C# - Binary reader in Big Endian?

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big endian vs little endian
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I'm trying to improve my understanding of the STFS file format by using a program to read all the different bits of information. Using a website with a reference of which offsets contain what information, I wrote some code that has a binary reader go through the file and place the values in the correct variables.

The problem is that all the data is SUPPOSED to be Big Endian, and everything the binary reader read is Little Endian. So, what's the best way to go about fixing this?

Can I create a mimic class of Binary reader that returns a reversed array of bytes? Is there something I can change in class instance that will make it read in big endian so I don't have to rewrite everything?

Any help is appreciated.

edit: I tried adding Encoding.BigEndianUnicode as a parameter, but it still reads little endian.

I'm not usually one to answer my own questions, but I've accomplished exactly what I wanted with some simple code:

class BinaryReader2 : BinaryReader { 
    public BinaryReader2(System.IO.Stream stream)  : base(stream) { }

    public override int ReadInt32()
    {
        var data = base.ReadBytes(4);
        Array.Reverse(data);
        return BitConverter.ToInt32(data, 0);
    }

    public Int16 ReadInt16()
    {
        var data = base.ReadBytes(2);
        Array.Reverse(data);
        return BitConverter.ToInt16(data, 0);
    }

    public Int64 ReadInt64()
    {
        var data = base.ReadBytes(8);
        Array.Reverse(data);
        return BitConverter.ToInt64(data, 0);
    }

    public UInt32 ReadUInt32()
    {
        var data = base.ReadBytes(4);
        Array.Reverse(data);
        return BitConverter.ToUInt32(data, 0);
    }

}

I knew that's what I wanted, but I didn't know how to write it. I found this page and it helped: http://www.codekeep.net/snippets/870c4ab3-419b-4dd2-a950-6d45beaf1295.aspx

Simple implementation of a big-endian BinaryReader in C#. · GitHub, Simple implementation of a big-endian BinaryReader in C#. BigEndianBinaryReader.cs. using System;. using  c# bitconverter endian (3) I'm trying to improve my understanding of the STFS file format by using a program to read all the different bits of information. Using a website with a reference of which offsets contain what information, I wrote some code that has a binary reader go through the file and place the values in the correct variables.

IMHO a slightly better answer as it doesn't require a different class to be newed-up, makes the big-endian calls obvious and allows big- and little-endian calls to be mixed in the stream.

public static class Helpers
{
  // Note this MODIFIES THE GIVEN ARRAY then returns a reference to the modified array.
  public static byte[] Reverse(this byte[] b)
  {
    Array.Reverse(b);
    return b;
  }

  public static UInt16 ReadUInt16BE(this BinaryReader binRdr)
  {
    return BitConverter.ToUInt16(binRdr.ReadBytesRequired(sizeof(UInt16)).Reverse(), 0);
  }

  public static Int16 ReadInt16BE(this BinaryReader binRdr)
  {
    return BitConverter.ToInt16(binRdr.ReadBytesRequired(sizeof(Int16)).Reverse(), 0);
  }

  public static UInt32 ReadUInt32BE(this BinaryReader binRdr)
  {
    return BitConverter.ToUInt32(binRdr.ReadBytesRequired(sizeof(UInt32)).Reverse(), 0);
  }

  public static Int32 ReadInt32BE(this BinaryReader binRdr)
  {
    return BitConverter.ToInt32(binRdr.ReadBytesRequired(sizeof(Int32)).Reverse(), 0);
  }

  public static byte[] ReadBytesRequired(this BinaryReader binRdr, int byteCount)
  {
    var result = binRdr.ReadBytes(byteCount);

    if (result.Length != byteCount)
      throw new EndOfStreamException(string.Format("{0} bytes required from stream, but only {1} returned.", byteCount, result.Length));

    return result;
  }
}

BinaryReader.ReadUInt16 Method (System.IO), Reads a 2-byte unsigned integer from the current stream using little-endian encoding and advances the position of the stream by two bytes. In BinaryReader, it is assuming big endian format and reading the data appropriately into an int, which should work regardless of CPU architecture. You should be able to write on big or little endian and read on the other CPU architecture without additional code. It's possible this is new as of .NET core

I'm not familiar with STFS, but changing endianess is relatively easy. "Network Order" is big endian, so all you need to do is translate from network to host order.

This is easy because there's already code that does that. Look at IPAddress.NetworkToHostOrder, as explained here: ntohs() and ntohl() equivalent?

C# BinaryReader and Little Endian, C# BinaryReader and Little Endian function ByteArrayToString() gives me this result: 0xF0FF that is in BigEndian and not in LittleEndian (infact I suppose that I  Read Int32Big Endian (Read Only Span<Byte>) Reads an Int32 from the beginning of a read-only span of bytes, as big endian. Read Int32Little Endian (Read Only Span<Byte>) Reads an Int32 from the beginning of a read-only span of bytes, as little endian.

In my opinion, you want to be careful doing this. The reason one would want to Convert from BigEndian to LittleEndian is if the bytes being read are in BigEndian and the OS calculating against them is operating in LittleEndian.

C# isn't a window only language anymore. With ports like Mono, and also other Microsoft Platforms like Windows Phone 7/8, Xbox 360/Xbox One, Windwos CE, Windows 8 Mobile, Linux With MONO, Apple with MONO, etc. It is quite possible the operating platform could be in BigEndian, in which case you'd be screwing yourself if you converted the code without doing any checks.

The BitConverter already has a field on it called "IsLittleEndian" you can use this to determine if the operating environment is in LittleEndian or not. Then you can do the reversing conditionally.

As such, I actually just wrote some byte[] extensions instead of making a big class:

    /// <summary>
    /// Get's a byte array from a point in a source byte array and reverses the bytes. Note, if the current platform is not in LittleEndian the input array is assumed to be BigEndian and the bytes are not returned in reverse order
    /// </summary>
    /// <param name="byteArray">The source array to get reversed bytes for</param>
    /// <param name="startIndex">The index in the source array at which to begin the reverse</param>
    /// <param name="count">The number of bytes to reverse</param>
    /// <returns>A new array containing the reversed bytes, or a sub set of the array not reversed.</returns>
    public static byte[] ReverseForBigEndian(this byte[] byteArray, int startIndex, int count)
    {
        if (BitConverter.IsLittleEndian)
            return byteArray.Reverse(startIndex, count);
        else
            return byteArray.SubArray(startIndex, count);

    }

    public static byte[] Reverse(this byte[] byteArray, int startIndex, int count)
    {
        byte[] ret = new byte[count];
        for (int i = startIndex + (count - 1); i >= startIndex; --i)
        {
            byte b = byteArray[i];
            ret[(startIndex + (count - 1)) - i] = b;
        }
        return ret;
    }

    public static byte[] SubArray(this byte[] byteArray, int startIndex, int count)
    {
        byte[] ret = new byte[count];
        for (int i = 0; i < count; ++i)            
            ret[0] = byteArray[i + startIndex];
        return ret;
    }

So imagine this example code:

byte[] fontBytes = byte[240000]; //some data loaded in here, E.G. a TTF TrueTypeCollection font file. (which is in BigEndian)

int _ttcVersionMajor = BitConverter.ToUint16(fontBytes.ReverseForBigEndian(4, 2), 0);

//output
_ttcVersionMajor = 1 //TCCHeader is version 1

BinaryReader -- can it be forced to read a BigEndian stream, Can BinaryReader be forced to read a stream, say a TCP/IP stream or memory stream or even file stream in big endian order or do I have to  I am using BinaryWriter class to write a binary file to disk. When I invoke the Write method, passing an unsigned short value, it writes it in little-endian format. For example: bw.Write(0xA000); writes the value in the binary file as 0x00 0xA0. Is there a way to make BInaryWriter use Big Endian?

A mostly-complete (for my purposes) drop-in replacement for BinaryReader that handles endianness correctly, unlike most of these answers. By default it works exactly like BinaryReader, but can be constructed to read in the required endianness. Additionally the Read<Primitive> methods are overloaded to allow you to specify the endianness to read a particular value in - useful in the (unlikely) scenario that you're dealing with a stream of mixed LE/BE data.

public class EndiannessAwareBinaryReader : BinaryReader
{
    public enum Endianness
    {
        Little,
        Big,
    }

    private readonly Endianness _endianness = Endianness.Little;

    public EndiannessAwareBinaryReader(Stream input) : base(input)
    {
    }

    public EndiannessAwareBinaryReader(Stream input, Encoding encoding) : base(input, encoding)
    {
    }

    public EndiannessAwareBinaryReader(Stream input, Encoding encoding, bool leaveOpen) : base(input, encoding, leaveOpen)
    {
    }

    public EndiannessAwareBinaryReader(Stream input, Endianness endianness) : base(input)
    {
        _endianness = endianness;
    }

    public EndiannessAwareBinaryReader(Stream input, Encoding encoding, Endianness endianness) : base(input, encoding)
    {
        _endianness = endianness;
    }

    public EndiannessAwareBinaryReader(Stream input, Encoding encoding, bool leaveOpen, Endianness endianness) : base(input, encoding, leaveOpen)
    {
        _endianness = endianness;
    }

    public override short ReadInt16() => ReadInt16(_endianness);

    public override int ReadInt32() => ReadInt32(_endianness);

    public override long ReadInt64() => ReadInt64(_endianness);

    public override ushort ReadUInt16() => ReadUInt16(_endianness);

    public override uint ReadUInt32() => ReadUInt32(_endianness);

    public override ulong ReadUInt64() => ReadUInt64(_endianness);

    public short ReadInt16(Endianness endianness) => BitConverter.ToInt16(ReadForEndianness(sizeof(short), endianness));

    public int ReadInt32(Endianness endianness) => BitConverter.ToInt32(ReadForEndianness(sizeof(int), endianness));

    public long ReadInt64(Endianness endianness) => BitConverter.ToInt64(ReadForEndianness(sizeof(long), endianness));

    public ushort ReadUInt16(Endianness endianness) => BitConverter.ToUInt16(ReadForEndianness(sizeof(ushort), endianness));

    public uint ReadUInt32(Endianness endianness) => BitConverter.ToUInt32(ReadForEndianness(sizeof(uint), endianness));

    public ulong ReadUInt64(Endianness endianness) => BitConverter.ToUInt64(ReadForEndianness(sizeof(ulong), endianness));

    private byte[] ReadForEndianness(int bytesToRead, Endianness endianness)
    {
        var bytesRead = ReadBytes(bytesToRead);

        if ((endianness == Endianness.Little && !BitConverter.IsLittleEndian)
            || (endianness == Endianness.Big && BitConverter.IsLittleEndian))
        {
            Array.Reverse(bytesRead);
        }

        return bytesRead;
    }
}

A More Powerful BinaryReader/Writer, Extending BinaryReader/Writer to support a different byte order, string Thus, it might parse data either in big or little endian, depending on  On big-endian system, higher-order bytes precede lower-order bytes. The following table illustrates the difference in the byte arrays that result from passing the integer 1,234,567,890 (0x499602D2) to the GetBytes(Int32) method.

Big-endian binary reader : Encoding « Internationalization I18N , Big-endian binary reader : Encoding « Internationalization I18N « C# / C Sharp. Big endian machine: I think a short is two bytes, so I'll read them off: location s is address 0 (W, or 0x12) and location s + 1 is address 1 (X, or 0x34). Since the first byte is biggest (I'm big-endian!), the number must be 256 * byte 0 + byte 1, or 256*W + X, or 0x1234.

Big Endian BinaryReader, using System; using System.IO; namespace Util { public class BigEndianReader : BinaryReader { private byte[] a16 = new byte[2]; Most other processors store integers in big endian format. So when a binary file is read and written on a different platform, there’s the possibility that you’ll have to flip the bytes around

Reading big-endian binary streams, IO.BinaryReader expects a stream that's encoded in a little-endian format, and there's currently no stream reading object in C# that supports  As with the previous example, the text stream starts with a byte order mark FE FF. This indicates a UTF-16 stream in big endian format. As this text is stored in big endian format, the most significant byte is encountered first in each two byte character. The letter ‘T’ has a value of 0x54 and is represented in 16 bit big endian as 00 54.

Comments
  • @HansPassant, Would this be one of those dlls that require me to make my code open source? Why do some dlls require that?
  • Walkerneo I deleted my answer because zmbq answered essentially the same thing 3 minutes before me. The concept of endianness does not apply to byte arrays, only to words, dwords, qwords, etc., that is to groups of 2, 4, 8 and so on bytes. I am sorry if it would mean changing a lot of code, but a man has to do what a man has to do.
  • Skeet sells books, the code has few strings attached. Check the license section on that page. Apache terms are here: apache.org/licenses/LICENSE-2.0.html
  • If what you are concerned about is extracting words, dwords, qwords etc. AND converting them to the proper endianness in one step, then this question has been answered elsewhere: stackoverflow.com/questions/1674160/…
  • @MikeNakis, Oh yeah, you're right about the byte arrays. I'm still learning :D
  • Off-topic, but your class's fields (a16 etc) are unnecessary. You assign an array to them during construction, but within each method you replace that array with a new array returned by the Read function. You could just put var a32 = base.ReadBytes... in each method and get rid of the fields.
  • They're not unnecessary, they're harmful. Turning what is (potentially, ignoring the share underlying stream) a thread-safe code into a shared state situation.
  • You probably want to check BitConverter.IsLittleEndian before reversing. If it is false you don't need to reverse.
  • @Gusdor Yes. You have to know the endianess of the source data and the endianess of BitConverter, if they don't match: reverse it.
  • Allocating an array for each read creates work for the GC. You might just call GetByte as many times as required, then shift/OR the bytes into place.
  • Remember to check BitConverter.IsLittleEndian before reversing.
  • looks like you need ".ToArray()" after the Reverse, since Reverse returns IEnumerable<byte> and not byte[] (which is what the BitConverter expects)
  • Since .NET Core, there is also a BinaryPrimitives class making this obsolete: docs.microsoft.com/en-us/dotnet/api/…