ocean.util.container.VoidBufferAsArrayOf

Struct template which wraps a void[] with an API allowing it to be safely used as an array of another type.

It is, of course, possible to simply cast a void[] to another type of array and use it directly. However, care must be taken when casting to an array type with a different element size. Experience has shown that this is likely to hit undefined behaviour. For example, casting the array then sizing it has been observed to cause segfaults, e.g.:

void[]* void_array; // acquired from somewhere

struct S { int i; hash_t h; }
auto s_array = cast(S[]*)void_array;
s_array.length = 23;

The exact reason for the segfaults is not known, but this usage appears to lead to corruption of internal GC data (possibly type metadata associated with the array's pointer).

Sizing the array first, then casting is fine, e.g.:

void[]* void_array; // acquired from somewhere

struct S { int i; hash_t h; }
(*void_array).length = 23 * S.sizeof;
auto s_array = cast(S[])*void_array;

The helper VoidBufferAsArrayOf simplifies this procedure and removes the risk of undefined behaviour by always handling the void[] as a void[] internally.