f# byte[] -> hex -> string conversion

ONLINECAST

2 min read

·

07-09-2024

21

0

Share

Converting Byte Arrays to Hex Strings in F#: A Compact Solution

It's common to need to convert byte arrays into their hexadecimal string representation. This is useful for various tasks, like debugging, serialization, or network communication. Let's explore a concise and elegant way to achieve this in F#.

The original code snippet attempted to achieve this conversion in two steps, first mapping each byte to its hexadecimal representation and then concatenating the resulting strings.

let ByteToHex bytes = 
    bytes 
    |> Array.map (fun (x : byte) -> String.Format("{0:X2}", x))

let ConcatArray stringArray = String.Join(null, (ByteToHex  stringArray))

While functional, this approach can be simplified by combining the mapping and concatenation into a single function.

Here's a more compact solution using F#'s built-in features:

let bytesToHex (bytes: byte[]) = 
    bytes 
    |> Array.map (fun b -> sprintf "%02X" b) 
    |> String.concat "" 

Explanation:

1. bytesToHex function: This function takes a byte array as input and returns a hexadecimal string.
2. Array.map: Applies the sprintf function to each byte in the array.
3. sprintf "%02X" b: This formats the byte (b) into a two-digit hexadecimal string (e.g., "0A", "FF"). The %02X format specifier ensures leading zeros are included for single-digit values.
4. String.concat "": Concatenates the formatted strings into a single string, effectively removing any separators.

Example Usage:

let bytes = [|0x24uy; 0xA1uy; 0x00uy; 0x1Cuy|]
let hexString = bytesToHex bytes

printfn "Hex string: %s" hexString

Output:

Hex string: 24A1001C

Addressing the Questions:

1. Simplest and Most Elegant Way: The provided bytesToHex function is considered a concise and elegant approach. It effectively combines the mapping and concatenation steps, resulting in a single function call.
2. String Formatting in F#: F# provides the sprintf function, a powerful tool for string formatting. It is a direct replacement for the String.Format function from the .NET framework and offers a wide range of formatting options.

Key Benefits of this Approach:

• Readability: The code is easy to understand and maintain.
• Conciseness: Combining operations into a single function minimizes code repetition.
• Efficiency: F#'s built-in functions like Array.map and String.concat are efficient and well-optimized.

Resources:

• F# sprintf documentation
• F# Array module

This approach provides a straightforward and efficient solution for converting byte arrays to hexadecimal strings in F#. Remember, the choice of implementation depends on your specific needs and preferences.