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extern crate memchr; use std::io::{Read, Result}; use std::cmp::min; use memchr::memchr; static DEFAULT_BUF_SIZE: usize = 8 * 1024; #[derive(Debug, Eq, PartialEq, PartialOrd)] pub enum Line { Return(usize), More(usize), } impl Line { pub fn amount(&self) -> usize { match *self { Line::Return(n) => n, Line::More(n) => n, } } } pub struct LineReader<R> { inner: R, buf: Vec<u8>, pos: usize, cap: usize, } impl<R: Read> LineReader<R> { pub fn new(inner: R) -> LineReader<R> { LineReader::with_capacity(DEFAULT_BUF_SIZE, inner) } pub fn with_capacity(capacity: usize, inner: R) -> LineReader<R> { let mut buf = Vec::with_capacity(capacity); unsafe { buf.set_len(capacity); } LineReader { inner, buf, pos: 0, cap: 0, } } fn fill_buf(&mut self) -> Result<&[u8]> { if self.pos >= self.cap { self.cap = self.inner.read(&mut self.buf)?; self.pos = 0; } Ok(&mut self.buf[self.pos..self.cap]) } fn read_buf(&mut self, buf: &mut [u8]) -> Result<Line> { let line = { self.fill_buf()?; if self.pos == self.cap { return Ok(Line::Return(0)); } let mut rem = self.fill_buf()?; if buf.len() < rem.len() { rem = &rem[..buf.len()]; } match memchr(b'\n', rem) { Some(n) => Line::Return((&rem[..n + 1]).read(buf)?), None => Line::More(rem.read(buf)?), } }; self.consume(line.amount()); Ok(line) } pub fn try_read_line(&mut self, buf: &mut [u8]) -> Result<Line> { let mut amt: usize = 0; let cap = buf.len(); while amt < cap { match self.read_buf(&mut buf[amt..])? { Line::Return(n) => { return Ok(Line::Return(amt + n)); } Line::More(n) => { amt += n; } } } Ok(Line::More(amt)) } fn consume(&mut self, n: usize) { self.pos = min(self.pos + n, self.cap); } } #[cfg(test)] mod tests { use Line; use LineReader; use std::io::Cursor; #[test] fn try_read_line() { let cur = Cursor::new(b"12\n345"); let mut reader = LineReader::new(cur.clone()); let mut buf = vec![0; 1]; assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::More(1))); assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::More(1))); assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::Return(1))); assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::More(1))); assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::More(1))); assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::More(1))); assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::Return(0))); let mut reader = LineReader::new(cur.clone()); let mut buf = vec![0; 2]; assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::More(2))); assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::Return(1))); assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::More(2))); assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::Return(1))); let mut reader = LineReader::new(cur.clone()); let mut buf = vec![0; 4]; assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::Return(3))); assert_eq!(reader.try_read_line(&mut buf).ok(), Some(Line::Return(3))); } }