byte[] with ASCII values to string to int

Question

So someone took int value, converted it to string then converted it to ASCII values and then finally to byte[] with inconsistent length 1 - 4 bytes.

e.g. 100 -> "100" -> { 49, 48, 48 }.

Now I need that int value and I did it like this:

{ 49, 48, 48 } -> '1' + '0' + '0' -> "100" -> 100

                switch (header[25].Count)
                {
                    case 1:
                        hex = "" + (char)header[25][0];
                        amountOfData = Convert.ToInt32(hex, 16);
                        break;

                    case 2:
                        hex = "" + (char)header[25][0] + (char)header[25][1];
                        amountOfData = Convert.ToInt32(hex, 16);
                        break;

                    case 3:
                        hex = "" + (char)header[25][0] + (char)header[25][1] + (char)header[25][2];
                        amountOfData = Convert.ToInt32(hex, 16);
                        break;

                    case 4:
                        hex = "" + (char)header[25][0] + (char)header[25][1] + (char)header[25][2] + (char)header[25][3];
                        amountOfData = Convert.ToInt32(hex, 16); ;
                        break;

                    default:
                        break;
                }

but maybe there is better solution...

EDIT: sorry for not mentioning that, but header is List<List<byte>>

int result = array.Aggregate(0, (s, a) => s * 10 + a - '0'); — Dmitrii Bychenko
– Dmitrii Bychenko, Commented May 9, 2022 at 7:46
what is the type of header[25]? is it a byte[]? a List<byte>? or...? — Marc Gravell
– Marc Gravell, Commented May 9, 2022 at 7:57
sorry for not mentioning that, but header is List<List<byte>> — Imm
– Imm, Commented May 9, 2022 at 8:01
and now I realized that I know one of the dimensions needed so it's List<byte>[] but it doesn't matter — Imm
– Imm, Commented May 9, 2022 at 8:06
side note: List<byte> seems like a very unusual choice here; not saying it is "wrong" as such - just: very unusual — Marc Gravell
– Marc Gravell, Commented May 9, 2022 at 8:08

Marc Gravell · Accepted Answer · 2022-05-09 08:07:49Z

2

You can use library functions to parse from byte-like data to primitives; you're talking about ASCII, which means that Utf8Parser will work fine for us (all ASCII is also valid UTF8, although the reverse is obviously not true); normally, we would expect that header[25] is a byte[], a segment there-of, or some other raw binary source, but: ultimately, something like:

var span = new ReadOnlySpan<byte>(header[25], 0, header[25].Count);
if (!Utf8Parser.TryParse(span, out int amountOfData, out _))
    ThrowSomeError(); // not an integer

If header[25] is something less convenient (like a List<byte> - I notice that in your example, your header[25] has a .Count not a .Length, which suggests it isn't a byte[]), then you can always either stackalloc a local buffer and copy the data out, or you can peek inside the list with CollectionMarshal.AsSpan<T>(List<T>), which returns a Span<T> from the underlying data:

var span = CollectionMarshal.AsSpan(header[25]);
if (!Utf8Parser.TryParse(span, out int amountOfData, out _))
    ThrowSomeError(); // not an integer

As a runnable example that just shows the API:

using System;
using System.Buffers.Text;

Span<byte> span = stackalloc byte[]  { 49, 48, 48 };
if (!Utf8Parser.TryParse(span, out int amountOfData, out _))
    throw new FormatException();
Console.WriteLine(amountOfData); // 100

edited May 9, 2022 at 8:07

answered May 9, 2022 at 8:02

Marc Gravell

1.1m273 gold badges2.6k silver badges3k bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

Imm Over a year ago

Thanks a lot. I tried your code and came to this solution with its help: int amountOfData = Convert.ToInt32(Encoding.ASCII.GetString(header[25].ToArray()), 16);

Imm Over a year ago

Actually I came to this

ReadOnlySpan<byte> span = new ReadOnlySpan<byte>(header[25].ToArray(), 0, header[25].Count); Utf8Parser.TryParse(span, out int amountOfData2, out _);

, but it returned 44 from { 52, 52, 68 } and not 44D as it should

Marc Gravell Over a year ago

@Imm in the original question, you were trying to parse an integer; if you are now dealing with strings, then that's just anyEncoding.GetString; in modern runtimes, the API accepts spans. For example, Encoding.UTF8.GetString(span)

Imm Over a year ago

oh, right, sorry about that, I overlook this fact even though it was in my original solution

Neil · Accepted Answer · 2022-05-09 07:57:55Z

2

You can use the Encoding/GetString method to convert bytes of different encodings (e.g. ASCII in your case) to a .NET string:

var input = new byte[] { 49, 48, 48 };
var str = Encoding.ASCII.GetString(input);
var result = int.Parse(str, NumberStyles.None, CultureInfo.InvariantCulture);

answered May 9, 2022 at 7:57

Neil

12.1k3 gold badges36 silver badges65 bronze badges

1 Comment

Marc Gravell Over a year ago

you can bypass the string step to avoid some overheads, btw (see my answer)

Collectives™ on Stack Overflow

byte[] with ASCII values to string to int

2 Answers 2

4 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

4 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related