> On Jun 27, 2017, at 12:28 AM, Jens Alfke <j...@mooseyard.com> wrote:
>
>> On Jun 26, 2017, at 7:38 PM, Rick Mann <rm...@latencyzero.com
>> <mailto:rm...@latencyzero.com>> wrote:
>>
>> But there's actually a POSIX "clone" API, and so I wonder if a copy is
>> different from a clone.
>
> The low level file copying API that I’m aware of is <copyfiles.h>, which is
> Apple specific. It has options for doing copy-on-write.
> I don’t know if NSFileManager’s copy method clones files. I would assume that
> it does, on APFS.
Well, I mean, you could always *try* it ;-)
import Foundation
func unclonedSize(of url: URL) throws -> off_t {
var list = attrlist(bitmapcount: UInt16(ATTR_BIT_MAP_COUNT),
reserved: 0,
commonattr: 0,
volattr: 0,
dirattr: 0,
fileattr: 0,
forkattr: attrgroup_t(ATTR_CMNEXT_PRIVATESIZE))
let bufsize = 4 + MemoryLayout<off_t>.size
let buf = UnsafeMutablePointer<UInt8>.allocate(capacity: bufsize)
defer { buf.deallocate(capacity: bufsize) }
let err = url.withUnsafeFileSystemRepresentation { getattrlist($0,
&list, buf, bufsize, UInt32(FSOPT_ATTR_CMN_EXTENDED)) }
if err != 0 { throw POSIXError.Code(rawValue: errno).map {
POSIXError($0) } ?? CocoaError(.fileReadUnknown) }
let attrsize = buf.withMemoryRebound(to: UInt32.self, capacity: 1) {
$0.pointee }
if attrsize < bufsize { throw CocoaError(.fileReadUnknown) }
var unclonedSize: off_t = 0
_ = withUnsafeMutableBytes(of: &unclonedSize) { memcpy($0.baseAddress!,
buf + 4, MemoryLayout<off_t>.size) }
return unclonedSize
}
do {
let sourceURL = URL(fileURLWithPath: "/tmp/tempfile1")
let destURL = URL(fileURLWithPath: "/tmp/tempfile2")
let sortaRandomData = Data(bytes: (0..<100 * 1024).map {
UInt8(extendingOrTruncating: $0) })
try sortaRandomData.write(to: sourceURL)
print("Uncloned size of source file: \(try unclonedSize(of:
sourceURL))")
try FileManager.default.copyItem(at: sourceURL, to: destURL)
print("Uncloned size of dest file: \(try unclonedSize(of: destURL))")
} catch {
print("Error occurred: \(error.localizedDescription)")
}
- - - - - - - - -
outputs:
Uncloned size of source file: 102400
Uncloned size of dest file: 0
So, it seems quite clear that (NS)FileManager does, in fact, clone the files
you tell it to copy. :-)
Charles
_______________________________________________
Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)
Please do not post admin requests or moderator comments to the list.
Contact the moderators at cocoa-dev-admins(at)lists.apple.com
Help/Unsubscribe/Update your Subscription:
https://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com
This email sent to arch...@mail-archive.com
