/*****************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * $Id$
 *
 * Upload to FTP, resuming failed transfers
 *
 * Compile for MinGW like this:
 *  gcc -Wall -pedantic -std=c99 ftpuploadwithresume.c -o ftpuploadresume.exe
 *  -lcurl -lmsvcr70
 *
 * Written by Philip Bock
 */

#include <stdlib.h>
#include <stdio.h>

#include <curl/curl.h>


/* The MinGW headers are missing a few Win32 function definitions,
   you shouldn't need this if you use VC++ */
int __cdecl _snscanf(const char * input, size_t length, const char * format, ...);


/* parse headers for Content-Length */
size_t getcontentlengthfunc(void *ptr, size_t size, size_t nmemb, void *stream) {
	int r;
	long len = 0;

	/* _snscanf() is Win32 specific */
	r = _snscanf(ptr, size * nmemb, "Content-Length: %ld\n", &len);

	if (r) /* Microsoft: we don't read the specs */
		*((long *) stream) = len;

	return size * nmemb;
}

/* discard downloaded data */
size_t discardfunc(void *ptr, size_t size, size_t nmemb, void *stream) {
	return size * nmemb;
}

/* read data to upload */
size_t readfunc(void *ptr, size_t size, size_t nmemb, void *stream)
{
	FILE *f = stream;
	size_t n;

	if (ferror(f))
		return CURL_READFUNC_ABORT;

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

	return n;
}


int upload(CURL *curlhandle, const char * remotepath, const char * localpath,
           long timeout, long tries)
{
	FILE *f;
	long uploaded_len = 0;
	CURLcode r = CURLE_GOT_NOTHING;
	int c;

	f = fopen(localpath, "rb");
	if (f == NULL) {
		perror(NULL);
		return 0;
	}

	curl_easy_setopt(curlhandle, CURLOPT_UPLOAD, TRUE);

	curl_easy_setopt(curlhandle, CURLOPT_URL, remotepath);

	if (timeout)
		curl_easy_setopt(curlhandle, CURLOPT_FTP_RESPONSE_TIMEOUT, timeout);

	curl_easy_setopt(curlhandle, CURLOPT_HEADERFUNCTION, getcontentlengthfunc);
	curl_easy_setopt(curlhandle, CURLOPT_HEADERDATA, &uploaded_len);

	curl_easy_setopt(curlhandle, CURLOPT_WRITEFUNCTION, discardfunc);

	curl_easy_setopt(curlhandle, CURLOPT_READFUNCTION, readfunc);
	curl_easy_setopt(curlhandle, CURLOPT_READDATA, f);

	curl_easy_setopt(curlhandle, CURLOPT_FTPPORT, "-"); /* disable passive mode */
	curl_easy_setopt(curlhandle, CURLOPT_FTP_CREATE_MISSING_DIRS, TRUE);

	curl_easy_setopt(curlhandle, CURLOPT_VERBOSE, TRUE);

	for (c = 0; (r != CURLE_OK) && (c < tries); c++) {
		/* are we resuming? */
		if (c) { /* yes */
			/* determine the length of the file already written */

			/*
			 * With NOBODY and NOHEADER, libcurl will issue a SIZE
			 * command, but the only way to retrieve the result is
			 * to parse the returned Content-Length header. Thus,
			 * getcontentlengthfunc(). We need discardfunc() above
			 * because HEADER will dump the headers to stdout
			 * without it.
			 */
			curl_easy_setopt(curlhandle, CURLOPT_NOBODY, TRUE);
			curl_easy_setopt(curlhandle, CURLOPT_HEADER, TRUE);

			r = curl_easy_perform(curlhandle);
			if (r != CURLE_OK)
				continue;

			curl_easy_setopt(curlhandle, CURLOPT_NOBODY, FALSE);
			curl_easy_setopt(curlhandle, CURLOPT_HEADER, FALSE);

			fseek(f, uploaded_len, SEEK_SET);

			curl_easy_setopt(curlhandle, CURLOPT_FTPAPPEND, TRUE);
		}
		else { /* no */
			curl_easy_setopt(curlhandle, CURLOPT_FTPAPPEND, FALSE);
		}

		r = curl_easy_perform(curlhandle);
	}

	fclose(f);

	if (r == CURLE_OK)
		return 1;
	else {
		fprintf(stderr, "%s\n", curl_easy_strerror(r));
		return 0;
	}
}

int main(int c, char **argv) {
	CURL *curlhandle = NULL;

	curl_global_init(CURL_GLOBAL_ALL);
	curlhandle = curl_easy_init();

	upload(curlhandle, "ftp://user:pass@host/path/file", "C:\\file", 0, 3);

	curl_easy_cleanup(curlhandle);
	curl_global_cleanup();

	return 0;
}