libs/web: add luci.http.write_json()

libs/web/luasrc/http.lua

@@ -29,8 +29,10 @@ local protocol = require "luci.http.protocol"
 local util  = require "luci.util"
 local string = require "string"
 local coroutine = require "coroutine"
+local table = require "table"
 
-local pairs, tostring, error = pairs, tostring, error
+local ipairs, pairs, next, type, tostring, error =
+	ipairs, pairs, next, type, tostring, error
 
 --- LuCI Web Framework high-level HTTP functions.
 module "luci.http"
@@ -276,14 +278,18 @@ end
 --- Create a querystring out of a table of key - value pairs.
 -- @param table		Query string source table
 -- @return			Encoded HTTP query string
-function build_querystring(table)
+function build_querystring(q)
-	local s="?"
+	local s = { "?" }
 
-	for k, v in pairs(table) do
+	for k, v in pairs(q) do
-		s = s .. urlencode(k) .. "=" .. urlencode(v) .. "&"
+		if #s > 1 then s[#s+1] = "&" end
+
+		s[#s+1] = urldecode(k)
+		s[#s+1] = "="
+		s[#s+1] = urldecode(v)
 	end
 
-	return s
+	return table.concat(s, "")
 end
 
 --- Return the URL-decoded equivalent of a string.
@@ -298,3 +304,37 @@ urldecode = protocol.urldecode
 -- @return			URL-encoded string
 -- @see urldecode
 urlencode = protocol.urlencode
+
+--- Send the given data as JSON encoded string.
+-- @param data		Data to send
+function write_json(x)
+	if x == nil then
+		write("null")
+	elseif type(x) == "table" then
+		local k, v
+		if type(next(x)) == "number" then
+			write("[ ")
+			for k, v in ipairs(x) do
+				write_json(v)
+				if next(x, k) then
+					write(", ")
+				end
+			end
+			write(" ]")
+		else
+			write("{ ")
+			for k, v in pairs(x) do
+			write("%q: " % k)
+				write_json(v)
+				if next(x, k) then
+					write(", ")
+				end
+			end
+			write(" }")
+		end
+	elseif type(x) == "number" or type(x) == "boolean" then
+		write(tostring(x))
+	elseif type(x) == "string" then
+		write("%q" % tostring(x))
+	end
+end