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-rw-r--r--system/doc/design_principles/spec_proc.xml49
1 files changed, 36 insertions, 13 deletions
diff --git a/system/doc/design_principles/spec_proc.xml b/system/doc/design_principles/spec_proc.xml
index 8de7a5fe03..69bf2e0448 100644
--- a/system/doc/design_principles/spec_proc.xml
+++ b/system/doc/design_principles/spec_proc.xml
@@ -130,7 +130,8 @@ ok
-export([alloc/0, free/1]).
-export([init/1]).
-export([system_continue/3, system_terminate/4,
- write_debug/3]).
+ write_debug/3,
+ system_get_state/1, system_replace_state/2]).
start_link() ->
proc_lib:start_link(ch4, init, [self()]).
@@ -156,15 +157,15 @@ init(Parent) ->
loop(Chs, Parent, Deb) ->
receive
{From, alloc} ->
- Deb2 = sys:handle_debug(Deb, {ch4, write_debug},
+ Deb2 = sys:handle_debug(Deb, fun ch4:write_debug/3,
ch4, {in, alloc, From}),
{Ch, Chs2} = alloc(Chs),
From ! {ch4, Ch},
- Deb3 = sys:handle_debug(Deb2, {ch4, write_debug},
+ Deb3 = sys:handle_debug(Deb2, fun ch4:write_debug/3,
ch4, {out, {ch4, Ch}, From}),
loop(Chs2, Parent, Deb3);
{free, Ch} ->
- Deb2 = sys:handle_debug(Deb, {ch4, write_debug},
+ Deb2 = sys:handle_debug(Deb, fun ch4:write_debug/3,
ch4, {in, {free, Ch}}),
Chs2 = free(Ch, Chs),
loop(Chs2, Parent, Deb2);
@@ -177,9 +178,16 @@ loop(Chs, Parent, Deb) ->
system_continue(Parent, Deb, Chs) ->
loop(Chs, Parent, Deb).
-system_terminate(Reason, Parent, Deb, Chs) ->
+system_terminate(Reason, _Parent, _Deb, _Chs) ->
exit(Reason).
+system_get_state(Chs) ->
+ {ok, Chs}.
+
+system_replace_state(StateFun, Chs) ->
+ NChs = StateFun(Chs),
+ {ok, NChs, NChs}.
+
write_debug(Dev, Event, Name) ->
io:format(Dev, "~p event = ~p~n", [Name, Event]).</pre>
<p>Example on how the simple debugging functions in <c>sys</c> can
@@ -281,10 +289,10 @@ sys:handle_debug(Deb, Func, Info, Event) => Deb1</code>
<p><c>Deb</c> is the debug structure.</p>
</item>
<item>
- <p><c>Func</c> is a tuple <c>{Module, Name}</c> (or a fun) and
- should specify a (user defined) function used to format
+ <p><c>Func</c> is a fun specifying
+ a (user defined) function used to format
trace output. For each system event, the format function is
- called as <c>Module:Name(Dev, Event, Info)</c>, where:</p>
+ called as <c>Func(Dev, Event, Info)</c>, where:</p>
<list type="bulleted">
<item>
<p><c>Dev</c> is the IO device to which the output should
@@ -319,15 +327,15 @@ sys:handle_debug(Deb, Func, Info, Event) => Deb1</code>
loop(Chs, Parent, Deb) ->
receive
{From, alloc} ->
- Deb2 = sys:handle_debug(Deb, {ch4, write_debug},
+ Deb2 = sys:handle_debug(Deb, fun ch4:write_debug/3,
ch4, {in, alloc, From}),
{Ch, Chs2} = alloc(Chs),
From ! {ch4, Ch},
- Deb3 = sys:handle_debug(Deb2, {ch4, write_debug},
+ Deb3 = sys:handle_debug(Deb2, fun ch4:write_debug/3,
ch4, {out, {ch4, Ch}, From}),
loop(Chs2, Parent, Deb3);
{free, Ch} ->
- Deb2 = sys:handle_debug(Deb, {ch4, write_debug},
+ Deb2 = sys:handle_debug(Deb, fun ch4:write_debug/3,
ch4, {in, {free, Ch}}),
Chs2 = free(Ch, Chs),
loop(Chs2, Parent, Deb2);
@@ -366,8 +374,15 @@ Module:system_terminate(Reason, Parent, Deb, State)</code>
<item><c>Module</c> is the name of the module.</item>
<item><c>Deb</c> is the debug structure.</item>
<item><c>State</c> is a term describing the internal state and
- is passed to <c>system_continue</c>/<c>system_terminate</c>.</item>
+ is passed to <c>system_continue</c>/<c>system_terminate</c>/
+ <c>system_get_state</c>/<c>system_replace_state</c>.</item>
</list>
+ <p>If the process should return its state <c>handle_system_msg</c> will call:</p>
+ <code type="none">
+Module:system_get_state(State)</code>
+ <p>or if the process should replace its state using the fun <c>StateFun</c>:</p>
+ <code type="none">
+Module:system_replace_state(StateFun, State)</code>
<p>In the example:</p>
<code type="none">
loop(Chs, Parent, Deb) ->
@@ -383,7 +398,15 @@ system_continue(Parent, Deb, Chs) ->
loop(Chs, Parent, Deb).
system_terminate(Reason, Parent, Deb, Chs) ->
- exit(Reason).</code>
+ exit(Reason).
+
+system_get_state(Chs) ->
+ {ok, Chs, Chs}.
+
+system_replace_state(StateFun, Chs) ->
+ NChs = StateFun(Chs),
+ {ok, NChs, NChs}.
+</code>
<p>If the special process is set to trap exits, note that if
the parent process terminates, the expected behavior is to
terminate with the same reason:</p>