Struct MmapDataSourceRw 

pub struct MmapDataSourceRw { /* private fields */ }

A read-write DataSource backed by a memory-mapped file.

Supports reading, writing, flushing, and seeking via the standard traits. Use MmapDataSourceRw::open to map an existing file, or MmapDataSourceRw::create to create and immediately map a new zero-filled file of a given byte length.

Safety

Internally this calls unsafe { MmapMut::map_mut(&file) }. The same invariant applies as for MmapDataSource: the file must not be accessed through any other handle while the mapping is live.

Implementations

impl MmapDataSourceRw

pub fn open(path: impl AsRef<Path>) -> Result<Self>

Opens path for read-write memory-mapped access.

The file must already exist and be non-empty.

Errors

Returns an error if the file cannot be opened, its metadata cannot be read, the file is empty, or mmap_mut fails.

pub fn create(path: impl AsRef<Path>, len: usize) -> Result<Self>

Creates a new file at path, extends it to len bytes, and maps it.

If path already exists it is truncated. The new file is zero-filled by the OS.

Errors

Returns an error if len == 0, the file cannot be created, set_len fails, or mmap_mut fails.

pub fn len(&self) -> usize

Returns the total mapped length in bytes.

pub fn is_empty(&self) -> bool

Returns true if the mapped region is empty.

pub fn flush(&self) -> Result<()>

Flushes outstanding changes to disk synchronously.

Errors

Returns an error if msync / FlushViewOfFile fails.

pub fn as_bytes(&self) -> &[u8]

Returns an immutable byte slice of the entire mapping.

pub fn as_bytes_mut(&mut self) -> &mut [u8]

Returns a mutable byte slice of the entire mapping.

pub fn read_at(&self, offset: usize, len: usize) -> Result<&[u8]>

Returns a byte slice for offset..offset+len without moving the cursor.

Errors

Returns OxiGdalError::OutOfBounds if offset + len > self.len().

pub fn write_at(&mut self, offset: usize, data: &[u8]) -> Result<()>

Overwrites data.len() bytes starting at offset.

Errors

Returns OxiGdalError::OutOfBounds if offset + data.len() > self.len().

pub fn path(&self) -> &Path

Returns the path of the underlying file.

Trait Implementations

impl DataSource for MmapDataSourceRw

fn size(&self) -> Result<u64>

Returns the total size of the data source in bytes

fn read_range(&self, range: ByteRange) -> Result<Vec<u8>>

Reads bytes from the specified range

fn supports_range_requests(&self) -> bool

Returns true if this data source supports range requests

fn read_ranges(&self, ranges: &[ByteRange]) -> Result<Vec<Vec<u8>>>

Reads bytes from multiple ranges (for optimization)

impl Debug for MmapDataSourceRw

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

Formats the value using the given formatter.

impl Read for MmapDataSourceRw

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

Pull some bytes from this source into the specified buffer, returning how many bytes were read.

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

Like read, except that it reads into a slice of buffers.

fn is_read_vectored(&self) -> bool

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

Determines if this Reader has an efficient read_vectored implementation.

fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize, Error>

Reads all bytes until EOF in this source, placing them into buf.

fn read_to_string(&mut self, buf: &mut String) -> Result<usize, Error>

Reads all bytes until EOF in this source, appending them to buf.

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

Reads the exact number of bytes required to fill buf.

fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<(), Error>

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

Pull some bytes from this source into the specified buffer.

fn read_buf_exact(&mut self, cursor: BorrowedCursor<'_>) -> Result<(), Error>

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

Reads the exact number of bytes required to fill cursor.

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

where Self: Sized,

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

fn bytes(self) -> Bytes<Self>

where Self: Sized,

Transforms this Read instance to an Iterator over its bytes.

fn chain<R>(self, next: R) -> Chain<Self, R>

where R: Read, Self: Sized,

Creates an adapter which will chain this stream with another.

fn take(self, limit: u64) -> Take<Self>

where Self: Sized,

Creates an adapter which will read at most limit bytes from it.

fn read_array<const N: usize>(&mut self) -> Result<[u8; N], Error>

where Self: Sized,

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

Read and return a fixed array of bytes from this source.

impl Seek for MmapDataSourceRw

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 Write for MmapDataSourceRw

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

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

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

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, args: 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.