34

我试图通过使用程序读取所有不同的信息位来提高我对 STFS 文件格式的理解。使用一个参考哪些偏移量包含哪些信息的网站，我编写了一些代码，它有一个二进制阅读器遍历文件并将值放在正确的变量中。

问题是所有数据都应该是 Big Endian，而二进制读取器读取的所有数据都是 Little Endian。那么，解决此问题的最佳方法是什么？

我可以创建一个模拟类的二进制读取器，它返回一个反转的字节数组吗？我可以在类实例中更改一些内容，使其以大端方式读取，因此我不必重写所有内容？

任何帮助表示赞赏。

编辑：我尝试添加 Encoding.BigEndianUnicode 作为参数，但它仍然读取小端。

4

7 回答 7

40

我通常不会回答自己的问题，但我已经用一些简单的代码完成了我想要的：

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);
    }

}

我知道这就是我想要的，但我不知道怎么写。我找到了这个页面，它有帮助： http: //www.codekeep.net/snippets/870c4ab3-419b-4dd2-a950-6d45beaf1295.aspx

于 2011-12-23T22:29:44.037 回答
14

恕我直言，这是一个更好的答案，因为它不需要更新不同的类，使大端调用显而易见，并允许在流中混合大端和小端调用。

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;
  }
}
于 2013-03-07T15:06:46.430 回答
8

我不熟悉 STFS，但改变字节顺序相对容易。“网络顺序”是大端顺序，所以您需要做的就是从网络顺序转换为主机顺序。

这很容易，因为已经有代码可以做到这一点。看一下IPAddress.NetworkToHostOrder，正如这里解释的那样：ntohs() 和 ntohl() 等效？

于 2011-12-23T21:49:29.710 回答
8

BinaryReader与这些答案中的大多数不同，一个最完整的（就我的目的而言）替代品可以正确处理字节序。默认情况下，它的工作方式与 完全一样BinaryReader，但可以构造为以所需的字节顺序读取。此外，这些Read<Primitive>方法被重载以允许您指定读取特定值的字节顺序 - 在您处理混合 LE/BE 数据流的（不太可能的）场景中很有用。

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;
    }
}
于 2019-10-11T12:43:34.940 回答
6

在我看来，你要小心这样做。想要从 BigEndian 转换为 LittleEndian 的原因是，如果正在读取的字节在 BigEndian 中，并且针对它们计算的操作系统在 LittleEndian 中运行。

C# 不再是一种仅限窗口的语言。使用 Mono 等端口，以及其他 Microsoft 平台，如 Windows Phone 7/8、Xbox 360/Xbox One、Windwos CE、Windows 8 Mobile、Linux With MONO、Apple with MONO 等。操作平台很可能在BigEndian，在这种情况下，如果你在不做任何检查的情况下转换代码，你会搞砸自己。

BitConverter 上已经有一个名为“IsLittleEndian”的字段，您可以使用它来确定操作环境是否为 LittleEndian。然后你可以有条件地进行倒车。

因此，我实际上只是编写了一些 byte[] 扩展而不是创建一个大类：

    /// <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;
    }

所以想象一下这个示例代码：

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
于 2014-02-06T07:39:05.827 回答
1

我已经扩展了Ian Kemp 的 出色建议，我正在使用BinaryPrimitives.NET Core 2.1+ 中提供的新的 .NET Core 2.1+，根据Stephen Toub 的帖子，它们的性能更高，并且可以在内部处理字节序和反转。

因此，如果您运行的是 .NET Core 2.1+，则绝对应该使用此版本：

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) => endianness == Endianness.Little
        ? BinaryPrimitives.ReadInt16LittleEndian(ReadBytes(sizeof(short)))
        : BinaryPrimitives.ReadInt16BigEndian(ReadBytes(sizeof(short)));

    public int ReadInt32(Endianness endianness) => endianness == Endianness.Little
        ? BinaryPrimitives.ReadInt32LittleEndian(ReadBytes(sizeof(int)))
        : BinaryPrimitives.ReadInt32BigEndian(ReadBytes(sizeof(int)));

    public long ReadInt64(Endianness endianness) => endianness == Endianness.Little
        ? BinaryPrimitives.ReadInt64LittleEndian(ReadBytes(sizeof(long)))
        : BinaryPrimitives.ReadInt64BigEndian(ReadBytes(sizeof(long)));

    public ushort ReadUInt16(Endianness endianness) => endianness == Endianness.Little
        ? BinaryPrimitives.ReadUInt16LittleEndian(ReadBytes(sizeof(ushort)))
        : BinaryPrimitives.ReadUInt16BigEndian(ReadBytes(sizeof(ushort)));

    public uint ReadUInt32(Endianness endianness) => endianness == Endianness.Little
        ? BinaryPrimitives.ReadUInt32LittleEndian(ReadBytes(sizeof(uint)))
        : BinaryPrimitives.ReadUInt32BigEndian(ReadBytes(sizeof(uint)));

    public ulong ReadUInt64(Endianness endianness) => endianness == Endianness.Little
        ? BinaryPrimitives.ReadUInt64LittleEndian(ReadBytes(sizeof(ulong)))
        : BinaryPrimitives.ReadUInt64BigEndian(ReadBytes(sizeof(ulong)));
}
于 2021-01-11T15:34:22.587 回答
0

你最好使用BinaryPrimitives类

        public override double ReadDouble()
        {
            return BinaryPrimitives.ReadDoubleBigEndian(ReadBytes(8));
        }

        public override short ReadInt16()
        {
            return BinaryPrimitives.ReadInt16BigEndian(ReadBytes(2));
        }

        public override int ReadInt32()
        {
            return BinaryPrimitives.ReadInt32BigEndian(ReadBytes(4));
        }

        public override long ReadInt64()
        {
            return BinaryPrimitives.ReadInt64BigEndian(ReadBytes(8));
        }

        public override float ReadSingle()
        {
            return BinaryPrimitives.ReadSingleBigEndian(ReadBytes(4));
        }

        public override ushort ReadUInt16()
        {
            return BinaryPrimitives.ReadUInt16BigEndian(ReadBytes(2));
        }

        public override uint ReadUInt32()
        {
            return BinaryPrimitives.ReadUInt32BigEndian(ReadBytes(4));
        }

        public override ulong ReadUInt64()
        {
            return BinaryPrimitives.ReadUInt64BigEndian(ReadBytes(8));
        }
于 2022-02-09T11:08:58.163 回答