SafeTypes

Introduction

Reference counting is a popular method for resource management. Its advantages include avoid copying, small overhead, and easy to reason with. However, when there's reference cycle, memory leak occurs. Typical solution to this is to use weak references. My comment on this is:

memory leak caused by reference cycle is a by-product of conflating memory management and data structure.

So instead of requiring the programmer to carefully implant weak references (and make them think "why the hell is it here?") I choose a differen approach, where users are required to specify a "semantic" when assigning object to containers. These semantics are easy to understand:

• keep

  The object will be used later elsewhere, do not decrease reference count.

• gave:

  The object will not be used any more elsewhere, change one of its reference to a container reference (known as "kept count" in the implementation). In other word: decrease the reference count and increase its kept count. This is most used when an object is created exclusively for saving on that container object.

• fast:

  The gave semantic invokes garbage collector after altering the reference and kept count - in case a reference cycle is created exactly when the assignment occurs. If the programmer can be sure that this won't occur, they can use this semantic for optimization.

Features

The library implements 3 types that're safe with regard to memory management:

• data: for storing arbitrary byte string, and can be resized safely.
• dict: a dictionary type that stores key-value pairs.
• list: the ordered set type.

The library uses SipHash in the dictionary type. According to its designer, this hash function can be keyed to deter attacks on hash collision in dict. Users are strongly advised to set the key to one that's securely generated and that's different each time the program is run.