46 lines
1.6 KiB
Go
46 lines
1.6 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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package fs
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import (
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"syscall"
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"github.com/syncthing/syncthing/lib/sync"
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)
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var (
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copyRangeMethods = make(map[CopyRangeMethod]copyRangeImplementation)
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mut = sync.NewMutex()
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)
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type copyRangeImplementation func(src, dst File, srcOffset, dstOffset, size int64) error
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func registerCopyRangeImplementation(copyMethod CopyRangeMethod, impl copyRangeImplementation) {
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mut.Lock()
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defer mut.Unlock()
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l.Debugln("Registering " + copyMethod.String() + " copyRange method")
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copyRangeMethods[copyMethod] = impl
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}
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// CopyRange tries to use the specified method to copy data between two files.
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// Takes size bytes at offset srcOffset from the source file, and copies the data to destination file at offset
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// dstOffset. If required, adjusts the size of the destination file to fit that much data.
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//
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// On Linux/BSD you can ask it to use ioctl and copy_file_range system calls, which if the underlying filesystem supports
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// it tries referencing existing data in the source file, instead of making a copy and taking up additional space.
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//
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// CopyRange does its best to have no effect on src and dst file offsets (copy operation should not affect it).
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func CopyRange(copyMethod CopyRangeMethod, src, dst File, srcOffset, dstOffset, size int64) error {
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if impl, ok := copyRangeMethods[copyMethod]; ok {
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return impl(src, dst, srcOffset, dstOffset, size)
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}
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return syscall.ENOTSUP
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}
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