Struct StableWriter

pub struct StableWriter<M: StableMemory = CanisterStableMemory>(/* private fields */);

A writer to the stable memory.

Warning: This will overwrite any existing data in stable memory as it writes, so ensure you set the offset value accordingly if you wish to preserve existing data.

Will attempt to grow the memory as it writes, and keep offsets and total capacity.

Implementations

impl<M: StableMemory> StableWriter<M>

pub fn with_memory(memory: M, offset: u64) -> Self

Creates a new StableWriter which writes to the selected memory

pub fn offset(&self) -> u64

Returns the offset of the writer

pub fn grow(&mut self, new_pages: u64) -> Result<(), StableMemoryError>

Attempts to grow the memory by adding new pages.

pub fn write(&mut self, buf: &[u8]) -> Result<usize, StableMemoryError>

Writes a byte slice to the buffer.

The only condition where this will error out is if it cannot grow the memory.

Trait Implementations

impl<M: Debug + StableMemory> Debug for StableWriter<M>

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

Formats the value using the given formatter.

impl Default for StableWriter

fn default() -> Self

Returns the “default value” for a type.

impl<M: StableMemory> From<StableIO<M>> for StableWriter<M>

fn from(io: StableIO<M>) -> Self

Converts to this type from the input type.

impl<M: StableMemory> Seek for StableWriter<M>

fn seek(&mut self, pos: SeekFrom) -> Result<u64>

Seek to an offset, in bytes, in a stream.

fn rewind(&mut self) -> Result<(), Error>

Rewind to the beginning of a stream.

fn stream_len(&mut self) -> Result<u64, Error>

🔬This is a nightly-only experimental API. (seek_stream_len)

Returns the length of this stream (in bytes).

fn stream_position(&mut self) -> Result<u64, Error>

Returns the current seek position from the start of the stream.

fn seek_relative(&mut self, offset: i64) -> Result<(), Error>

Seeks relative to the current position.

impl<M: StableMemory> Write for StableWriter<M>

fn write(&mut self, buf: &[u8]) -> Result<usize, Error>

Writes a buffer into this writer, returning how many bytes were written.

fn flush(&mut self) -> Result<(), Error>

Flushes this output stream, ensuring that all intermediately buffered contents reach their destination.

fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize, Error>

Like write, except that it writes from a slice of buffers.

fn is_write_vectored(&self) -> bool

🔬This is a nightly-only experimental API. (can_vector)

Determines if this Writer has an efficient write_vectored implementation.

fn write_all(&mut self, buf: &[u8]) -> Result<(), Error>

Attempts to write an entire buffer into this writer.

fn write_all_vectored(&mut self, bufs: &mut [IoSlice<'_>]) -> Result<(), Error>

🔬This is a nightly-only experimental API. (write_all_vectored)

Attempts to write multiple buffers into this writer.

fn write_fmt(&mut self, fmt: Arguments<'_>) -> Result<(), Error>

Writes a formatted string into this writer, returning any error encountered.

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

Creates a “by reference” adapter for this instance of Write.