Use Rust's BufWriter

Rust's BufWriter is highly optimized. Use it instead of a custom one.
Wrap it in a newtype so that we can implement `cbor4ii`s `enc::Write`.

Author: vmx

src/lib.rs

@@ -1,9 +1,10 @@
+use std::io::{BufWriter as IoBufWriter, Write};
+
 use anyhow::{anyhow, Result};
 use cbor4ii::core::{
     dec::{self, Decode, Read},
     enc::{self, Encode},
     major, types,
-    utils::BufWriter,
 };
 use cid::{multibase, Cid};
 use pyo3::pybacked::PyBackedStr;
@@ -18,6 +19,28 @@ mod marker {
     pub const F64: u8 = 0xfb;
 }
 
+struct BufWriter<W: Write>(IoBufWriter<W>);
+
+impl<W: Write> BufWriter<W> {
+    pub fn new(inner: W) -> Self {
+        BufWriter(IoBufWriter::new(inner))
+    }
+
+    pub fn buffer(&self) -> &[u8] {
+        self.0.buffer()
+    }
+}
+
+impl<W: Write> enc::Write for BufWriter<W> {
+    type Error = std::io::Error;
+
+    #[inline]
+    fn push(&mut self, input: &[u8]) -> Result<(), Self::Error> {
+        self.0.write_all(input)?;
+        Ok(())
+    }
+}
+
 // Based on cbor4ii/src/utils.rs.
 /// An in-memory reader.
 struct SliceReader<'a> {