Add. Basic cache class

Fix. When memcache stopped and mod_memcache loaded dialplan did not build from DB.

resources/install/scripts/resources/functions/cache.lua

@@ -0,0 +1,63 @@
+-- @usage cache = require "resources.functions.cache"
+-- value = cache.get(key)
+-- if not value then
+--   ...
+--   cache.set(key, value, expire)
+-- end
+--
+
+require "resources.functions.trim";
+
+local api = api or freeswitch.API();
+
+local Cache = {}
+
+local function check_error(result)
+  result = trim(result or '')
+
+  if result and result:sub(1, 4) == '-ERR' then
+    return nil, trim(result:sub(5))
+  end
+
+  if result == 'INVALID COMMAND!' and not Cache.support() then
+      return nil, 'INVALID COMMAND'
+  end
+
+  return result
+end
+
+function Cache.support()
+  -- assume it is not unloadable
+  if Cache._support then
+    return true
+  end
+  Cache._support = (trim(api:execute('module_exists', 'mod_memcache')) == 'true')
+  return Cache._support
+end
+
+--- Get element from cache
+--
+-- @tparam key string
+-- @return[1] string value
+-- @return[2] nil
+-- @return[2] error string `e.g. 'NOT FOUND'
+-- @note error string does not contain `-ERR` prefix
+function Cache.get(key)
+  local result, err = check_error(api:execute('memcache', 'get ' .. key))
+  if not result then return nil, err end
+  return (result:gsub("'", "'"))
+end
+
+function Cache.set(key, value, expire)
+  value = value:gsub("'", "'"):gsub("\\", "\\\\")
+  expire = expire and tostring(expire) or ""
+  return check_error(api:execute("memcache", "set " .. key .. " '" .. value .. "' " .. expire))
+end
+
+function Cache.del(key)
+  local result, err = check_error(api:execute("memcache", "set " .. key .. " '" .. value .. "' " .. expire))
+  if not result then return nil, err end
+  return result == '+OK'
+end
+
+return Cache