[4096];
var convert2 = new Converter() { Byte = arr2 };
int len;
while ((len = target.Read(arr1, 0, 4096)) != 0)
{
if (compareTo.Read(arr2, 0, 4096) != len)
return false;
for (var i = 0; i < (len/8) + 1; i++)
if (convert1.UInt64[i] != convert2.UInt64[i])
return false;
}
return true;
}
finally
{
target.Position = origa;
compareTo.Position = origb;
}
}
}
}
的问题是,convert1.UInt64[i] != convert2.UInt64[i]
if
块(返回false
),甚至当值相等正在评估。我单独检查了每一项,然后检查了“不等于”的结果。 我在纯怀疑:
我还没有与指令指针乱 - 这是怎样的代码执行和钟表销是活。
任何想法如何发生?
如果你添加{ – rerun
看起来像一个参考比较(不同的对象,总是false)正在发生,而不是一个值比较 – Alex
我很困惑,两个结构属性都有FieldOffset 0,你怎么知道你比较苹果和苹果? – mtijn