读取C＃中的结构数组

Question

I've seen here , and also googling for "marshal" several ways to convert a byte array to a struct.

But what I'm looking for is if there is a way to read an array of structs from a file (ok, whatever memory input) in one step?

I mean, load an array of structs from file normally takes more CPU time (a read per field using a BinaryReader) than IO time. Is there any workaround?

I'm trying to load about 400K structs from a file as fast as possible.

Thanks

pablo

Answer 1

Following URL may be of interest to you.

http://www.codeproject.com/KB/files/fastbinaryfileinput.aspx

Or otherwise I think of pseudo code like the following:

readbinarydata in a single shot and convert back to structure..

public struct YourStruct
{ 
    public int First;
    public long Second;
    public double Third;
}

static unsafe byte[] YourStructToBytes( YourStruct s[], int arrayLen )
{
    byte[] arr = new byte[ sizeof(YourStruct) * arrayLen ];
    fixed( byte* parr = arr )
    { 
        * ( (YourStruct * )parr) = s; 
    }
    return arr;
}

static unsafe YourStruct[] BytesToYourStruct( byte[] arr, int arrayLen )
{
    if( arr.Length < (sizeof(YourStruct)*arrayLen) )
        throw new ArgumentException();
    YourStruct s[];
    fixed( byte* parr = arr )
    { 
        s = * ((YourStruct * )parr); 
    }
    return s;
}

Now you can read bytearray from the file in a single shot and convert back to strucure using BytesToYourStruct

Hope you can implement this idea and check...

Answer 2

I found a potential solution at this site - http://www.eggheadcafe.com/software/aspnet/32846931/writingreading-an-array.aspx

It says basically to use Binary Formatter like this:

FileStream fs = new FileStream("DataFile.dat", FileMode.Create); BinaryFormatter formatter = new BinaryFormatter(); formatter.Serialize(fs, somestruct);

I also found two questions from this site - Reading a C/C++ data structure in C# from a byte array and How to marshal an array of structs - (.Net/C# => C++)

I haven't done this before, being a C# .NET beginner myself. I hope this solution helps.