Trait FileIo

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pub trait FileIo: Send + Sync {
Show 13 methods    // Required methods
    fn requires_alignment(&self) -> bool;
    fn read_at(&self, buf: &mut [u8], off: u64) -> Result<()>;
    fn write_at(&self, buf: &[u8], off: u64) -> Result<()>;
    fn sync_data(&self) -> Result<()>;
    fn sync_full(&self) -> Result<()>;
    fn sync_full_primitive(&self) -> &'static str;
    fn sync_dir(&self) -> Result<()>;
    fn len(&self) -> Result<u64>;
    fn set_len(&self, n: u64) -> Result<()>;

    // Provided methods
    fn manages_free_pages(&self) -> bool { ... }
    fn pop_free_page(&self) -> Result<Option<u32>> { ... }
    fn push_free_page(&self, _page: u32) -> Result<()> { ... }
    fn stats(&self) -> Option<&IoStats> { ... }
}

Required Methods§

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fn requires_alignment(&self) -> bool

True when this file demands page-aligned offsets, lengths and buffers. The WAL is byte-addressed and always opens Buffered, so it never does.

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fn read_at(&self, buf: &mut [u8], off: u64) -> Result<()>

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fn write_at(&self, buf: &[u8], off: u64) -> Result<()>

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fn sync_data(&self) -> Result<()>

A data barrier that does NOT force the drive’s own write cache: the write is durable against an OS crash, not necessarily against a loss of power to the drive. fdatasync on Linux; plain fsync on macOS.

Deliberately not std::fs::File::sync_data: libstd’s implementation calls fcntl(F_FULLFSYNC) on macOS (a safety choice in std, not a bug), which is exactly the strong, ~65x-costlier barrier sync_full exists to name separately. Going through it here would make Normal and Full issue the identical primitive on macOS while differing on Linux – the SyncMode label would say one thing and the hardware would hear another, and differently on different platforms.

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fn sync_full(&self) -> Result<()>

The strongest barrier this platform can issue: durable even against a loss of power to the drive. fcntl(F_FULLFSYNC) on macOS (roughly 65x the cost of sync_data on the same hardware); File::sync_all (ordinary fsync) elsewhere.

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