| // 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) (written int64, err error, handled bool) { |
| if err := dstFD.writeLock(); err != nil { |
| return 0, err, false |
| } |
| defer dstFD.writeUnlock() |
| |
| if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil { |
| return 0, err, false |
| } |
| |
| dst := dstFD.Sysfd |
| for remain > 0 { |
| n := maxSendfileSize |
| if int64(n) > remain { |
| n = int(remain) |
| } |
| n, err = syscall.Sendfile(dst, src, nil, n) |
| if n > 0 { |
| written += int64(n) |
| remain -= int64(n) |
| continue |
| } else if err != syscall.EAGAIN && err != syscall.EINTR { |
| // This includes syscall.ENOSYS (no kernel |
| // support) and syscall.EINVAL (fd types which |
| // don't implement sendfile), and other errors. |
| // We should end the loop when there is no error |
| // returned from sendfile(2) or it is not a retryable error. |
| break |
| } |
| if err == syscall.EINTR { |
| continue |
| } |
| if err = dstFD.pd.waitWrite(dstFD.isFile); err != nil { |
| break |
| } |
| } |
| handled = written != 0 || (err != syscall.ENOSYS && err != syscall.EINVAL) |
| return |
| } |