Add tests to show BufRead can be used after decoding

Copy the test from `gzip::bufread` to demonstrate that it also works
for `zlib` and `deflate`.

src/deflate/bufread.rs

@@ -243,3 +243,50 @@ impl<W: BufRead + Write> Write for DeflateDecoder<W> {
  self.get_mut().flush()
  }
 }
+
+#[cfg(test)]
+mod test {
+ use crate::bufread::DeflateDecoder;
+ use crate::deflate::write;
+ use crate::Compression;
+ use std::io::{Read, Write};
+
+ // DeflateDecoder consumes one deflate archive and then returns 0 for subsequent reads, allowing any
+ // additional data to be consumed by the caller.
+ #[test]
+ fn decode_extra_data() {
+ let expected = "Hello World";
+
+ let compressed = {
+ let mut e = write::DeflateEncoder::new(Vec::new(), Compression::default());
+ e.write(expected.as_ref()).unwrap();
+ let mut b = e.finish().unwrap();
+ b.push(b'x');
+ b
+ };
+
+ let mut output = Vec::new();
+ let mut decoder = DeflateDecoder::new(compressed.as_slice());
+ let decoded_bytes = decoder.read_to_end(&mut output).unwrap();
+ assert_eq!(decoded_bytes, output.len());
+ let actual = std::str::from_utf8(&output).expect("String parsing error");
+ assert_eq!(
+ actual, expected,
+ "after decompression we obtain the original input"
+ );
+
+ output.clear();
+ assert_eq!(
+ decoder.read(&mut output).unwrap(),
+ 0,
+ "subsequent read of decoder returns 0, but inner reader can return additional data"
+ );
+ let mut reader = decoder.into_inner();
+ assert_eq!(
+ reader.read_to_end(&mut output).unwrap(),
+ 1,
+ "extra data is accessible in underlying buf-read"
+ );
+ assert_eq!(output, b"x");
+ }
+}

src/zlib/bufread.rs

@@ -251,3 +251,50 @@ impl<R: BufRead + Write> Write for ZlibDecoder<R> {
  self.get_mut().flush()
  }
 }
+
+#[cfg(test)]
+mod test {
+ use crate::bufread::ZlibDecoder;
+ use crate::zlib::write;
+ use crate::Compression;
+ use std::io::{Read, Write};
+
+ // GzDecoder consumes one gzip member and then returns 0 for subsequent reads, allowing any
+ // additional data to be consumed by the caller.
+ #[test]
+ fn decode_extra_data() {
+ let expected = "Hello World";
+
+ let compressed = {
+ let mut e = write::ZlibEncoder::new(Vec::new(), Compression::default());
+ e.write(expected.as_ref()).unwrap();
+ let mut b = e.finish().unwrap();
+ b.push(b'x');
+ b
+ };
+
+ let mut output = Vec::new();
+ let mut decoder = ZlibDecoder::new(compressed.as_slice());
+ let decoded_bytes = decoder.read_to_end(&mut output).unwrap();
+ assert_eq!(decoded_bytes, output.len());
+ let actual = std::str::from_utf8(&output).expect("String parsing error");
+ assert_eq!(
+ actual, expected,
+ "after decompression we obtain the original input"
+ );
+
+ output.clear();
+ assert_eq!(
+ decoder.read(&mut output).unwrap(),
+ 0,
+ "subsequent read of decoder returns 0, but inner reader can return additional data"
+ );
+ let mut reader = decoder.into_inner();
+ assert_eq!(
+ reader.read_to_end(&mut output).unwrap(),
+ 1,
+ "extra data is accessible in underlying buf-read"
+ );
+ assert_eq!(output, b"x");
+ }
+}