The Sha2 compression functions were re-written to execute the message
scheduling calculations in the same loop as the rest of the compression
function. The compiler is able to generate much better code. Additionally,
innermost part of the compression functions were turned into macros to
reduce code duplicate and to make the functions more concise.
There are 2 main pieces of functionality in cryptoutil.rs:
* A set of unsafe function for efficiently reading and writing u32 and u64
values. All of these functions are fairly easy to audit to confirm that
they do what they are supposed to.
* A FixedBuffer struct. This struct keeps track of input data until there
is enough of it to execute the a function on it which expects a fixed
block of data.
The Sha2 module was rewritten to take advantage of the new functions in
cryptoutil as well as FixedBuffer. The result is that the duplicate code
for maintaining a buffer of input data is removed from the Sha512 and
Sha256 implementation. Additionally, the FixedBuffer code is much more
efficient than the previous code was.
The result_X() methods just calculate an output of a fixed size. They don't
really have much to do with running the actually hash algorithm until the very
last step - the output. It makes much more sense to put all this logic into
the Digest impls for each specific variation on the hash function.
The code was arranged so that the core Sha2 code came first, and then
all of the various implementation of Digest followed along later. The
problem is that the Sha512 compression function code is far away from
the Sha512 Digest implementation, so, if you are trying to read over
the code, you need to scroll all around the file for no good reason. The
code was rearranged so that all of the Sha512 code is in one place and
all of the Sha256 code is in another and so that all impls for a struct
are near the definition of that struct.
* Rename struct Sha1State to Sha1
* Remove all use of @ types
* Use fixed length vectors
* Move all of the inner functions from inside sha1() to top level, private functions
* Sha1 instances are now created via Sha1::new()
* Update all constant names to uppercase
* Remove unecessary assert_eq!s
* Remove check_vec_eq() helper function; use vec::eq() instead
