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
+}