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# 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.
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