Convert byte array to int

Question

I am trying to do some conversion in C#, and I am not sure how to do this:

private int byteArray2Int(byte[] bytes)
{
    // bytes = new byte[] {0x01, 0x03, 0x04};

    // how to convert this byte array to an int?

    return BitConverter.ToInt32(bytes, 0); // is this correct? 
    // because if I have a bytes = new byte [] {0x32} => I got an exception
}

private string byteArray2String(byte[] bytes)
{
   return System.Text.ASCIIEncoding.ASCII.GetString(bytes);

   // but then I got a problem that if a byte is 0x00, it show 0x20
}

Could anyone give me some ideas?

You could just use a cast if you like living life on the edge. — Matt Parkins, Jun 18 '14 at 14:37

score 28 · Accepted Answer · edited May 23 '17 at 10:34

28

BitConverter is the correct approach.

Your problem is because you only provided 8 bits when you promised 32. Try instead a valid 32-bit number in the array, such as new byte[] { 0x32, 0, 0, 0 }.

If you want an arbitrary length array converted, you can implement this yourself:

ulong ConvertLittleEndian(byte[] array)
{
    int pos = 0;
    ulong result = 0;
    foreach (byte by in array) {
        result |= ((ulong)by) << pos;
        pos += 8;
    }
    return result;
}

It's not clear what the second part of your question (involving strings) is supposed to produce, but I guess you want hex digits? BitConverter can help with that too, as described in an earlier question.

edited May 23 '17 at 10:34

Community

1
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answered May 29 '11 at 00:17

Ben Voigt

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a list of bytes is fine as I declared as above I think – olidev May 29 '11 at 00:19
1

`foreach` in byte conversion look really insane( – Mikant May 29 '11 at 00:34
@Mikant: Can you explain what you think the problem is? It works for me: http://ideone.com/ML8Nb – Ben Voigt May 29 '11 at 00:38
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usually we use such a type of conversion to gain speed... not to worry about the environment we work in. `foreach` sugar may slow the `work` up to hundreds of times... i just want to say that usage of the `foreach` keyword 'must' be consciously recognized – Mikant May 29 '11 at 00:56
@Mikant: I think you're confusing this with some other case. `foreach` on arrays is very fast. If there were a generic interface here, such as `IEnumerable`, there could be performance problems. But the code I show has no "hundreds of times" overhead. You could probably squeeze out a few more percent by unrolling, but that's all. – Ben Voigt May 29 '11 at 01:05
How can I go back from ulong to my own bytes array? – HMagdy May 27 '14 at 15:24
This function you suggested gives warning: warning CS0675: Bitwise-or operator used on a sign-extended operand; consider casting to a smaller unsigned type first. Why? – Oct 15 '15 at 07:20

score 3 · Answer 2 · edited Jun 29 '15 at 13:09

3

byte[] bytes = { 0, 0, 0, 25 };

// If the system architecture is little-endian (that is, little end first), 
// reverse the byte array. 
if (BitConverter.IsLittleEndian)
  Array.Reverse(bytes);

int i = BitConverter.ToInt32(bytes, 0);
Console.WriteLine("int: {0}", i);

edited Jun 29 '15 at 13:09

josliber

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answered Jun 29 '15 at 12:02

Barak Rosenfeld

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score 1 · Answer 3 · answered Dec 28 '13 at 19:15

A fast and simple way of doing this is just to copy the bytes to an integer using Buffer.BlockCopy:

UInt32[] pos = new UInt32[1];
byte[] stack = ...
Buffer.BlockCopy(stack, 0, pos, 0, 4);

This has the added benefit of being able to parse numerous integers into an array just by manipulating offsets..

score 1 · Answer 4 · answered May 29 '11 at 00:23

1

this is correct, but you're missing, that Convert.ToInt32 'wants' 32 bits (32/8 = 4 bytes) of information to make a conversion, so you cannot convert just One byte: `new byte [] {0x32}
absolutely the the same trouble you have. and do not forget about the encoding you use: from encoding to encoding you have 'different byte count per symbol'

answered May 29 '11 at 00:23

Mikant

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1 is OK. question 2 is not clear for me, so which encoding format should I use? thanks in advance – olidev May 29 '11 at 00:41

Convert byte array to int

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