Tuple-like types used in Pool.

Slots has types t1, ..., t12 of arities 1 to 12 that are isomorphic to tuple types of the corresponding arities. Type ('a0, ..., 'a<N-1>) t<N> corresponds to 'a0 * ... * 'a<N-1>.

A pool. 'slots will look like ('a1, ..., 'an) Slots.tn, and the pool holds tuples of type 'a1 * ... * 'an.

pointer_is_valid t pointer returns true iff pointer points to a live tuple in t, i.e. pointer is not null, not free, and is in the range of t.

A pointer might not be in the range of a pool if it comes from another pool for example. In this case unsafe_get/set functions would cause a segfault.

id_of_pointer t pointer returns an id that is unique for the lifetime of pointer's tuple. When the tuple is freed, the id is no longer valid, and pointer_of_id_exn will fail on it. Pointer.null () has a distinct id from all non-null pointers.

pointer_of_id_exn t id returns the pointer corresponding to id. It fails if the tuple corresponding to id was already freed.

create slots ~capacity ~dummy creates an empty pool that can hold up to capacity N-tuples. The slots of dummy are stored in free tuples. create raises if capacity < 0 || capacity > max_capacity ~slots_per_tuple.

max_capacity returns the maximum capacity allowed when creating a pool.

capacity returns the maximum number of tuples that the pool can hold.

length returns the number of tuples currently in the pool.

  0 <= length t <= capacity t

grow t ~capacity returns a new pool t' with the supplied capacity. The new pool is to be used as a replacement for t. All live tuples in t are now live in t', and valid pointers to tuples in t are now valid pointers to the identical tuple in t'. It is an error to use t after calling grow t.

grow raises if the supplied capacity isn't larger than capacity t.

is_full t returns true if no more tuples can be allocated in t.

free t pointer frees the tuple pointed to by pointer from t.

unsafe_free t pointer frees the tuple pointed to by pointer without checking pointer_is_valid

new<N> t a0 ... a<N-1> returns a new tuple from the pool, with the tuple's slots initialized to a0 ... a<N-1>. new raises if is_full t.

get_tuple t pointer allocates an OCaml tuple isomorphic to the pool t's tuple pointed to by pointer. The tuple gets copied, but its slots do not.

get t pointer slot gets slot of the tuple pointed to by pointer in pool t.

set t pointer slot a sets to a the slot of the tuple pointed to by pointer in pool t.

In get and set, it is an error to refer to a pointer that has been freed. It is also an error to use a pointer with any pool other than the one the pointer was new'd from or grown to. These errors will lead to undefined behavior, but will not segfault.

unsafe_get is comparable in speed to get for immediate values, and 5%-10% faster for pointers.

unsafe_get and unsafe_set skip bounds checking, and can thus segfault.

An Unsafe pool is like an ordinary pool, except that the create function does not require an initial element. The pool stores a dummy value for each slot. Such a pool is only safe if one never accesses a slot from a freed tuple.

Debug builds a pool in which every function can run invariant on its pool argument(s) and/or print a debug message to stderr, as determined by !check_invariant and !show_messages, which are initially both true.

Error_check builds a pool that has additional error checking for pointers, in particular to detect using a freed pointer or multiply freeing a pointer.