From d89159fdb42878d283da47cfb25685009cd9c5c7 Mon Sep 17 00:00:00 2001
From: jcmichelou <jean-claude.michelou@spinetix.com>
Date: Sat, 2 Sep 2017 16:56:45 +0200
Subject: [PATCH] debug.[hc]: Add a log handler callback.

---
 include/coap/debug.h |  5 +++++
 libcoap-1.sym        |  1 +
 src/debug.c          | 43 +++++++++++++++++++++++++++++--------------
 3 files changed, 35 insertions(+), 14 deletions(-)

diff --git a/include/coap/debug.h b/include/coap/debug.h
index 64e965be..f475ad72 100644
--- a/include/coap/debug.h
+++ b/include/coap/debug.h
@@ -41,6 +41,11 @@ coap_log_t coap_get_log_level(void);
 /** Sets the log level to the specified value. */
 void coap_set_log_level(coap_log_t level);
 
+typedef void (*coap_log_handler_t) (coap_log_t level, const char *message);
+
+/** Add a custom log callback, use NULL to reset default handler */
+void coap_set_log_handler(coap_log_handler_t handler);
+
 /** Returns a zero-terminated string with the name of this library. */
 const char *coap_package_name(void);
 
diff --git a/libcoap-1.sym b/libcoap-1.sym
index d893ad5c..c082d67c 100644
--- a/libcoap-1.sym
+++ b/libcoap-1.sym
@@ -145,6 +145,7 @@ coap_session_set_mtu
 coap_session_str
 coap_set_app_data
 coap_set_event_handler
+coap_set_log_handler
 coap_set_log_level
 coap_show_pdu
 coap_socket_bind_udp
diff --git a/src/debug.c b/src/debug.c
index c9b26c8f..06849287 100644
--- a/src/debug.c
+++ b/src/debug.c
@@ -489,30 +489,45 @@ coap_show_pdu(const coap_pdu_t *pdu) {
   fflush(COAP_DEBUG_FD);
 }
 
+static coap_log_handler_t log_handler = NULL;
+
+void coap_set_log_handler(coap_log_handler_t handler) {
+  log_handler = handler;
+}
 
 void 
 coap_log_impl(coap_log_t level, const char *format, ...) {
-  char timebuf[32];
-  coap_tick_t now;
-  va_list ap;
-  FILE *log_fd;
 
   if (maxlog < level)
     return;
+
+  if (log_handler) {
+    char message[128];
+    va_list ap;
+    va_start(ap, format);
+    vsnprintf( message, sizeof(message), format, ap);
+    va_end(ap);
+    log_handler(level, message);
+  } else {
+    char timebuf[32];
+    coap_tick_t now;
+    va_list ap;
+    FILE *log_fd;
   
-  log_fd = level <= LOG_CRIT ? COAP_ERR_FD : COAP_DEBUG_FD;
+    log_fd = level <= LOG_CRIT ? COAP_ERR_FD : COAP_DEBUG_FD;
 
-  coap_ticks(&now);
-  if (print_timestamp(timebuf,sizeof(timebuf), now))
-    fprintf(log_fd, "%s ", timebuf);
+    coap_ticks(&now);
+    if (print_timestamp(timebuf,sizeof(timebuf), now))
+      fprintf(log_fd, "%s ", timebuf);
 
-  if (level <= LOG_DEBUG)
-    fprintf(log_fd, "%s ", loglevels[level]);
+    if (level <= LOG_DEBUG)
+      fprintf(log_fd, "%s ", loglevels[level]);
 
-  va_start(ap, format);
-  vfprintf(log_fd, format, ap);
-  va_end(ap);
-  fflush(log_fd);
+    va_start(ap, format);
+    vfprintf(log_fd, format, ap);
+    va_end(ap);
+    fflush(log_fd);
+  }
 }
 
 static struct packet_num_interval {