Struct PreparedDataMapping 

pub struct PreparedDataMapping<'a, S: Storage + 'static> {
    storage: &'a S,
    offset: u64,
    length: u64,
    state: Option<Box<dyn Any>>,
}

Data mapping that has been prepared, but not committed yet.

Returned by FormatAccess::prepare_data_mapping(): Says where to write the data for the range that is to be mapped. Once that data has been written, pass this object to FormatAccess::commit_data_mapping() to make the mapping visible.

Dropping this object without committing it discards any prepared mapping change.

Until this object is committed or dropped, any other I/O on the image may wait for it.

Fields

storage: &'a S

Storage object to write the data to.

offset: u64

Offset in storage to write the data to.

length: u64

Length of the mapping.

state: Option<Box<dyn Any>>

Driver-specific state required to commit this mapping; None if nothing needs to be committed.

Implementations

impl<'a, S: Storage + 'static> PreparedDataMapping<'a, S>

pub fn existing(storage: &'a S, offset: u64, length: u64) -> Self

Create a prepared mapping that does not require anything to be committed.

For use by format drivers, e.g. when the mapping exists already.

pub fn to_commit( storage: &'a S, offset: u64, length: u64, state: Box<dyn Any>, ) -> Self

Create a prepared mapping that must be committed, using the driver-specific state.

For use by format drivers. Dropping state must discard the prepared mapping.

pub fn storage(&self) -> &'a S

Storage object to write the data to.

pub fn offset(&self) -> u64

Offset in Self::storage() to write the data to.

pub fn length(&self) -> u64

Length of the mapping.

pub fn is_nonblocking(&self) -> bool

Whether holding this object can delay other I/O on the image.

true means the range only becomes visible once it is committed, and other I/O on the image may be blocked in order not to interfere with that.

false means holding it will never delay other I/O. In this case, the mapping is visible already: the range keeps reading as it does now, and committing it will most likely do nothing (FormatAccess::commit_data_mapping() must still be called by users, though).

pub fn into_state(self) -> Option<Box<dyn Any>>

Take the driver-specific state, if any.

For use by format drivers.

pub(crate) fn limit_length(&mut self, max_length: u64)

Limit the length of the mapping to max_length.

Trait Implementations

impl<S: Storage + 'static> Debug for PreparedDataMapping<'_, S>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.