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