initmain

1 files changed, 47 insertions, 0 deletions

diff --git a/src/peekable_bufreader.rs b/src/peekable_bufreader.rs
new file mode 100644
index 0000000..ae02155
--- /dev/null
+++ b/src/peekable_bufreader.rs
@@ -0,0 +1,47 @@
+use async_std::prelude::*;
+use async_std::io::BufReader;
+use async_std::io::Read;
+
+pub struct PeekableBufReader<T>
+    where T: Read + Unpin {
+    reader: BufReader<T>,
+    buffer: [u8; 1],
+    peeked_last: bool,
+}
+
+impl<T> PeekableBufReader<T>
+    where T: Read + Unpin {
+    pub fn new(reader: BufReader<T>) -> Self {
+        Self {
+            reader,
+            buffer: [0],
+            peeked_last: false,
+        }
+    }
+
+    pub async fn next(&mut self) -> Option<u8> {
+        if self.peeked_last {
+            self.peeked_last = false;
+            Some(self.buffer[0])
+        } else {
+            match self.reader.read(&mut self.buffer).await.ok()? {
+                1 => Some(self.buffer[0]),
+                _ => None,
+            }
+        }
+    }
+
+    pub async fn peek(&mut self) -> Option<&u8> {
+        if self.peeked_last {
+            Some(&self.buffer[0])
+        } else {
+            match self.reader.read(&mut self.buffer).await.ok()? {
+                1 => {
+                    self.peeked_last = true;
+                    Some(&self.buffer[0])
+                },
+                _ => None,
+            }
+        }
+    }
+}