1 files changed, 149 insertions, 0 deletions
diff --git a/src/objective-c/GRPCClient/GRPCTransport.mm b/src/objective-c/GRPCClient/GRPCTransport.mm
new file mode 100644
index 0000000000..c55beca0c4
--- /dev/null
+++ b/src/objective-c/GRPCClient/GRPCTransport.mm
@@ -0,0 +1,149 @@
+/*
+ *
+ * Copyright 2019 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#import "GRPCTransport.h"
+
+static const GRPCTransportID gGRPCCoreSecureID = "io.grpc.transport.core.secure";
+static const GRPCTransportID gGRPCCoreInsecureID = "io.grpc.transport.core.insecure";
+
+const struct GRPCDefaultTransportImplList GRPCDefaultTransportImplList = {
+    .core_secure = gGRPCCoreSecureID, .core_insecure = gGRPCCoreInsecureID};
+
+static const GRPCTransportID gDefaultTransportID = gGRPCCoreSecureID;
+
+static GRPCTransportRegistry *gTransportRegistry = nil;
+static dispatch_once_t initTransportRegistry;
+
+BOOL TransportIDIsEqual(GRPCTransportID lhs, GRPCTransportID rhs) {
+  // Directly comparing pointers works because we require users to use the id provided by each
+  // implementation, not coming up with their own string.
+  return lhs == rhs;
+}
+
+NSUInteger TransportIDHash(GRPCTransportID transportID) {
+  if (transportID == NULL) {
+    transportID = gDefaultTransportID;
+  }
+  return [NSString stringWithCString:transportID encoding:NSUTF8StringEncoding].hash;
+}
+
+@implementation GRPCTransportRegistry {
+  NSMutableDictionary<NSString *, id<GRPCTransportFactory>> *_registry;
+  id<GRPCTransportFactory> _defaultFactory;
+}
+
++ (instancetype)sharedInstance {
+  dispatch_once(&initTransportRegistry, ^{
+    gTransportRegistry = [[GRPCTransportRegistry alloc] init];
+    NSAssert(gTransportRegistry != nil, @"Unable to initialize transport registry.");
+    if (gTransportRegistry == nil) {
+      NSLog(@"Unable to initialize transport registry.");
+      [NSException raise:NSGenericException format:@"Unable to initialize transport registry."];
+    }
+  });
+  return gTransportRegistry;
+}
+
+- (instancetype)init {
+  if ((self = [super init])) {
+    _registry = [NSMutableDictionary dictionary];
+  }
+  return self;
+}
+
+- (void)registerTransportWithID:(GRPCTransportID)transportID
+                        factory:(id<GRPCTransportFactory>)factory {
+  NSString *nsTransportID = [NSString stringWithCString:transportID encoding:NSUTF8StringEncoding];
+  NSAssert(_registry[nsTransportID] == nil, @"The transport %@ has already been registered.",
+           nsTransportID);
+  if (_registry[nsTransportID] != nil) {
+    NSLog(@"The transport %@ has already been registered.", nsTransportID);
+    return;
+  }
+  _registry[nsTransportID] = factory;
+
+  // if the default transport is registered, mark it.
+  if (0 == strcmp(transportID, gDefaultTransportID)) {
+    _defaultFactory = factory;
+  }
+}
+
+- (id<GRPCTransportFactory>)getTransportFactoryWithID:(GRPCTransportID)transportID {
+  if (transportID == NULL) {
+    if (_defaultFactory == nil) {
+      // fall back to default transport if no transport is provided
+      [NSException raise:NSInvalidArgumentException
+                  format:@"Did not specify transport and unable to find a default transport."];
+      return nil;
+    }
+    return _defaultFactory;
+  }
+  NSString *nsTransportID = [NSString stringWithCString:transportID encoding:NSUTF8StringEncoding];
+  id<GRPCTransportFactory> transportFactory = _registry[nsTransportID];
+  if (transportFactory == nil) {
+    if (_defaultFactory != nil) {
+      // fall back to default transport if no transport is found
+      NSLog(@"Unable to find transport with id %s; falling back to default transport.",
+            transportID);
+      return _defaultFactory;
+    } else {
+      [NSException raise:NSInvalidArgumentException
+                  format:@"Unable to find transport with id %s", transportID];
+      return nil;
+    }
+  }
+  return transportFactory;
+}
+
+@end
+
+@implementation GRPCTransport
+
+- (dispatch_queue_t)dispatchQueue {
+  [NSException raise:NSGenericException
+              format:@"Implementations should override the dispatch queue"];
+  return nil;
+}
+
+- (void)startWithRequestOptions:(nonnull GRPCRequestOptions *)requestOptions
+                    callOptions:(nonnull GRPCCallOptions *)callOptions {
+  [NSException raise:NSGenericException
+              format:@"Implementations should override the methods of GRPCTransport"];
+}
+
+- (void)writeData:(nonnull id)data {
+  [NSException raise:NSGenericException
+              format:@"Implementations should override the methods of GRPCTransport"];
+}
+
+- (void)cancel {
+  [NSException raise:NSGenericException
+              format:@"Implementations should override the methods of GRPCTransport"];
+}
+
+- (void)finish {
+  [NSException raise:NSGenericException
+              format:@"Implementations should override the methods of GRPCTransport"];
+}
+
+- (void)receiveNextMessages:(NSUInteger)numberOfMessages {
+  [NSException raise:NSGenericException
+              format:@"Implementations should override the methods of GRPCTransport"];
+}
+
+@end