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use std::{cell::RefCell, cmp::min, rc::Rc};
use anyhow::Result;
use crate::RwBuilder;
/// Type for building readers and writers on top of a `Vec` in memory.
/// It is itself an `RwBuilder`, but can't be created through one.
/// This is why we call it a source.
#[derive(Debug, Default)]
pub struct Builder {
/// The inner `Vec` which is used to write data to and read data from
/// It is shared between the reader and the writer
buffer: Rc<RefCell<Vec<u8>>>,
}
impl RwBuilder for Builder {
type Reader = Reader;
type Writer = Writer;
fn reader(&self) -> Result<Self::Reader> {
Ok(Reader { buffer: Rc::clone(&self.buffer), bytes_read: 0 })
fn writer(&self) -> Result<Self::Writer> {
Ok(Writer { buffer: Rc::clone(&self.buffer) })
/// Reading from a `Vec`
#[derive(Debug)]
pub struct Reader {
/// The buffer shared between the builder, reader and writer
/// The read position in the buffer
bytes_read: usize,
impl std::io::Read for Reader {
fn read(&mut self, buf: &mut [u8]) -> std::io::Result<usize> {
let borrowed = self.buffer.borrow();
let byte_count = min(borrowed.len() - self.bytes_read, buf.len());
buf[..byte_count].copy_from_slice(&borrowed[self.bytes_read..self.bytes_read + byte_count]);
self.bytes_read += byte_count;
Ok(byte_count)
impl std::io::Write for Writer {
fn write(&mut self, buf: &[u8]) -> std::io::Result<usize> {
let mut borrowed = self.buffer.borrow_mut();
let byte_count = buf.len();
borrowed.extend_from_slice(buf);
fn flush(&mut self) -> std::io::Result<()> {
Ok(())
/// Writing to a `Vec`
pub struct Writer {