What is the D way to map a binary file to a structure?

[mzfhhhh via Digitalmars-d-learn]

On Saturday, 29 August 2015 at 12:56:08 UTC, cym13 wrote:
> Hi,
>
> Let's say I have a simple binary file whose structure is 
> well-known. Here is
> an example which stores points:
>
> struct Point {
>     long x;
>     long y;
>     long z;
> }
>
> struct BinFile {
>     uint    magicNumber;  // Some identifier
>     ulong   pointsNumber;
>     Point[] points;       // Array of pointsNumber points.
> }
>
> What is the best way to read some file and fill a structure 
> with it? Would
> reading the file into a void[] and then casting it to the 
> struct work with
> things like internal struct padding?

struct Point {
      long x;
      long y;
      long z;
}

struct BinFile {
     uint    magicNumber;  // Some identifier
     ulong   pointsNumber;
     Point[] points;       // Array of pointsNumber points.

     this(ubyte [] buf)
     {
         auto f = cast(BinFile *)buf.ptr;
         this = cast(BinFile)*f;
         this.points = 
(cast(Point*)&f.points)[0..cast(uint)this.pointsNumber];
     }
}