source/lib/async_req.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    Infrastructure for async requests
   4    Copyright (C) Volker Lendecke 2008
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include "includes.h"
  21
  22 /**
  23  * @brief Print an async_req structure
  24  * @param[in] mem_ctx   The memory context for the result
  25  * @param[in] req       The request to be printed
  26  * @retval              Text representation of req
  27  *
  28  * This is a default print function for async requests. Implementations should
  29  * override this with more specific information.
  30  *
  31  * This function should not be used by async API users, this is non-static
  32  * only to allow implementations to easily provide default information in
  33  * their specific functions.
  34  */
  35
  36 char *async_req_print(TALLOC_CTX *mem_ctx, struct async_req *req)
  37 {
  38         return talloc_asprintf(mem_ctx, "async_req: state=%d, status=%s, "
  39                                "priv=%s", req->state, nt_errstr(req->status),
  40                                talloc_get_name(req->private_data));
  41 }
  42
  43 /**
  44  * @brief Create an async request
  45  * @param[in] mem_ctx   The memory context for the result
  46  * @param[in] ev        The event context this async request will be driven by
  47  * @retval              A new async request
  48  *
  49  * The new async request will be initialized in state ASYNC_REQ_IN_PROGRESS
  50  */
  51
  52 struct async_req *async_req_new(TALLOC_CTX *mem_ctx, struct event_context *ev)
  53 {
  54         struct async_req *result;
  55
  56         result = TALLOC_ZERO_P(mem_ctx, struct async_req);
  57         if (result == NULL) {
  58                 return NULL;
  59         }
  60         result->state = ASYNC_REQ_IN_PROGRESS;
  61         result->event_ctx = ev;
  62         result->print = async_req_print;
  63         return result;
  64 }
  65
  66 /**
  67  * @brief An async request has successfully finished
  68  * @param[in] req       The finished request
  69  *
  70  * async_req_done is to be used by implementors of async requests. When a
  71  * request is successfully finished, this function calls the user's completion
  72  * function.
  73  */
  74
  75 void async_req_done(struct async_req *req)
  76 {
  77         req->status = NT_STATUS_OK;
  78         req->state = ASYNC_REQ_DONE;
  79         if (req->async.fn != NULL) {
  80                 req->async.fn(req);
  81         }
  82 }
  83
  84 /**
  85  * @brief An async request has seen an error
  86  * @param[in] req       The request with an error
  87  * @param[in] status    The error code
  88  *
  89  * async_req_done is to be used by implementors of async requests. When a
  90  * request can not successfully completed, the implementation should call this
  91  * function with the appropriate status code.
  92  */
  93
  94 void async_req_error(struct async_req *req, NTSTATUS status)
  95 {
  96         req->status = status;
  97         req->state = ASYNC_REQ_ERROR;
  98         if (req->async.fn != NULL) {
  99                 req->async.fn(req);
 100         }
 101 }
 102
 103 /**
 104  * @brief Timed event callback
 105  * @param[in] ev        Event context
 106  * @param[in] te        The timed event
 107  * @param[in] now       zero time
 108  * @param[in] priv      The async request to be finished
 109  */
 110
 111 static void async_trigger(struct event_context *ev, struct timed_event *te,
 112                           struct timeval now, void *priv)
 113 {
 114         struct async_req *req = talloc_get_type_abort(priv, struct async_req);
 115
 116         TALLOC_FREE(te);
 117         if (NT_STATUS_IS_OK(req->status)) {
 118                 async_req_done(req);
 119         }
 120         else {
 121                 async_req_error(req, req->status);
 122         }
 123 }
 124
 125 /**
 126  * @brief Finish a request before it started processing
 127  * @param[in] req       The finished request
 128  * @param[in] status    The success code
 129  *
 130  * An implementation of an async request might find that it can either finish
 131  * the request without waiting for an external event, or it can't even start
 132  * the engine. To present the illusion of a callback to the user of the API,
 133  * the implementation can call this helper function which triggers an
 134  * immediate timed event. This way the caller can use the same calling
 135  * conventions, independent of whether the request was actually deferred.
 136  */
 137
 138 bool async_post_status(struct async_req *req, NTSTATUS status)
 139 {
 140         req->status = status;
 141
 142         if (event_add_timed(req->event_ctx, req, timeval_zero(),
 143                             async_trigger, req) == NULL) {
 144                 return false;
 145         }
 146         return true;
 147 }
 148
 149 /**
 150  * @brief Helper function for nomem check
 151  * @param[in] p         The pointer to be checked
 152  * @param[in] req       The request being processed
 153  *
 154  * Convenience helper to easily check alloc failure within a callback
 155  * implementing the next step of an async request.
 156  *
 157  * Call pattern would be
 158  * \code
 159  * p = talloc(mem_ctx, bla);
 160  * if (async_req_nomem(p, req)) {
 161  *      return;
 162  * }
 163  * \endcode
 164  */
 165
 166 bool async_req_nomem(const void *p, struct async_req *req)
 167 {
 168         if (p != NULL) {
 169                 return false;
 170         }
 171         async_req_error(req, NT_STATUS_NO_MEMORY);
 172         return true;
 173 }