/* Copyright (C) 2019  C. McEnroe <june@causal.agency>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *
 * Additional permission under GNU GPL version 3 section 7:
 *
 * If you modify this Program, or any covered work, by linking or
 * combining it with OpenSSL (or a modified version of that library),
 * containing parts covered by the terms of the OpenSSL License and the
 * original SSLeay license, the licensors of this Program grant you
 * additional permission to convey the resulting work. Corresponding
 * Source for a non-source form of such a combination shall include the
 * source code for the parts of OpenSSL used as well as that of the
 * covered work.
 */

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

typedef int Read(void *, char *, int);
typedef int Write(void *, const char *, int);
typedef fpos_t Seek(void *, fpos_t, int);
typedef int Close(void *);

struct Funopen {
	void *cookie;
	Read *readfn;
	Write *writefn;
	Close *closefn;
};

static ssize_t cookieRead(void *cookie, char *buf, size_t size) {
	struct Funopen *funopen = cookie;
	return funopen->readfn(funopen->cookie, buf, size);
}

static ssize_t cookieWrite(void *cookie, const char *buf, size_t size) {
	struct Funopen *funopen = cookie;
	return funopen->writefn(funopen->cookie, buf, size);
}

static int cookieClose(void *cookie) {
	struct Funopen *funopen = cookie;
	int ret = 0;
	if (funopen->closefn) ret = funopen->closefn(funopen->cookie);
	free(cookie);
	return ret;
}

FILE *funopen(
	const void *cookie,
	Read *readfn, Write *writefn, Seek *seekfn, Close *closefn
) {
	struct Funopen *funopen = malloc(sizeof(*funopen));
	if (!funopen) return NULL;
	funopen->cookie = (void *)cookie;
	funopen->readfn = readfn;
	funopen->writefn = writefn;
	assert(!seekfn);
	funopen->closefn = closefn;
	cookie_io_functions_t fns = {
		.read = (readfn ? cookieRead : NULL),
		.write = (writefn ? cookieWrite : NULL),
		.close = cookieClose,
	};
	return fopencookie(funopen, (!readfn ? "w" : !writefn ? "r" : "r+"), fns);
}