C# array within a struct
Use fixed size buffers:
[StructLayout(LayoutKind.Explicit)]
unsafe struct headerUnion // 2048 bytes in header
{
[FieldOffset(0)]
public fixed byte headerBytes[2048];
[FieldOffset(0)]
public headerLayout header;
}
Alternativ you can just use the struct and read it with the following extension method:
private static T ReadStruct<T>(this BinaryReader reader)
where T : struct
{
Byte[] buffer = new Byte[Marshal.SizeOf(typeof(T))];
reader.Read(buffer, 0, buffer.Length);
GCHandle handle = default(GCHandle);
try
{
handle = GCHandle.Alloc(buffer, GCHandleType.Pinned);
return (T)Marshal.PtrToStructure(handle.AddrOfPinnedObject(), typeof(T));
}
finally
{
if (handle.IsAllocated)
handle.Free();
}
}
Unmanaged structures can contain embedded arrays. By default, these embedded array fields are marshaled as a SAFEARRAY. In the following example, s1 is an embedded array that is allocated directly within the structure itself.
Unmanaged representation
struct MyStruct {
short s1[128];
}
Arrays can be marshaled as UnmanagedType.ByValArray, which requires you to set the MarshalAsAttribute.SizeConst field. The size can be set only as a constant. The following code shows the corresponding managed definition of MyStruct. C#VB
[StructLayout(LayoutKind.Sequential)]
public struct MyStruct {
[MarshalAs(UnmanagedType.ByValArray, SizeConst=128)] public short[] s1;
}
I wouldn't use that pattern in the first place. This kind of memory mapping may be appropriate in c, but not in a high level language like C#.
I'd just write a call to the binary reader for each member I want to read. This means you can use classes and write them in a clean high level way.
It also takes care of endian issues. Whereas memory mapping will break when used on different endian systems.
Related question: Casting a byte array to a managed structure
So your code would look similar to the following (add access modifiers etc.):
class Record
{
char[] name;
int dt1;
}
class Block {
char[] version;
int field1;
int field2;
RECORD[] records;
char[] filler1;
}
class MyReader
{
BinaryReader Reader;
Block ReadBlock()
{
Block block=new Block();
block.version=Reader.ReadChars(4);
block.field1=Reader.ReadInt32();
block.field2=Reader.ReadInt32();
block.records=new Record[15];
for(int i=0;i<block.records.Length;i++)
block.records[i]=ReadRecord();
block.filler1=Reader.ReadChars(24);
return block;
}
Record ReadRecord()
{
...
}
public MyReader(BinaryReader reader)
{
Reader=reader;
}
}