// Copyright 2018 The gVisor Authors. 
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License. 
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
// See the License for the specific language governing permissions and
// limitations under the License. 

package linux

import (
	"gvisor.dev/gvisor/pkg/sentry/arch"
	"gvisor.dev/gvisor/pkg/sentry/fs"
	"gvisor.dev/gvisor/pkg/sentry/kernel"
	"gvisor.dev/gvisor/pkg/syserror"
)

// LINT.IfChange

// Lseek implements linux syscall lseek(2). 
func Lseek(t *kernel. Task, args arch. SyscallArguments) (uintptr, *kernel. SyscallControl, error) {
	fd := args[0].Int()
	offset := args[1].Int64()
	whence := args[2].Int()

	file := t.GetFile(fd)
	if file == nil {
		return 0, nil, syserror. EBADF
	}
	defer file. DecRef(t)

	var sw fs. SeekWhence
	switch whence {
	case 0:
		sw = fs. SeekSet
	case 1:
		sw = fs. SeekCurrent
	case 2:
		sw = fs. SeekEnd
	default:
		return 0, nil, syserror. EINVAL
	}

	offset, serr := file. Seek(t, sw, offset)
	err := handleIOError(t, false /* partialResult */, serr, syserror. ERESTARTSYS, "lseek", file)
	if err ! = nil {
		return 0, nil, err
	}
	return uintptr(offset), nil, err
}

// LINT.ThenChange(vfs2/read_write.go)
