examples/sftpuploadresume: resume upload via CURLOPT_APPEND

#                            | (__| |_| |  _ <| |___

#                             \___|\___/|_| \_\_____|

#

# Copyright (C) 1998 - 2017, Daniel Stenberg, <daniel@haxx.se>, et al.

# Copyright (C) 1998 - 2018, 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

  imap-tls imap-multi url2file sftpget ftpsget postinmemory http2-download \

  http2-upload http2-serverpush getredirect ftpuploadfrommem               \

  ftpuploadresume sslbackend postit2-formadd multi-formadd                 \

  shared-connection-cache

  shared-connection-cache sftpuploadresume

# These examples require external dependencies that may not be commonly

# available on POSIX systems, so don't bother attempting to compile them here.

/***************************************************************************

 *                                  _   _ ____  _

 *  Project                     ___| | | |  _ \| |

 *                             / __| | | | |_) | |

 *                            | (__| |_| |  _ <| |___

 *                             \___|\___/|_| \_\_____|

 *

 * Copyright (C) 1998 - 2018, 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.haxx.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.

 *

 ***************************************************************************/

/* <DESC>

 * Upload to SFTP, resuming a previously aborted transfer.

 * </DESC>

 */

#include <stdlib.h>

#include <stdio.h>

#include <curl/curl.h>

/* read data to upload */

static size_t readfunc(void *ptr, size_t size, size_t nmemb, void *stream)

{

  FILE *f = (FILE *)stream;

  size_t n;

  if(ferror(f))

    return CURL_READFUNC_ABORT;

  n = fread(ptr, size, nmemb, f) * size;

  return n;

}

/*

 * sftpGetRemoteFileSize returns the remote file size in byte; -1 on error

 */

static curl_off_t sftpGetRemoteFileSize(const char *i_remoteFile)

{

  CURLcode result = CURLE_GOT_NOTHING;

  curl_off_t remoteFileSizeByte = -1;

  CURL *curlHandlePtr = NULL;

  curlHandlePtr = curl_easy_init();

  curl_easy_setopt(curlHandlePtr, CURLOPT_VERBOSE, 1L);

  curl_easy_setopt(curlHandlePtr, CURLOPT_URL, i_remoteFile);

  curl_easy_setopt(curlHandlePtr, CURLOPT_NOPROGRESS, 1);

  curl_easy_setopt(curlHandlePtr, CURLOPT_NOBODY, 1);

  curl_easy_setopt(curlHandlePtr, CURLOPT_HEADER, 1);

  curl_easy_setopt(curlHandlePtr, CURLOPT_FILETIME, 1);

  result = curl_easy_perform(curlHandlePtr);

  if(CURLE_OK == result) {

    result = curl_easy_getinfo(curlHandlePtr,

                               CURLINFO_CONTENT_LENGTH_DOWNLOAD_T,

                               &remoteFileSizeByte);

    printf("filesize: %ld \n", remoteFileSizeByte);

  }

  curl_easy_cleanup(curlHandlePtr);

  return remoteFileSizeByte;

}

static int sftpResumeUpload(CURL *curlhandle, const char *remotepath,

                            const char *localpath)

{

  FILE *f = NULL;

  CURLcode result = CURLE_GOT_NOTHING;

  curl_off_t remoteFileSizeByte = sftpGetRemoteFileSize(remotepath);

  if(-1 == remoteFileSizeByte) {

    printf("Error reading the remote file size: unable to resume upload\n");

    return -1;

  }

  f = fopen(localpath, "rb");

  if(!f) {

    perror(NULL);

    return 0;

  }

  curl_easy_setopt(curlhandle, CURLOPT_UPLOAD, 1L);

  curl_easy_setopt(curlhandle, CURLOPT_URL, remotepath);

  curl_easy_setopt(curlhandle, CURLOPT_READFUNCTION, readfunc);

  curl_easy_setopt(curlhandle, CURLOPT_READDATA, f);

  fseek(f, remoteFileSizeByte, SEEK_SET);

  curl_easy_setopt(curlhandle, CURLOPT_APPEND, 1L);

  result = curl_easy_perform(curlhandle);

  fclose(f);

  if(result == CURLE_OK)

    return 1;

  else {

    fprintf(stderr, "%s\n", curl_easy_strerror(result));

    return 0;

  }

}

int main(void)

{

  const char *remote = "sftp://user:pass@example.com/path/filename";

  const char *filename = "filename";

  CURL *curlhandle = NULL;

  curl_global_init(CURL_GLOBAL_ALL);

  curlhandle = curl_easy_init();

  if(!sftpResumeUpload(curlhandle, remote, filename)) {

    printf("resumed upload using curl %s failed\n", curl_version());

  }

  curl_easy_cleanup(curlhandle);

  curl_global_cleanup();

  return 0;

}