Added interrupt method to cancel/interrupt pending database operation

src/fmdb/FMDatabase.h

@@ -613,6 +613,15 @@ typedef int(^FMDBExecuteStatementsCallbackBlock)(NSDictionary *resultsDictionary
 
 - (BOOL)inTransaction;
 
+/** Interupt pending database operation
+
+ This method causes any pending database operation to abort and return at its earliest opportunity
+
+ @return `YES` on success; `NO` on failure. If failed, you can call `<lastError>`, `<lastErrorCode>`, or `<lastErrorMessage>` for diagnostic information regarding the failure.
+
+ */
+
+- (BOOL)interrupt;
 
 ///----------------------------------------
 /// @name Cached statements and result sets

src/fmdb/FMDatabase.m

@@ -1039,6 +1039,12 @@ - (BOOL)executeUpdate:(NSString*)sql error:(NSError**)outErr withArgumentsInArra
     if (SQLITE_DONE == rc) {
         // all is well, let's return.
     }
+    else if (SQLITE_INTERRUPT == rc) {
+        if (_logsErrors) {
+            NSLog(@"Error calling sqlite3_step. Query was interrupted (%d: %s) SQLITE_INTERRUPT", rc, sqlite3_errmsg(_db));
+            NSLog(@"DB Query: %@", sql);
+        }
+    }
     else if (SQLITE_ERROR == rc) {
         if (_logsErrors) {
             NSLog(@"Error calling sqlite3_step (%d: %s) SQLITE_ERROR", rc, sqlite3_errmsg(_db));
@@ -1247,6 +1253,15 @@ - (BOOL)inTransaction {
     return _inTransaction;
 }
 
+- (BOOL)interrupt
+{
+    if (_db) {
+        sqlite3_interrupt([self sqliteHandle]);
+        return YES;
+    }
+    return NO;
+}
+
 #if SQLITE_VERSION_NUMBER >= 3007000
 
 static NSString *FMDBEscapeSavePointName(NSString *savepointName) {

src/fmdb/FMDatabaseQueue.h

@@ -130,6 +130,10 @@
 
 - (void)close;
 
+/** Interupt pending database operation. */
+
+- (void)interrupt;
+
 ///-----------------------------------------------
 /// @name Dispatching database operations to queue
 ///-----------------------------------------------

src/fmdb/FMDatabaseQueue.m

@@ -116,6 +116,11 @@ - (void)close {
     FMDBRelease(self);
 }
 
+- (void)interrupt
+{
+    [[self database] interrupt];
+}
+
 - (FMDatabase*)database {
     if (!_db) {
         _db = FMDBReturnRetained([FMDatabase databaseWithPath:_path]);