Struct design_pattern_examples_rust::adapter::adapter_functions::DataReaderWriter

pub struct DataReaderWriter {
    _data_handle: i32,
    _block_number: MemoryBlockNumber,
    pub memory_block_byte_size: usize,
}

Represents a data reader/writer to a caller. Adapts the functions from the Adapter_BackEnd DLL (as wrapped by the functions in adapter_backend.rs).

Fields

_data_handle: i32

_block_number: MemoryBlockNumber

memory_block_byte_size: usize

Number of bytes in the currently opened memory block.

Implementations

impl DataReaderWriter

pub fn new(block_number: MemoryBlockNumber) -> DataReaderWriter

Constructor for DataReaderWriter struct.

Parameters

• blockNumber

  A value from the MemoryBlockNumber enumeration indicating the block of memory to open.

pub fn open(&mut self) -> Result<(), String>

Open a memory block for access. Which memory block to open is specified in the constructor. If this is successful, the memory block is open for reading and writing. Call close() to shut down access to the memory block.

pub fn close(&mut self) -> Result<(), String>

Closes a memory block from access. If this is successful, the same memory block can be opened again by a call to open(). Otherwise, instantiate the DataReaderWriter structure again to specify a different memory block.

fn _drop_close(&mut self)

Called by Drop::drop() to ensure the memory handle is closed. Does nothing if the handle is already closed (or was never opened). Ignores any errors returned from close() if the memory handle was left opened.

pub fn read(&self, byte_offset: i32, max_bytes: usize) -> Result<Vec<u8>, String>

Read a requested number of bytes from the currently opened memory block.

Parameters

• byte_offset

  Offset into the memory block to start reading from.

• maxBytes

  The number of bytes to read.

Returns

If successful, returns Ok(Vec<u8>) containing the bytes that were actually read; otherwise, returns Err(String) containing the reason for the failure.

pub fn write( &self, byte_offset: i32, bytes_to_write: &Vec<u8> ) -> Result<usize, String>

Write a requested number of bytes to the currently opened memory block.

Parameters

• byte_offset

  Byte offset into the memory block indicating where to start writing.

• bytes_to_write

  Vector of bytes to write to the memory block. All of the bytes will be written – up to the end of the memory block.

Returns

If successful, returns Ok(i32) containing the number of bytes actually written; otherwise, returns Err(String) containing the reason for the failure.

Trait Implementations

impl Drop for DataReaderWriter

fn drop(&mut self)

Makes sure the current memory block is closed in the event that an error caused an early return from the function that owned the DataReaderWriter instance.