diff options
Diffstat (limited to 'system/apis')
| -rw-r--r-- | system/apis/json.lua | 209 |
1 files changed, 209 insertions, 0 deletions
diff --git a/system/apis/json.lua b/system/apis/json.lua new file mode 100644 index 0000000..3bef482 --- /dev/null +++ b/system/apis/json.lua @@ -0,0 +1,209 @@ +------------------------------------------------------------------ utils +local controls = {["\n"]="\\n", ["\r"]="\\r", ["\t"]="\\t", ["\b"]="\\b", ["\f"]="\\f", ["\""]="\\\"", ["\\"]="\\\\"} + +local function isArray(t) + local max = 0 + for k,v in pairs(t) do + if type(k) ~= "number" then + return false + elseif k > max then + max = k + end + end + return max == #t +end + +local whites = {['\n']=true; ['\r']=true; ['\t']=true; [' ']=true; [',']=true; [':']=true} +function removeWhite(str) + while whites[str:sub(1, 1)] do + str = str:sub(2) + end + return str +end + +------------------------------------------------------------------ encoding + +local function encodeCommon(val, pretty, tabLevel, tTracking) + local str = "" + + -- Tabbing util + local function tab(s) + str = str .. ("\t"):rep(tabLevel) .. s + end + + local function arrEncoding(val, bracket, closeBracket, iterator, loopFunc) + str = str .. bracket + if pretty then + str = str .. "\n" + tabLevel = tabLevel + 1 + end + for k,v in iterator(val) do + tab("") + loopFunc(k,v) + str = str .. "," + if pretty then str = str .. "\n" end + end + if pretty then + tabLevel = tabLevel - 1 + end + if str:sub(-2) == ",\n" then + str = str:sub(1, -3) .. "\n" + elseif str:sub(-1) == "," then + str = str:sub(1, -2) + end + tab(closeBracket) + end + + -- Table encoding + if type(val) == "table" then + assert(not tTracking[val], "Cannot encode a table holding itself recursively") + tTracking[val] = true + if isArray(val) then + arrEncoding(val, "[", "]", ipairs, function(k,v) + str = str .. encodeCommon(v, pretty, tabLevel, tTracking) + end) + else + arrEncoding(val, "{", "}", pairs, function(k,v) + assert(type(k) == "string", "JSON object keys must be strings", 2) + str = str .. encodeCommon(k, pretty, tabLevel, tTracking) + str = str .. (pretty and ": " or ":") .. encodeCommon(v, pretty, tabLevel, tTracking) + end) + end + -- String encoding + elseif type(val) == "string" then + str = '"' .. val:gsub("[%c\"\\]", controls) .. '"' + -- Number encoding + elseif type(val) == "number" or type(val) == "boolean" then + str = tostring(val) + else + error("JSON only supports arrays, objects, numbers, booleans, and strings", 2) + end + return str +end + +function encode(val) + return encodeCommon(val, false, 0, {}) +end + +function encodePretty(val) + return encodeCommon(val, true, 0, {}) +end + +------------------------------------------------------------------ decoding + +local decodeControls = {} +for k,v in pairs(controls) do + decodeControls[v] = k +end + +function parseBoolean(str) + if str:sub(1, 4) == "true" then + return true, removeWhite(str:sub(5)) + else + return false, removeWhite(str:sub(6)) + end +end + +function parseNull(str) + return nil, removeWhite(str:sub(5)) +end + +local numChars = {['e']=true; ['E']=true; ['+']=true; ['-']=true; ['.']=true} +function parseNumber(str) + local i = 1 + while numChars[str:sub(i, i)] or tonumber(str:sub(i, i)) do + i = i + 1 + end + local val = tonumber(str:sub(1, i - 1)) + str = removeWhite(str:sub(i)) + return val, str +end + +function parseString(str) + str = str:sub(2) + local s = "" + while str:sub(1,1) ~= "\"" do + local next = str:sub(1,1) + str = str:sub(2) + assert(next ~= "\n", "Unclosed string") + + if next == "\\" then + local escape = str:sub(1,1) + str = str:sub(2) + + next = assert(decodeControls[next..escape], "Invalid escape character") + end + + s = s .. next + end + return s, removeWhite(str:sub(2)) +end + +function parseArray(str) + str = removeWhite(str:sub(2)) + + local val = {} + local i = 1 + while str:sub(1, 1) ~= "]" do + local v = nil + v, str = parseValue(str) + val[i] = v + i = i + 1 + str = removeWhite(str) + end + str = removeWhite(str:sub(2)) + return val, str +end + +function parseObject(str) + str = removeWhite(str:sub(2)) + + local val = {} + while str:sub(1, 1) ~= "}" do + local k, v = nil, nil + k, v, str = parseMember(str) + val[k] = v + str = removeWhite(str) + end + str = removeWhite(str:sub(2)) + return val, str +end + +function parseMember(str) + local k = nil + k, str = parseValue(str) + local val = nil + val, str = parseValue(str) + return k, val, str +end + +function parseValue(str) + local fchar = str:sub(1, 1) + if fchar == "{" then + return parseObject(str) + elseif fchar == "[" then + return parseArray(str) + elseif tonumber(fchar) ~= nil or numChars[fchar] then + return parseNumber(str) + elseif str:sub(1, 4) == "true" or str:sub(1, 5) == "false" then + return parseBoolean(str) + elseif fchar == "\"" then + return parseString(str) + elseif str:sub(1, 4) == "null" then + return parseNull(str) + end + return nil +end + +function decode(str) + str = removeWhite(str) + t = parseValue(str) + return t +end + +function decodeFromFile(path) + local file = assert(fs.open(path, "r")) + local decoded = decode(file.readAll()) + file.close() + return decoded +end
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