Add precomputed constants for common cases.

There are now 2 features that control the amount of precomputed
constants. They can either be 0, 12, or 256. Most users will likely want
to go with the 12, so this is the default feature.

1 files changed, 14 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 2548c46..955daf8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -18,6 +18,20 @@
 //! [`PasswordMaker`] is the main part of this crate. You give it settings similar to those of a PasswordMaker Pro profile,
 //! and it gives you a password that's hopfully the same you'd get from PasswordMaker Pro for the same input.
 //! 
+//! # Features
+//! The library comes with a set of precomputed powers to (slightly) speed up computation in common use cases. By default, constants
+//! for the lengths of the pre-defined character sets of PasswordMaker Pro are included (10, 16, 32, 52, 62, 94), amounting to a total
+//! of 360 bytes on a 32bit machine, and 408 bytes on a 64bit machine (and some instructions to read them). For all other character
+//! set lengths the values are computed at runtime when needed. Those values are in the (default-enabled)
+//! `precomputed_common_max_powers` feature.
+//! 
+//! If you prefer simpler code and want to save a couple of bytes in the binary, you can disable `default-features` to use runtime
+//! computation for all values, at the cost of a slight performance impact.
+//! 
+//! On the other hand, if binary size is not of concern, you might want to enable the `precomputed_max_powers` feature.
+//! This feature enables precomputed powers for all bases in the range 2..130. It therefore needs 7680 bytes on a 32bit machine, and
+//! 8704 bytes on a 64bit machine (plus some extra instructions).
+//! 
 //! # Warning
 //! This library has NOT been tested on 16bit machines. It might work, but probably does not.