Add reader

src/bin/pica/commands/convert/binary.rs

@@ -1,8 +1,10 @@
 use std::ffi::OsString;
 use std::fs::File;
-use std::io::{self, stdout, BufWriter, Write};
+use std::io::{self, stdin, stdout, BufReader, BufWriter, Read, Write};
 
-use pica_record::io::ByteRecordWrite;
+use pica_record::io::{
+    ByteRecordWrite, ReadPicaError, RecordsIterator,
+};
 use pica_record::ByteRecord;
 
 pub(crate) struct BinaryWriter {
@@ -22,6 +24,31 @@ impl BinaryWriter {
     }
 }
 
+pub(crate) struct BinaryReader {
+    inner: BufReader<Box<dyn Read>>,
+}
+
+impl BinaryReader {
+    pub(crate) fn new(input: Option<OsString>) -> io::Result<Self> {
+        let inner: BufReader<Box<dyn Read>> =
+            if let Some(filename) = input {
+                BufReader::new(Box::new(File::open(filename)?))
+            } else {
+                BufReader::new(Box::new(stdin()))
+            };
+
+        Ok(Self { inner })
+    }
+}
+
+impl RecordsIterator for BinaryReader {
+    type Item<'a> = Result<ByteRecord<'a>, ReadPicaError> where Self: 'a;
+
+    fn next(&mut self) -> Option<Self::Item<'_>> {
+        todo!()
+    }
+}
+
 impl ByteRecordWrite for BinaryWriter {
     fn write_byte_record(
         &mut self,