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99 lines
2.5 KiB
Rust
99 lines
2.5 KiB
Rust
use crate::error::{TapeError, TapeResult};
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use std::io::ErrorKind;
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use tokio::io::{AsyncBufRead, AsyncBufReadExt};
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/// An Input reader to asynchronously read a type
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/// that implements AsyncBufRead and AsyncSeek.
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pub struct InputReader {
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inner: Box<dyn AsyncBufRead + Unpin + Send>,
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buf: String,
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index: usize,
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}
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impl InputReader {
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/// Creates a new Input Reader
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pub fn new<T: AsyncBufRead + Unpin + Send + 'static>(inner: T) -> Self {
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Self {
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inner: Box::new(inner),
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buf: String::new(),
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index: 0,
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}
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}
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/// Reads the next char consuming it in the process
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#[inline]
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pub async fn consume(&mut self) -> TapeResult<char> {
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self.seek_to(self.index + 1).await?;
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self.read_current().await
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}
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/// Returns the next char without forwarding
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#[inline]
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pub async fn peek(&mut self) -> TapeResult<char> {
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self.seek_to(self.index + 1).await?;
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let char = self.read_current().await?;
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self.seek_to(self.index - 1).await?;
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Ok(char)
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}
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/// Returns if EOF has been reached
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#[inline]
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pub async fn check_eof(&mut self) -> bool {
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if let Err(TapeError::EOF) = self.peek().await {
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true
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} else {
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false
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}
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}
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/// Returns the previous char
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#[inline]
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pub async fn previous(&mut self) -> Option<char> {
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self.read_current().await.ok()
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}
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/// Seeks to a given index
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pub async fn seek_to(&mut self, to_index: usize) -> TapeResult<()> {
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while to_index >= self.buf.len() {
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let mut line = String::new();
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self.inner.read_line(&mut line).await.map_err(|e| {
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if e.kind() == ErrorKind::UnexpectedEof {
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TapeError::EOF
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} else {
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TapeError::TokioIoError(e)
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}
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})?;
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if line.is_empty() {
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break;
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}
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self.buf.push_str(&line);
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}
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self.index = to_index;
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Ok(())
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}
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/// Returns the current index
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pub fn index(&self) -> usize {
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self.index
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}
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/// Reads the next char returning \x00 for EOF
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async fn read_current(&mut self) -> TapeResult<char> {
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if self.index == 0 {
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return Err(TapeError::IndexError);
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}
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let result = self
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.buf
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.get(self.index - 1..self.index)
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.ok_or(TapeError::EOF)?
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.chars()
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.next()
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.ok_or(TapeError::EOF);
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result
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}
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}
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