thefloatingbrain/cppborrow

Compile-time C++ borrowing mechanism like what's in Rust

C++ Borrowing Class

Compile-time C++ borrowing mechanism like what's in Rust: Resources will be borrowed, moveed, or copyed instead of ambiguously "passed" everywhere. The mechanism will decide when to free resources. People might not like this since either borrow, move or copy have to be specified for any "passing". But this do makes sure everything will be "safe" at runtime.

Usage

int main()
{
	resource _a;

	box<resource> a(_a);// To `borrow`, `move`, or `copy`, resource have to be wrapped like this.
						// Here, `a` seals resource from `_a`, which means generally `_a` can no longer be used anymore.
						// If `_a` have to be used, write `_a` as `std::cref(_a)` which will result in a deep copy.
						// It is recommended that all resources are wrapped in `box` to avoid C++ swap outside control of `box`.
						// By the way, C++17 might allow class template deduction which means `box a(_a)` will be legal
	
	*a;					// Access wrapped data using `operator*`

	{
		auto b=a.borrow();// `b` borrows resource from `a`. It shares resource with `a` but don't free that.
		( *a ).xxx();		// `a` is still able to access `b`
	}

	{
		auto b=a.move();	// `b` steals resource from `a`. If `a` borrowed resource from somebody else, a compiling
						// error will be given since `a` do not own the resource. Accessing `a` after this will throw
						// a runtime error. (There's no way to make this a compile time error since, this is C++)
						// Also, accessing empty-initialized box will also throw a runtime error. At least everything is
						// well defined.
	}

	{	
		auto b=a.copy();	// `b` owns a duplicate of resource inside `a`. They don't share the same memory space anymore.
	}
    return 0;
}