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

/*  tpax: a topological pax implementation            */

/*  Copyright (C) 2020  Z. Gilboa                     */

/*  Released under GPLv2 and GPLv3; see COPYING.TPAX. */

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

#define _GNU_SOURCE

#include <fcntl.h>

#include <limits.h>

#include <stdlib.h>

#include <unistd.h>

#include <string.h>

#include <stdio.h>

/* mkostemp might be guarded by non-standard macros */

/* unless HAVE_NO_MKOSTEMP, assume it is available */

extern int mkstemp(char *);

extern int mkostemp(char *, int);

/* __fs_tmpfile() atomically provides a private tmpfile */

static int tpax_tmpfile_by_framework(void)

{

#ifdef _MIDIPIX_ABI

	extern int __fs_tmpfile(int);

	return __fs_tmpfile(O_CLOEXEC);

#else

	return (-1);

#endif

}

/* O_TMPFILE atomically provides a private tmpfile */

static int tpax_tmpfile_by_kernel(void)

{

#ifdef O_TMPFILE

	return openat(AT_FDCWD,"/tmp",O_RDWR|O_TMPFILE|O_CLOEXEC,0);

#else

	return (-1);

#endif

}

/* mk{o}stemp() provides a non-private tmpfile */

static int tpax_mkostemp(char * tmplate)

{

	int fd;

#ifdef HAVE_NO_MKOSTEMP

	if ((fd = mkstemp(tmplate)) >= 0)

		fcntl(fd,F_SETFD,FD_CLOEXEC);

#else

	fd = mkostemp(tmplate,O_CLOEXEC);

#endif

	return fd;

}

int tpax_tmpfile(void)

{

	int             fd;

	unsigned        seed;

	char            tmplate[64];

	/* try with __fs_tmpfile() */

	if ((fd = tpax_tmpfile_by_framework()) >= 0)

		return fd;

	/* try with O_TMPFILE */

	if ((fd = tpax_tmpfile_by_kernel()) >= 0)

		return fd;

	/* fallback to mk{o}stemp */

	seed = getpid();

	memset(tmplate,0,sizeof(tmplate));

	snprintf(tmplate,sizeof(tmplate),"/tmp/tpax_%d_%d_%d_XXXXXXXXXXXX",

		getppid(),getpid(),rand_r(&seed));

	return tpax_mkostemp(tmplate);

}