lib/pingpong.h

#ifndef HEADER_CURL_PINGPONG_H
#define HEADER_CURL_PINGPONG_H
/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) 1998 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 ***************************************************************************/

#include "curl_setup.h"

#if !defined(CURL_DISABLE_IMAP) || !defined(CURL_DISABLE_FTP) || \
  !defined(CURL_DISABLE_POP3) || !defined(CURL_DISABLE_SMTP)
#define USE_PINGPONG
#endif

/* forward-declaration, this is defined in urldata.h */
struct connectdata;

typedef enum {
  PPTRANSFER_BODY, /* yes do transfer a body */
  PPTRANSFER_INFO, /* do still go through to get info/headers */
  PPTRANSFER_NONE  /* don't get anything and don't get info */
} curl_pp_transfer;

/*
 * 'pingpong' is the generic struct used for protocols doing server<->client
 * conversations in a back-and-forth style such as FTP, IMAP, POP3, SMTP etc.
 *
 * It holds response cache and non-blocking sending data.
 */
struct pingpong {
  char *cache;     /* data cache between getresponse()-calls */
  size_t cache_size;  /* size of cache in bytes */
  size_t nread_resp;  /* number of bytes currently read of a server response */
  char *linestart_resp; /* line start pointer for the server response
                           reader function */
  bool pending_resp;  /* set TRUE when a server response is pending or in
                         progress, and is cleared once the last response is
                         read */
  char *sendthis; /* allocated pointer to a buffer that is to be sent to the
                     server */
  size_t sendleft; /* number of bytes left to send from the sendthis buffer */
  size_t sendsize; /* total size of the sendthis buffer */
  struct curltime response; /* set to Curl_now() when a command has been sent
                               off, used to time-out response reading */
  timediff_t response_time; /* When no timeout is given, this is the amount of
                               milliseconds we await for a server response. */
  struct dynbuf sendbuf;

  /* Function pointers the protocols MUST implement and provide for the
     pingpong layer to function */

  CURLcode (*statemachine)(struct Curl_easy *data, struct connectdata *conn);
  bool (*endofresp)(struct Curl_easy *data, struct connectdata *conn,
                    char *ptr, size_t len, int *code);
};

#define PINGPONG_SETUP(pp,s,e)                   \
  do {                                           \
    pp->response_time = RESP_TIMEOUT;            \
    pp->statemachine = s;                        \
    pp->endofresp = e;                           \
  } while(0)

/*
 * Curl_pp_statemach()
 *
 * called repeatedly until done. Set 'wait' to make it wait a while on the
 * socket if there's no traffic.
 */
CURLcode Curl_pp_statemach(struct Curl_easy *data, struct pingpong *pp,
                           bool block, bool disconnecting);

/* initialize stuff to prepare for reading a fresh new response */
void Curl_pp_init(struct Curl_easy *data, struct pingpong *pp);

/* setup for the transfer */
void Curl_pp_setup(struct pingpong *pp);

/* Returns timeout in ms. 0 or negative number means the timeout has already
   triggered */
timediff_t Curl_pp_state_timeout(struct Curl_easy *data,
                                 struct pingpong *pp, bool disconnecting);


/***********************************************************************
 *
 * Curl_pp_sendf()
 *
 * Send the formatted string as a command to a pingpong server. Note that
 * the string should not have any CRLF appended, as this function will
 * append the necessary things itself.
 *
 * made to never block
 */
CURLcode Curl_pp_sendf(struct Curl_easy *data,
                       struct pingpong *pp,
                       const char *fmt, ...);

/***********************************************************************
 *
 * Curl_pp_vsendf()
 *
 * Send the formatted string as a command to a pingpong server. Note that
 * the string should not have any CRLF appended, as this function will
 * append the necessary things itself.
 *
 * made to never block
 */
CURLcode Curl_pp_vsendf(struct Curl_easy *data,
                        struct pingpong *pp,
                        const char *fmt,
                        va_list args);

/*
 * Curl_pp_readresp()
 *
 * Reads a piece of a server response.
 */
CURLcode Curl_pp_readresp(struct Curl_easy *data,
                          curl_socket_t sockfd,
                          struct pingpong *pp,
                          int *code, /* return the server code if done */
                          size_t *size); /* size of the response */


CURLcode Curl_pp_flushsend(struct Curl_easy *data,
                           struct pingpong *pp);

/* call this when a pingpong connection is disconnected */
CURLcode Curl_pp_disconnect(struct pingpong *pp);

int Curl_pp_getsock(struct Curl_easy *data, struct pingpong *pp,
                    curl_socket_t *socks);


/***********************************************************************
 *
 * Curl_pp_moredata()
 *
 * Returns whether there are still more data in the cache and so a call
 * to Curl_pp_readresp() will not block.
 */
bool Curl_pp_moredata(struct pingpong *pp);

#endif /* HEADER_CURL_PINGPONG_H */