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

/*  slibtool: a skinny libtool implementation, written in C        */

/*  Copyright (C) 2016--2021  SysDeer Technologies, LLC            */

/*  Released under the Standard MIT License; see COPYING.SLIBTOOL. */

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

#include <fcntl.h>

#include <stdlib.h>

#include <limits.h>

#include <errno.h>

#include <sys/stat.h>

#include <slibtool/slibtool.h>

#include "slibtool_driver_impl.h"

#include "slibtool_readlink_impl.h"

#ifdef HAVE_SYS_SYSCALL_H

#include <sys/syscall.h>

#endif

#ifdef _MIDIPIX_ABI

#include <sys/fs.h>

#endif

#ifndef ENOTSUP

#define ENOTSUP EOPNOTSUPP

#endif

#ifdef SYS___realpathat

extern long syscall(int, ...);

#endif

int slbt_realpath(

	int             fdat,

	const char *    path,

	int             options,

	char *          buf,

	size_t          buflen)

{

	int             ret;

	int             fd;

	int             fdproc;

	struct stat     st;

	struct stat     stproc;

	char    procfspath[36];

	/* common validation */

	if (!buf || (options & O_CREAT)) {

		errno = EINVAL;

		return -1;

	}

	/* framework-based wrapper */

#ifdef _MIDIPIX_ABI

	return __fs_rpath(fdat,path,options,buf,buflen);

#endif

#ifdef SYS___realpathat

	return syscall(SYS___realpathat,fdat,path,buf,buflen,0);

#endif

	/* buflen */

	if (buflen < PATH_MAX) {

		errno = ENOBUFS;

		return -1;

	}

	/* AT_FDCWD */

	if (fdat == AT_FDCWD) {

		return realpath(path,buf) ? 0 : -1;

	}

	/* /proc/self/fd */

	if ((fd = openat(fdat,path,options,0)) < 0)

		return -1;

	sprintf(procfspath,"/proc/self/fd/%d",fd);

	if (slbt_readlinkat(fdat,procfspath,buf,buflen)) {

		close(fd);

		return -1;

	}

	if ((fdproc = openat(AT_FDCWD,buf,options|O_NOFOLLOW,0)) < 0) {

		close(fd);

		errno = ELOOP;

		return -1;

	}

	ret = fstat(fd,&st) || fstat(fdproc,&stproc);

	close(fd);

	close(fdproc);

	if (ret || (st.st_dev != stproc.st_dev) || (st.st_ino != stproc.st_ino)) {

		errno = ENOTSUP;

		return -1;

	}

	return 0;

}