Last Updated: October 10, 2020

Fast byte array to hex string conversion in C#

This is by far the fastest way to convert a list of bytes to an hex string.
Can you beat it?

private static readonly string[] _base16CharTable = new[]
{
    "00", "01", "02", "03", "04", "05", "06", "07", 
    "08", "09", "0A", "0B", "0C", "0D", "0E", "0F",
    "10", "11", "12", "13", "14", "15", "16", "17", 
    "18", "19", "1A", "1B", "1C", "1D", "1E", "1F",
    "20", "21", "22", "23", "24", "25", "26", "27", 
    "28", "29", "2A", "2B", "2C", "2D", "2E", "2F",
    "30", "31", "32", "33", "34", "35", "36", "37", 
    "38", "39", "3A", "3B", "3C", "3D", "3E", "3F",
    "40", "41", "42", "43", "44", "45", "46", "47", 
    "48", "49", "4A", "4B", "4C", "4D", "4E", "4F",
    "50", "51", "52", "53", "54", "55", "56", "57", 
    "58", "59", "5A", "5B", "5C", "5D", "5E", "5F",
    "60", "61", "62", "63", "64", "65", "66", "67", 
    "68", "69", "6A", "6B", "6C", "6D", "6E", "6F",
    "70", "71", "72", "73", "74", "75", "76", "77", 
    "78", "79", "7A", "7B", "7C", "7D", "7E", "7F",
    "80", "81", "82", "83", "84", "85", "86", "87", 
    "88", "89", "8A", "8B", "8C", "8D", "8E", "8F",
    "90", "91", "92", "93", "94", "95", "96", "97", 
    "98", "99", "9A", "9B", "9C", "9D", "9E", "9F",
    "A0", "A1", "A2", "A3", "A4", "A5", "A6", "A7", 
    "A8", "A9", "AA", "AB", "AC", "AD", "AE", "AF",
    "B0", "B1", "B2", "B3", "B4", "B5", "B6", "B7", 
    "B8", "B9", "BA", "BB", "BC", "BD", "BE", "BF",
    "C0", "C1", "C2", "C3", "C4", "C5", "C6", "C7", 
    "C8", "C9", "CA", "CB", "CC", "CD", "CE", "CF",
    "D0", "D1", "D2", "D3", "D4", "D5", "D6", "D7", 
    "D8", "D9", "DA", "DB", "DC", "DD", "DE", "DF",
    "E0", "E1", "E2", "E3", "E4", "E5", "E6", "E7", 
    "E8", "E9", "EA", "EB", "EC", "ED", "EE", "EF",
    "F0", "F1", "F2", "F3", "F4", "F5", "F6", "F7", 
    "F8", "F9", "FA", "FB", "FC", "FD", "FE", "FF"
};

public static string ConvertToBase16Fast2(IList<byte> input)
{
    if (input == null || input.Count <= 0)
        return string.Empty;

    var stringBuilder = new StringBuilder(input.Count * 2);

    for (var i = 0; i < input.Count; ++i)        
        stringBuilder.Append(_base16CharTable[input[i]]);

    return stringBuilder.ToString();
}

Written by Sascha Kiefer

Say Thanks

Respond

Related protips

Don't use Array.forEach, use for() instead

1.234M

Why you should always append DOM elements using DocumentFragments

96.51K

Box / Unboxing vs. Encapsulation: Java's `Map<Something, Integer>`

77.9K

2 Responses

Add your response

drdigit

The fastest appender in StringBuilder is the character appender. If you replace the char table with a flat string you will gain better performance depending on the size of the input up to 30%. Also defining a capacity for the StringBuilder may become a performance killer for really long input on heavy loaded systems.

private static readonly string flat = string.Join("", _base16CharTable);

public static string YesICan(IList<byte> input)
{
if (input == null || input.Count < 1)
return string.Empty;
int
x = 0,
i = 0;
var sb = new StringBuilder();
while (i < input.Count)
{
x = input[i++] << 1;
sb.Append(flat[x]);
sb.Append(flat[x + 1]);
}
return sb.ToString();
}

For an unsafe code approach (beating all) check this:
http://www.codeproject.com/Tips/447938/High-performance-Csharp-byte-array-to-hex-string-t

Cheers

over 1 year ago ·

mrnetpilgrim

How about new Convert.ToHexString ?

over 1 year ago ·