49 lines
1.3 KiB
Go
49 lines
1.3 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
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// +build linux
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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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"golang.org/x/sys/unix"
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)
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func init() {
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registerCopyRangeImplementation(CopyRangeMethodCopyFileRange, copyRangeImplementationForBasicFile(copyRangeCopyFileRange))
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}
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func copyRangeCopyFileRange(src, dst basicFile, srcOffset, dstOffset, size int64) error {
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for size > 0 {
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// From MAN page:
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//
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// If off_in is not NULL, then off_in must point to a buffer that
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// specifies the starting offset where bytes from fd_in will be read.
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// The file offset of fd_in is not changed, but off_in is adjusted
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// appropriately.
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//
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// Also, even if explicitly not stated, the same is true for dstOffset
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n, err := withFileDescriptors(src, dst, func(srcFd, dstFd uintptr) (int, error) {
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return unix.CopyFileRange(int(srcFd), &srcOffset, int(dstFd), &dstOffset, int(size), 0)
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})
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if n == 0 && err == nil {
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return 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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return nil
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}
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