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-rw-r--r--src/internal/poll/writev.go92
1 files changed, 92 insertions, 0 deletions
diff --git a/src/internal/poll/writev.go b/src/internal/poll/writev.go
new file mode 100644
index 0000000..75c8b64
--- /dev/null
+++ b/src/internal/poll/writev.go
@@ -0,0 +1,92 @@
+// 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.
+
+//go:build unix
+
+package poll
+
+import (
+ "io"
+ "runtime"
+ "syscall"
+)
+
+// 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
+ if runtime.GOOS == "aix" || runtime.GOOS == "solaris" {
+ // IOV_MAX is set to XOPEN_IOV_MAX on AIX and Solaris.
+ maxVec = 16
+ }
+
+ 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, newIovecWithBase(&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
+ }
+ if fd.iovecs == nil {
+ fd.iovecs = new([]syscall.Iovec)
+ }
+ *fd.iovecs = iovecs // cache
+
+ var wrote uintptr
+ wrote, err = writev(fd.Sysfd, iovecs)
+ if wrote == ^uintptr(0) {
+ wrote = 0
+ }
+ TestHookDidWritev(int(wrote))
+ n += int64(wrote)
+ consume(v, int64(wrote))
+ for i := range iovecs {
+ iovecs[i] = syscall.Iovec{}
+ }
+ if err != nil {
+ if err == syscall.EINTR {
+ continue
+ }
+ if err == syscall.EAGAIN {
+ if err = fd.pd.waitWrite(fd.isFile); err == nil {
+ continue
+ }
+ }
+ break
+ }
+ if n == 0 {
+ err = io.ErrUnexpectedEOF
+ break
+ }
+ }
+ return n, err
+}