如何将字节数组转换为十六进制字符串,反之亦然?


当前回答

这是我的纯二进制解决方案,不需要库查找,也支持大写/小写:

public static String encode(byte[] bytes, boolean uppercase) {
    char[] result = new char[2 * bytes.length];
    for (int i = 0; i < bytes.length; i++) {
        byte word = bytes[i];
        byte left = (byte) ((0XF0 & word) >>> 4);
        byte right = (byte) ((byte) 0X0F & word);

        int resultIndex = i * 2;
        result[resultIndex] = encode(left, uppercase);
        result[resultIndex + 1] = encode(right, uppercase);
    }
    return new String(result);
}

public static char encode(byte value, boolean uppercase) {
    int characterCase = uppercase ? 0 : 32;
    if (value > 15 || value < 0) {
        return '0';
    }
    if (value > 9) {
        return (char) (value + 0x37 | characterCase);
    }
    return (char) (value + 0x30);
}

其他回答

测试:十六进制字符串到字节数组

我注意到,大多数测试都是在将Bytes数组转换为十六进制字符串的函数上执行的。因此,在这篇文章中,我将关注另一方面:将十六进制字符串转换为字节数组的函数。若您只对结果感兴趣,可以跳到“摘要”部分。测试代码文件在文章末尾提供。

标签

我想根据接受的答案(Tomalak)将函数命名为StringToByteArrayV1,或将其快捷到V1。其余函数将以相同的方式命名:V2、V3、V4、…、。。。,等

参与功能索引

Tomalak的StringToByteArrayV1(公认答案)Mykroft的StringToByteArrayV2(使用SoapHexBinary)drphrozen的StringToByteArrayV3(查找表)CoperNick的StringToByteArrayV4(字节操作)Chris F编写的StringToByteArrayV5_1(字节操作)Chris F的StringToByteArrayV5_2(V5_1+根据Amir Rezaei的评论修改)Chris F的StringToByteArrayV5_3(V5_2+根据Ben Voigt的评论对其进行了修改)(您可以在发布后的测试代码中看到它的最终形状)Ben Mosher编写的StringToByteArrayV6(字节操作)Maratius的StringToByteArrayV7(字节操作-安全版本)Maratius的StringToByteArrayV8(字节操作-不安全版本)StringToByteArrayV9(按Geograph)AlejandroAlis编写的StringToByteArrayV10Fredrik Hu编写的StringToByteArrayV11Maarten Bodewes编写的StringToByteArrayV12ClausAndersen编写的StringToByteArrayV13Stas Makutin编写的StringToByteArrayV14JJJ的StringToByteArrayV15JamieSee的StringToByteArrayV16spacepille的StringToByteArrayV17Gregory Morse编写的StringToByteArrayV18Rick编写的StringToByteArrayV19SandRock的StringToByteArrayV20Paul编写的StringToByteArrayV21

正确性测试

我通过传递1字节的所有256个可能值来测试正确性,然后检查输出是否正确。结果:

V18中以“00”开头的字符串有问题(请参阅Roger Stewart对此的评论)。除了通过所有测试。如果十六进制字符串字母是大写的:所有函数都成功传递如果十六进制字符串字母是小写的,则以下函数失败:V5_1、V5_2、v7、V8、V15、V19

注:V5_3解决了这个问题(V5_1和V5_2)

性能测试

我已经使用Stopwatch类进行了性能测试。

长字符串的性能

input length: 10,000,000 bytes
runs: 100
average elapsed time per run:
V1 = 136.4ms
V2 = 104.5ms
V3 = 22.0ms
V4 = 9.9ms
V5_1 = 10.2ms
V5_2 = 9.0ms
V5_3 = 9.3ms
V6 = 18.3ms
V7 = 9.8ms
V8 = 8.8ms
V9 = 10.2ms
V10 = 19.0ms
V11 = 12.2ms
V12 = 27.4ms
V13 = 21.8ms
V14 = 12.0ms
V15 = 14.9ms
V16 = 15.3ms
V17 = 9.5ms
V18 got excluded from this test, because it was very slow when using very long string
V19 = 222.8ms
V20 = 66.0ms
V21 = 15.4ms

V1 average ticks per run: 1363529.4
V2 is more fast than V1 by: 1.3 times (ticks ratio)
V3 is more fast than V1 by: 6.2 times (ticks ratio)
V4 is more fast than V1 by: 13.8 times (ticks ratio)
V5_1 is more fast than V1 by: 13.3 times (ticks ratio)
V5_2 is more fast than V1 by: 15.2 times (ticks ratio)
V5_3 is more fast than V1 by: 14.8 times (ticks ratio)
V6 is more fast than V1 by: 7.4 times (ticks ratio)
V7 is more fast than V1 by: 13.9 times (ticks ratio)
V8 is more fast than V1 by: 15.4 times (ticks ratio)
V9 is more fast than V1 by: 13.4 times (ticks ratio)
V10 is more fast than V1 by: 7.2 times (ticks ratio)
V11 is more fast than V1 by: 11.1 times (ticks ratio)
V12 is more fast than V1 by: 5.0 times (ticks ratio)
V13 is more fast than V1 by: 6.3 times (ticks ratio)
V14 is more fast than V1 by: 11.4 times (ticks ratio)
V15 is more fast than V1 by: 9.2 times (ticks ratio)
V16 is more fast than V1 by: 8.9 times (ticks ratio)
V17 is more fast than V1 by: 14.4 times (ticks ratio)
V19 is more SLOW than V1 by: 1.6 times (ticks ratio)
V20 is more fast than V1 by: 2.1 times (ticks ratio)
V21 is more fast than V1 by: 8.9 times (ticks ratio)

V18的长串性能

V18 took long time at the previous test, 
so let's decrease length for it:  
input length: 1,000,000 bytes
runs: 100
average elapsed time per run: V1 = 14.1ms , V18 = 146.7ms
V1 average ticks per run: 140630.3
V18 is more SLOW than V1 by: 10.4 times (ticks ratio)

短字符串的性能

input length: 100 byte
runs: 1,000,000
V1 average ticks per run: 14.6
V2 is more fast than V1 by: 1.4 times (ticks ratio)
V3 is more fast than V1 by: 5.9 times (ticks ratio)
V4 is more fast than V1 by: 15.7 times (ticks ratio)
V5_1 is more fast than V1 by: 15.1 times (ticks ratio)
V5_2 is more fast than V1 by: 18.4 times (ticks ratio)
V5_3 is more fast than V1 by: 16.3 times (ticks ratio)
V6 is more fast than V1 by: 5.3 times (ticks ratio)
V7 is more fast than V1 by: 15.7 times (ticks ratio)
V8 is more fast than V1 by: 18.0 times (ticks ratio)
V9 is more fast than V1 by: 15.5 times (ticks ratio)
V10 is more fast than V1 by: 7.8 times (ticks ratio)
V11 is more fast than V1 by: 12.4 times (ticks ratio)
V12 is more fast than V1 by: 5.3 times (ticks ratio)
V13 is more fast than V1 by: 5.2 times (ticks ratio)
V14 is more fast than V1 by: 13.4 times (ticks ratio)
V15 is more fast than V1 by: 9.9 times (ticks ratio)
V16 is more fast than V1 by: 9.2 times (ticks ratio)
V17 is more fast than V1 by: 16.2 times (ticks ratio)
V18 is more fast than V1 by: 1.1 times (ticks ratio)
V19 is more SLOW than V1 by: 1.6 times (ticks ratio)
V20 is more fast than V1 by: 1.9 times (ticks ratio)
V21 is more fast than V1 by: 11.4 times (ticks ratio)

测试代码

在使用以下代码之前,最好先阅读本文下面的免责声明部分https://github.com/Ghosticollis/performance-tests/blob/main/MTestPerformance.cs

总结

由于性能良好,我建议使用以下函数之一,并支持大写和小写:

CoperNick的StringToByteArrayV4StringToByteArrayV9(按Geograph)spacepille的StringToByteArrayV17StringToByteArrayV5_3基本上由Chris F开发(它基于V5_1,但我根据Amir Rezaei和Ben Voigt的评论对其进行了增强)。

以下是V5_3的最终形状:

static byte[] HexStringToByteArrayV5_3(string hexString) {
    int hexStringLength = hexString.Length;
    byte[] b = new byte[hexStringLength / 2];
    for (int i = 0; i < hexStringLength; i += 2) {
        int topChar = hexString[i];
        topChar = (topChar > 0x40 ? (topChar & ~0x20) - 0x37 : topChar - 0x30) << 4;
        int bottomChar = hexString[i + 1];
        bottomChar = bottomChar > 0x40 ? (bottomChar & ~0x20) - 0x37 : bottomChar - 0x30;
        b[i / 2] = (byte)(topChar + bottomChar);
    }
    return b;
}

免责声明

警告:我没有适当的测试知识。这些原始测试的主要目的是快速概述所有发布的函数的优点。如果您需要准确的结果,请使用适当的测试工具。

最后,我想说,我是新来的,在斯塔科弗洛活跃,如果我的职位空缺,我很抱歉。如果您能发表评论,我们将不胜感激。

对于Java 8,我们可以使用Byte.toUnsignedInt

public static String convertBytesToHex(byte[] bytes) {
    StringBuilder result = new StringBuilder();
    for (byte byt : bytes) {
        int decimal = Byte.toUnsignedInt(byt);
        String hex = Integer.toHexString(decimal);
        result.append(hex);
    }
    return result.toString();
}

这个问题也可以使用查找表来解决。这将需要编码器和解码器的少量静态存储器。然而,这种方法很快:

编码器表512字节或1024字节(两次大小写(如果是大写和小写)需要)解码器表256字节或64 KiB(单个字符查找或双字符查找)

我的解决方案使用1024字节作为编码表,256字节用于解码。

解码

private static readonly byte[] LookupTable = new byte[] {
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF,
  0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF
};

private static byte Lookup(char c)
{
  var b = LookupTable[c];
  if (b == 255)
    throw new IOException("Expected a hex character, got " + c);
  return b;
}

public static byte ToByte(char[] chars, int offset)
{
  return (byte)(Lookup(chars[offset]) << 4 | Lookup(chars[offset + 1]));
}

编码

private static readonly char[][] LookupTableUpper;
private static readonly char[][] LookupTableLower;

static Hex()
{
  LookupTableLower = new char[256][];
  LookupTableUpper = new char[256][];
  for (var i = 0; i < 256; i++)
  {
    LookupTableLower[i] = i.ToString("x2").ToCharArray();
    LookupTableUpper[i] = i.ToString("X2").ToCharArray();
  }
}

public static char[] ToCharLower(byte[] b, int bOffset)
{
  return LookupTableLower[b[bOffset]];
}

public static char[] ToCharUpper(byte[] b, int bOffset)
{
  return LookupTableUpper[b[bOffset]];
}

比较

StringBuilderToStringFromBytes:   106148
BitConverterToStringFromBytes:     15783
ArrayConvertAllToStringFromBytes:  54290
ByteManipulationToCharArray:        8444
TableBasedToCharArray:              5651 *

*这个解决方案

Note

在解码过程中,可能会发生IOException和IndexOutOfRangeException(如果字符的值太高>256)。应该实现对流或数组进行去/编码的方法,这只是概念的证明。

.NET 5已添加Convert.ToHexString方法。

对于使用旧版本.NET的用户

internal static class ByteArrayExtensions
{
    
    public static string ToHexString(this byte[] bytes, Casing casing = Casing.Upper)
    {
        Span<char> result = stackalloc char[0];
        if (bytes.Length > 16)
        {
            var array = new char[bytes.Length * 2];
            result = array.AsSpan();
        }
        else
        {
            result = stackalloc char[bytes.Length * 2];
        }

        int pos = 0;
        foreach (byte b in bytes)
        {
            ToCharsBuffer(b, result, pos, casing);
            pos += 2;
        }

        return result.ToString();
    }

    private static void ToCharsBuffer(byte value, Span<char> buffer, int startingIndex = 0, Casing casing = Casing.Upper)
    {
        uint difference = (((uint)value & 0xF0U) << 4) + ((uint)value & 0x0FU) - 0x8989U;
        uint packedResult = ((((uint)(-(int)difference) & 0x7070U) >> 4) + difference + 0xB9B9U) | (uint)casing;

        buffer[startingIndex + 1] = (char)(packedResult & 0xFF);
        buffer[startingIndex] = (char)(packedResult >> 8);
    }
}

public enum Casing : uint
{
    // Output [ '0' .. '9' ] and [ 'A' .. 'F' ].
    Upper = 0,

    // Output [ '0' .. '9' ] and [ 'a' .. 'f' ].
    Lower = 0x2020U,
}

改编自.NET存储库https://github.com/dotnet/runtime/blob/v5.0.3/src/libraries/System.Private.CoreLib/src/System/Convert.cshttps://github.com/dotnet/runtime/blob/v5.0.3/src/libraries/Common/src/System/HexConverter.cs

此版本的ByteArrayToHexViaByteManipulation可能更快。

从我的报告中:

ByteArrayToHexViaByteManipulation3:1.68次平均滴答声(超过1000次),17,5XByteArrayToHexViaByteManipulation2:1,73平均滴答(超过1000次),16,9XByteArrayToHexViaByteManipulation:2,90平均刻度(超过1000次),10,1XByteArrayToHexViaLookupAndShift:3.22平均刻度(超过1000次),9,1X...静态专用只读字符[]hexAlphabet=新字符[]{'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};静态字符串ByteArrayToHexViaByteManipulation3(byte[]字节){char[]c=新字符[bytes.Length*2];字节b;for(int i=0;i<bytes.Length;i++){b=((字节)(字节[i]>>4));c[i*2]=十六进制字母[b];b=((字节)(字节[i]&0xF));c[i*2+1]=十六进制字母[b];}返回新字符串(c);}

我认为这是一个优化:

    static private readonly char[] hexAlphabet = new char[]
        {'0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'};
    static string ByteArrayToHexViaByteManipulation4(byte[] bytes)
    {
        char[] c = new char[bytes.Length * 2];
        for (int i = 0, ptr = 0; i < bytes.Length; i++, ptr += 2)
        {
            byte b = bytes[i];
            c[ptr] = hexAlphabet[b >> 4];
            c[ptr + 1] = hexAlphabet[b & 0xF];
        }
        return new string(c);
    }