--SHA2 is big-endian
local bytes2word = function(b0,b1,b2,b3)
	local i = b0; i = LSHIFT(i,8);
	i = OR(i,b1); i = LSHIFT(i,8);
	i = OR(i,b2); i = LSHIFT(i,8);
	i = OR(i,b3);
	return i;
end

local word2bytes = function(word)
	local b0,b1,b2,b3;
	b3 = AND(word,0xFF); word = RSHIFT(word,8);
	b2 = AND(word,0xFF); word = RSHIFT(word,8);
	b1 = AND(word,0xFF); word = RSHIFT(word,8);
	b0 = AND(word,0xFF);
	return b0,b1,b2,b3;
end

local bytes2dword = function(b0,b1,b2,b3,b4,b5,b6,b7)
	local i = bytes2word(b0,b1,b2,b3);
	local j = bytes2word(b4,b5,b6,b7);
	return (i*0x100000000)+j;
end

local dword2bytes = function(i)
	local b4,b5,b6,b7 = word2bytes(i);
	local b0,b1,b2,b3 = word2bytes(Math.floor(i/0x100000000));
	return b0,b1,b2,b3,b4,b5,b6,b7;
end 




local SHA2_256 = function()

	local queue = Queue();

	local h0 = 0x6a09e667;
	local h1 = 0xbb67ae85;
	local h2 = 0x3c6ef372;
	local h3 = 0xa54ff53a;
	local h4 = 0x510e527f;
	local h5 = 0x9b05688c;
	local h6 = 0x1f83d9ab;
	local h7 = 0x5be0cd19;

	local public = {};

	local processBlock = function()
		local a = h0;
		local b = h1;
		local c = h2;
		local d = h3;
		local e = h4;
		local f = h5;
		local g = h6;
		local h = h7;

		local w = {};

		for i=0,15 do
			w[i] = bytes2word(queue.pop(),queue.pop(),queue.pop(),queue.pop());
		end

		for i=16,63 do
			local s0 = XOR(RROT(w[i-15],7), XOR(RROT(w[i-15],18), RSHIFT(w[i-15],3)));
			local s1 = XOR(RROT(w[i-2],17), XOR(RROT(w[i-2], 19), RSHIFT(w[i-2],10)));
			w[i] = AND(w[i-16] + s0 + w[i-7] + s1, 0xFFFFFFFF);
		end

		for i=0,63 do
			local s1 = XOR(RROT(e,6), XOR(RROT(e,11),RROT(e,25)));
			local ch = XOR(AND(e,f), AND(NOT(e),g));
			local temp1 = h + s1 + ch + CONSTANTS[i+1] + w[i];
			local s0 = XOR(RROT(a,2), XOR(RROT(a,13), RROT(a,22)));
			local maj = XOR(AND(a,b), XOR(AND(a,c), AND(b,c)));
			local temp2 = s0 + maj;

			h = g;
			g = f;
			f = e;
			e = d + temp1;
			d = c;
			c = b;
			b = a;
			a = temp1 + temp2;
		end

		h0 = AND(h0 + a, 0xFFFFFFFF);
		h1 = AND(h1 + b, 0xFFFFFFFF);
		h2 = AND(h2 + c, 0xFFFFFFFF);
		h3 = AND(h3 + d, 0xFFFFFFFF);
		h4 = AND(h4 + e, 0xFFFFFFFF);
		h5 = AND(h5 + f, 0xFFFFFFFF);
		h6 = AND(h6 + g, 0xFFFFFFFF);
		h7 = AND(h7 + h, 0xFFFFFFFF);
	end

	public.init = function()
		queue.reset();

		h0 = 0x6a09e667;
		h1 = 0xbb67ae85;
		h2 = 0x3c6ef372;
		h3 = 0xa54ff53a;
		h4 = 0x510e527f;
		h5 = 0x9b05688c;
		h6 = 0x1f83d9ab;
		h7 = 0x5be0cd19;

		return public;
	end

	public.update = function(bytes)
		for b in bytes do
			queue.push(b);
			if queue.size() >= 64 then processBlock(); end
		end

		return public;
	end

	public.finish = function()
		local bits = queue.getHead() * 8;

		queue.push(0x80);
		while ((queue.size()+7) % 64) < 63 do
			queue.push(0x00);
		end

		local b0,b1,b2,b3,b4,b5,b6,b7 = dword2bytes(bits);

		queue.push(b0);
		queue.push(b1);
		queue.push(b2);
		queue.push(b3);
		queue.push(b4);
		queue.push(b5);
		queue.push(b6);
		queue.push(b7);

		while queue.size() > 0 do
			processBlock();
		end

		return public;
	end
	
	public.asBytes = function()
		local  b0, b1, b2, b3 = word2bytes(h0);
		local  b4, b5, b6, b7 = word2bytes(h1);
		local  b8, b9,b10,b11 = word2bytes(h2);
		local b12,b13,b14,b15 = word2bytes(h3);
		local b16,b17,b18,b19 = word2bytes(h4);
		local b20,b21,b22,b23 = word2bytes(h5);
		local b24,b25,b26,b27 = word2bytes(h6);
		local b28,b29,b30,b31 = word2bytes(h7);


		return {  b0, b1, b2, b3, b4, b5, b6, b7, b8, b9,b10,b11,b12,b13,b14,b15
				,b16,b17,b18,b19,b20,b21,b22,b23,b24,b25,b26,b27,b28,b29,b30,b31};	
	end

	public.asHex = function()
		local  b0, b1, b2, b3 = word2bytes(h0);
		local  b4, b5, b6, b7 = word2bytes(h1);
		local  b8, b9,b10,b11 = word2bytes(h2);
		local b12,b13,b14,b15 = word2bytes(h3);
		local b16,b17,b18,b19 = word2bytes(h4);
		local b20,b21,b22,b23 = word2bytes(h5);
		local b24,b25,b26,b27 = word2bytes(h6);
		local b28,b29,b30,b31 = word2bytes(h7);

		local fmt = "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x"		

		return String.format(fmt, b0, b1, b2, b3, b4, b5, b6, b7, b8, b9,b10,b11,b12,b13,b14,b15
				,b16,b17,b18,b19,b20,b21,b22,b23,b24,b25,b26,b27,b28,b29,b30,b31);
	end

	return public;

end

return SHA2_256;