HexConverter

High-Performance hexadecimal converter with support of Span<T> and buffering.

Installation

Available on nuget

PM> Install-Package HexConverter

Requirements:

System.Memory (>= 4.5.3)

Why?

Dotnet core implementation do not take advantage of Span<T> to slice the memory without allocations and don't use stackalloc/pooled memory to avoid heap allocations, making the code slow.

Getting started

Hexadecimal string to byte array

Using Linq

As you can see you have allocations for each two char in the hexString because is doing a substring and you have an allocation for the byte array.

string hexString = "01AAB1DC10DD";
bytes[] bytes = Enumerable.Range(0, hexString.Length)
                                .Where(x => x % 2 == 0)
                                .Select(x => Convert.ToByte(hexString.Substring(x, 2), 16))
                                .ToArray()
/*bytes items:
{ 0x01, 0xAA, 0xB1, 0xDC, 0x10, 0xDD }
*/

Using HexConverter

You get just the allocation for the final array.

string hexString = "01AAB1DC10DD";
bytes[] bytes = HexConverter.GetBytes(hexString);

/*bytes items:
{ 0x01, 0xAA, 0xB1, 0xDC, 0x10, 0xDD }
*/

Using HexConverter with pooled array

Zero allocation, and easy to use. Optimise for strings longer than 100 characters.

string hexString = "01AAB1DC10DD";
using var pooledBytes = HexConverter.GetBytesPooled(hexString);

/*bytes.ArraySegment items:
{ 0x01, 0xAA, 0xB1, 0xDC, 0x10, 0xDD }
*/

Using HexConverter with stackalloc buffer

Zero allocation, and optimise for small hex string.

string hexString = "01AAB1DC10DD";
Span<byte> buffer = stackalloc byte[HexConverter.GetBytesCount(hexString)];
int count = HexConverter.GetBytes(hexString, buffer);

/*buffer items:
{ 0x01, 0xAA, 0xB1, 0xDC, 0x10, 0xDD }
*/

Byte array to hexadecimal string

Using Linq

With this linq implementation you have allocation for the intermidiate array, and a string per each byte and the a new one for the final string.

byte[] vals = { 0x01, 0xAA, 0xB1, 0xDC, 0x10, 0xDD };
string str = string.Concat(vals.Select(b => b.ToString("x2")));
Console.WriteLine(str);

/*Output:
  01AAB1DC10DD
 */

Using HexConverter

You get just the allocation for the final string.

byte[] vals = { 0x01, 0xAA, 0xB1, 0xDC, 0x10, 0xDD };
string str = HexConverter.GetString(vals);
Console.WriteLine(str);

/*Output:
  01AAB1DC10DD
 */

Using HexConverter with pooled array

Zero allocation, and easy to use. Optimise for array longer than 100 items.

byte[] vals = { 0x01, 0xAA, 0xB1, 0xDC, 0x10, 0xDD };
using var pooledChars = HexConverter.GetCharsPooled(vals);
Console.WriteLine(pooledChars.ArraySegment.AsSpan());

/*Output:
  01AAB1DC10DD
 */

Using HexConverter with stackalloc buffer

Zero allocation, and optimise for small byte arrays.

byte[] vals = { 0x01, 0xAA, 0xB1, 0xDC, 0x10, 0xDD };
Span<byte> buffer = stackalloc byte[HexConverter.GetBytesCount(vals)];
HexConverter.GetChars(vals, buffer);
Console.WriteLine(buffer.AsSpan());

/*Output:
  01AAB1DC10DD
 */

Benchmarks

Lower is better