I love this feature, but I'm unsure how it works. Can someone
explain me, how the compiler deduce that he should read 4
bytes for each index (the 'at' function)? The type is void*,
not int*.
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import std.stdio;
import core.stdc.stdlib : calloc, realloc, free;
import core.stdc.string : memcpy;
struct Tarray {
void* ptr;
size_t length;
size_t capacity;
~this() {
.free(this.ptr);
this.ptr = null;
}
}
void push(T)(ref Tarray arr, T elem) {
if (arr.length == arr.capacity)
arr.reserve(T.sizeof);
memcpy(&arr.ptr[arr.length++], &elem, T.sizeof);
}
void reserve(ref Tarray arr, size_t typeOf, size_t cap = 0) {
if (arr.capacity != 0) {
arr.capacity = cap == 0 ? (arr.capacity * 2) + 1 :
arr.capacity + cap;
arr.ptr = .realloc(arr.ptr, arr.capacity * typeOf);
} else {
arr.capacity = cap == 0 ? 3 : cap;
arr.ptr = .calloc(arr.capacity, typeOf);
}
}
void at(T)(ref Tarray arr, size_t index, T* elem) {
if (index >= arr.length || elem is null)
return;
memcpy(elem, &arr.ptr[index], T.sizeof);
}
void main() {
Tarray arr;
arr.push(42);
int a;
arr.at(0, &a);
writeln(a, "::", arr.length, "::", arr.capacity);
arr.push(23);
arr.at(1, &a);
writeln(a, "::", arr.length, "::", arr.capacity);
arr.push(1337);
arr.at(2, &a);
writeln(a, "::", arr.length, "::", arr.capacity);
arr.push(ushort.max + 1);
arr.at(3, &a);
writeln(a, "::", arr.length, "::", arr.capacity);
}
----
