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// Copyright 2020 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 hostfd
import (
"unsafe"
"golang.org/x/sys/unix"
)
const (
sizeofIovec = unsafe.Sizeof(unix.Iovec{})
sizeofMsghdr = unsafe.Sizeof(unix.Msghdr{})
)
func iovecsReadWrite(sysno uintptr, fd int32, iovs []unix.Iovec, offset int64, flags uint32) (uintptr, unix.Errno) {
var total uintptr
for start := 0; start < len(iovs); start += MaxReadWriteIov {
last := true
size := len(iovs) - start
if size > MaxReadWriteIov {
last = false
size = MaxReadWriteIov
}
curOff := offset
if offset >= 0 {
curOff = offset + int64(total)
}
cur, _, e := unix.Syscall6(sysno, uintptr(fd), uintptr((unsafe.Pointer)(&iovs[start])), uintptr(size), uintptr(curOff), 0 /* pos_h */, uintptr(flags))
if cur > 0 {
total += cur
}
if e != 0 {
return total, e
}
if last {
break
}
// If this was a short read/write, then break.
var curTotal uint64
for i := range iovs[start : start+size] {
curTotal += iovs[i].Len
}
if uint64(cur) < curTotal {
break
}
}
return total, 0
}
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