diff options
Diffstat (limited to 'system/doc/design_principles/spec_proc.xml')
| -rw-r--r-- | system/doc/design_principles/spec_proc.xml | 65 |
1 files changed, 44 insertions, 21 deletions
diff --git a/system/doc/design_principles/spec_proc.xml b/system/doc/design_principles/spec_proc.xml index 8de7a5fe03..e4fb5fdca7 100644 --- a/system/doc/design_principles/spec_proc.xml +++ b/system/doc/design_principles/spec_proc.xml @@ -4,7 +4,7 @@ <chapter> <header> <copyright> - <year>1997</year><year>2013</year> + <year>1997</year><year>2014</year> <holder>Ericsson AB. All Rights Reserved.</holder> </copyright> <legalnotice> @@ -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> @@ -408,11 +431,11 @@ loop(...) -> <section> <title>User-Defined Behaviours</title> - <p>To implement a user-defined behaviour, write code similar to + <p><marker id="behaviours"/>To implement a user-defined behaviour, write code similar to code for a special process but calling functions in a callback module for handling specific tasks.</p> <p>If it is desired that the compiler should warn for missing callback - functions, as it does for the OTP behaviours, add callback attributes in the + functions, as it does for the OTP behaviours, add <c>-callback</c> attributes in the behaviour module to describe the expected callbacks:</p> <code type="none"> -callback Name1(Arg1_1, Arg1_2, ..., Arg1_N1) -> Res1. @@ -422,15 +445,15 @@ loop(...) -> <p>where <c>NameX</c> are the names of the expected callbacks and <c>ArgX_Y</c>, <c>ResX</c> are types as they are described in Specifications for functions in <seealso marker="../reference_manual/typespec">Types and - Function Specifications</seealso>. The whole syntax of spec attributes is - supported by callback attributes.</p> + Function Specifications</seealso>. The whole syntax of <c>-spec</c> attribute is + supported by <c>-callback</c> attribute.</p> <p>Alternatively you may directly implement and export the function:</p> <code type="none"> behaviour_info(callbacks) -> - [{Name1,Arity1},...,{NameN,ArityN}].</code> - <p>where each <c>{Name,Arity}</c> specifies the name and arity of a callback + [{Name1, Arity1},...,{NameN, ArityN}].</code> + <p>where each <c>{Name, Arity}</c> specifies the name and arity of a callback function. This function is otherwise automatically generated by the compiler - using the callback attributes.</p> + using the <c>-callback</c> attributes.</p> <p>When the compiler encounters the module attribute <c>-behaviour(Behaviour).</c> in a module <c>Mod</c>, it will call <c>Behaviour:behaviour_info(callbacks)</c> and compare the result with the |