luci-base: add luci.util.serialize_json()

Signed-off-by: Jo-Philipp Wich <jow@openwrt.org>

diff --git a/modules/luci-base/luasrc/util.lua b/modules/luci-base/luasrc/util.lua
index 42de3dd729bb8fbd3d91486ce46001bfadab2e1a..e5dff63ddb3c824829a25d1281fd9bdb5cae7695 100644 (file)
--- a/modules/luci-base/luasrc/util.lua
+++ b/modules/luci-base/luasrc/util.lua
@@ -710,6 +710,64 @@ function ubus(object, method, data)
        end
 end
 
+--- Convert data structure to JSON
+-- @param data         The data to serialize
+-- @param writer       A function to write a chunk of JSON data (optional)
+-- @return                     String containing the JSON if called without write callback
+function serialize_json(x, cb)
+       local rv, push = nil, cb
+       if not push then
+               rv = { }
+               push = function(tok) rv[#rv+1] = tok end
+       end
+
+       if x == nil then
+               push("null")
+       elseif type(x) == "table" then
+               -- test if table is array like
+               local k, v
+               local n1, n2 = 0, 0
+               for k in pairs(x) do n1 = n1 + 1 end
+               for k in ipairs(x) do n2 = n2 + 1 end
+
+               if n1 == n2 and n1 > 0 then
+                       push("[")
+                       for k = 1, n2 do
+                               if k > 1 then
+                                       push(",")
+                               end
+                               serialize_json(x[k], push)
+                       end
+                       push("]")
+               else
+                       push("{")
+                       for k, v in pairs(x) do
+                               push("%q:" % tostring(k))
+                               serialize_json(v, push)
+                               if next(x, k) then
+                                       push(",")
+                               end
+                       end
+                       push("}")
+               end
+       elseif type(x) == "number" or type(x) == "boolean" then
+               if (x ~= x) then
+                       -- NaN is the only value that doesn't equal to itself.
+                       push("Number.NaN")
+               else
+                       push(tostring(x))
+               end
+       else
+               push('"%s"' % tostring(x):gsub('["%z\1-\31]',
+                       function(c) return '\\u%04x' % c:byte(1) end))
+       end
+
+       if not cb then
+               return table.concat(rv, "")
+       end
+end
+
+
 --- Returns the absolute path to LuCI base directory.
 -- @return             String containing the directory path
 function libpath()