fix logic error in fill_buffer (#336)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bincode"
-version = "1.3.0" # remember to update html_root_url
+version = "1.3.1" # remember to update html_root_url
 authors = ["Ty Overby <ty@pre-alpha.com>", "Francesco Mazzoli <f@mazzo.li>", "David Tolnay <dtolnay@gmail.com>", "Zoey Riordan <zoey@dos.cafe>"]
 exclude = ["logo.png", "examples/*", ".gitignore", ".travis.yml"]
 

src/de/read.rs

@@ -141,12 +141,7 @@ where
     R: io::Read,
 {
     fn fill_buffer(&mut self, length: usize) -> Result<()> {
-        // Reserve and fill extra space if needed
-        let current_length = self.temp_buffer.len();
-        if length > current_length {
-            self.temp_buffer.reserve_exact(length - current_length);
-            self.temp_buffer.resize(length, 0);
-        }
+        self.temp_buffer.resize(length, 0);
 
         self.reader.read_exact(&mut self.temp_buffer)?;
 
@@ -185,3 +180,23 @@ where
         visitor.visit_bytes(&self.temp_buffer[..])
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::IoReader;
+
+    #[test]
+    fn test_fill_buffer() {
+        let buffer = vec![0u8; 64];
+        let mut reader = IoReader::new(buffer.as_slice());
+
+        reader.fill_buffer(20).unwrap();
+        assert_eq!(20, reader.temp_buffer.len());
+
+        reader.fill_buffer(30).unwrap();
+        assert_eq!(30, reader.temp_buffer.len());
+
+        reader.fill_buffer(5).unwrap();
+        assert_eq!(5, reader.temp_buffer.len());
+    }
+}

src/lib.rs

@@ -24,7 +24,7 @@
 //! Support for `i128` and `u128` is automatically enabled on Rust toolchains
 //! greater than or equal to `1.26.0` and disabled for targets which do not support it
 
-#![doc(html_root_url = "https://docs.rs/bincode/1.3.0")]
+#![doc(html_root_url = "https://docs.rs/bincode/1.3.1")]
 #![crate_name = "bincode"]
 #![crate_type = "rlib"]
 #![crate_type = "dylib"]

tests/test.rs

@@ -880,3 +880,21 @@ fn test_varint_length_prefixes() {
         (1 + std::mem::size_of::<u32>()) as u64
     ); // 2 ** 16 + 1
 }
+
+#[test]
+fn test_byte_vec_struct() {
+    #[derive(PartialEq, Eq, Clone, Serialize, Deserialize, Debug)]
+    struct ByteVecs {
+        a: Vec<u8>,
+        b: Vec<u8>,
+        c: Vec<u8>,
+    };
+
+    let byte_struct = ByteVecs {
+        a: vec![2; 20],
+        b: vec![3; 30],
+        c: vec![1; 10],
+    };
+
+    the_same(byte_struct);
+}