fcntl adding apple F_PREALLOCATE flag. #2393
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I am working on the CI issues, they are not related to this PR Update: CI fixed in #2394, you can rebase your branch now:) |
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Gentle ping on this PR, would you like to rebase and finish it? |
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seems libc 0.2.154 not yet available (just the tag on the repo but not yet published maybe) ? |
Right, it has been yanked, we have to wait for rust-lang/libc#3682 |
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The issue has been fixed, please rebase your branch:) |
| @@ -692,6 +692,9 @@ pub enum FcntlArg<'a> { | |||
| /// Return the full path without firmlinks of the fd. | |||
| #[cfg(apple_targets)] | |||
| F_GETPATH_NOFIRMLINK(&'a mut PathBuf), | |||
| /// Pre-allocate storage with different policies on fd. | |||
| #[cfg(apple_targets)] | |||
| F_PREALLOCATE(&'a libc::fstore_t), | |||
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The associated buffer has an OUT field:
typedef struct fstore {
u_int32_t fst_flags; /* IN: flags word */
int fst_posmode; /* IN: indicates offset field */
off_t fst_offset; /* IN: start of the region */
off_t fst_length; /* IN: size of the region */
off_t fst_bytesalloc; /* OUT: number of bytes allocated */
} fstore_t;i.e., the buffer can be written, if we use an immutable reference here, then UB could happen
Ref: https://keith.github.io/xcode-man-pages/fcntl.2.html#F_PREALLOCATE
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I just tried implementing this on my mac, I think we should create a helper type for those IN fields, and return the OUT field through fcntl().
For that fst_falgs field, we would create a bitflags struct, for fst_posmode, a Rust enum would suffice.
And F_ALLOCATEPERSIST is not available in libc, we should add it first.
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libc PR filed: rust-lang/libc#3713
Update: PR merged
What does this PR do
Checklist:
CONTRIBUTING.md