nativelibc/posix-io/lseek.c

/*	A part of the Native C Library for Windows NT
	Copyright 2007-2015 PC GO Ld.

	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 2 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.
*/

#include <windows.h>
#include <nt.h>
#include <unistd.h>
#include <errno.h>

off_t lseek(int fd, off_t offset, int whence) {
	IO_STATUS_BLOCK io_status;
	FILE_POSITION_INFORMATION position;
	FILE_STANDARD_INFORMATION standard;
	long int status = NtQueryInformationFile((void *)fd, &io_status, &position, sizeof position, FilePositionInformation);
	//if(status < 0) return -1;
	if(__set_errno_from_ntstatus(status)) return -1;
	switch(whence) {
		case SEEK_SET:
			position.CurrentByteOffset.QuadPart = offset;
			break;
		case SEEK_CUR:
			position.CurrentByteOffset.QuadPart += offset;
			break;
		case SEEK_END:
			status = NtQueryInformationFile((void *)fd, &io_status, &standard, sizeof standard, FileStandardInformation);
			//if(status < 0) return -1;
			if(__set_errno_from_ntstatus(status)) return -1;
			position.CurrentByteOffset.QuadPart = standard.EndOfFile.QuadPart + offset;
			break;
		default:
			errno = EINVAL;
			return -1;
	}
	status = NtSetInformationFile((void *)fd, &io_status, &position, sizeof position, FilePositionInformation);
	return __set_errno_from_ntstatus(status) ? -1 : position.CurrentByteOffset.QuadPart;
}