util.json: Initial commit.

1 files changed, 356 insertions, 0 deletions

diff --git a/util/json.lua b/util/json.lua
new file mode 100644
index 00000000..40939bb4
--- /dev/null
+++ b/util/json.lua
@@ -0,0 +1,356 @@
+
+local type = type;
+local t_insert, t_concat, t_remove = table.insert, table.concat, table.remove;
+local s_char = string.char;
+local tostring, tonumber = tostring, tonumber;
+local pairs, ipairs = pairs, ipairs;
+local next = next;
+local error = error;
+local newproxy, getmetatable = newproxy, getmetatable;
+local print = print;
+
+--module("json")
+local json = {};
+
+local null = newproxy and newproxy(true) or {};
+if getmetatable and getmetatable(null) then
+	getmetatable(null).__tostring = function() return "null"; end;
+end
+json.null = null;
+
+local escapes = {
+	["\""] = "\\\"", ["\\"] = "\\\\", ["\b"] = "\\b",
+	["\f"] = "\\f", ["\n"] = "\\n", ["\r"] = "\\r", ["\t"] = "\\t"};
+local unescapes = {
+	["\""] = "\"", ["\\"] = "\\", ["/"] = "/",
+	b = "\b", f = "\f", n = "\n", r = "\r", t = "\t"};
+for i=0,31 do
+	local ch = s_char(i);
+	if not escapes[ch] then escapes[ch] = ("\\u%.4X"):format(i); end
+end
+
+local valid_types = {
+	number  = true,
+	string  = true,
+	table   = true,
+	boolean = true
+};
+local special_keys = {
+	__array = true;
+	__hash  = true;
+};
+
+local simplesave, tablesave, arraysave, stringsave;
+
+function stringsave(o, buffer)
+	-- FIXME do proper utf-8 and binary data detection
+	t_insert(buffer, "\""..(o:gsub(".", escapes)).."\"");
+end
+
+function arraysave(o, buffer)
+	t_insert(buffer, "[");
+	if next(o) then
+		for i,v in ipairs(o) do
+			simplesave(v, buffer);
+			t_insert(buffer, ",");
+		end
+		t_remove(buffer);
+	end
+	t_insert(buffer, "]");
+end
+
+function tablesave(o, buffer)
+	local __array = {};
+	local __hash = {};
+	local hash = {};
+	for i,v in ipairs(o) do
+		__array[i] = v;
+	end
+	for k,v in pairs(o) do
+		local ktype, vtype = type(k), type(v);
+		if valid_types[vtype] or v == null then
+			if ktype == "string" and not special_keys[k] then
+				hash[k] = v;
+			elseif (valid_types[ktype] or k == null) and __array[k] == nil then
+				__hash[k] = v;
+			end
+		end
+	end
+	if next(__hash) ~= nil or next(hash) ~= nil or next(__array) == nil then
+		t_insert(buffer, "{");
+		local mark = #buffer;
+		for k,v in pairs(hash) do
+			stringsave(k, buffer);
+			t_insert(buffer, ":");
+			simplesave(v, buffer);
+			t_insert(buffer, ",");
+		end
+		if next(__hash) ~= nil then
+			t_insert(buffer, "\"__hash\":[");
+			for k,v in pairs(__hash) do
+				simplesave(k, buffer);
+				t_insert(buffer, ",");
+				simplesave(v, buffer);
+				t_insert(buffer, ",");
+			end
+			t_remove(buffer);
+			t_insert(buffer, "]");
+			t_insert(buffer, ",");
+		end
+		if next(__array) then
+			t_insert(buffer, "\"__array\":");
+			arraysave(__array, buffer);
+			t_insert(buffer, ",");
+		end
+		if mark ~= #buffer then t_remove(buffer); end
+		t_insert(buffer, "}");
+	else
+		arraysave(__array, buffer);
+	end
+end
+
+function simplesave(o, buffer)
+	local t = type(o);
+	if t == "number" then
+		t_insert(buffer, tostring(o));
+	elseif t == "string" then
+		stringsave(o, buffer);
+	elseif t == "table" then
+		tablesave(o, buffer);
+	elseif t == "boolean" then
+		t_insert(buffer, (o and "true" or "false"));
+	else
+		t_insert(buffer, "null");
+	end
+end
+
+function json.encode(obj)
+	local t = {};
+	simplesave(obj, t);
+	return t_concat(t);
+end
+
+-----------------------------------
+
+
+function json.decode(json)
+	local pos = 1;
+	local current = {};
+	local stack = {};
+	local ch, peek;
+	local function next()
+		ch = json:sub(pos, pos);
+		pos = pos+1;
+		peek = json:sub(pos, pos);
+		return ch;
+	end
+	
+	local function skipwhitespace()
+		while ch and (ch == "\r" or ch == "\n" or ch == "\t" or ch == " ") do
+			next();
+		end
+	end
+	local function skiplinecomment()
+		repeat next(); until not(ch) or ch == "\r" or ch == "\n";
+		skipwhitespace();
+	end
+	local function skipstarcomment()
+		next(); next(); -- skip '/', '*'
+		while peek and ch ~= "*" and peek ~= "/" do next(); end
+		if not peek then error("eof in star comment") end
+		next(); next(); -- skip '*', '/'
+		skipwhitespace();
+	end
+	local function skipstuff()
+		while true do
+			skipwhitespace();
+			if ch == "/" and peek == "*" then
+				skipstarcomment();
+			elseif ch == "/" and peek == "*" then
+				skiplinecomment();
+			else
+				return;
+			end
+		end
+	end
+	
+	local readvalue;
+	local function readarray()
+		local t = {};
+		next(); -- skip '['
+		skipstuff();
+		if ch == "]" then next(); return t; end
+		t_insert(t, readvalue());
+		while true do
+			skipstuff();
+			if ch == "]" then next(); return t; end
+			if not ch then error("eof while reading array");
+			elseif ch == "," then next();
+			elseif ch then error("unexpected character in array, comma expected"); end
+			if not ch then error("eof while reading array"); end
+			t_insert(t, readvalue());
+		end
+	end
+	
+	local function checkandskip(c)
+		local x = ch or "eof";
+		if x ~= c then error("unexpected "..x..", '"..c.."' expected"); end
+		next();
+	end
+	local function readliteral(lit, val)
+		for c in lit:gmatch(".") do
+			checkandskip(c);
+		end
+		return val;
+	end
+	local function readstring()
+		local s = "";
+		checkandskip("\"");
+		while ch do
+			while ch and ch ~= "\\" and ch ~= "\"" do
+				s = s..ch; next();
+			end
+			if ch == "\\" then
+				next();
+				if unescapes[ch] then
+					s = s..unescapes[ch];
+					next();
+				elseif ch == "u" then
+					local seq = "";
+					for i=1,4 do
+						next();
+						if not ch then error("unexpected eof in string"); end
+						if not ch:match("[0-9a-fA-F]") then error("invalid unicode escape sequence in string"); end
+						seq = seq..ch;
+					end
+					s = s..s.char(tonumber(seq, 16)); -- FIXME do proper utf-8
+					next();
+				else error("invalid escape sequence in string"); end
+			end
+			if ch == "\"" then
+				next();
+				return s;
+			end
+		end
+		error("eof while reading string");
+	end
+	local function readnumber()
+		local s = "";
+		if ch == "-" then
+			s = s..ch; next();
+			if not ch:match("[0-9]") then error("number format error"); end
+		end
+		if ch == "0" then
+			s = s..ch; next();
+			if ch:match("[0-9]") then error("number format error"); end
+		else
+			while ch and ch:match("[0-9]") do
+				s = s..ch; next();
+			end
+		end
+		if ch == "." then
+			s = s..ch; next();
+			if not ch:match("[0-9]") then error("number format error"); end
+			while ch and ch:match("[0-9]") do
+				s = s..ch; next();
+			end
+			if ch == "e" or ch == "E" then
+				s = s..ch; next();
+				if ch == "+" or ch == "-" then
+					s = s..ch; next();
+					if not ch:match("[0-9]") then error("number format error"); end
+					while ch and ch:match("[0-9]") do
+						s = s..ch; next();
+					end
+				end
+			end
+		end
+		return tonumber(s);
+	end
+	local function readmember(t)
+		local k = readstring();
+		checkandskip(":");
+		t[k] = readvalue();
+	end
+	local function fixobject(obj)
+		local __array = obj.__array;
+		if __array then
+			obj.__array = nil;
+			for i,v in ipairs(__array) do
+				t_insert(obj, v);
+			end
+		end
+		local __hash = obj.__hash;
+		if __hash then
+			obj.__hash = nil;
+			local k;
+			for i,v in ipairs(__hash) do
+				if k ~= nil then
+					obj[k] = v; k = nil;
+				else
+					k = v;
+				end
+			end
+		end
+		return obj;
+	end
+	local function readobject()
+		local t = {};
+		next(); -- skip '{'
+		skipstuff();
+		if ch == "}" then next(); return t; end
+		if not ch then error("eof while reading object"); end
+		readmember(t);
+		while true do
+			skipstuff();
+			if ch == "}" then next(); return fixobject(t); end
+			if not ch then error("eof while reading object");
+			elseif ch == "," then next();
+			elseif ch then error("unexpected character in object, comma expected"); end
+			if not ch then error("eof while reading object"); end
+			readmember(t);
+		end
+	end
+	
+	function readvalue()
+		skipstuff();
+		while ch do
+			if ch == "{" then
+				return readobject();
+			elseif ch == "[" then
+				return readarray();
+			elseif ch == "\"" then
+				return readstring();
+			elseif ch:match("[%-0-9%.]") then
+				return readnumber();
+			elseif ch == "n" then
+				return readliteral("null", null);
+			elseif ch == "t" then
+				return readliteral("true", true);
+			elseif ch == "f" then
+				return readliteral("false", false);
+			else
+				error("invalid character at value start: "..ch);
+			end
+		end
+		error("eof while reading value");
+	end
+	next();
+	return readvalue();
+end
+
+function json.test(object)
+	local encoded = json.encode(object);
+	local decoded = json.decode(encoded);
+	local recoded = json.encode(decoded);
+	if encoded ~= recoded then
+		print("FAILED");
+		print("encoded:", encoded);
+		print("recoded:", recoded);
+	else
+		print(encoded);
+	end
+	return encoded == recoded;
+end
+
+return json;