Logging

Macros
#define	LLL_ERR   (1 << 0)
#define	LLL_WARN   (1 << 1)
#define	LLL_NOTICE   (1 << 2)
#define	LLL_INFO   (1 << 3)
#define	LLL_DEBUG   (1 << 4)
#define	LLL_PARSER   (1 << 5)
#define	LLL_HEADER   (1 << 6)
#define	LLL_EXT   (1 << 7)
#define	LLL_CLIENT   (1 << 8)
#define	LLL_LATENCY   (1 << 9)
#define	LLL_USER   (1 << 10)
#define	LLL_THREAD   (1 << 11)
#define	LLL_COUNT   (12) /* set to count of valid flags */
#define	_LWS_LINIT   (LLL_ERR | LLL_USER | LLL_WARN | LLL_NOTICE)
#define	_LWS_LBS   0
#define	_LWS_LBC   0
#define	_LWS_ENABLED_LOGS   (((_LWS_LINIT) | (_LWS_LBS)) & ~(_LWS_LBC))
#define	lwsl_err(...)   _lws_log(LLL_ERR, __VA_ARGS__)
#define	lwsl_warn(...)   _lws_log(LLL_WARN, __VA_ARGS__)
#define	lwsl_notice(...)   _lws_log(LLL_NOTICE, __VA_ARGS__)
#define	lwsl_info(...)   do {} while(0)
#define	lwsl_debug(...)   do {} while(0)
#define	lwsl_parser(...)   do {} while(0)
#define	lwsl_header(...)   do {} while(0)
#define	lwsl_ext(...)   do {} while(0)
#define	lwsl_client(...)   do {} while(0)
#define	lwsl_latency(...)   do {} while(0)
#define	lwsl_thread(...)   do {} while(0)
#define	lwsl_user(...)   _lws_log(LLL_USER, __VA_ARGS__)
#define	lwsl_hexdump_err(...)   lwsl_hexdump_level(LLL_ERR, __VA_ARGS__)
#define	lwsl_hexdump_warn(...)   lwsl_hexdump_level(LLL_WARN, __VA_ARGS__)
#define	lwsl_hexdump_notice(...)   lwsl_hexdump_level(LLL_NOTICE, __VA_ARGS__)
#define	lwsl_hexdump_info(...)   lwsl_hexdump_level(LLL_INFO, __VA_ARGS__)
#define	lwsl_hexdump_debug(...)   lwsl_hexdump_level(LLL_DEBUG, __VA_ARGS__)

Functions
LWS_VISIBLE LWS_EXTERN int	lwsl_timestamp (int level, char *p, int len)
LWS_VISIBLE LWS_EXTERN void	_lws_log (int filter, const char *format,...) LWS_FORMAT(2)
LWS_VISIBLE LWS_EXTERN void	_lws_logv (int filter, const char *format, va_list vl)
LWS_VISIBLE LWS_EXTERN void	lwsl_hexdump_level (int level, const void *vbuf, size_t len)
LWS_VISIBLE LWS_EXTERN void	lwsl_hexdump (const void *buf, size_t len)
LWS_VISIBLE LWS_EXTERN void	lws_set_log_level (int level, void(*log_emit_function)(int level, const char *line))
LWS_VISIBLE LWS_EXTERN void	lwsl_emit_syslog (int level, const char *line)
LWS_VISIBLE LWS_EXTERN void	lwsl_emit_stderr (int level, const char *line)
LWS_VISIBLE LWS_EXTERN void	lwsl_emit_stderr_notimestamp (int level, const char *line)
LWS_VISIBLE LWS_EXTERN int	lwsl_visible (int level)

Detailed Description

Logging

Lws provides flexible and filterable logging facilities, which can be used inside lws and in user code.

Log categories may be individually filtered bitwise, and directed to built-in sinks for syslog-compatible logging, or a user-defined function.

Function Documentation

lws_set_log_level()

LWS_VISIBLE LWS_EXTERN void lws_set_log_level	(	int	level,
		void(*)(int level, const char *line)	log_emit_function
	)

#include <include/libwebsockets/lws-logs.h>

lws_set_log_level() - Set the logging bitfield

Parameters

level	OR together the LLL_ debug contexts you want output from
log_emit_function	NULL to leave it as it is, or a user-supplied function to perform log string emission instead of the default stderr one.

log level defaults to "err", "warn" and "notice" contexts enabled and emission on stderr. If stderr is a tty (according to isatty()) then the output is coloured according to the log level using ANSI escapes.

lwsl_emit_stderr()

LWS_VISIBLE LWS_EXTERN void lwsl_emit_stderr	(	int	level,
		const char *	line
	)

#include <include/libwebsockets/lws-logs.h>

lwsl_emit_stderr() - helper log emit function writes to stderr

Parameters

level	one of LLL_ log level indexes
line	log string

You use this by passing the function pointer to lws_set_log_level(), to set it as the log emit function, it is not called directly.

It prepends a system timestamp like [2018/11/13 07:41:57:3989]

If stderr is a tty, then ansi colour codes are added.

lwsl_emit_stderr_notimestamp()

LWS_VISIBLE LWS_EXTERN void lwsl_emit_stderr_notimestamp	(	int	level,
		const char *	line
	)

#include <include/libwebsockets/lws-logs.h>

lwsl_emit_stderr_notimestamp() - helper log emit function writes to stderr

Parameters

level	one of LLL_ log level indexes
line	log string

You use this by passing the function pointer to lws_set_log_level(), to set it as the log emit function, it is not called directly.

If stderr is a tty, then ansi colour codes are added.

lwsl_emit_syslog()

LWS_VISIBLE LWS_EXTERN void lwsl_emit_syslog	(	int	level,
		const char *	line
	)

#include <include/libwebsockets/lws-logs.h>

lwsl_emit_syslog() - helper log emit function writes to system log

Parameters

level	one of LLL_ log level indexes
line	log string

You use this by passing the function pointer to lws_set_log_level(), to set it as the log emit function, it is not called directly.

lwsl_hexdump()

LWS_VISIBLE LWS_EXTERN void lwsl_hexdump	(	const void *	buf,
		size_t	len
	)

#include <include/libwebsockets/lws-logs.h>

lwsl_hexdump() - helper to hexdump a buffer (DEBUG builds only)

Parameters

buf	buffer start to dump
len	length of buffer to dump

Calls through to lwsl_hexdump_level(LLL_DEBUG, ... for compatability. It's better to use lwsl_hexdump_level(level, ... directly so you can control the visibility.

lwsl_hexdump_level()

LWS_VISIBLE LWS_EXTERN void lwsl_hexdump_level	(	int	level,
		const void *	vbuf,
		size_t	len
	)

#include <include/libwebsockets/lws-logs.h>

lwsl_hexdump_level() - helper to hexdump a buffer at a selected debug level

Parameters

level	one of LLL_ constants
vbuf	buffer start to dump
len	length of buffer to dump

If level is visible, does a nice hexdump -C style dump of vbuf for len bytes. This can be extremely convenient while debugging.

lwsl_timestamp()

LWS_VISIBLE LWS_EXTERN int lwsl_timestamp	(	int	level,
		char *	p,
		int	len
	)

#include <include/libwebsockets/lws-logs.h>

lwsl_timestamp: generate logging timestamp string

Parameters

level	logging level
p	char * buffer to take timestamp
len	length of p

returns length written in p

lwsl_visible()

LWS_VISIBLE LWS_EXTERN int lwsl_visible

(

int

level

)

#include <include/libwebsockets/lws-logs.h>

lwsl_visible() - returns true if the log level should be printed

Parameters

level

one of LLL_ log level indexes

This is useful if you have to do work to generate the log content, you can skip the work if the log level used to print it is not actually enabled at runtime.