Data commit

Task/Bitwise-IO/Lua/bitwise-io-1.lua

@@ -0,0 +1,70 @@
+local function BitWriter() return {
+    accumulator = 0, -- For current byte.
+    bitCount    = 0, -- Bits set in current byte.
+    outChars    = {},
+
+    -- writer:writeBit( bit )
+    writeBit = function(writer, bit)
+        writer.bitCount = writer.bitCount + 1
+        if bit > 0 then
+            writer.accumulator = writer.accumulator + 2^(8-writer.bitCount)
+        end
+        if writer.bitCount == 8 then
+            writer:_flush()
+        end
+    end,
+
+    -- writer:writeLsb( value, width )
+    writeLsb = function(writer, value, width)
+        for i = 1, width do
+            writer:writeBit(value%2)
+            value = math.floor(value/2)
+        end
+    end,
+
+    -- dataString = writer:getOutput( )
+    getOutput = function(writer)
+        writer:_flush()
+        return table.concat(writer.outChars)
+    end,
+
+    _flush = function(writer)
+        if writer.bitCount == 0 then  return  end
+
+        table.insert(writer.outChars, string.char(writer.accumulator))
+        writer.accumulator = 0
+        writer.bitCount    = 0
+    end,
+} end
+
+local function BitReader(data) return {
+    bitPosition = 0, -- Absolute position in 'data'.
+
+    -- bit = reader:readBit( ) -- Returns nil at end-of-data.
+    readBit = function(reader)
+        reader.bitPosition = reader.bitPosition + 1
+        local bytePosition = math.floor((reader.bitPosition-1)/8) + 1
+
+        local byte = data:byte(bytePosition)
+        if not byte then  return nil  end
+
+        local bitIndex = ((reader.bitPosition-1)%8) + 1
+        return math.floor(byte / 2^(8-bitIndex)) % 2
+    end,
+
+    -- value = reader:readLsb( width ) -- Returns nil at end-of-data.
+    readLsb = function(reader, width)
+        local accumulator = 0
+
+        for i = 1, width do
+            local bit = reader:readBit()
+            if not bit then  return nil  end
+
+            if bit > 0 then
+                accumulator = accumulator + 2^(i-1)
+            end
+        end
+
+        return accumulator
+    end,
+} end

Task/Bitwise-IO/Lua/bitwise-io-2.lua

@@ -0,0 +1,37 @@
+-- Test writing.
+local writer = BitWriter()
+local input  = "Beautiful moon!"
+
+for i = 1, #input do
+    writer:writeLsb(input:byte(i), 7)
+end
+
+local data = writer:getOutput() -- May include padding at the end.
+
+-- Test reading.
+local reader = BitReader(data)
+local chars  = {}
+
+for i = 1, #input do -- Assume the amount of characters is the same as when we wrote the data.
+    chars[i] = string.char(reader:readLsb(7))
+end
+
+local output = table.concat(chars)
+
+-- Show results.
+local hexToBin = {["0"]="0000",["1"]="0001",["2"]="0010",["3"]="0011",
+                  ["4"]="0100",["5"]="0101",["6"]="0110",["7"]="0111",
+                  ["8"]="1000",["9"]="1001",["a"]="1010",["b"]="1011",
+                  ["c"]="1100",["d"]="1101",["e"]="1110",["f"]="1111"}
+local function charToHex(c)
+    return string.format("%02x", c:byte())
+end
+local function formatBinary(data)
+    return (data:gsub(".", charToHex)
+                :gsub(".", hexToBin)
+                :gsub("........", "%0 "))
+end
+
+print("In:   "..input)
+print("Out:  "..output)
+print("Data: "..formatBinary(data))