diff --git a/Cargo.lock b/Cargo.lock
index 02c5ddd..531bb58 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -38,6 +38,7 @@ version = "2.0.0"
 dependencies = [
  "base64",
  "getrandom",
+ "libc",
  "openssl",
  "rustc_version",
  "smallvec",
@@ -71,9 +72,9 @@ dependencies = [
 
 [[package]]
 name = "libc"
-version = "0.2.90"
+version = "0.2.133"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ba4aede83fc3617411dc6993bc8c70919750c1c257c6ca6a502aed6e0e2394ae"
+checksum = "c0f80d65747a3e43d1596c7c5492d95d5edddaabd45a7fcdb02b95f644164966"
 
 [[package]]
 name = "once_cell"
diff --git a/Cargo.toml b/Cargo.toml
index ef8e145..2d45577 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -3,17 +3,21 @@ name = "chacha20"
 description = "chacha20_poly1305 encryption tool"
 version = "2.0.0"
 authors = ["Avril <flanchan@cumallover.me>"]
-edition = "2018"
+edition = "2021"
 license = "gpl-3.0-or-later"
 
 [features]
+default = ["mmap"]
 
+# Try to map inputs/outputs before using buffers
+mmap = ["libc"]
 # Explicitly clear buffers and cache after use
 explicit_clear = []
 
 [dependencies]
 base64 = "0.13"
 getrandom = "0.2"
+libc = { version = "0.2.133", optional = true }
 openssl = "0.10"
 smallvec = {version = "1.6", features=["union"]}
 
diff --git a/src/main.rs b/src/main.rs
index ba986c9..d488e32 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -81,6 +81,27 @@ fn keys() -> Result<(Mode, Key, IV), base64::DecodeError>
     Ok((mode, key, iv))
 }
 
+const USE_MMAP: bool = if cfg!(feature="mmap") {
+    true
+} else {
+    false
+};
+
+#[cfg(feature="mmap")]
+mod mapped;
+
+#[allow(unreachable_code)]
+fn try_mmap(decrypt: bool, key: Key, iv: IV) -> std::io::Result<i32>
+{
+    #[cfg(feature="mmap")] return mapped::try_process(if decrypt {
+	cha::decrypter(key, iv).expect("Failed to create decrypter")
+    } else {
+	cha::encrypter(key, iv).expect("Failed to create encrypter")
+    }).map(|_| 0);
+    
+    unreachable!("Built without feature `mmap`, but still tried to call into it. This is a bug")
+}
+
 fn main() {
 
     let (mode, key, iv) = keys().expect("Failed to read keys from argv (base64)");
@@ -88,14 +109,26 @@ fn main() {
     let stdout = std::io::stdout();
     let input = std::io::stdin();
 
+    // Attempt a mapped solution
+    if USE_MMAP && mode != Mode::Keygen {
+	match try_mmap(mode == Mode::Decrypt, key, iv) {
+	    Ok(0) => return,
+	    Ok(n) => std::process::exit(n),
+	    Err(err) => if cfg!(debug_assertions) {
+		eprintln!("Failed to mmap input or output for processing, falling back to stream: {}", err);
+	    }
+	}
+    } 
     // Streaming
     use std::io::Write;
     match mode 
     {
 	Mode::Encrypt => {
+	    
 	    let mut output = stream::Sink::encrypt(stdout.lock(), key, iv).expect("Failed to create encrypter");
 	    std::io::copy(&mut input.lock(), &mut output).expect("Failed to encrypt");
 	    output.flush().expect("Failed to flush stdout");
+	    
 	},
 	Mode::Decrypt => {
 	    let mut output = stream::Sink::decrypt(stdout.lock(), key, iv).expect("Failed to create decrypter");
diff --git a/src/mapped.rs b/src/mapped.rs
new file mode 100644
index 0000000..7b9d3ee
--- /dev/null
+++ b/src/mapped.rs
@@ -0,0 +1,110 @@
+//! Use memory mapping to process the entire stream at once
+use super::*;
+
+use std::os::unix::prelude::*;
+use std::{
+    io,
+    fs,
+    ptr,
+    ops,
+    mem::{
+	self,
+	MaybeUninit,
+    },
+    borrow::BorrowMut,
+    convert::{TryFrom, TryInto,},
+};
+use libc::{
+    mmap, munmap, madvise, MAP_FAILED,
+};
+use openssl::symm::Crypter;
+
+#[derive(Debug)]
+struct MapInner
+{
+    mem: ptr::NonNull<u8>,
+    size: usize
+}
+
+impl ops::Drop for MapInner
+{
+    #[inline]
+    fn drop(&mut self)
+    {
+	unsafe {
+	    munmap(self.mem.as_ptr() as *mut _, self.size);
+	}
+    }
+}
+
+#[inline] 
+pub fn raw_file_size(fd: &(impl AsRawFd + ?Sized)) -> io::Result<u64>
+{
+    use libc::fstat;
+    let mut stat = MaybeUninit::uninit();
+    match unsafe { fstat(fd.as_raw_fd(), stat.as_mut_ptr()) } {
+	0 => match unsafe {stat.assume_init()}.st_size {
+	    x if x < 0 => Err(io::Error::new(io::ErrorKind::InvalidInput, format!("File from {} is too large", fd.as_raw_fd()))),
+	    x => Ok(x as u64),
+	},
+	_ => Err(io::Error::last_os_error()),
+    }
+}
+
+#[derive(Debug)]
+pub struct Mapped<T: ?Sized>
+{
+    mem: MapInner,
+    file: T
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash, Copy, PartialOrd, Ord)]
+pub enum MapMode
+{
+    ReadOnly,
+    ReadWrite,
+    WriteOnly,
+}
+//TODO: impl MapMode -> fn as_prot() -> c_int, fn as_flags() -> c_int
+
+impl<T: AsRawFd> Mapped<T>
+{
+    pub fn try_new_sized(file: T, size: u64, rw: MapMode) -> io::Result<Self>
+    {
+	todo!("mem: mmap(0, size, rw.prot(), MAP_SHARED (For rw: *Write*), MAP_PRIVATE [TODO: add support for| MAP_HUGE_] (For rw: ReadOnly), file.as_raw_fd(), 0) != MAP_FAILED (TODO: maybe madvise?)")
+    }
+    #[inline(always)] 
+    pub fn try_new(file: T, rw: MapMode) -> io::Result<Self>
+    {
+	let size = raw_file_size(&file)?;
+	Self::try_new_sized(file, size, rw)
+    }
+}
+/*
+impl<T: AsRawFd> TryFrom<T> for Mapped<T>
+{
+    type Error = io::Error;
+
+    fn try_from(from: T) -> Result<Self, Self::Error>
+    {
+	Self::try_new(from, raw_file_size(&from)?)
+    }
+}*/
+
+
+fn process_mapped_files<T, U>(mode: &mut Crypter, input: &mut Mapped<T>, output: &mut Mapped<U>) -> io::Result<()>
+where T: AsRawFd + ?Sized,
+U: AsRawFd + ?Sized
+{
+    todo!("mode.update(input.slice(), output.slice()); /* unneeded: mode.finalize(input.slice(), output.slice()) */ ");
+}
+
+#[inline] 
+pub fn try_process(mut mode: impl BorrowMut<Crypter>) -> io::Result<io::Result<()>>
+{
+    let mode = mode.borrow_mut();
+    /*let mstdin = Mapped::try_new(input)?;
+    let mstdout = Mapped::try_new(output)?;*/ //TODO: if failed to map output, but input is successful (TODO: XXX: implement other way around), we can fall back to wrapping output in `Sink`.
+    todo!("Try to map the stdin and stdout streams, if that fails, return Err(last_os_err).");
+    todo!("return Ok(process_mapped_files(mode, mstdin, mstdout, key, iv))")
+}