73 lines
2.1 KiB
Go
73 lines
2.1 KiB
Go
// Copyright (C) 2019 The Syncthing Authors.
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this file,
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// You can obtain one at https://mozilla.org/MPL/2.0/.
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//go:build linux || solaris
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// +build linux solaris
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package fs
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import (
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"io"
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"syscall"
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)
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func init() {
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registerCopyRangeImplementation(CopyRangeMethodSendFile, copyRangeImplementationForBasicFile(copyRangeSendFile))
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}
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func copyRangeSendFile(src, dst basicFile, srcOffset, dstOffset, size int64) error {
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// Check that the destination file has sufficient space
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if fi, err := dst.Stat(); err != nil {
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return err
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} else if fi.Size() < dstOffset+size {
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if err := dst.Truncate(dstOffset + size); err != nil {
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return err
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}
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}
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// Record old dst offset.
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oldDstOffset, err := dst.Seek(0, io.SeekCurrent)
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if err != nil {
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return err
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}
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defer func() { _, _ = dst.Seek(oldDstOffset, io.SeekStart) }()
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// Seek to the offset we expect to write
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if oldDstOffset != dstOffset {
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if n, err := dst.Seek(dstOffset, io.SeekStart); err != nil {
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return err
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} else if n != dstOffset {
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return io.ErrUnexpectedEOF
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}
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}
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for size > 0 {
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// From the MAN page:
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//
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// If offset is not NULL, then it points to a variable holding the file offset from which sendfile() will start
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// reading data from in_fd. When sendfile() returns, this variable will be set to the offset of the byte
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// following the last byte that was read. If offset is not NULL, then sendfile() does not modify the current
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// file offset of in_fd; otherwise the current file offset is adjusted to reflect the number of bytes read from
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// in_fd.
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n, err := withFileDescriptors(dst, src, func(dstFd, srcFd uintptr) (int, error) {
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return syscall.Sendfile(int(dstFd), int(srcFd), &srcOffset, int(size))
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})
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if n == 0 && err == nil {
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err = io.ErrUnexpectedEOF
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}
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if err != nil && err != syscall.EAGAIN {
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return err
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}
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// Handle case where err == EAGAIN and n == -1 (it's not clear if that can happen)
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if n > 0 {
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size -= int64(n)
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}
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}
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_, err = dst.Seek(oldDstOffset, io.SeekStart)
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return err
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}
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