mirror of https://go.googlesource.com/go
67 lines
1.8 KiB
Go
67 lines
1.8 KiB
Go
// Copyright 2015 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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package poll
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import "syscall"
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// Not strictly needed, but very helpful for debugging, see issue #10221.
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//
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//go:cgo_import_dynamic _ _ "libsendfile.so"
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//go:cgo_import_dynamic _ _ "libsocket.so"
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// maxSendfileSize is the largest chunk size we ask the kernel to copy
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// at a time.
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const maxSendfileSize int = 4 << 20
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// SendFile wraps the sendfile system call.
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func SendFile(dstFD *FD, src int, pos, remain int64) (written int64, err error, handled bool) {
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defer func() {
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TestHookDidSendFile(dstFD, src, written, err, handled)
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}()
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if err := dstFD.writeLock(); err != nil {
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return 0, err, false
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}
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defer dstFD.writeUnlock()
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if err := dstFD.pd.prepareWrite(dstFD.isFile); err != nil {
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return 0, err, false
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}
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dst := dstFD.Sysfd
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for remain > 0 {
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n := maxSendfileSize
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if int64(n) > remain {
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n = int(remain)
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}
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pos1 := pos
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n, err = syscall.Sendfile(dst, src, &pos1, n)
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if err == syscall.EAGAIN || err == syscall.EINTR {
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// partial write may have occurred
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n = int(pos1 - pos)
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}
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if n > 0 {
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pos += int64(n)
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written += int64(n)
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remain -= int64(n)
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continue
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} else if err != syscall.EAGAIN && err != syscall.EINTR {
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// This includes syscall.ENOSYS (no kernel
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// support) and syscall.EINVAL (fd types which
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// don't implement sendfile), and other errors.
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// We should end the loop when there is no error
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// returned from sendfile(2) or it is not a retryable error.
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break
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}
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if err == syscall.EINTR {
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continue
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}
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if err = dstFD.pd.waitWrite(dstFD.isFile); err != nil {
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break
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}
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}
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handled = written != 0 || (err != syscall.ENOSYS && err != syscall.EINVAL)
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return
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}
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