1 files changed, 77 insertions, 0 deletions
diff --git a/SmartDeviceLink/SDLGlobals.m b/SmartDeviceLink/SDLGlobals.m
new file mode 100644
index 000000000..7f122c01e
--- /dev/null
+++ b/SmartDeviceLink/SDLGlobals.m
@@ -0,0 +1,77 @@
+//
+//  SDLGlobals.m
+//  SmartDeviceLink-iOS
+//
+//  Created by Joel Fischer on 8/5/15.
+//  Copyright (c) 2015 smartdevicelink. All rights reserved.
+//
+
+#import "SDLGlobals.h"
+
+static const NSUInteger maxProxyVersion = 4;
+
+
+@interface SDLGlobals ()
+
+@property (assign, nonatomic) NSUInteger protocolVersion;
+
+@end
+
+
+@implementation SDLGlobals
+
++ (instancetype)globals {
+    static SDLGlobals *sharedGlobals = nil;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        sharedGlobals = [[SDLGlobals alloc] init];
+    });
+
+    return sharedGlobals;
+}
+
+- (instancetype)init {
+    self = [super init];
+    if (!self) {
+        return nil;
+    }
+
+    _protocolVersion = 1;
+    _maxHeadUnitVersion = 0;
+
+    return self;
+}
+
+
+#pragma mark - Custom Getters / Setters
+
+- (void)setMaxHeadUnitVersion:(NSUInteger)maxHeadUnitVersion {
+    self.protocolVersion = MIN(maxHeadUnitVersion, maxProxyVersion);
+
+    _maxHeadUnitVersion = maxHeadUnitVersion;
+}
+
+- (NSUInteger)maxMTUSize {
+    switch (self.protocolVersion) {
+        case 1: // fallthrough
+        case 2: {
+            // HAX: This was set to 1024 at some point, for an unknown reason. We can't change it because of backward compatibility & validation concerns. The actual MTU for v1/2 is 1500 bytes.
+            return 1024;
+        } break;
+        case 3: // fallthrough
+        case 4: {
+            // If the head unit isn't running v3/4, but that's the connection scheme we're using, then we have to know that they could be running an MTU that's not 128k, so we default back to the v1/2 MTU for safety.
+            if (self.maxHeadUnitVersion > maxProxyVersion) {
+                return 1024;
+            } else {
+                return 131084;
+            }
+        } break;
+        default: {
+            NSAssert(NO, @"Unknown version number: %@", @(self.protocolVersion));
+            return 0;
+        }
+    }
+}
+
+@end