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
– Matt Parkins, Commented Jun 18, 2014 at 14:37

Community · Accepted Answer · 2017-05-23 10:34:15Z

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, 2017 at 10:34

CommunityBot

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answered May 29, 2011 at 0:17

Ben Voigt

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7 Comments

olidev Over a year ago

a list of bytes is fine as I declared as above I think

Mikant Over a year ago

foreach in byte conversion look really insane(

Ben Voigt Over a year ago

@Mikant: Can you explain what you think the problem is? It works for me: ideone.com/ML8Nb

Mikant Over a year ago

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

Ben Voigt Over a year ago

@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<byte>, 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.

|

josliber · Accepted Answer · 2015-06-29 13:09:57Z

4

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, 2015 at 13:09

josliber

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answered Jun 29, 2015 at 12:02

Barak Rosenfeld

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Comments

Mikant · Accepted Answer · 2011-05-29 00:23:59Z

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, 2011 at 0:23

Mikant

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1 Comment

olidev Over a year ago

1 is OK. question 2 is not clear for me, so which encoding format should I use? thanks in advance

JGU · Accepted Answer · 2013-12-28 19:15:30Z

1

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..

answered Dec 28, 2013 at 19:15

JGU

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