/*
 * Unix SMB/CIFS implementation.
 * Samba system utilities
 * Copyright (C) Andrew Tridgell 1992-1998
 * Copyright (C) Jeremy Allison  1998-2005
 * Copyright (C) Timur Bakeyev        2005
 * Copyright (C) Bjoern Jacke    2006-2007
 *
 * 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 <http://www.gnu.org/licenses/>.
 */

#include "replace.h"
#include "system/filesys.h"
#include "lib/util/sys_rw.h"

bool sys_valid_io_range(off_t offset, size_t length)
{
	uint64_t last_byte_ofs;

	if (offset < 0) {
		return false;
	}

	if (offset > INT64_MAX) {
		return false;
	}

	if (length > UINT32_MAX) {
		return false;
	}

	last_byte_ofs = (uint64_t)offset + (uint64_t)length;
	if (last_byte_ofs > INT64_MAX) {
		return false;
	}

	return true;
}

bool sys_io_ranges_overlap(size_t c1, off_t o1,
			   size_t c2, off_t o2)
{
	if (c1 == 0 || c2 == 0) {
		return false;
	}
	if (o2 < o1) {
		/*
		 *          o1
		 *          |····c1····|
		 *  o2
		 *  |····c2···| ?
		 */
		return (o2 + c2 > o1);
	} else {
		/*
		 *  o1
		 *  |····c1···|
		 *          o2
		 *          |····c2····| ?
		 */
		return (o1 + c1 > o2);
	}
}

/*******************************************************************
A read wrapper that will deal with EINTR/EWOULDBLOCK
********************************************************************/

ssize_t sys_read(int fd, void *buf, size_t count)
{
	ssize_t ret;

	do {
		ret = read(fd, buf, count);
	} while (ret == -1 && (errno == EINTR || errno == EAGAIN ||
			       errno == EWOULDBLOCK));

	return ret;
}

/**
 * read wrapper, void variant:
 * This is intended to be used as a void variant of
 * read in situations where the caller wants to ignore
 * the result. Hence not checking for EAGAIN|EWOULDBLOCK.
 */
void sys_read_v(int fd, void *buf, size_t count)
{
	ssize_t ret;

	do {
		ret = read(fd, buf, count);
	} while (ret == -1 && errno == EINTR);
}


/*******************************************************************
A write wrapper that will deal with EINTR/EWOULDBLOCK.
********************************************************************/

ssize_t sys_write(int fd, const void *buf, size_t count)
{
	ssize_t ret;

	do {
		ret = write(fd, buf, count);
	} while (ret == -1 && (errno == EINTR || errno == EAGAIN ||
			       errno == EWOULDBLOCK));

	return ret;
}

/**
 * write wrapper to deal with EINTR and friends.
 * void-variant that ignores the number of bytes written.
 * This is intended to be used as a void variant of
 * write in situations where the caller wants to ignore
 * the result. Hence not checking for EAGAIN|EWOULDBLOCK.
 */
void sys_write_v(int fd, const void *buf, size_t count)
{
	ssize_t ret;

	do {
		ret = write(fd, buf, count);
	} while (ret == -1 && errno == EINTR);
}


/*******************************************************************
A writev wrapper that will deal with EINTR.
********************************************************************/

ssize_t sys_writev(int fd, const struct iovec *iov, int iovcnt)
{
	ssize_t ret;

	do {
		ret = writev(fd, iov, iovcnt);
	} while (ret == -1 && (errno == EINTR || errno == EAGAIN ||
			       errno == EWOULDBLOCK));

	return ret;
}

/*******************************************************************
A pread wrapper that will deal with EINTR
********************************************************************/

ssize_t sys_pread(int fd, void *buf, size_t count, off_t off)
{
	ssize_t ret;

	do {
		ret = pread(fd, buf, count, off);
	} while (ret == -1 && errno == EINTR);
	return ret;
}

/*******************************************************************
 A pread wrapper that will deal with EINTR and never return a short
 read unless pread returns zero meaning EOF.
********************************************************************/

ssize_t sys_pread_full(int fd, void *buf, size_t count, off_t off)
{
	ssize_t total_read = 0;
	uint8_t *curr_buf = (uint8_t *)buf;
	size_t curr_count = count;
	off_t curr_off = off;
	bool ok;

	ok = sys_valid_io_range(off, count);
	if (!ok) {
		errno = EINVAL;
		return -1;
	}

	while (curr_count != 0) {
		ssize_t ret = sys_pread(fd,
					curr_buf,
					curr_count,
					curr_off);

		if (ret == -1) {
			return -1;
		}
		if (ret == 0) {
			/* EOF */
			break;
		}

		if (ret > curr_count) {
			errno = EIO;
			return -1;
		}

		curr_buf += ret;
		curr_count -= ret;
		curr_off += ret;

		total_read += ret;
	}

	return total_read;
}

/*******************************************************************
A write wrapper that will deal with EINTR
********************************************************************/

ssize_t sys_pwrite(int fd, const void *buf, size_t count, off_t off)
{
	ssize_t ret;

	do {
		ret = pwrite(fd, buf, count, off);
	} while (ret == -1 && errno == EINTR);
	return ret;
}

/*******************************************************************
 A pwrite wrapper that will deal with EINTR and never allow a short
 write unless the file system returns an error.
********************************************************************/

ssize_t sys_pwrite_full(int fd, const void *buf, size_t count, off_t off)
{
	ssize_t total_written = 0;
	const uint8_t *curr_buf = (const uint8_t *)buf;
	size_t curr_count = count;
	off_t curr_off = off;
	bool ok;

	ok = sys_valid_io_range(off, count);
	if (!ok) {
		errno = EINVAL;
		return -1;
	}

	while (curr_count != 0) {
		ssize_t ret = sys_pwrite(fd,
					 curr_buf,
					 curr_count,
					 curr_off);

		if (ret == -1) {
			return -1;
		}
		if (ret == 0) {
			/* Ensure we can never spin. */
			errno = ENOSPC;
			return -1;
		}

		if (ret > curr_count) {
			errno = EIO;
			return -1;
		}

		curr_buf += ret;
		curr_count -= ret;
		curr_off += ret;

		total_written += ret;
	}

	return total_written;
}