ctdb/common/pkt_read.h

   1 /*
   2    API for reading packets using fixed and dynamic buffer
   3
   4    Copyright (C) Amitay Isaacs 2015
   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 #ifndef __CTDB_PKT_READ_H__
  21 #define __CTDB_PKT_READ_H__
  22
  23 #include <talloc.h>
  24 #include <tevent.h>
  25
  26 /**
  27  * @file pkt_read.h
  28  *
  29  * @brief Read a packet using fixed size buffer or allocated memory.
  30  *
  31  * CTDB communication uses lots of small packets.  This abstraction avoids the
  32  * need to allocate memory for small packets.  Only if the received packet is
  33  * larger than the fixed memory buffer, use talloc to allocate memory.
  34  */
  35
  36 /**
  37  * @brief Start async computation to read a packet
  38  *
  39  * This returns a tevent request to read a packet from given fd.  The fd
  40  * should be nonblocking. Freeing this request will free all the memory
  41  * associated with the request.
  42  *
  43  * @param[in] mem_ctx Talloc memory context
  44  * @param[in] ev Tevent context
  45  * @param[in] fd The non-blocking file/socket descriptor to read from
  46  * @param[in] initial Initial amount of data to read
  47  * @param[in] buf The static buffer to read data in
  48  * @param[in] buflen The size of the static buffer
  49  * @param[in] more The function to check if the bytes read forms a packet
  50  * @param[in] private_data Private data to pass to more function
  51  * @return new tevent request or NULL on failure
  52  */
  53 struct tevent_req *pkt_read_send(TALLOC_CTX *mem_ctx,
  54                                  struct tevent_context *ev,
  55                                  int fd, size_t initial,
  56                                  uint8_t *buf, size_t buflen,
  57                                  ssize_t (*more)(uint8_t *buf,
  58                                                  size_t buflen,
  59                                                  void *private_data),
  60                                  void *private_data);
  61
  62 /**
  63  * @brief Function to actually read data from the socket
  64  *
  65  * This function should be called, when tevent fd event is triggered.  This
  66  * function has the syntax of tevent_fd_handler_t.  The private_data for this
  67  * function is the tevent request created by pkt_read_send function.
  68  *
  69  * @param[in] ev Tevent context
  70  * @param[in] fde Tevent fd context
  71  * @param[in] flags Tevent fd flags
  72  * @param[in] req The active tevent request
  73  */
  74 void pkt_read_handler(struct tevent_context *ev, struct tevent_fd *fde,
  75                       uint16_t flags, struct tevent_req *req);
  76
  77 /**
  78  * @brief Retrieve a packet
  79  *
  80  * This function returns the pkt read from fd.
  81  *
  82  * @param[in] req Tevent request
  83  * @param[in] mem_ctx Talloc memory context
  84  * @param[out] pbuf The pointer to the buffer
  85  * @param[out] free_buf Boolean to indicate that caller should free buffer
  86  * @param[out] perrno errno in case of failure
  87  * @return the size of the pkt, or -1 on failure
  88  *
  89  * If the pkt data is dynamically allocated, then it is moved under the
  90  * specified talloc memory context and free_buf is set to true.  It is the
  91  * responsibility of the caller to the free the memory returned.
  92  *
  93  * If the pkt data is stored in the fixed buffer, then free_buf is set to false.
  94  */
  95 ssize_t pkt_read_recv(struct tevent_req *req, TALLOC_CTX *mem_ctx,
  96                       uint8_t **pbuf, bool *free_buf, int *perrno);
  97
  98 #endif /* __CTDB_PKT_READ_H__ */