diff --git a/src/mapped.rs b/src/mapped.rs
index b664d14..cc39620 100644
--- a/src/mapped.rs
+++ b/src/mapped.rs
@@ -11,7 +11,7 @@ use std::{
 	self,
 	MaybeUninit,
     },
-    borrow::BorrowMut,
+    borrow::{BorrowMut, Cow},
     convert::{TryFrom, TryInto,},
 };
 use libc::{
@@ -166,9 +166,11 @@ fn translate_hugetlb_size(size: usize) -> mapped_file::hugetlb::HugePage
 	    .or_else(|| sizes_kb.iter().nth(1)
 		     .or_else(|| sizes_kb.first()))
     }
+    const MB: usize = 1024*1024;
+    const GB: usize = 1024 * MB;
     match size {
-	0..(1024*1024) => mapped_file::hugetlb::HugePage::Smallest,
-	(1024*1024)..(1024*1024*1024) => mapped_file::hugetlb::HugePage::Selected(check_func),
+	0..MB => mapped_file::hugetlb::HugePage::Smallest,
+	MB..GB => mapped_file::hugetlb::HugePage::Selected(check_func),
 	very_high => mapped_file::hugetlb::HugePage::Largest,
     }
 }
@@ -191,6 +193,194 @@ fn create_sized_temp_mapping(size: usize) -> io::Result<(MappedFile<MemoryFile>,
     MappedFile::new(file, size, Perm::ReadWrite, Flags::Shared).map(|x| (x, false))
 }
 
+type MappedMemoryFile = MappedFile<mapped_file::file::memory::MemoryFile>;
+
+/// How a mapped operation should optimally take place
+//TODO: Make optimised mapping operations for each one, like `fn process(self, enc: &mut Crypter) -> io::Result<usize>`
+pub enum OpTable<T, U>
+{
+    /// Both input and output are mapped
+    Both(MappedFile<T>, MappedFile<U>),
+    /// Input is mapped, but output is not. Work is done through a temporary map, then copied to `U`.
+    Input(MappedFile<T>, MappedMemoryFile, U),
+    /// Output is mapped, but input is not. Work is done from a temporary map
+    Output(T, MappedMemoryFile, MappedFile<U>),
+    /// Streaming mode (`read()`+`write()` only)
+    Neither(T, U),
+}
+
+impl<T, U> OpTable<T, U>
+{
+    /// Consume into either a mapping line, or the in/out tuple if neither are mapped.
+    #[inline] 
+    pub fn only_mapped(self) -> Result<Self, (T, U)>
+    {
+	match self {
+	    Self::Neither(t, u) => Err((t, u)),
+	    this => Ok(this),
+	}
+    }
+}
+
+impl<T: io::Read+AsRawFd, U: io::Write+AsRawFd> OpTable<T, U>
+{
+    fn pre_process(&mut self) -> io::Result<()>
+    {
+	match self {
+	    Self::Both(input, output)
+		=> {
+		    let _ = input.advise(mapped_file::Advice::Sequential, Some(true));
+		    let _ = output.advise(mapped_file::Advice::Sequential, None);
+		},
+	    Self::Input(input, mem)
+		=> {
+		    let _ = input.advise(mapped_file::Advice::Sequential, Some(true));
+		    let _ = mem.advise(mapped_file::Advice::Sequential, None);
+		},
+	    Self::Output(input, mem, _)
+		=> {
+		    let _ = mem.advise(mapped_file::Advice::Sequential, Some(true));
+		    std::io::copy(&mut input, &mut mem)?;
+		},
+	    _ => (),
+	}
+	Ok(())
+    }
+    fn post_process(&mut self) -> io::Result<()>
+    {
+	match self {
+	    Self::Both(_, output) => drop(output.flush(mapped_file::Flush::Wait)?),
+	    Self::Input(_, mut mem, mut output) => drop(std::io::copy(&mut mem, &mut output)?),
+	    Self::Output(_, _, mut output) => drop(output.flush(mapped_file::Flush::Wait)?),
+	    Self::Neither(_, stream) => stream.flush()?,
+	    _ => (),
+	}
+	Ok(())
+    }
+    /// Execute this en/decryption in an optimised function
+    pub fn execute(mut self, mut mode: impl BorrowMut<Crypter>) -> io::Result<usize>
+    {
+	self.pre_process()?;
+	let mode: &mut Crypter = mode.borrow_mut();
+	match self {
+	    Self::Both(mut input, mut output) => {
+		let len = std::cmp::min(input.len(), output.len());
+		process_mapped_files(mode, &mut input, &mut output)?;
+		
+		self.post_process()?;
+		Ok(len)
+	    },
+	    Self::Input(mut input, mut output, _) => {
+		let len = std::cmp::min(input.len(), output.len());
+		process_mapped_files(mode, &mut input, &mut output)?;
+
+		self.post_process()?;
+		Ok(len)
+	    },
+	    Self::Output(_, mut input, mut output) => {
+		let len = std::cmp::min(input.len(), output.len());
+		process_mapped_files(mode, &mut input, &mut output)?;
+
+		self.post_process()?;
+		Ok(len)
+	    },
+	    Self::Neither(sin, sout) => {
+		const BUFFER_SIZE: usize = 1024*1024;
+		macro_rules! try_allocmem {
+		    ($size:expr) => {
+			{
+			    let size = usize::from($size);
+			    let hsz = mapped_file::hugetlb::HugePage::Dynamic { kilobytes: size/1024 }; // 1MB buffer 
+			    hsz.compute_huge()
+				.and_then(|huge| mapped_file::file::memory::MemoryFile::with_size_hugetlb(size, huge).ok())
+				.or_else(|| mapped_file::file::memory::MemoryFile::with_size(size).ok())
+				.and_then(|file| MappedFile::new(file, size, Perm::ReadWrite, Flags::Private).ok())
+			}
+		    };
+		    ($mem:expr, $size:expr) => {
+			$mem.map(|x| Cow::Borrowed(&mut x[..])).unwrap_or_else(|| Cow::Owned(vec![0u8; $size]));
+		    }
+		}
+		let mut _mem = try_allocmem!(BUFFER_SIZE);
+		let mut _memo = try_allocmem!(BUFFER_SIZE);
+		let mut buffer = try_allocmem!(_mem, BUFFER_SIZE);
+		let mut buffero = try_allocmem!(_memo, BUFFER_SIZE);
+		let mut read =0;
+		let mut cur;
+		while { cur = sin.read(&mut buffer[..])?; cur > 0 } {
+		    /*let cur =*/ mode.update(&buffer[..cur], &mut buffero[..cur])?;
+		    sout.write_all(&buffero[..cur])?;
+		    read += cur;
+		}
+
+		self.post_process()?;
+		Ok(read)
+	    },
+	}
+    }
+}
+
+#[inline] 
+fn sized_then_or<T: AsRawFd, U, F>(stream: T, trans: F) -> Result<U, T>
+    where F: FnOnce(T, usize) -> U
+{
+    let Some(size): usize = raw_file_size(&stream).and_then(u64::into).ok() else { return Err(stream); };
+    Some(trans(stream, trans))
+}
+
+#[inline] 
+fn map_size_or<T: AsRawFd, U, F>(stream: T, size: usize, trans: F) -> Result<U, T>
+    where F: FnOnce(MappedFile<T>, usize) -> U
+{
+    if try_map_to(&stream, size) {
+	// Sized
+	match MappedFile::try_new(stream, size, Perm::ReadWrite, Flags::Shared) {
+	    Ok(map) => Ok(trans(map, size)),
+	    Err(e) => Err(e.into_inner()),
+	}
+    } else {
+	// Unsized
+	Err(stream)
+    }
+}
+
+/// Create an optimised call table for the cryptographic transformation from `from` to `to`.
+pub fn create_process<T: AsRawFd, U: AsRawFd>(from: T, to: U) -> OpTable<T, U>
+{
+    let (input, buffsz) = match sized_then_or(from, |input, input_size| {
+	(match MappedFile::try_new(input, input_size, Perm::Readonly, Flags::Private) {
+	    Ok(m) => Ok(m),
+	    Err(e) => Err(e.into_inner()),
+	}, input_size)
+    }) {
+	Ok((i, bs)) => (i, Some(bs)),
+	Err(e) => (Err(e), None),
+    };
+    
+    let (output, outsz) = {
+	if let Some(buffsz) = buffsz.or_else(|| raw_file_size(&to).ok()) {
+	    match map_size_or(to, buffsz, |mmap, size| {
+		(mmap, size)
+	    }) {
+		Ok((m, s)) => (Ok(m), Some(s)),
+		Err(e) => (Err(e), if buffsz == 0 { None } else { Some(buffsz) }),
+	    }
+	} else {
+	    Err((to, None))
+	}
+    };
+
+    match ((input, buffsz), (output, outsz)) {
+	// Check for all combinations of mapping successes or failures
+	((Ok(min), isz), (Ok(mout), osz)) => OpTable::Both(min, mout),
+	((Ok(min), isz), (Err(sout), osz)) => OpTable::Input(min, create_sized_temp_mapping(isz.or(osz)), sout),
+	((Err(sin), isz), (Ok(mout), osz)) => OpTable::Output(sin, create_sized_temp_mapping(osz.or(isz)), mout),
+	((Err(sin, isz), (Err(sout), osz))) => OpTable::Neither(sin, sout),
+    }
+}
+
+    #[cfg(feature="try_process-old")] 
+    const _:() = {
 pub fn try_process(mut mode: impl BorrowMut<Crypter>) -> io::Result<io::Result<()>>
 {
     let mode = mode.borrow_mut();
@@ -286,3 +476,4 @@ pub fn try_process(mut mode: impl BorrowMut<Crypter>) -> io::Result<io::Result<(
     //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))")
 }
+    };