Convert integer result to error reason

OpenVPN Adapter/NSError+Message.h

@@ -0,0 +1,15 @@
+//
+//  NSError+Message.h
+//  OpenVPN Adapter
+//
+//  Created by Sergey Abramchuk on 06.09.17.
+//
+//
+
+#import <Foundation/Foundation.h>
+
+@interface NSError (Message)
+
++ (NSString *)reasonFromResult:(NSInteger)result;
+
+@end

OpenVPN Adapter/NSError+Message.m

@@ -0,0 +1,28 @@
+//
+//  NSError+Message.m
+//  OpenVPN Adapter
+//
+//  Created by Sergey Abramchuk on 06.09.17.
+//
+//
+
+#import <mbedtls/error.h>
+
+#import "NSError+Message.h"
+
+@implementation NSError (Message)
+
++ (NSString *)reasonFromResult:(NSInteger)result {
+    size_t length = 1024;
+    char *buffer = malloc(length);
+    
+    mbedtls_strerror(result, buffer, length);
+    
+    NSString *reason = [NSString stringWithUTF8String:buffer];
+    
+    free(buffer);
+    
+    return reason;
+}
+
+@end