Clean up delegate credentials provider (#118)

- rename .c file. had a typo and was inconsistent with others.
- don't have 2 different shutdown callbacks in options, just offer 1.
- don't force user to clean up memory allocated by new_delegate()

include/aws/auth/credentials.h

@@ -406,21 +406,26 @@ struct aws_credentials_provider_chain_default_options {
     struct aws_client_bootstrap *bootstrap;
 };
 
+typedef int(aws_credentials_provider_delegate_get_credentials_fn)(
+    void *delegate_user_data,
+    aws_on_get_credentials_callback_fn callback,
+    void *callback_user_data);
+
 /**
  * Configuration options for the delegate credentials provider.
  */
 struct aws_credentials_provider_delegate_options {
     struct aws_credentials_provider_shutdown_options shutdown_options;
 
     /**
-     * Provide the vtable of functions to get credentials.
+     * Delegated get_credentials() callback.
      */
-    struct aws_credentials_provider_vtable *provider_vtable;
+    aws_credentials_provider_delegate_get_credentials_fn *get_credentials;
 
     /**
-     * Optional implementation.
+     * User data for delegated callbacks.
      */
-    void *impl;
+    void *delegate_user_data;
 };
 
 AWS_EXTERN_C_BEGIN

source/credentials_provider_delegate.c

@@ -0,0 +1,64 @@
+/**
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0.
+ */
+
+#include <aws/auth/private/credentials_utils.h>
+
+struct aws_credentials_provider_delegate_impl {
+    aws_credentials_provider_delegate_get_credentials_fn *get_credentials;
+    void *user_data;
+};
+
+static int s_credentials_provider_delegate_get_credentials(
+    struct aws_credentials_provider *provider,
+    aws_on_get_credentials_callback_fn callback,
+    void *callback_user_data) {
+
+    struct aws_credentials_provider_delegate_impl *impl = provider->impl;
+    return impl->get_credentials(impl->user_data, callback, callback_user_data);
+}
+
+static void s_credentials_provider_delegate_destroy(struct aws_credentials_provider *provider) {
+    aws_credentials_provider_invoke_shutdown_callback(provider);
+    aws_mem_release(provider->allocator, provider);
+}
+
+static struct aws_credentials_provider_vtable s_credentials_provider_delegate_vtable = {
+    .get_credentials = s_credentials_provider_delegate_get_credentials,
+    .destroy = s_credentials_provider_delegate_destroy,
+};
+
+struct aws_credentials_provider *aws_credentials_provider_new_delegate(
+    struct aws_allocator *allocator,
+    struct aws_credentials_provider_delegate_options *options) {
+
+    AWS_ASSERT(options);
+    AWS_ASSERT(options->get_credentials);
+
+    struct aws_credentials_provider *provider = NULL;
+    struct aws_credentials_provider_delegate_impl *impl = NULL;
+
+    aws_mem_acquire_many(
+        allocator,
+        2,
+        &provider,
+        sizeof(struct aws_credentials_provider),
+        &impl,
+        sizeof(struct aws_credentials_provider_delegate_impl));
+
+    if (!provider) {
+        return NULL;
+    }
+
+    AWS_ZERO_STRUCT(*provider);
+    AWS_ZERO_STRUCT(*impl);
+
+    aws_credentials_provider_init_base(provider, allocator, &s_credentials_provider_delegate_vtable, impl);
+    provider->shutdown_options = options->shutdown_options;
+
+    impl->get_credentials = options->get_credentials;
+    impl->user_data = options->delegate_user_data;
+
+    return provider;
+}