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// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// +build darwin dragonfly freebsd linux netbsd openbsd
package poll
import (
"io"
"syscall"
"unsafe"
)
// Writev wraps the writev system call.
func (fd *FD) Writev(v *[][]byte) (int64, error) {
if err := fd.writeLock(); err != nil {
return 0, err
}
defer fd.writeUnlock()
if err := fd.pd.prepareWrite(fd.isFile); err != nil {
return 0, err
}
var iovecs []syscall.Iovec
if fd.iovecs != nil {
iovecs = *fd.iovecs
}
// TODO: read from sysconf(_SC_IOV_MAX)? The Linux default is
// 1024 and this seems conservative enough for now. Darwin's
// UIO_MAXIOV also seems to be 1024.
maxVec := 1024
var n int64
var err error
for len(*v) > 0 {
iovecs = iovecs[:0]
for _, chunk := range *v {
if len(chunk) == 0 {
continue
}
iovecs = append(iovecs, syscall.Iovec{Base: &chunk[0]})
if fd.IsStream && len(chunk) > 1<<30 {
iovecs[len(iovecs)-1].SetLen(1 << 30)
break // continue chunk on next writev
}
iovecs[len(iovecs)-1].SetLen(len(chunk))
if len(iovecs) == maxVec {
break
}
}
if len(iovecs) == 0 {
break
}
fd.iovecs = &iovecs // cache
wrote, _, e0 := syscall.Syscall(syscall.SYS_WRITEV,
uintptr(fd.Sysfd),
uintptr(unsafe.Pointer(&iovecs[0])),
uintptr(len(iovecs)))
if wrote == ^uintptr(0) {
wrote = 0
}
TestHookDidWritev(int(wrote))
n += int64(wrote)
consume(v, int64(wrote))
if e0 == syscall.EAGAIN {
if err = fd.pd.waitWrite(fd.isFile); err == nil {
continue
}
} else if e0 != 0 {
err = syscall.Errno(e0)
}
if err != nil {
break
}
if n == 0 {
err = io.ErrUnexpectedEOF
break
}
}
return n, err
}
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