sha2.lua

--[=[

	SHA-256/-384/-512 hashing.
	Written by Cosmin Apreutesei. Public Domain.

sha[256|384|512](s[, size]) -> s
sha[256|384|512](cdata, size) -> s

	Compute the SHA-2 hash of a string or a cdata buffer.

sha2[256|384|512]_digest() -> digest

	Get a SHA-2 digest closure that can consume multiple data chunks:

	digest(s[, size])      add a string
	digest(cdata, size)    add a cdata buffer
	digest() -> s          return the hash

All functions return the binary representation of the hash.
To get the hex representation, use tohex().

]=]

if not ... then
	require'sha2_test'
	require'sha2_hmac_test'
	return
end

local ffi = require'ffi'
local C = ffi.load'sha2'

ffi.cdef[[
enum {
	SHA256_BLOCK_LENGTH  = 64,
	SHA256_DIGEST_LENGTH = 32,
	SHA384_BLOCK_LENGTH = 128,
	SHA384_DIGEST_LENGTH = 48,
	SHA512_BLOCK_LENGTH = 128,
	SHA512_DIGEST_LENGTH = 64,
};
typedef struct _SHA256_CTX {
	uint32_t	state[8];
	uint64_t	bitcount;
	uint8_t	buffer[SHA256_BLOCK_LENGTH];
} SHA256_CTX;
typedef struct _SHA512_CTX {
	uint64_t	state[8];
	uint64_t	bitcount[2];
	uint8_t	buffer[SHA512_BLOCK_LENGTH];
} SHA512_CTX;
typedef SHA512_CTX SHA384_CTX;

void SHA256_Init(SHA256_CTX *);
void SHA256_Update(SHA256_CTX*, const uint8_t*, size_t);
void SHA256_Final(uint8_t[SHA256_DIGEST_LENGTH], SHA256_CTX*);

void SHA384_Init(SHA384_CTX*);
void SHA384_Update(SHA384_CTX*, const uint8_t*, size_t);
void SHA384_Final(uint8_t[SHA384_DIGEST_LENGTH], SHA384_CTX*);

void SHA512_Init(SHA512_CTX*);
void SHA512_Update(SHA512_CTX*, const uint8_t*, size_t);
void SHA512_Final(uint8_t[SHA512_DIGEST_LENGTH], SHA512_CTX*);
]]

local u8a = ffi.typeof'uint8_t[?]'

local function digest_function(Context, Init, Update, Final, DIGEST_LENGTH)
	return function()
		local ctx = Context()
		local result = u8a(DIGEST_LENGTH)
		Init(ctx)
		return function(data, size)
			if data then
				Update(ctx, data, size or #data)
			else
				Final(result, ctx)
				return ffi.string(result, DIGEST_LENGTH)
			end
		end
	end
end

local function hash_function(digest_function)
	return function(data, size)
		local d = digest_function(); d(data, size); return d()
	end
end

_G[C] = true --pin C!

sha256_digest = digest_function(ffi.typeof'SHA256_CTX', C.SHA256_Init, C.SHA256_Update, C.SHA256_Final, C.SHA256_DIGEST_LENGTH)
sha384_digest = digest_function(ffi.typeof'SHA384_CTX', C.SHA384_Init, C.SHA384_Update, C.SHA384_Final, C.SHA384_DIGEST_LENGTH)
sha512_digest = digest_function(ffi.typeof'SHA512_CTX', C.SHA512_Init, C.SHA512_Update, C.SHA512_Final, C.SHA512_DIGEST_LENGTH)
sha256 = hash_function(sha256_digest)
sha384 = hash_function(sha384_digest)
sha512 = hash_function(sha512_digest)