读取二进制文件到一个结构 [英] Read binary file into a struct

问题描述

我试图读取使用C＃的二进制数据。我对在我想读的文件的数据的布局的所有信息。我能读由大块大块的数据，即获得第一个40字节的数据将其转换为字符串，得到下一个40个字节的...

I'm trying to read binary data using C#. I have all information about the layout of the data in the files I want to read. I'm able to read the data "chunk by chunk", i.e. getting the first 40 bytes of data converting it to a string, get the next 40 bytes, ...

由于至少有三个不同的slighlty版本的数据，我想将数据直接读入一个结构。它只是感觉比通过阅读它逐行这么多的权利。

Since there are at least three slighlty different version of the data, I would like to read the data directly into a struct. It just feels so much more right than by reading it "line by line".

我曾尝试以下方法，但无济于事：

I have tried the following approach but to no avail:

StructType aStruct;
int count = Marshal.SizeOf(typeof(StructType));
byte[] readBuffer = new byte[count];
BinaryReader reader = new BinaryReader(stream);
readBuffer = reader.ReadBytes(count);
GCHandle handle = GCHandle.Alloc(readBuffer, GCHandleType.Pinned);
aStruct = (StructType) Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(StructType));
handle.Free();

\r

流是打开的FileStream从中我已经开始从阅读。我使用Marshal.PtrToStructure时得到一个AccessViolationException。

The stream is an opened FileStream from which I have began to read from. I get an AccessViolationException when using Marshal.PtrToStructure.

流包含比我试图阅读，因为我在文件的结尾数据不感兴趣的更多信息。

The stream contains more information than I'm trying to read since I'm not interested in data at the end of the file.

该结构的定义是这样的：

The struct is defined like:

[StructLayout(LayoutKind.Explicit)]
struct StructType
{
    [FieldOffset(0)]
    public string FileDate;
    [FieldOffset(8)]
    public string FileTime;
    [FieldOffset(16)]
    public int Id1;
    [FieldOffset(20)]
    public string Id2;
}

\r

例子code由原来的改变，使这个问题更短。

The examples code is changed from original to make this question shorter.

我将如何从一个文件到一个结构读取二进制数据？

How would I read binary data from a file into a struct?

推荐答案

问题是在字符串取值在你的结构。我发现，封送类型，如字节/短路/ int是没有问题的;但是当你需要集结成一个复杂的类型，如字符串，你需要你的结构来显式地模仿非托管类型。你可以用的MarshalAs ATTRIB做到这一点。

The problem is the strings in your struct. I found that marshaling types like byte/short/int is not a problem; but when you need to marshal into a complex type such as a string, you need your struct to explicitly mimic an unmanaged type. You can do this with the MarshalAs attrib.

有关你的榜样，下面应该工作：

For your example, the following should work:

[StructLayout(LayoutKind.Explicit)]
struct StructType
{
    [FieldOffset(0)]
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 8)]
    public string FileDate;

    [FieldOffset(8)]
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 8)]
    public string FileTime;

    [FieldOffset(16)]
    public int Id1;

    [FieldOffset(20)]
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 66)] //Or however long Id2 is.
    public string Id2;
}

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