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// 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 usermem
import (
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/hostarch"
"gvisor.dev/gvisor/pkg/safemem"
"gvisor.dev/gvisor/pkg/syserror"
)
const maxInt = int(^uint(0) >> 1)
// BytesIO implements IO using a byte slice. Addresses are interpreted as
// offsets into the slice. Reads and writes beyond the end of the slice return
// EFAULT.
type BytesIO struct {
Bytes []byte
}
// CopyOut implements IO.CopyOut.
func (b *BytesIO) CopyOut(ctx context.Context, addr hostarch.Addr, src []byte, opts IOOpts) (int, error) {
rngN, rngErr := b.rangeCheck(addr, len(src))
if rngN == 0 {
return 0, rngErr
}
return copy(b.Bytes[int(addr):], src[:rngN]), rngErr
}
// CopyIn implements IO.CopyIn.
func (b *BytesIO) CopyIn(ctx context.Context, addr hostarch.Addr, dst []byte, opts IOOpts) (int, error) {
rngN, rngErr := b.rangeCheck(addr, len(dst))
if rngN == 0 {
return 0, rngErr
}
return copy(dst[:rngN], b.Bytes[int(addr):]), rngErr
}
// ZeroOut implements IO.ZeroOut.
func (b *BytesIO) ZeroOut(ctx context.Context, addr hostarch.Addr, toZero int64, opts IOOpts) (int64, error) {
if toZero > int64(maxInt) {
return 0, syserror.EINVAL
}
rngN, rngErr := b.rangeCheck(addr, int(toZero))
if rngN == 0 {
return 0, rngErr
}
zeroSlice := b.Bytes[int(addr) : int(addr)+rngN]
for i := range zeroSlice {
zeroSlice[i] = 0
}
return int64(rngN), rngErr
}
// CopyOutFrom implements IO.CopyOutFrom.
func (b *BytesIO) CopyOutFrom(ctx context.Context, ars hostarch.AddrRangeSeq, src safemem.Reader, opts IOOpts) (int64, error) {
dsts, rngErr := b.blocksFromAddrRanges(ars)
n, err := src.ReadToBlocks(dsts)
if err != nil {
return int64(n), err
}
return int64(n), rngErr
}
// CopyInTo implements IO.CopyInTo.
func (b *BytesIO) CopyInTo(ctx context.Context, ars hostarch.AddrRangeSeq, dst safemem.Writer, opts IOOpts) (int64, error) {
srcs, rngErr := b.blocksFromAddrRanges(ars)
n, err := dst.WriteFromBlocks(srcs)
if err != nil {
return int64(n), err
}
return int64(n), rngErr
}
func (b *BytesIO) rangeCheck(addr hostarch.Addr, length int) (int, error) {
if length == 0 {
return 0, nil
}
if length < 0 {
return 0, syserror.EINVAL
}
max := hostarch.Addr(len(b.Bytes))
if addr >= max {
return 0, syserror.EFAULT
}
end, ok := addr.AddLength(uint64(length))
if !ok || end > max {
return int(max - addr), syserror.EFAULT
}
return length, nil
}
func (b *BytesIO) blocksFromAddrRanges(ars hostarch.AddrRangeSeq) (safemem.BlockSeq, error) {
switch ars.NumRanges() {
case 0:
return safemem.BlockSeq{}, nil
case 1:
block, err := b.blockFromAddrRange(ars.Head())
return safemem.BlockSeqOf(block), err
default:
blocks := make([]safemem.Block, 0, ars.NumRanges())
for !ars.IsEmpty() {
block, err := b.blockFromAddrRange(ars.Head())
if block.Len() != 0 {
blocks = append(blocks, block)
}
if err != nil {
return safemem.BlockSeqFromSlice(blocks), err
}
ars = ars.Tail()
}
return safemem.BlockSeqFromSlice(blocks), nil
}
}
func (b *BytesIO) blockFromAddrRange(ar hostarch.AddrRange) (safemem.Block, error) {
n, err := b.rangeCheck(ar.Start, int(ar.Length()))
if n == 0 {
return safemem.Block{}, err
}
return safemem.BlockFromSafeSlice(b.Bytes[int(ar.Start) : int(ar.Start)+n]), err
}
// BytesIOSequence returns an IOSequence representing the given byte slice.
func BytesIOSequence(buf []byte) IOSequence {
return IOSequence{
IO: &BytesIO{buf},
Addrs: hostarch.AddrRangeSeqOf(hostarch.AddrRange{0, hostarch.Addr(len(buf))}),
}
}
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