81 lines
2 KiB
Go
81 lines
2 KiB
Go
// Copyright 2011 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 (
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"io"
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"syscall"
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)
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// SendFile wraps the TransmitFile call.
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func SendFile(fd *FD, src syscall.Handle, n int64) (written int64, err error) {
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if fd.kind == kindPipe {
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// TransmitFile does not work with pipes
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return 0, syscall.ESPIPE
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}
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if err := fd.writeLock(); err != nil {
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return 0, err
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}
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defer fd.writeUnlock()
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o := &fd.wop
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o.handle = src
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// TODO(brainman): skip calling syscall.Seek if OS allows it
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curpos, err := syscall.Seek(o.handle, 0, io.SeekCurrent)
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if err != nil {
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return 0, err
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}
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if n <= 0 { // We don't know the size of the file so infer it.
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// Find the number of bytes offset from curpos until the end of the file.
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n, err = syscall.Seek(o.handle, -curpos, io.SeekEnd)
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if err != nil {
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return
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}
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// Now seek back to the original position.
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if _, err = syscall.Seek(o.handle, curpos, io.SeekStart); err != nil {
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return
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}
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}
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// TransmitFile can be invoked in one call with at most
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// 2,147,483,646 bytes: the maximum value for a 32-bit integer minus 1.
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// See https://docs.microsoft.com/en-us/windows/win32/api/mswsock/nf-mswsock-transmitfile
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const maxChunkSizePerCall = int64(0x7fffffff - 1)
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for n > 0 {
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chunkSize := maxChunkSizePerCall
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if chunkSize > n {
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chunkSize = n
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}
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o.qty = uint32(chunkSize)
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o.o.Offset = uint32(curpos)
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o.o.OffsetHigh = uint32(curpos >> 32)
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nw, err := execIO(o, func(o *operation) error {
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return syscall.TransmitFile(o.fd.Sysfd, o.handle, o.qty, 0, &o.o, nil, syscall.TF_WRITE_BEHIND)
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})
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if err != nil {
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return written, err
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}
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curpos += int64(nw)
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// Some versions of Windows (Windows 10 1803) do not set
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// file position after TransmitFile completes.
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// So just use Seek to set file position.
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if _, err = syscall.Seek(o.handle, curpos, io.SeekStart); err != nil {
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return written, err
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}
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n -= int64(nw)
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written += int64(nw)
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}
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return
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}
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