Trait ioat::ReadAt
[−]
[src]
pub trait ReadAt {
fn read_at(&mut self, pos: u64, buf: &mut [u8]) -> Result<usize>;
fn read_exact_at(&mut self, pos: u64, buf: &mut [u8]) -> Result<()> { ... }
}The ReadAt trait allows for atomically reading bytes from a source at specific offsets.
As an example, this trait is implemented by File. Unlike Read,
however, it is not implemented for &File, since the implementation
is not thread-safe. If two threads where to call read_at at once,
a race condition could occur, where one thread seeks and the other
thread reads.
For this reason, ReadAt is not automatically implemented for all
Read + Seek types. If a Read + Seek type is guaranteed to not
seek in parallel with a call to read_at, it can be wrapped in
AssertThreadSafe.
Required Methods
fn read_at(&mut self, pos: u64, buf: &mut [u8]) -> Result<usize>
Reads some bytes from pos bytes into the source.
This method returns the number of bytes read or an error, if the
bytes could not be read. If Ok(n) is returned, then it is
guaranteed, that 0 <= n <= buf.len().
Errors
This method can return any I/O error.
Provided Methods
fn read_exact_at(&mut self, pos: u64, buf: &mut [u8]) -> Result<()>
Reads exactly buf.len() bytes from pos bytes into the source.
This is usually handled by repeatedly calling read_at until
the buffer is full. This method is an analogue to read_exact
for Read.
Errors
If read_at() returns an error, then this method immediately
propagates that error by returning.
If read_at() returns Ok(0) to indicate the end of the source
has been reached before buf has been filled, then this method
errs with an error of kind UnexpectedEof. Any bytes read up
until this point are discarded.