NAME

       TSConfig Functions - TSConfig API function

SYNOPSIS

          #include <ts/ts.h>

       typedef void (*TSConfigDestroyFunc)(void*)

       unsigned int TSConfigSet(unsigned int id, void *data, TSConfigDestroyFunc funcp)

       TSConfig TSConfigGet(unsigned int id)

       void TSConfigRelease(unsigned int id, TSConfig configp)

       void *TSConfigDataGet(TSConfig configp)

DESCRIPTION

       These functions provide a mechanism to safely update configurations for a plugin.

       If  a  plugin stores its configuration in a data structure, updating that structure due to changes in the
       configuration file can be dangerous due to the asynchronous nature of plugin  callbacks.  To  avoid  that
       problem these functions allow a plugin to register a configuration and then later replace it with another
       instance without changing the instance in use by plugin callbacks. This  works  in  the  same  manner  as
       shared  pointer.  When  a  plugin  needs  to  access the configuration data, it calls TSConfigGet() which
       returns a pointer that will remain valid until the  plugin  calls  TSConfigRelease().  The  configuration
       instance  is  updated  with  TSConfigSet()  which will update an internal pointer but will not change any
       instance in use via TSConfigGet(). When the last in use pointer is released,  the  old  configuration  is
       destructed  using  the  function  passed  to func:TSConfigSet. This handles the overlapping configuration
       update case correctly.

       Initialization is done with TSConfigSet(). The id should be zero on the first call.  This will allocate a
       slot  for  the  configuration,  which is returned. Subsequent calls must use this value. If the id is not
       zero, that value is returned. In general, the code will look something like

          class Config { ... }; // Configuration data.
          int Config_Id = 0;
          //...
          void ConfigUpdate() {
             Config* cfg = new Config;
             cfg.load(); // load config...
             Config_Id = TSConfigSet(Config_Id, cfg,
                [](void* cfg){delete static_cast<Config*>(config);});
          }
          //...
          PluginInit() {
             // ...
             ConfigUpdate();
             // ...
          }

       Config_Id is a global variable holding the configuration id, which is updated  by  the  return  value  of
       TSConfigSet().

       The  configuration  instance is retrieved with TSConfigGet(). This returns a wrapper class from which the
       configuration can be extracted with TSConfigDataGet(). The wrapper is used to release  the  configuration
       instance when it is no longer in use. The code in a callback tends to look like

          int callback() {
             auto cfg_ref = TSConfigGet(Config_Id);
             Config* cfg = static_cast<Config*>(TSConfigDataGet(cfg_ref));
             // ... use cfg
             TSConfigRelease(Config_Id, cfg_ref);
          }

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