在C#中将ulong映射为long？

2019-06-27 22:05:14 阅读：1023 来源： 互联网

我试图将ulong映射到long(反之亦然),并将uint映射到int(反之亦然),如下所示 – 以便将值保存在带有签名类型的MS-SQL数据库中仅限整数和大整数.

我这样做是因为我必须检查(在数据库中)一个数字(uint,ulong)是否在一堆uint / ulong范围内的哪个范围内(IPs-v4& v6;实际上ulong实际上是uint128组成的两个ulongs).

有没有更有效的方法来实现这一点,我有这里的代码：

public static ulong SignedLongToUnsignedLong(long signedLongValue)
{
    ulong backConverted = 0;

    // map ulong to long [ 9223372036854775808 = abs(long.MinValue) ]
    if (signedLongValue < 0)
    {
        // Cannot take abs from MinValue
        backConverted = (ulong)System.Math.Abs(signedLongValue - 1);
        backConverted = 9223372036854775808 - backConverted - 1;
    }
    else
    {
        backConverted = (ulong)signedLongValue;
        backConverted += 9223372036854775808;
    }

    return backConverted;
}


public static long UnsignedLongToSignedLong(ulong unsignedLongValue)
{
    // map ulong to long [ 9223372036854775808 = abs(long.MinValue) ]
    return (long) (unsignedLongValue - 9223372036854775808);
}


public static int UnsignedIntToSignedInt(uint unsignedIntValue)
{
    // map uint to int [ 2147483648 = abs(long.MinValue) ]
    return (int)(unsignedIntValue - 2147483648);
}


public static uint SignedIntToUnsignedInt(int signedIntValue)
{
    uint backConverted = 0;

    // map ulong to long [ 2147483648 = abs(long.MinValue) ]
    if (signedIntValue < 0)
    {
        // Cannot take abs from MinValue
        backConverted = (uint)System.Math.Abs(signedIntValue - 1);
        backConverted = 2147483648 - backConverted - 1;
    }
    else
    {
        backConverted = (uint)signedIntValue;
        backConverted += 2147483648;
    }

    return backConverted;
}


public static void TestLong()
{
    long min_long = -9223372036854775808;
    long max_long = 9223372036854775807;

    ulong min_ulong = ulong.MinValue; // 0
    ulong max_ulong = ulong.MaxValue; // 18446744073709551615  = (2^64)-1

    long dbValueMin = UnsignedLongToSignedLong(min_ulong);
    long dbValueMax = UnsignedLongToSignedLong(max_ulong);


    ulong valueFromDbMin = SignedLongToUnsignedLong(dbValueMin);
    ulong valueFromDbMax = SignedLongToUnsignedLong(dbValueMax);

    System.Console.WriteLine(dbValueMin);
    System.Console.WriteLine(dbValueMax);

    System.Console.WriteLine(valueFromDbMin);
    System.Console.WriteLine(valueFromDbMax);
}


public static void TestInt()
{
    int min_int = -2147483648; // int.MinValue
    int max_int = 2147483647; // int.MaxValue

    uint min_uint= uint.MinValue; // 0
    uint max_uint = uint.MaxValue; // 4294967295 = (2^32)-1


    int dbValueMin = UnsignedIntToSignedInt(min_uint);
    int dbValueMax = UnsignedIntToSignedInt(max_uint);

    uint valueFromDbMin = SignedIntToUnsignedInt(dbValueMin);
    uint valueFromDbMax = SignedIntToUnsignedInt(dbValueMax);

    System.Console.WriteLine(dbValueMin);
    System.Console.WriteLine(dbValueMax);

    System.Console.WriteLine(valueFromDbMin);
    System.Console.WriteLine(valueFromDbMax);
}

解决方法:

要从ulong映射到long,请强制转换并添加long.MinValue.要从long返回到ulong,请减去long.MinValue和cast.在任何一种情况下,都使用未经检查的上下文,以便忽略溢出条件.

public static long MapUlongToLong(ulong ulongValue)
{
    return unchecked((long)ulongValue + long.MinValue);
}

public static ulong MapLongToUlong(long longValue)
{
    return unchecked((ulong)(longValue - long.MinValue));
}

uint和int的逻辑完全相似.

标签：c,net,uint,data-conversion,ulong
来源： https://codeday.me/bug/20190627/1309065.html

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在C#中将ulong映射为long？