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// Copyright 2018 Google Inc.
//
// 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 host
import (
"syscall"
"unsafe"
)
// buildIovec builds an iovec slice from the given []byte slice.
func buildIovec(bufs [][]byte) (uintptr, []syscall.Iovec) {
var length uintptr
iovecs := make([]syscall.Iovec, 0, 10)
for i := range bufs {
if l := len(bufs[i]); l > 0 {
length += uintptr(l)
iovecs = append(iovecs, syscall.Iovec{
Base: &bufs[i][0],
Len: uint64(l),
})
}
}
return length, iovecs
}
func fdReadVec(fd int, bufs [][]byte, control []byte, peek bool) (readLen uintptr, msgLen uintptr, controlLen uint64, err error) {
flags := uintptr(syscall.MSG_DONTWAIT | syscall.MSG_TRUNC)
if peek {
flags |= syscall.MSG_PEEK
}
length, iovecs := buildIovec(bufs)
var msg syscall.Msghdr
if len(control) != 0 {
msg.Control = &control[0]
msg.Controllen = uint64(len(control))
}
if len(iovecs) != 0 {
msg.Iov = &iovecs[0]
msg.Iovlen = uint64(len(iovecs))
}
n, _, e := syscall.RawSyscall(syscall.SYS_RECVMSG, uintptr(fd), uintptr(unsafe.Pointer(&msg)), flags)
if e != 0 {
return 0, 0, 0, e
}
if n > length {
return length, n, msg.Controllen, nil
}
return n, n, msg.Controllen, nil
}
func fdWriteVec(fd int, bufs [][]byte) (uintptr, error) {
_, iovecs := buildIovec(bufs)
var msg syscall.Msghdr
if len(iovecs) > 0 {
msg.Iov = &iovecs[0]
msg.Iovlen = uint64(len(iovecs))
}
n, _, e := syscall.RawSyscall(syscall.SYS_SENDMSG, uintptr(fd), uintptr(unsafe.Pointer(&msg)), syscall.MSG_DONTWAIT|syscall.MSG_NOSIGNAL)
if e != 0 {
return 0, e
}
return n, nil
}
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