# SHA


Usage is very straightforward:
```julia
julia> using SHA

julia> bytes2hex(sha256("test"))
"9f86d081884c7d659a2feaa0c55ad015a3bf4f1b2b0b822cd15d6c15b0f00a08"
```

Each exported function (at the time of this writing, SHA-1, SHA-2 224, 256, 384 and 512, and SHA-3 224, 256, 384 and 512 functions are implemented) takes in either an `AbstractVector{UInt8}`, an `AbstractString` or an `IO` object.  This makes it trivial to checksum a file:

```julia
shell> cat /tmp/test.txt
test
julia> using SHA

julia> open("/tmp/test.txt") do f
           sha2_256(f)
       end
32-element Array{UInt8,1}:
 0x9f
 0x86
 0xd0
 0x81
 0x88
 0x4c
 0x7d
 0x65
    ⋮
 0x5d
 0x6c
 0x15
 0xb0
 0xf0
 0x0a
 0x08
```

Due to the colloquial usage of `sha256` to refer to `sha2_256`, convenience functions are provided, mapping `shaxxx()` function calls to `sha2_xxx()`.  For SHA-3, no such colloquialisms exist and the user must use the full `sha3_xxx()` names.

`shaxxx()` takes `AbstractString` and array-like objects (`NTuple` and `Array`) with elements of type `UInt8`.

To create a hash from multiple items the `SHAX_XXX_CTX()` types can be used to create a stateful hash object that
is updated with `update!` and finalized with `digest!`

```julia
julia> ctx = SHA2_256_CTX()
SHA2 256-bit hash state

julia> update!(ctx, b"some data")
0x0000000000000009

julia> update!(ctx, b"some more data")
0x0000000000000017

julia> digest!(ctx)
32-element Vector{UInt8}:
 0xbe
 0xcf
 0x23
 0xda
 0xaf
 0x02
    ⋮
 0x25
 0x52
 0x19
 0xa0
 0x8b
 0xc5
```

Note that, at the time of this writing, the SHA3 code is not optimized, and as such is roughly an order of magnitude slower than SHA2.