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process.ex
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/
process.ex
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defmodule Process do
@moduledoc """
Conveniences for working with processes and the process dictionary.
Besides the functions available in this module, the `Kernel` module
exposes and auto-imports some basic functionality related to processes
available through the functions:
* `Kernel.spawn/1` and `Kernel.spawn/3`
* `Kernel.spawn_link/1` and `Kernel.spawn_link/3`
* `Kernel.spawn_monitor/1` and `Kernel.spawn_monitor/3`
* `Kernel.self/0`
* `Kernel.send/2`
"""
@doc """
Returns `true` if the process exists and is alive, that is,
is not exiting and has not exited. Otherwise, returns `false`.
`pid` must refer to a process at the local node.
"""
@spec alive?(pid) :: boolean
def alive?(pid) do
:erlang.is_process_alive(pid)
end
@doc """
Returns all key-values in the dictionary.
"""
@spec get :: [{term, term}]
def get do
:erlang.get()
end
@doc """
Returns the value for the given `key`.
"""
@spec get(term) :: term
@spec get(term, default :: term) :: term
def get(key, default \\ nil) do
case :erlang.get(key) do
:undefined ->
default
value ->
value
end
end
@doc """
Returns all keys
"""
@spec get_keys() :: [term]
def get_keys do
:erlang.get_keys()
end
@doc """
Returns all keys that have the given `value`.
"""
@spec get_keys(term) :: [term]
def get_keys(value) do
:erlang.get_keys(value)
end
@doc """
Stores the given key-value in the process dictionary.
"""
@spec put(term, term) :: term | nil
def put(key, value) do
nillify :erlang.put(key, value)
end
@doc """
Deletes the given `key` from the dictionary.
"""
@spec delete(term) :: term | nil
def delete(key) do
nillify :erlang.erase(key)
end
@doc """
Sends an exit signal with the given reason to the pid.
The following behaviour applies if reason is any term except `:normal` or `:kill`:
1. If pid is not trapping exits, pid will exit with the given reason.
2. If pid is trapping exits, the exit signal is transformed into a message
`{:EXIT, from, reason}` and delivered to the message queue of pid.
3. If reason is the atom `:normal`, pid will not exit (unless it is the calling
process's pid, in which case it will exit with the reason `:normal`).
If it is trapping exits, the exit signal is transformed into a message
`{:EXIT, from, :normal}` and delivered to its message queue.
4. If reason is the atom `:kill`, that is if `exit(pid, :kill)` is called,
an untrappable exit signal is sent to pid which will unconditionally
exit with exit reason `:killed`.
Inlined by the compiler.
## Examples
Process.exit(pid, :kill)
"""
@spec exit(pid, term) :: true
def exit(pid, reason) do
:erlang.exit(pid, reason)
end
@doc """
Sends a message to the given process.
If the option `:noconnect` is used and sending the message would require an
auto-connection to another node the message is not sent and `:noconnect` is
returned.
If the option `:nosuspend` is used and sending the message would cause the
sender to be suspended the message is not sent and `:nosuspend` is returned.
Otherwise the message is sent and `:ok` is returned.
## Examples
iex> Process.send({:name, :node_does_not_exist}, :hi, [:noconnect])
:noconnect
"""
@spec send(dest, msg, [option]) :: result when
dest: pid | port | atom | {atom, node},
msg: any,
option: :noconnect | :nosuspend,
result: :ok | :noconnect | :nosuspend
def send(dest, msg, options) do
:erlang.send(dest, msg, options)
end
@doc """
Sends `msg` to `dest` after `time` milliseconds.
If `dest` is a pid, it must be the pid of a local process, dead or alive.
If `dest` is an atom, it must be the name of a registered process
which is looked up at the time of delivery. No error is given if the name does
not refer to a process.
This function returns a timer reference, which can be read or canceled with
`:erlang.read_timer/1`, `:erlang.start_timer/3` and `:erlang.cancel_timer/1`.
Note `time` cannot be greater than `4294967295`.
Finally, the timer will be automatically canceled if the given `dest` is a pid
which is not alive or when the given pid exits. Note that timers will not be
automatically canceled when `dest` is an atom (as the atom resolution is done
on delivery).
"""
@spec send_after(pid | atom, term, non_neg_integer) :: reference
def send_after(dest, msg, time) do
:erlang.send_after(time, dest, msg)
end
@type spawn_opt :: :link | :monitor | {:priority, :low | :normal | :high} |
{:fullsweep_after, non_neg_integer} |
{:min_heap_size, non_neg_integer} |
{:min_bin_vheap_size, non_neg_integer}
@type spawn_opts :: [spawn_opt]
@doc """
Spawns the given module and function passing the given args
according to the given options.
The result depends on the given options. In particular,
if `:monitor` is given as an option, it will return a tuple
containing the pid and the monitoring reference, otherwise
just the spawned process pid.
It also accepts extra options, for the list of available options
check http://www.erlang.org/doc/man/erlang.html#spawn_opt-4
Inlined by the compiler.
"""
@spec spawn((() -> any), spawn_opts) :: pid | {pid, reference}
def spawn(fun, opts) do
:erlang.spawn_opt(fun, opts)
end
@doc """
Spawns the given module and function passing the given args
according to the given options.
The result depends on the given options. In particular,
if `:monitor` is given as an option, it will return a tuple
containing the pid and the monitoring reference, otherwise
just the spawned process pid.
It also accepts extra options, for the list of available options
check http://www.erlang.org/doc/man/erlang.html#spawn_opt-4
Inlined by the compiler.
"""
@spec spawn(module, atom, list, spawn_opts) :: pid | {pid, reference}
def spawn(mod, fun, args, opts) do
:erlang.spawn_opt(mod, fun, args, opts)
end
@doc """
The calling process starts monitoring the item given.
It returns the monitor reference.
See http://www.erlang.org/doc/man/erlang.html#monitor-2 for more info.
Inlined by the compiler.
"""
@spec monitor(pid | {reg_name :: atom, node :: atom} | reg_name :: atom) :: reference
def monitor(item) do
:erlang.monitor(:process, item)
end
@doc """
If `monitor_ref` is a reference which the calling process
obtained by calling `monitor/1`, this monitoring is turned off.
If the monitoring is already turned off, nothing happens.
See http://www.erlang.org/doc/man/erlang.html#demonitor-2 for more info.
Inlined by the compiler.
"""
@spec demonitor(reference) :: true
@spec demonitor(reference, options :: [:flush | :info]) :: boolean
def demonitor(monitor_ref, options \\ []) do
:erlang.demonitor(monitor_ref, options)
end
@doc """
Returns a list of process identifiers corresponding to all the
processes currently existing on the local node.
Note that a process that is exiting, exists but is not alive, i.e.,
`alive?/1` will return `false` for a process that is exiting,
but its process identifier will be part of the result returned.
See http://www.erlang.org/doc/man/erlang.html#processes-0 for more info.
"""
@spec list :: [pid]
def list do
:erlang.processes()
end
@doc """
Creates a link between the calling process and another process
(or port) `pid`, if there is not such a link already.
See http://www.erlang.org/doc/man/erlang.html#link-1 for more info.
Inlined by the compiler.
"""
@spec link(pid | port) :: true
def link(pid) do
:erlang.link(pid)
end
@doc """
Removes the link, if there is one, between the calling process and
the process or port referred to by `pid`. Returns `true` and does not
fail, even if there is no link or `id` does not exist
See http://www.erlang.org/doc/man/erlang.html#unlink-1 for more info.
Inlined by the compiler.
"""
@spec unlink(pid | port) :: true
def unlink(pid) do
:erlang.unlink(pid)
end
@doc """
Associates the name with a pid or a port identifier. `name`, which must
be an atom, can be used instead of the pid / port identifier with the
`Kernel.send/2` function.
`Process.register/2` will fail with `ArgumentError` if the pid supplied
is no longer alive, (check with `alive?/1`) or if the name is
already registered (check with `whereis/1`).
"""
@spec register(pid | port, atom) :: true
def register(pid, name) when not name in [nil, false, true] do
:erlang.register(name, pid)
end
@doc """
Removes the registered name, associated with a pid or a port identifier.
See http://www.erlang.org/doc/man/erlang.html#unregister-1 for more info.
"""
@spec unregister(atom) :: true
def unregister(name) do
:erlang.unregister(name)
end
@doc """
Returns the pid or port identifier with the registered name.
Returns `nil` if the name is not registered.
See http://www.erlang.org/doc/man/erlang.html#whereis-1 for more info.
"""
@spec whereis(atom) :: pid | port | nil
def whereis(name) do
nillify :erlang.whereis(name)
end
@doc """
Returns the pid of the group leader for the process which evaluates the function.
"""
@spec group_leader :: pid
def group_leader do
:erlang.group_leader
end
@doc """
Sets the group leader of `pid` to `leader`. Typically, this is used when a processes
started from a certain shell should have a group leader other than `:init`.
"""
@spec group_leader(pid, leader :: pid) :: true
def group_leader(pid, leader) do
:erlang.group_leader(leader, pid)
end
@doc """
Returns a list of names which have been registered using `register/2`.
"""
@spec registered :: [atom]
def registered do
:erlang.registered()
end
@typep process_flag :: :trap_exit | :error_handler | :min_heap_size |
:min_bin_vheap_size | :priority | :save_calls |
:sensitive
@doc """
Sets certain flags for the process which calls this function.
Returns the old value of the flag.
See http://www.erlang.org/doc/man/erlang.html#process_flag-2 for more info.
"""
@spec flag(process_flag, term) :: term
def flag(flag, value) do
:erlang.process_flag(flag, value)
end
@doc """
Sets certain flags for the process `pid`, in the same manner as `flag/2`.
Returns the old value of the flag. The allowed values for `flag` are
only a subset of those allowed in `flag/2`, namely: `save_calls`.
See http://www.erlang.org/doc/man/erlang.html#process_flag-3 for more info.
"""
@spec flag(pid, :save_calls, non_neg_integer) :: non_neg_integer
def flag(pid, flag, value) do
:erlang.process_flag(pid, flag, value)
end
@doc """
Returns information about the process identified by `pid` or `nil` if the process
is not alive.
Use this only for debugging information.
See http://www.erlang.org/doc/man/erlang.html#process_info-1 for more info.
"""
@spec info(pid) :: Keyword.t
def info(pid) do
nillify :erlang.process_info(pid)
end
@doc """
Returns information about the process identified by `pid`
or `nil` if the process is not alive.
See http://www.erlang.org/doc/man/erlang.html#process_info-2 for more info.
"""
@spec info(pid, atom) :: {atom, term} | nil
def info(pid, spec)
def info(pid, :registered_name) do
case :erlang.process_info(pid, :registered_name) do
:undefined -> nil
[] -> {:registered_name, []}
other -> other
end
end
def info(pid, spec) when is_atom(spec) do
nillify :erlang.process_info(pid, spec)
end
@compile {:inline, nillify: 1}
defp nillify(:undefined), do: nil
defp nillify(other), do: other
end