add reset method

Author: newpavlov

block-buffer/CHANGELOG.md

@@ -9,7 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - `ReadBuffer` type ([#823])
 - Optional implementation of the `Zeroize` trait ([#963])
 - Generic `serialize` and `deserialize` methods ([#1200])
-- `ReadBuffer::{read_cached, write_block}` methods ([#1201])
+- `ReadBuffer::{read_cached, write_block, reset}` methods ([#1201])
 
 ### Changed
 - Block sizes must be bigger than 0 and smaller than 256.

block-buffer/src/read.rs

@@ -121,6 +121,11 @@ impl<BS: ArraySize> ReadBuffer<BS> {
         unsafe { self.set_pos_unchecked(read_len) };
     }
 
+    /// Reset buffer into exhausted state.
+    pub fn reset(&mut self) {
+        self.buffer[0] = BS::U8;
+    }
+
     /// Write remaining data inside buffer into `buf`, fill remaining space
     /// in `buf` with blocks generated by `gen_block`, and save leftover data
     /// from the last generated block into the buffer for future use.

block-buffer/tests/mod.rs

@@ -108,9 +108,9 @@ fn test_read() {
     assert_eq!(buf.remaining(), 1);
 
     buf.write_block(0, |_| unreachable!(), |_| unreachable!());
-    assert_eq!(buf.remaining(), 0);
+    assert_eq!(buf.remaining(), 1);
     let res = buf.read_cached(10);
-    assert!(res.is_empty());
+    assert_eq!(res, [7]);
 
     buf.write_block(1, &mut g, |buf| assert_eq!(buf, [8]));
     assert_eq!(buf.remaining(), 3);