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lstring.lua

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+-- Lengthed string API
+--  by LDDestroier
+
+local LString = {}
+
+local default_key_size = 1
+local default_value_size = 1
+
+function LString.Error( sMsg, tContext )
+	LString.__error = {
+		message = sMsg,
+		context = tContext
+	}
+	error(sMsg, 1)
+end
+
+-- converts number to a string of byte characters
+function LString.NumToBytes( number, length )
+	length = length or default_value_size
+	assert(type(length) == "number", "must specify byte length")
+	local output = ""
+	for i = 1, length do
+		output = output .. string.char(
+			math.floor(number / 2^(8 * (i - 1))) % 256
+		)
+	end
+	return output
+end
+
+-- converts a string of bytes back into a number
+function LString.BytesToNum( bytes, length )
+	assert( type(bytes) == "string", "bytes must be represented as string" )
+	length = length or #bytes
+	local output = 0
+	for i = 1, length do
+		output = output + (string.byte(bytes:sub(i, i)) * 2 ^ (8 * (i - 1)))
+	end
+	return output
+end
+
+-- returns lengthed string, and whether or not it was truncated to the byte limit
+function LString.MakeLString( sInput, nSize )
+	local limit = 2^(nSize * 8) - 1
+	return LString.NumToBytes(math.min(tostring(sInput):len(), limit), nSize) .. tostring(sInput):sub(1, limit),
+	tostring(sInput):len() > limit
+end
+
+local tAbbr = {
+	string = "s",
+	number = "n",
+	table = "t",
+	boolean = "b"
+}
+
+function LString.GetLString( sInput, nSize, nIterator )
+	nIterator = nIterator or 1
+	nSize = nSize or default_value_size
+	local len = LString.BytesToNum(sInput:sub(nIterator), nSize)
+	return sInput:sub(nSize + nIterator, nSize + len + nIterator - 1), nIterator + len + nSize
+end
+
+function LString.GetLTypeString( sInput, nSize, nIterator, tTypeSizeOverride )
+	nIterator = nIterator or 1
+	local ltype = sInput:sub(nIterator, nIterator)
+	if (tTypeSizeOverride[ltype]) then
+		nSize = tTypeSizeOverride[ltype]
+	end
+	local output
+	nIterator = nIterator + 1
+	output, nIterator = LString.GetLString(sInput, nSize, nIterator)
+	return output, nIterator, ltype
+end
+
+-- serializes a table of strings, numbers, and tables containing them
+
+function LString.serialize( tInput, nKeySize, nValueSize, bOmitType )
+	local output = ""
+	local count = 0
+
+	nKeySize = nKeySize or default_key_size
+	nValueSize = nValueSize or default_value_size
+
+	for k,v in pairs(tInput) do
+		if ( not tAbbr[type(k)] ) then
+			LString.Error("bad serialize! key must be string, number, boolean, or a table containing only them", {
+				tInput = tInput,
+				key = k,
+				value = v
+			})
+
+		elseif ( not tAbbr[type(v)] ) then
+			LString.Error("bad serialize! key must be string, number, boolean, or a table containing only them", {
+				tInput = tInput,
+				key = k,
+				value = v
+			})
+		end
+		
+		if (bOmitType) then
+			if ( type(k) == "table" ) then
+				LString.Error("cannot use table as key if omitting type", {
+					tInput = tInput,
+					key = k,
+					value = v
+				})
+			else
+				output = output .. LString.MakeLString(k, nKeySize)
+			end
+
+			if ( type(v) == "table" ) then
+				LString.Error("cannot use table as value if omitting type", {
+					tInput = tInput,
+					key = k,
+					value = v
+				})
+
+			else
+				output = output .. LString.MakeLString(v, nValueSize)
+			end
+
+		else
+			output = output .. tAbbr[type(k)]
+			if ( type(k) == "table" ) then
+				-- table values must have a length of 32 bits
+				output = output .. LString.MakeLString(LString.serialize(k, nKeySize, nValueSize), 4)
+
+			elseif ( type(k) == "boolean" ) then
+				output = output .. LString.MakeLString(k and "T" or "F", 1)
+			
+			else
+				output = output .. LString.MakeLString(k, nKeySize)
+			end
+
+			output = output .. tAbbr[type(v)]
+			if ( type(v) == "table" ) then
+				-- table values must have a length of 32 bits
+				output = output .. LString.MakeLString(LString.serialize(v, nKeySize, nValueSize), 4)
+
+			elseif ( type(v) == "boolean" ) then
+				output = output .. LString.MakeLString(v and "T" or "F", 1)
+			
+			else
+				output = output .. LString.MakeLString(v, nValueSize)
+			end
+		end
+
+		count = count + 1
+	end
+
+	output = LString.NumToBytes(count, 2) .. output
+
+	return output
+end
+LString.serialise = LString.serialize
+
+-- will assume every key and value are strings
+function LString.serializeTypeless(sInput, nKeySize, nValueSize)
+	return LString.serialize(sInput, nKeySize, nValueSize, 1, true)
+end
+LString.serialiseTypeless = LString.serializeTypeless
+
+function LString.unserialize( sInput, nKeySize, nValueSize, nIterator, bOmitType )
+	nKeySize = nKeySize or default_key_size
+	nValueSize = nValueSize or default_value_size
+
+	local tOutput = {}
+	nIterator = nIterator or 1
+	local count = LString.BytesToNum(sInput:sub(nIterator), 2)
+	nIterator = nIterator + 2
+	local lkey, lval, ltype
+
+	for i = 1, count do
+		if (bOmitType) then
+			ltype = "s"
+			lkey, nIterator = LString.GetLString(sInput, nKeySize, nIterator)
+		else
+			lkey, nIterator, ltype = LString.GetLTypeString(sInput, nKeySize, nIterator, {['t'] = 4, ['b'] = 1})
+		end
+
+		if (ltype == "n") then
+			lkey = tonumber(lkey)
+
+		elseif (ltype == "t") then
+			lkey = LString.unserialize(lkey, nKeySize, nValueSize)
+		
+		elseif (ltype == "b") then
+			lkey = lkey == "T"
+		end
+		
+		if (bOmitType) then
+			ltype = "s"
+			lval, nIterator = LString.GetLString(sInput, nValueSize, nIterator)
+		else
+			lval, nIterator, ltype = LString.GetLTypeString(sInput, nValueSize, nIterator, {['t'] = 4, ['b'] = 1})
+		end
+
+		if (ltype == "n") then
+			lval = tonumber(lval)
+
+		elseif (ltype == "t") then
+			lval = LString.unserialize(lval, nKeySize, nValueSize, 1, bOmitType)
+		
+		elseif (ltype == "b") then
+			lval = lval == "T"
+		end
+
+		tOutput[lkey] = lval
+	end
+
+	return tOutput, nIterator
+end
+LString.unserialise = LString.unserialize
+
+function LString.unserializeTypeless(sInput, nKeySize, nValueSize)
+	return LString.unserialize(sInput, nKeySize, nValueSize, 1, true)
+end
+LString.unserialiseTypeless = LString.unserializeTypeless
+
+return LString