Module espace_util

A set of utility function to support the rest of the espace modules.

Copyright © (C) 2019, Fred Youhanaie

Authors: Fred Youhanaie (fyrlang@anydata.co.uk).

Description

A set of utility function to support the rest of the espace modules.

Function Index

eval_out/1Conditionally evaluate a tuple and out the result to the unnamed instance.
eval_out/2Conditionally evaluate a tuple and out the result to a named instance.
inst_to_name/2 Convert an instance name to longer prefixed name.
wait4etsmgr/4wait for etsmgr to (re)start, then ask it to manage our table.

Function Details

eval_out/1

eval_out(Tuple_in::tuple()) -> done

Conditionally evaluate a tuple and out the result to the unnamed instance.

See eval_out/2 for details.

eval_out/2

eval_out(Inst_name::atom(), Tuple_in::tuple()) -> done

Conditionally evaluate a tuple and out the result to a named instance.

The elements of the output tuple correspond to those of Tuple_in. If any of the elements of Tuple_in are recognized as function, then the corresponding output element will be the value of the function.

Two types of patterns are recognized as functions and are evaluated. A normal function expression of arity zero, fun () -> expr end. And, a tuple with two elements, a function expresion of arity N and a list of length N, N can be zero.

Any other pattern will move the element to the output tuple untouched.

inst_to_name/2

inst_to_name(Prefix::atom(), Inst_name::atom()) -> atom()

Convert an instance name to longer prefixed name.

This is used for obtaining the instance specific server/table names. For example inst_to_name(espace_sup, aaa) will return espace_sup_aaa.

If the instance name is espace, then the prefix is returned without an instance name suffix. For example inst_to_name(espace_sup, espace) will return espace_sup.

wait4etsmgr/4

wait4etsmgr(Inst_name::atom(), X2::init | recover, Table_name::atom(), Table_opts::term()) -> {ok, pid(), ets:tab()} | {error, term()}

wait for etsmgr to (re)start, then ask it to manage our table.

There are two occassions where this function is called:

  1. init - start/restart of our gen_server that owns a table, in this case we do not have, or know of, the ETS table. So we ask etsmgr to create a new table using etsmgr:new_table/4. If etsmgr is already managing such a table that does not already belong to another process, then that table will be given to us.
  2. recover - recovery of the etsmgr server, in this case we ask etsmgr to start managing our ETS table.


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