From 85acf717764cb0e5ab30043b0ea3cb13164baa78 Mon Sep 17 00:00:00 2001
From: Takeru Ohta <phjgt308@gmail.com>
Date: Sun, 21 May 2023 10:54:18 +0900
Subject: [PATCH] Add `unread_decoded_data` methods to decoders

---
 src/deflate/decode.rs |  7 +++++++
 src/gzip.rs           |  7 +++++++
 src/zlib.rs           | 26 ++++++++++++++++++++++++++
 3 files changed, 40 insertions(+)

diff --git a/src/deflate/decode.rs b/src/deflate/decode.rs
index 273201c..492e2e4 100644
--- a/src/deflate/decode.rs
+++ b/src/deflate/decode.rs
@@ -72,6 +72,13 @@ where
         self.bit_reader.into_inner()
     }
 
+    /// Returns the data that has been decoded but has not yet been read.
+    ///
+    /// This method is useful to retrieve partial decoded data when the decoding process is failed.
+    pub fn unread_decoded_data(&self) -> &[u8] {
+        self.lz77_decoder.buffer()
+    }
+
     pub(crate) fn reset(&mut self) {
         self.bit_reader.reset();
         self.lz77_decoder.clear();
diff --git a/src/gzip.rs b/src/gzip.rs
index 29eee42..52d4e1a 100644
--- a/src/gzip.rs
+++ b/src/gzip.rs
@@ -1011,6 +1011,13 @@ where
         self.reader.into_inner()
     }
 
+    /// Returns the data that has been decoded but has not yet been read.
+    ///
+    /// This method is useful to retrieve partial decoded data when the decoding process is failed.
+    pub fn unread_decoded_data(&self) -> &[u8] {
+        self.reader.unread_decoded_data()
+    }
+
     fn with_header(inner: R, header: Header) -> Self {
         Decoder {
             header,
diff --git a/src/zlib.rs b/src/zlib.rs
index 39add9a..e801c68 100644
--- a/src/zlib.rs
+++ b/src/zlib.rs
@@ -374,6 +374,13 @@ where
     pub fn into_inner(self) -> R {
         self.reader.into_inner()
     }
+
+    /// Returns the data that has been decoded but has not yet been read.
+    ///
+    /// This method is useful to retrieve partial decoded data when the decoding process is failed.
+    pub fn unread_decoded_data(&self) -> &[u8] {
+        self.reader.unread_decoded_data()
+    }
 }
 impl<R> io::Read for Decoder<R>
 where
@@ -928,4 +935,23 @@ mod tests {
         decoder.read_to_end(&mut buf).unwrap();
         assert_eq!(buf, b"Hello World");
     }
+
+    #[test]
+    fn issue71() {
+        let encoded_data = [
+            120, 218, 251, 255, 207, 144, 193, 138, 193, 151, 161, 146, 33, 143, 33, 149, 161, 156,
+            161, 24, 72, 38, 51, 148, 48, 100, 50, 228, 3, 69, 120, 25, 184, 24,
+        ];
+
+        let mut decoder = Decoder::new(&encoded_data[..]).unwrap();
+        let mut buf = Vec::new();
+        let result = decoder.read_to_end(&mut buf);
+        assert!(result.is_err());
+
+        let decoded_data = [
+            255, 254, 49, 0, 58, 0, 77, 0, 121, 0, 110, 0, 101, 0, 119, 0, 115, 0, 101, 0, 99, 0,
+            116, 0, 105, 0, 111, 0, 110, 0, 13, 0, 10,
+        ];
+        assert_eq!(decoder.unread_decoded_data(), decoded_data);
+    }
 }