#include "dynarr.h"

/// Allocate a new DynArrHeader with count=0 and capacity=0.
/// Returns a pointer to the data region immediately following the header.
void *new_header(void) {
	DynArrHeader *h = malloc(sizeof(DynArrHeader));
	exists(h);
	h->count    = 0;
	h->capacity = 0;
	return h + 1;
}

/// Return a tight copy of arr (capacity == count).
/// elem_size is the size of one element in bytes.
void *copy_header(void *arr, size_t elem_size) {
	DynArrHeader *src = da_header(arr);
	size_t bytes = sizeof(DynArrHeader) + src->count * elem_size;
	DynArrHeader *dst = malloc(bytes);
	exists(dst);
	memcpy(dst, src, bytes);
	dst->capacity = dst->count;
	return dst + 1;
}