如何将十六进制字符串转换为字节数组？

Question

我们可以使用C#中的内置函数将十六进制字符串转换为字节数组,还是必须为此创建自定义方法？

Answer 1

这是一个很好玩的LINQ示例.

public static byte[] StringToByteArray(string hex) {
    return Enumerable.Range(0, hex.Length)
                     .Where(x => x % 2 == 0)
                     .Select(x => Convert.ToByte(hex.Substring(x, 2), 16))
                     .ToArray();
}

Answer 2

我做了一些研究,发现byte.Parse甚至比Convert.ToByte慢.我能想到的最快转换使用每字节大约15个滴答.

    public static byte[] StringToByteArrayFastest(string hex) {
        if (hex.Length % 2 == 1)
            throw new Exception("The binary key cannot have an odd number of digits");

        byte[] arr = new byte[hex.Length >> 1];

        for (int i = 0; i < hex.Length >> 1; ++i)
        {
            arr[i] = (byte)((GetHexVal(hex[i << 1]) << 4) + (GetHexVal(hex[(i << 1) + 1])));
        }

        return arr;
    }

    public static int GetHexVal(char hex) {
        int val = (int)hex;
        //For uppercase A-F letters:
        return val - (val < 58 ? 48 : 55);
        //For lowercase a-f letters:
        //return val - (val < 58 ? 48 : 87);
        //Or the two combined, but a bit slower:
        //return val - (val < 58 ? 48 : (val < 97 ? 55 : 87));
    }

//也适用于.NET Micro Framework,其中(在SDK4.3中)byte.Parse(string)仅允许整数格式.

Answer 3

以下代码通过逐字节解析字符串将十六进制字符串更改为字节数组.

public static byte[] ConvertHexStringToByteArray(string hexString)
{
    if (hexString.Length % 2 != 0)
    {
        throw new ArgumentException(String.Format(CultureInfo.InvariantCulture, "The binary key cannot have an odd number of digits: {0}", hexString));
    }

    byte[] data = new byte[hexString.Length / 2];
    for (int index = 0; index < data.Length; index++)
    {
        string byteValue = hexString.Substring(index * 2, 2);
        data[index] = byte.Parse(byteValue, NumberStyles.HexNumber, CultureInfo.InvariantCulture);
    }

    return data; 
}

Answer 4

我认为这可行.

public static byte[] StrToByteArray(string str)
    {
        Dictionary<string, byte> hexindex = new Dictionary<string, byte>();
        for (int i = 0; i <= 255; i++)
            hexindex.Add(i.ToString("X2"), (byte)i);

        List<byte> hexres = new List<byte>();
        for (int i = 0; i < str.Length; i += 2)            
            hexres.Add(hexindex[str.Substring(i, 2)]);

        return hexres.ToArray();
    }