Objective-C wrapper around WireguardGo.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

WireGuardNetworkExtension/WireGuardGoWrapper.m

@@ -0,0 +1,56 @@
+//
+//  WireGuardGoWrapper.m
+//  WireGuardNetworkExtension
+//
+//  Created by Jeroen Leenarts on 21-06-18.
+//  Copyright © 2018 Wireguard. All rights reserved.
+//
+
+#import "WireGuardGoWrapper.h"
+
+#include "wireguard.h"
+
+/// Trampoline function
+static ssize_t do_read(const void *ctx, const unsigned char *buf, size_t len);
+/// Trampoline function
+static ssize_t do_write(const void *ctx, const unsigned char *buf, size_t len);
+
+@interface WireGuardGoWrapper ()
+
+@property (nonatomic, assign) int handle;
+@property (nonatomic, assign) BOOL isClosed;
+
+@end
+
+@implementation WireGuardGoWrapper
+
+- (void) turnOnWithInterfaceName: (NSString *)interfaceName settingsString: (NSString *)settingsString
+{
+    const char * ifName = [interfaceName UTF8String];
+    const char * settings = [settingsString UTF8String];
+
+    self.handle = wgTurnOn((gostring_t){ .p = ifName, .n = interfaceName.length }, (gostring_t){ .p = settings, .n = settingsString.length }, do_read, do_write, (__bridge void *)(self));
+}
+
+- (void) turnOff
+{
+    self.isClosed = YES;
+    wgTurnOff(self.handle);
+}
+
+@end
+
+static ssize_t do_read(const void *ctx, const unsigned char *buf, size_t len)
+{
+    WireGuardGoWrapper *wrapper = (__bridge WireGuardGoWrapper *)ctx;
+    printf("Reading from instance with ctx %p into buffer %p of length %zu\n", ctx, buf, len);
+    sleep(1);
+    return wrapper.isClosed ? -1 : 0;
+}
+
+static ssize_t do_write(const void *ctx, const unsigned char *buf, size_t len)
+{
+    WireGuardGoWrapper *wrapper = (__bridge WireGuardGoWrapper *)ctx;
+    printf("Writing from instance with ctx %p into buffer %p of length %zu\n", ctx, buf, len);
+    return len;
+}