update README

Cargo.lock

@@ -34,7 +34,7 @@ checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
 [[package]]
 name = "chacha20"
-version = "1.0.2"
+version = "1.1.0"
 dependencies = [
  "base64",
  "getrandom",

README.md

@@ -9,6 +9,15 @@ Run `cargo build --release`, the binary will be built to `./target/release/chach
 Run `cargo test && cargo build && ./test.sh debug` to test the program.
 Alternatively, run `./test.sh` after building to test the release build's correctness.
 
+## Features
+To enable explicit buffer clearing, compile with the option `--features explicit_clear`. 
+
+The `explicit_clear` feature forces any temporary work buffers to be zeroed out in memory when the corresponding stream is flushed itself. 
+It requires the nonstandard glibc extension `explicit_bzero(void*, size_t)` to build.
+On x86 targets with the Rust nightly toolchain installed, this will also force a cache flush of the corresponding memory address.
+This is *usually not needed*, and can cause a slowdown; but it prevents any lingering data being left in the buffer.
+The unit test `remainder()` checks the process' memory map for leftover data in the working buffer when testing with this feature enabled.
+
 # Usage
 Copies stdin to stdout while encrypting or decrypting with the stream cipher `chacha20_poly1305`.