mirror of
https://github.com/FlightControl-Master/MOOSE.git
synced 2026-08-18 13:16:03 +00:00
Frank
259 lines
7.8 KiB
Lua
259 lines
7.8 KiB
Lua
--- Minimal JSON helper for the MOOSE Bridge V1 prototype.
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-- This is deliberately small and covers the V1 command/ack/heartbeat/snapshot payloads.
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MOOSE_BRIDGE_JSON = MOOSE_BRIDGE_JSON or {}
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local json = MOOSE_BRIDGE_JSON
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local function escape(value)
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value = tostring(value or "")
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value = value:gsub('\\', '\\\\')
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value = value:gsub('"', '\\"')
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value = value:gsub('\n', '\\n')
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value = value:gsub('\r', '\\r')
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value = value:gsub('\t', '\\t')
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return value
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end
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local function is_array(value)
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if type(value) ~= "table" then
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return false
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end
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local max_index = 0
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local count = 0
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for key, _ in pairs(value) do
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if type(key) ~= "number" or key < 1 or key % 1 ~= 0 then
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return false
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end
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if key > max_index then
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max_index = key
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end
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count = count + 1
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end
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return count == max_index
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end
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local function encode_value(value)
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local t = type(value)
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if value == nil then
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return "null"
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elseif t == "boolean" then
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return value and "true" or "false"
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elseif t == "number" then
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return tostring(value)
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elseif t == "string" then
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return '"' .. escape(value) .. '"'
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elseif t == "table" then
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local parts = {}
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if is_array(value) then
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for index = 1, #value do
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parts[#parts + 1] = encode_value(value[index])
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end
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return "[" .. table.concat(parts, ",") .. "]"
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end
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for k, v in pairs(value) do
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parts[#parts + 1] = '"' .. escape(k) .. '":' .. encode_value(v)
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end
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return "{" .. table.concat(parts, ",") .. "}"
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end
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return '"' .. escape(value) .. '"'
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end
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function json.encode(value)
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return encode_value(value)
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end
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local function decode_error(text, index, message)
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error("JSON decode error at byte " .. tostring(index) .. ": " .. message .. " near " .. string.format("%q", text:sub(index, index + 20)))
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end
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local function skip_ws(text, index)
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while index <= #text do
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local char = text:sub(index, index)
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if char ~= " " and char ~= "\n" and char ~= "\r" and char ~= "\t" then break end
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index = index + 1
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end
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return index
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end
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local function utf8_char(codepoint)
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if codepoint <= 0x7F then
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return string.char(codepoint)
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elseif codepoint <= 0x7FF then
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return string.char(
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0xC0 + math.floor(codepoint / 0x40),
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0x80 + (codepoint % 0x40)
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)
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elseif codepoint <= 0xFFFF then
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return string.char(
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0xE0 + math.floor(codepoint / 0x1000),
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0x80 + (math.floor(codepoint / 0x40) % 0x40),
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0x80 + (codepoint % 0x40)
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)
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elseif codepoint <= 0x10FFFF then
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return string.char(
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0xF0 + math.floor(codepoint / 0x40000),
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0x80 + (math.floor(codepoint / 0x1000) % 0x40),
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0x80 + (math.floor(codepoint / 0x40) % 0x40),
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0x80 + (codepoint % 0x40)
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)
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end
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return "?"
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end
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local parse_value
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local function parse_string(text, index)
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if text:sub(index, index) ~= '"' then decode_error(text, index, "expected string") end
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index = index + 1
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local parts = {}
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local start = index
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while index <= #text do
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local char = text:sub(index, index)
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if char == '"' then
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parts[#parts + 1] = text:sub(start, index - 1)
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return table.concat(parts), index + 1
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elseif char == "\\" then
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parts[#parts + 1] = text:sub(start, index - 1)
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local escape_char = text:sub(index + 1, index + 1)
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if escape_char == '"' or escape_char == "\\" or escape_char == "/" then
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parts[#parts + 1] = escape_char
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index = index + 2
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elseif escape_char == "b" then
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parts[#parts + 1] = "\b"
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index = index + 2
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elseif escape_char == "f" then
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parts[#parts + 1] = "\f"
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index = index + 2
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elseif escape_char == "n" then
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parts[#parts + 1] = "\n"
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index = index + 2
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elseif escape_char == "r" then
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parts[#parts + 1] = "\r"
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index = index + 2
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elseif escape_char == "t" then
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parts[#parts + 1] = "\t"
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index = index + 2
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elseif escape_char == "u" then
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local hex = text:sub(index + 2, index + 5)
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local codepoint = tonumber(hex, 16)
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if not codepoint then decode_error(text, index, "invalid unicode escape") end
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index = index + 6
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if codepoint >= 0xD800 and codepoint <= 0xDBFF and text:sub(index, index + 1) == "\\u" then
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local low = tonumber(text:sub(index + 2, index + 5), 16)
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if low and low >= 0xDC00 and low <= 0xDFFF then
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codepoint = 0x10000 + ((codepoint - 0xD800) * 0x400) + (low - 0xDC00)
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index = index + 6
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end
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end
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parts[#parts + 1] = utf8_char(codepoint)
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else
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decode_error(text, index, "invalid escape sequence")
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end
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start = index
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else
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index = index + 1
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end
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end
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decode_error(text, index, "unterminated string")
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end
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local function parse_number(text, index)
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local start = index
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if text:sub(index, index) == "-" then index = index + 1 end
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while text:sub(index, index):match("%d") do index = index + 1 end
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if text:sub(index, index) == "." then
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index = index + 1
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while text:sub(index, index):match("%d") do index = index + 1 end
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end
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local exponent = text:sub(index, index)
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if exponent == "e" or exponent == "E" then
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index = index + 1
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local sign = text:sub(index, index)
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if sign == "+" or sign == "-" then index = index + 1 end
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while text:sub(index, index):match("%d") do index = index + 1 end
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end
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local raw = text:sub(start, index - 1)
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local value = tonumber(raw)
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if value == nil then decode_error(text, start, "invalid number") end
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return value, index
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end
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local function parse_array(text, index)
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index = skip_ws(text, index + 1)
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local result = {}
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if text:sub(index, index) == "]" then return result, index + 1 end
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while index <= #text do
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local value
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value, index = parse_value(text, index)
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result[#result + 1] = value
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index = skip_ws(text, index)
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local char = text:sub(index, index)
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if char == "]" then return result, index + 1 end
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if char ~= "," then decode_error(text, index, "expected ',' or ']'") end
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index = skip_ws(text, index + 1)
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end
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decode_error(text, index, "unterminated array")
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end
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local function parse_object(text, index)
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index = skip_ws(text, index + 1)
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local result = {}
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if text:sub(index, index) == "}" then return result, index + 1 end
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while index <= #text do
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local key
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key, index = parse_string(text, index)
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index = skip_ws(text, index)
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if text:sub(index, index) ~= ":" then decode_error(text, index, "expected ':'") end
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index = skip_ws(text, index + 1)
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local value
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value, index = parse_value(text, index)
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result[key] = value
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index = skip_ws(text, index)
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local char = text:sub(index, index)
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if char == "}" then return result, index + 1 end
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if char ~= "," then decode_error(text, index, "expected ',' or '}'") end
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index = skip_ws(text, index + 1)
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end
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decode_error(text, index, "unterminated object")
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end
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parse_value = function(text, index)
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index = skip_ws(text, index)
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local char = text:sub(index, index)
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if char == '"' then return parse_string(text, index) end
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if char == "{" then return parse_object(text, index) end
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if char == "[" then return parse_array(text, index) end
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if char == "-" or char:match("%d") then return parse_number(text, index) end
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if text:sub(index, index + 3) == "true" then return true, index + 4 end
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if text:sub(index, index + 4) == "false" then return false, index + 5 end
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if text:sub(index, index + 3) == "null" then return nil, index + 4 end
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decode_error(text, index, "unexpected value")
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end
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function json.decode(text)
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if type(text) ~= "string" then error("JSON decode expects a string") end
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local value, index = parse_value(text, 1)
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index = skip_ws(text, index)
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if index <= #text then decode_error(text, index, "trailing characters") end
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if type(value) ~= "table" then error("JSON command must decode to an object") end
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if type(value.params) ~= "table" then value.params = {} end
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return value
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end
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return json
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