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computer/0/apis/bitreader.lua

@@ -0,0 +1,107 @@
+local bit = bit
+
+local function readBit_b8(self)
+	if (self.current > 8) then
+		return false, false
+	end
+
+	self.current = self.current + 1
+	local v = bit.band(self._value, self._bits[self.current])
+
+	return self.current < 8, v > 0
+
+end
+
+local function new(self, value)
+	self.current = 0
+	self._value = value
+
+end
+
+function Bits8()
+	-- Represents a byte, allows reading a bit at a time.
+	local self = {}
+
+	self.current = 0
+	self._value = 0
+	self._bits = {128, 64, 32, 16, 8, 4, 2, 1}
+
+	self.readBit = readBit_b8
+	self.new = new
+
+	return self
+
+end
+
+
+
+local function readBit_br(self)
+	local s, v = self.cb:readBit()
+	if (not s) then
+		self.pointer = self.pointer + 1
+		self.cb:new(self.data[self.pointer])
+
+	end
+
+	return v
+
+end
+
+local function readBits(self, n)
+	local bt = self._bittable
+	for i = 1, n do
+		bt[i] = self:readBit()
+		
+	end
+	for i = n+1, #bt do
+		bt[i] = nil
+		
+	end
+
+	return bt
+
+end
+
+local function readNumber(self, n)
+	local m = 0
+
+	local t = self:readBits(n)
+	for i = 1, #t do
+		m = m * 2
+		if (t[i]) then
+			m = m + 1
+
+		end
+
+	end
+
+	return m
+
+end
+
+local function reset(self)
+	self.cb = Bits8()
+	self.pointer = 1
+	self.cb:new(self.data[self.pointer])
+
+end
+
+function BitReader(data)
+	-- Class to read bits individually from a table of bytes.
+	local self = {}
+
+	self.data = data
+	self.cb = Bits8()
+	self.pointer = 1
+	self.cb:new(self.data[self.pointer])
+
+	self.readBit = readBit_br
+	self.readBits = readBits
+	self.readNumber = readNumber
+	self.reset = reset
+
+	self._bittable = {}
+
+	return self
+
+end