NAME

       TSVConnArgs - TSVConnArgs API function

SYNOPSIS

       #include <ts/ts.h>

       TSReturnCode   TSVConnArgIndexReserve(const  char  *name,  const  char  *description,  int
       *arg_idx)

       TSReturnCode  TSVConnArgIndexNameLookup(const  char  *name,  int  *arg_idx,   const   char
       **description)

       TSReturnCode   TSVConnArgIndexLookup(int   arg_idx,   const   char   **name,   const  char
       **description)

       void TSVConnArgSet(TSVConn vc, int arg_idx, void *arg)

       void *TSVConnArgGet(TSVConn vc, int arg_idx)

DESCRIPTION

       Virtual connection objects (API type TSVConn) support an array of void * values  that  are
       controlled  entirely  by  plugins.  These are not used in any way by the core. This allows
       plugins to store data associated with a specific virtual connection for later retrieval by
       the  same  plugin  in  a  different  hook  or by another plugin. Because the core does not
       interact with these values any cleanup is the responsibility of the plugin.

       To avoid collisions between plugins a plugin should first reserve an index in the array by
       calling  TSVConnArgIndexReserve()  passing  it  an  identifying name, a description, and a
       pointer to an integer which will get the reserved index. The function  returns  TS_SUCCESS
       if  an  index  was  reserved, TS_ERROR if not (most likely because all of the indices have
       already been reserved). Generally this will be a file or library scope global which is set
       at  plugin  initialization. Note the reservation is by convention - nothing stops a plugin
       from interacting with a TSVConn arg it has not reserved.

       To look up the owner of a reserved index use TSVConnArgIndexNameLookup(). If the  name  is
       found as an owner, the function returns TS_SUCCESS and arg_index is updated with the index
       reserved under that name. If description is not nullptr then it will be updated  with  the
       description  for  that  reserved  index.  This enables communication between plugins where
       plugin "A" reserves an index under a well known name and plugin "B" locates the  index  by
       looking it up under that name.

       The  owner  of a reserved index can be found with TSVConnArgIndexLookup(). If arg_index is
       reserved then the function returns TS_SUCCESS and name and description are  updated.  name
       must point at a valid character pointer but description can be nullptr.

       Manipulating  the  array is simple. TSVConnArgSet() sets the array slot at arg_idx for the
       vc to the value arg. Note this sets the value only for the specific  TSVConn.  The  values
       can  be retrieved with TSVConnArgGet() which returns the specified value. Values that have
       not been set are nullptr.

HOOKS

       Although these can be used from any hook that has access to a TSVConn it will generally be
       the case that TSVConnArgSet() will be used in early intervention hooks and TSVConnArgGet()
       in session / transaction hooks. Cleanup should be done on the TS_VCONN_CLOSE_HOOK.

       Appendix

       NOTE:
          This is originally from Issue 2388. It has been extended based on discussions with Kees
          and Leif Hedstrom at the ATS summit.

COPYRIGHT

       2021, dev@trafficserver.apache.org