api/json.lua

-- Implementation of ElvishJerricco's JSON api
local api = { LoadOrder = 100 }
function api.Build()
  local whites={["\n"]=true,["\r"]=true,["\t"]=true,[" "]=true,[","]=true,[":"]=true}
  local numChars={["e"]=true,["E"]=true,["+"]=true,["-"]=true,["."]=true}
  local escaped={["\n"]="\\n",["\r"]="\\r",["\t"]="\\t",["\b"]="\\b",["\f"]="\\f",["\""]="\\\"",["\\"]="\\\\"}
  local iescaped={}
  for k,v in pairs(escaped) do iescaped[v]=k end
  function removeWhite(s) while whites[s:sub(1,1)] do s=s:sub(2) end return s end
  function parseBoolean(s) local v=s:sub(1,4)=="true" return v,removeWhite(s:sub(v and 5 or 6)) end
  function parseNull(s) return nil,removeWhite(s:sub(5)) end
  function parseNumber(s) local i=1 while numChars[s:sub(i,i)] or tonumber(s:sub(i,i)) do i=i+1 end local v=tonumber(s:sub(1,i-1)) s=removeWhite(s:sub(i)) return v,s end
  function parseString(s) s=s:sub(2) local v="" while s:sub(1,1)~="\"" do local n=s:sub(1,1) s=s:sub(2) assert(n~="\n","Unclosed string") if n=="\\" then local e=s:sub(1,1) s=s:sub(2) n=assert(iescaped[n..e],"Invalid escape character") end v=v..n end return v,removeWhite(s:sub(2)) end
  function parseArray(s) s=removeWhite(s:sub(2)) local a,i={},1 while s:sub(1,1)~="]" do local v = nil v,s=parseValue(s) a[i]=v i=i+1 s=removeWhite(s) end s=removeWhite(s:sub(2)) return a,s end
  function parseObject(s) s=removeWhite(s:sub(2)) local t={} while s:sub(1,1)~="}" do local k,v=nil,nil k,v,s=parseMember(s) t[k]=v s=removeWhite(s) end s=removeWhite(s:sub(2)) return t,s end
  function parseMember(s) local k,v=nil,nil k,s=parseValue(s) v,s=parseValue(s) return k,v,s end
  function parseValue(s) local f=s:sub(1,1) if f=="{" then return parseObject(s) elseif f=="[" then return parseArray(s) elseif tonumber(f)~=nil or numChars[f] then return parseNumber(s) elseif s:sub(1,4)=="true" or s:sub(1,5)=="false" then return parseBoolean(s) elseif f=="\"" then return parseString(s) elseif s:sub(1,4)=="null" then return parseNull(s) end return nil end
  local json = {}
  function json:parse(s) return parseValue(removeWhite(s)) end
  function json:stringify(t,p,u,o)
    local s = ""
    p,u,o=p or false,u or 0,o or {}
    local function tab(i) s=s..("\t"):rep(u)..i end
    local function encoding(t,b,c,i,l)
      s=s..b
      if p then s=s.."\n" u=u+1 end
      for k,v in i(t) do
        tab("")
        l(k,v)
        s=s..","
        if p then s=s.."\n" end
      end
      if p then u=u-1 end
      if s:sub(-2)==",\n" then s=s:sub(1,-3).."\n"
      elseif s:sub(-1)=="," then s=s:sub(1,-2) end
      tab(c)
    end
    if type(t)=="table" then
      assert(not o[t],"Cannot handle cyclic tables")
      o[t]=true
      if table.isArray(t) then
        encoding(t,"[","]",ipairs,function(k,v)
          s=s..self:stringify(v,p,u,o)
        end)
      else
        encoding(t,"{","}",pairs,function(k,v)
          assert(type(k)=="string","JSON Object keys must be strings",2)
          s=s..self:stringify(k,p,u,o)
          s=s..(p and ": " or ":")..self:stringify(v,p,u,o)
        end)
      end
    elseif type(t)=="string" then s="\""..t:gsub("[%c\"\\]",escaped).."\""
    elseif type(t)=="number" or type(t)=="boolean" then s=tostring(t)
    else error("JSON only supports arrays, objects, numbers, booleans and strings",2) end
    return s
  end
  return json
end
return api