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

/*  tpax: a topological pax implementation                    */

/*  Copyright (C) 2020--2021  SysDeer Technologies, LLC       */

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

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

#include <stdint.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <fcntl.h>

#include <errno.h>

#include <grp.h>

#include <pwd.h>

#include <sys/stat.h>

#include <tpax/tpax.h>

#include <tpax/tpax_specs.h>

#include "tpax_driver_impl.h"

#include "tpax_tmpfile_impl.h"

#include "tpax_errinfo_impl.h"

#ifndef ssizeof

#define ssizeof(x) (ssize_t)(sizeof(x))

#endif

int tpax_file_create_tmpfs_snapshot(

	const struct tpax_driver_ctx *  dctx,

	int                             fdat,

	const char *                    path,

	const struct stat *             srcst)

{

	int          fdsrc;

	int          fdtmp;

	char *       ch;

	ssize_t      nread;

	ssize_t      nbytes;

	ssize_t      ret;

	void *       buf;

	size_t       buflen;

	struct stat  dstst;

	/* record errors */

	tpax_driver_set_ectx(

		dctx,0,path);

	/* tmpfile */

	if ((fdtmp = tpax_tmpfile()) < 0)

		return TPAX_SYSTEM_ERROR(dctx);

	/* buffer */

	buf = tpax_get_driver_anon_map_addr(

		dctx,&buflen);

	/* open */

	if ((fdsrc = openat(fdat,path,O_CLOEXEC|O_NOCTTY|O_NOFOLLOW,0)) < 0) {

		close(fdtmp);

		return TPAX_SYSTEM_ERROR(dctx);

	}

	/* stat compare */

	if ((fstat(fdsrc,&dstst)) < 0) {

		close(fdsrc);

		close(fdtmp);

		return TPAX_SYSTEM_ERROR(dctx);

	} else if (tpax_stat_compare(srcst,&dstst)) {

		close(fdsrc);

		close(fdtmp);

		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FILE_CHANGED);

	}

	/* read/write loop */

	for (nread=0; nread<srcst->st_size; ) {

		nbytes = read(fdsrc,buf,buflen);

		while ((nbytes < 0) && (errno == EINTR))

			nbytes = read(fdsrc,buf,buflen);

		if (nbytes < 0) {

			close(fdsrc);

			close(fdtmp);

			return TPAX_SYSTEM_ERROR(dctx);

		} else if (nbytes == 0) {

			close(fdsrc);

			close(fdtmp);

			return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FLOW_ERROR);

		} else {

			nread += nbytes;

		}

		for (ch=buf; nbytes; ch+=ret) {

			ret = write(fdtmp,ch,nbytes);

			while ((ret < 0) && (errno == EINTR))

				ret = write(fdtmp,ch,nbytes);

			if (ret < 0) {

				close(fdsrc);

				close(fdtmp);

				return TPAX_SYSTEM_ERROR(dctx);

			} else {

				nbytes -= ret;

			}

		}

	}

	/* stat compare */

	if ((fstat(fdsrc,&dstst)) < 0) {

		close(fdsrc);

		close(fdtmp);

		return TPAX_SYSTEM_ERROR(dctx);

	} else if (tpax_stat_compare(srcst,&dstst)) {

		close(fdsrc);

		close(fdtmp);

		return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FILE_CHANGED);

	}

	/* yay */

	close(fdsrc);

	return fdtmp;

}