write struct as raw data to file

[Ali Çehreli]

Correcting my sloppy code. :)

On 9/26/21 8:53 AM, Ali Çehreli wrote:
 >    // We need an array Ses (length of 1 in this case)
 >    auto ses = new S[1];

Allocating a dynamic array there is egregious pessimization. The 
following works the same but this time the static array of a single S 
will be on the stack:

   S[1] ses;

 >    // Note the array of S passed to rawWrite
 >    File(name, "w").rawWrite([S(42, 1.5)]);

Similarly, a temporary dynamic array is created there. Instead, we can 
have single S and make a slice of length 1 from that element:

   // Note the array of S passed to rawWrite
   auto s = S(42, 1.5);
   File(name, "w").rawWrite((&s)[0..1]);

The expression passed to rawWrite is complicated. It takes advantage of 
D's "make a slice from a pointer" feature.

- &s is a pointer to variable s
- If p is a pointer, the syntax p[0..length] makes a slice of 'length' 
elements starting from 'p'.

In this case, we are treating the variable 's' as a slice of 1.

Ali