Derive Clone for InflateState to allow random-access reads (#157)

I am implementing Seek for a wrapper that reads deflated files.  To do this, I will
inflate the file once and save the dictionary and inflate state at several points in
the file.  Later, when I want to seek to some random place in the file, I will use the
cloned state+dict to position to a known file position and then inflate until I reach
the data I need.

To support this, I need to be able to Clone the InflateState and its parts (the current
dictionary).  Derive Clone for InflateState, HuffmanTable and DecompressorOxide.

miniz_oxide/src/inflate/core.rs

@@ -12,6 +12,7 @@ use self::output_buffer::OutputBuffer;
 pub const TINFL_LZ_DICT_SIZE: usize = 32_768;
 
 /// A struct containing huffman code lengths and the huffman code tree used by the decompressor.
+#[derive(Clone)]
 struct HuffmanTable {
     /// Length of the code at each index.
     pub code_size: [u8; MAX_HUFF_SYMBOLS_0],
@@ -166,6 +167,7 @@ type BitBuffer = u32;
 
 /// Main decompression struct.
 ///
+#[derive(Clone)]
 pub struct DecompressorOxide {
     /// Current state of the decompressor.
     state: core::State,

miniz_oxide/src/inflate/stream.rs

@@ -57,6 +57,7 @@ impl ResetPolicy for FullReset {
 
 /// A struct that compbines a decompressor with extra data for streaming decompression.
 ///
+#[derive(Clone)]
 pub struct InflateState {
     /// Inner decompressor struct
     decomp: DecompressorOxide,
@@ -420,4 +421,67 @@ mod test {
         // Should still have the checksum read from the header file.
         assert_eq!(state.decompressor().adler32_header(), Some(459605011))
     }
+
+    #[test]
+    fn test_partial_continue() {
+        let encoded = [
+            120u8, 156, 243, 72, 205, 201, 201, 215, 81, 168, 202, 201, 76, 82, 4, 0, 27, 101, 4,
+            19,
+        ];
+
+        // Feed input bytes one at a time to the decompressor
+        let mut out = vec![0; 50];
+        let mut state = InflateState::new_boxed(DataFormat::Zlib);
+        let mut part_in = 0;
+        let mut part_out = 0;
+        for i in 1..=encoded.len() {
+            let res = inflate(&mut state, &encoded[part_in..i], &mut out[part_out..], MZFlush::None);
+            let status = res.status.expect("Failed to decompress!");
+            if i == encoded.len() {
+                assert_eq!(status, MZStatus::StreamEnd);
+            } else {
+                assert_eq!(status, MZStatus::Ok);
+            }
+            part_out += res.bytes_written as usize;
+            part_in += res.bytes_consumed;
+        }
+
+        assert_eq!(out[..part_out as usize], b"Hello, zlib!"[..]);
+        assert_eq!(part_in, encoded.len());
+        assert_eq!(state.decompressor().adler32(), Some(459605011));
+    }
+
+
+    // Inflate part of a stream and clone the inflate state.
+    // Discard the original state and resume the stream from the clone.
+    #[test]
+    fn test_rewind_and_resume() {
+        let encoded = [
+            120u8, 156, 243, 72, 205, 201, 201, 215, 81, 168, 202, 201, 76, 82, 4, 0, 27, 101, 4,
+            19,
+        ];
+        let decoded = b"Hello, zlib!";
+
+        // Feed partial input bytes to the decompressor
+        let mut out = vec![0; 50];
+        let mut state = InflateState::new_boxed(DataFormat::Zlib);
+        let res1 = inflate(&mut state, &encoded[..10], &mut out, MZFlush::None);
+        let status = res1.status.expect("Failed to decompress!");
+        assert_eq!(status, MZStatus::Ok);
+
+        // Clone the state and discard the original
+        let mut resume = state.clone();
+        drop(state);
+
+        // Resume the stream using the cloned state
+        let res2 = inflate(&mut resume, &encoded[res1.bytes_consumed..], &mut out[res1.bytes_written..], MZFlush::Finish);
+        let status = res2.status.expect("Failed to decompress!");
+        assert_eq!(status, MZStatus::StreamEnd);
+
+        assert_eq!(res1.bytes_consumed + res2.bytes_consumed, encoded.len());
+        assert_eq!(res1.bytes_written + res2.bytes_written, decoded.len());
+        assert_eq!(&out[..res1.bytes_written + res2.bytes_written as usize], decoded);
+        assert_eq!(resume.decompressor().adler32(), Some(459605011));
+    }
+
 }