...

example.d

// It turns out that combination of std.conv.emplace and FFI::MemoryPointer.new 
// can make our life much easier (at least, for structs). 
// See example at https://gist.github.com/2337729

extern (C) void* malloc(size_t sz); 
extern (C) void free(void *p); 

class DefaultMemoryManagement {
    mixin template memoryManagement() {}
}

class ManualMemoryManagement {
    mixin template memoryManagement() {
         new(size_t sz)
         {
             void* p;
             p = malloc(sz);
             return p;
         }
         delete(void* p)
         {
             free(p);
         }
    }
}

class TFileParser(T)
{
    mixin T.memoryManagement;
}

alias TFileParser!DefaultMemoryManagement FileParser;
alias TFileParser!ManualMemoryManagement  FFIFileParser;

void main () {
    auto f = new FileParser;
    auto g = new FFIFileParser; delete g;
}