syncthing/lib/fs/basicfs_copy_range_copyfilerange.go

48 lines
1.3 KiB
Go

// Copyright (C) 2019 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
// +build linux
package fs
import (
"io"
"syscall"
"golang.org/x/sys/unix"
)
func init() {
registerCopyRangeImplementation(CopyRangeMethodCopyFileRange, copyRangeImplementationForBasicFile(copyRangeCopyFileRange))
}
func copyRangeCopyFileRange(src, dst basicFile, srcOffset, dstOffset, size int64) error {
for size > 0 {
// From MAN page:
//
// If off_in is not NULL, then off_in must point to a buffer that
// specifies the starting offset where bytes from fd_in will be read.
// The file offset of fd_in is not changed, but off_in is adjusted
// appropriately.
//
// Also, even if explicitly not stated, the same is true for dstOffset
n, err := withFileDescriptors(src, dst, func(srcFd, dstFd uintptr) (int, error) {
return unix.CopyFileRange(int(srcFd), &srcOffset, int(dstFd), &dstOffset, int(size), 0)
})
if n == 0 && err == nil {
return io.ErrUnexpectedEOF
}
if err != nil && err != syscall.EAGAIN {
return err
}
// Handle case where err == EAGAIN and n == -1 (it's not clear if that can happen)
if n > 0 {
size -= int64(n)
}
}
return nil
}