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// Copyright 2019 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 gofer
import (
"syscall"
"unsafe"
"gvisor.dev/gvisor/pkg/safemem"
)
// Preconditions: !dsts.IsEmpty().
func hostPreadv(fd int32, dsts safemem.BlockSeq, off int64) (uint64, error) {
// No buffering is necessary regardless of safecopy; host syscalls will
// return EFAULT if appropriate, instead of raising SIGBUS.
if dsts.NumBlocks() == 1 {
// Use pread() instead of preadv() to avoid iovec allocation and
// copying.
dst := dsts.Head()
n, _, e := syscall.Syscall6(syscall.SYS_PREAD64, uintptr(fd), dst.Addr(), uintptr(dst.Len()), uintptr(off), 0, 0)
if e != 0 {
return 0, e
}
return uint64(n), nil
}
iovs := safemem.IovecsFromBlockSeq(dsts)
n, _, e := syscall.Syscall6(syscall.SYS_PREADV, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)), uintptr(off), 0, 0)
if e != 0 {
return 0, e
}
return uint64(n), nil
}
// Preconditions: !srcs.IsEmpty().
func hostPwritev(fd int32, srcs safemem.BlockSeq, off int64) (uint64, error) {
// No buffering is necessary regardless of safecopy; host syscalls will
// return EFAULT if appropriate, instead of raising SIGBUS.
if srcs.NumBlocks() == 1 {
// Use pwrite() instead of pwritev() to avoid iovec allocation and
// copying.
src := srcs.Head()
n, _, e := syscall.Syscall6(syscall.SYS_PWRITE64, uintptr(fd), src.Addr(), uintptr(src.Len()), uintptr(off), 0, 0)
if e != 0 {
return 0, e
}
return uint64(n), nil
}
iovs := safemem.IovecsFromBlockSeq(srcs)
n, _, e := syscall.Syscall6(syscall.SYS_PWRITEV, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[0])), uintptr(len(iovs)), uintptr(off), 0, 0)
if e != 0 {
return 0, e
}
return uint64(n), nil
}
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