Collapsing ranges in sparse files in APFS?
Collapsing ranges in sparse files in APFS?
- Subject: Collapsing ranges in sparse files in APFS?
- From: Jens Alfke <email@hidden>
- Date: Sun, 20 Jan 2019 15:14:25 -0800
I’m looking into sparse-file operations in APFS. I see I can use fcntl to
preallocate space and to punch holes in a file. But I don’t see a command to
remove a byte range from a file without leaving a hole, equivalent to the
FALLOC_FL_COLLAPSE_RANGE mode of Linux’s fallocate, described thus:
> Specifying the FALLOC_FL_COLLAPSE_RANGE flag (available since Linux 3.15) in
> mode removes a byte range from a file, without leaving a hole. The byte range
> to be collapsed starts at offset and continues for len bytes. At the
> completion of the operation, the contents of the file starting at the
> location offset+len will be appended at the location offset, and the file
> will be len bytes smaller.
Is there such an operation in Darwin, with an APFS filesystem?
—Jens
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