added custom log callback

Author: sy-c

src/ReadoutDatabase.cxx

@@ -13,7 +13,9 @@
 typedef bool my_bool;
 #endif
 
-ReadoutDatabase::ReadoutDatabase(const char* cx) {
+ReadoutDatabase::ReadoutDatabase(const char* cx, int v, const LogCallback& cb) {
+  verbose = v;
+  theLogCallback = cb;
 
   char *db_db=nullptr, *db_user=nullptr, *db_pwd=nullptr, *db_host=nullptr;
   char *p=nullptr,*ptr,*lptr;
@@ -77,9 +79,7 @@ ReadoutDatabase::ReadoutDatabase(const char* cx) {
     goto open_failed;
   }
 
-  if (verbose) {
-    printf("Using DB %s @ %s\n", db_db, db_host);
-  }
+  log("Using database " + std::string(db_db) + "@" + std::string(db_host));
 
   // try to connect
   if (mysql_real_connect(db,db_host,db_user,db_pwd,db_db,0,nullptr,0)==nullptr) {
@@ -158,9 +158,7 @@ int ReadoutDatabase::query(int maxRetry, const char *inQuery,...) {
     return -1;
   }
 
-  if (verbose) {
-    printf("Executing query: %s\n", query);
-  }
+  log("Executing query: "  + std::string(query));
 
   if (maxRetry <= 0) {
     maxRetry = 1;
@@ -298,3 +296,13 @@ const char* ReadoutDatabase::getError() {
 const char* ReadoutDatabase::getQuery() {
   return lastQuery.c_str();
 }
+
+void ReadoutDatabase::log(const std::string &msg) {
+  if (verbose) {
+    if (theLogCallback!=nullptr) {
+      theLogCallback(msg);
+    } else {
+      printf("%s\n", msg.c_str());
+    }
+  }
+}

src/ReadoutDatabase.h

@@ -3,10 +3,14 @@
 #include <stdint.h>
 #include <vector>
 #include <string>
+#include <functional>
 
 class ReadoutDatabase {
 public:
-  ReadoutDatabase(const char* cx); // create a handle to DB. Connection string in the form user:pwd@host/dbname
+  // an optional user-provided logging function for all DB-related ops
+  typedef std::function<void(const std::string &)> LogCallback;
+
+  ReadoutDatabase(const char* cx, int verbose = 0, const LogCallback& cb = nullptr); // create a handle to DB. Connection string in the form user:pwd@host/dbname
   ~ReadoutDatabase();
 
   // admin database structure
@@ -42,6 +46,9 @@ class ReadoutDatabase {
   int maxRetry = 20; // number of query retries
   int retryTimeout = 50; // retry interval (milliseconds)
 
+  LogCallback theLogCallback;
+  void log(const std::string &log);
+
   std::string lastError = ""; // error string of last query, if any
   std::string lastQuery = ""; // last query executed  
 };