Generalize Transformer's logger module and move here.

CMakeLists.txt

@@ -54,5 +54,5 @@ set_target_properties(lua-tch PROPERTIES
 
 install(TARGETS lua-tch
  LIBRARY DESTINATION lib/lua)
-install(FILES src/Lua/tableprint.lua src/Lua/inet.lua
+install(FILES src/Lua/tableprint.lua src/Lua/inet.lua src/Lua/logger.lua
  DESTINATION lib/lua/tch)

src/Lua/logger.lua

@@ -0,0 +1,186 @@
+--[[
+Copyright (c) 2016 Technicolor Delivery Technologies, SAS
+
+The source code form of this lua-tch component is subject
+to the terms of the Clear BSD license.
+
+You can redistribute it and/or modify it under the terms of the
+Clear BSD License (http:https://directory.fsf.org/wiki/License:ClearBSD)
+
+See LICENSE file for more details.
+]]
+
+---
+-- Logging module.
+--
+-- Intended way of using:
+--
+-- - Load it using require():
+-- local logger = require("tch.logger")
+-- - Initialize using `logger.init`. Pass the name of your module,
+-- the desired global log level (1 to 6), syslog options of interest
+-- and default syslog facility.
+-- local posix = require("tch.posix")
+-- logger.init("mymodule", 3, posix.LOG_PID + posix.LOG_CONS, posix.LOG_USER)
+-- - Create zero or more logging objects for different parts of your application
+-- where each object can optionally have its own name and log level. On that
+-- object you have a log function for each log level and a function to change
+-- the log level. You can also clear the specific log level and fall back to
+-- the global log level.
+-- local log = logger.new("mymodule", 2)
+-- log:critical("%s:%d", "oops", 42)
+-- log:error(....)
+-- log:warning(....)
+-- log:notice(....)
+-- log:info(....)
+-- log:debug(....)
+-- log:set_log_level(4)
+-- - Use the methods on the global logging object to send log output. The
+-- global logging object is the module itself.
+-- logger:critical(....)
+-- logger:error(....)
+-- @module tch.logger
+-- @see tch.posix
+
+local setmetatable = setmetatable
+local format = string.format
+
+local posix = require("tch.posix")
+
+-- Our logger module has 6 log levels, ranging from 1 to 6.
+-- To each level corresponds a syslog priority.
+local syslog_priorities = {
+ posix.LOG_CRIT,
+ posix.LOG_ERR,
+ posix.LOG_WARNING,
+ posix.LOG_NOTICE,
+ posix.LOG_INFO,
+ posix.LOG_DEBUG,
+}
+
+-- module table with default global log level
+local M = { log_level = 3 }
+
+-- metatable for logger instances
+local logger = {}
+logger.__index = logger
+
+--- Create a new logger object with its own log level and optionally a name.
+-- @string modname Optional name of the module using the logger. It will
+-- be added to each log message, if present. This name is in addition
+-- to the global name set in `init`.
+-- @int log_level The initial log level. If not given then the
+-- global log level will be used.
+-- @treturn logger The newly created logger instance.
+function M.new(modname, log_level)
+ local self = {
+ modname = modname,
+ log_level = log_level
+ }
+ setmetatable(self, logger)
+ return self
+end
+
+--- Initialize the logger module.
+-- This isn't strictly necessary but it allows you configure a name
+-- that is prepended to every log message, a different default log level,
+-- additional syslog options or a different default syslog facility.
+-- The function may be called multiple times.
+-- @string name This name will be prepended to every log message,
+-- including those generated using logger objects created with `new`.
+-- @int log_level The global log level as a number from 1 to 6.
+-- 1 is the most important level, 6 the least. A level outside
+-- this range will be ignored and the default level (3) will be used.
+-- @int[opt=0] syslog_options Bitwise OR of syslog option constants.
+-- @int[opt=tch.posix.LOG_DAEMON] syslog_facility Syslog facility to use.
+-- @see openlog(3)
+
+function M.init(name, log_level, syslog_options, syslog_facility)
+ posix.openlog(name, syslog_options or 0, syslog_facility or posix.LOG_DAEMON)
+ M:set_log_level(log_level)
+end
+
+-- actually log the message but only if log level says so
+local function log(logger, log_level, fmt, ...)
+ if log_level <= (logger.log_level or M.log_level) then
+ local msg
+ local modname = logger.modname
+ if modname then
+ msg = format("[%s] " .. fmt, modname, ...)
+ else
+ msg = format(fmt, ...)
+ end
+ posix.syslog(syslog_priorities[log_level], msg)
+ end
+end
+
+--- Logger methods.
+-- @type logger
+
+--- Log a critical message.
+-- @string fmt Format of the log message of critical severity.
+-- @param[opt] ... Arguments of the format string, if any.
+-- @see string.format
+function logger:critical(fmt, ...)
+ log(self, 1, fmt, ...)
+end
+
+--- Log an error message.
+-- @string fmt Format of the log message of error severity.
+-- @param[opt] ... Arguments of the format string, if any.
+-- @see string.format
+function logger:error(fmt, ...)
+ log(self, 2, fmt, ...)
+end
+
+--- Log a warning message.
+-- @string fmt Format of the log message of warning severity.
+-- @param[opt] ... Arguments of the format string, if any.
+-- @see string.format
+function logger:warning(fmt, ...)
+ log(self, 3, fmt, ...)
+end
+
+--- Log a notice message.
+-- @string fmt Format of the log message of notice severity.
+-- @param[opt] ... Arguments of the format string, if any.
+-- @see string.format
+function logger:notice(fmt, ...)
+ log(self, 4, fmt, ...)
+end
+
+--- Log an informational message.
+-- @string fmt Format of the log message of info severity.
+-- @param[opt] ... Arguments of the format string, if any.
+-- @see string.format
+function logger:info(fmt, ...)
+ log(self, 5, fmt, ...)
+end
+
+--- Log a debug message.
+-- @string fmt Format of the log message of debug severity.
+-- @param[opt] ... Arguments of the format string, if any.
+-- @see string.format
+function logger:debug(fmt, ...)
+ log(self, 6, fmt, ...)
+end
+
+--- Change or clear the log level of this logger.
+-- @int log_level The new log level. It must be a number from 1 to 6.
+-- A level outside this range will be ignored.
+-- Pass `nil` to clear this logger's specific log level
+-- and use the global log level.
+function logger:set_log_level(log_level)
+ if log_level == nil then
+ if self ~= M then
+ self.log_level = nil
+ end
+ elseif log_level >= 0 and log_level <= 6 then
+ self.log_level = log_level
+ end
+end
+
+-- turn the module itself in a global logger object
+setmetatable(M, logger)
+
+return M