// Copyright 2011 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. package poll import "syscall" // maxSendfileSize is the largest chunk size we ask the kernel to copy // at a time. const maxSendfileSize int = 4 << 20 // SendFile wraps the sendfile system call. func SendFile(dstFD *FD, src int, remain int64) (int64, error) { if err := dstFD.writeLock(); err != nil { return 0, err } defer dstFD.writeUnlock() if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil { return 0, err } dst := dstFD.Sysfd var written int64 var err error for remain > 0 { n := maxSendfileSize if int64(n) > remain { n = int(remain) } n, err1 := syscall.Sendfile(dst, src, nil, n) if n > 0 { written += int64(n) remain -= int64(n) } else if n == 0 && err1 == nil { break } if err1 == syscall.EINTR { continue } if err1 == syscall.EAGAIN { if err1 = dstFD.pd.waitWrite(dstFD.isFile); err1 == nil { continue } } if err1 != nil { // This includes syscall.ENOSYS (no kernel // support) and syscall.EINVAL (fd types which // don't implement sendfile) err = err1 break } } return written, err }