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/**
* Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0.
*/
#include <aws/common/condition_variable.h>
#include <aws/common/mutex.h>
#include <aws/common/promise.h>
#include <aws/common/ref_count.h>
struct aws_promise {
struct aws_allocator *allocator;
struct aws_mutex mutex;
struct aws_condition_variable cv;
struct aws_ref_count rc;
bool complete;
int error_code;
void *value;
/* destructor for value, will be invoked if the value is not taken */
void (*dtor)(void *);
};
static void s_aws_promise_dtor(void *ptr) {
struct aws_promise *promise = ptr;
aws_condition_variable_clean_up(&promise->cv);
aws_mutex_clean_up(&promise->mutex);
if (promise->value && promise->dtor) {
promise->dtor(promise->value);
}
aws_mem_release(promise->allocator, promise);
}
struct aws_promise *aws_promise_new(struct aws_allocator *allocator) {
struct aws_promise *promise = aws_mem_calloc(allocator, 1, sizeof(struct aws_promise));
promise->allocator = allocator;
aws_ref_count_init(&promise->rc, promise, s_aws_promise_dtor);
aws_mutex_init(&promise->mutex);
aws_condition_variable_init(&promise->cv);
return promise;
}
struct aws_promise *aws_promise_acquire(struct aws_promise *promise) {
aws_ref_count_acquire(&promise->rc);
return promise;
}
void aws_promise_release(struct aws_promise *promise) {
aws_ref_count_release(&promise->rc);
}
static bool s_promise_completed(void *user_data) {
struct aws_promise *promise = user_data;
return promise->complete;
}
void aws_promise_wait(struct aws_promise *promise) {
aws_mutex_lock(&promise->mutex);
aws_condition_variable_wait_pred(&promise->cv, &promise->mutex, s_promise_completed, promise);
aws_mutex_unlock(&promise->mutex);
}
bool aws_promise_wait_for(struct aws_promise *promise, size_t nanoseconds) {
aws_mutex_lock(&promise->mutex);
aws_condition_variable_wait_for_pred(
&promise->cv, &promise->mutex, (int64_t)nanoseconds, s_promise_completed, promise);
const bool complete = promise->complete;
aws_mutex_unlock(&promise->mutex);
return complete;
}
bool aws_promise_is_complete(struct aws_promise *promise) {
aws_mutex_lock(&promise->mutex);
const bool complete = promise->complete;
aws_mutex_unlock(&promise->mutex);
return complete;
}
void aws_promise_complete(struct aws_promise *promise, void *value, void (*dtor)(void *)) {
aws_mutex_lock(&promise->mutex);
AWS_FATAL_ASSERT(!promise->complete && "aws_promise_complete: cannot complete a promise more than once");
promise->value = value;
promise->dtor = dtor;
promise->complete = true;
/* Notify before unlocking to prevent a race condition where the recipient spuriously
* awakens after the unlock, sees a fulfilled promise, and attempts to free its resources
* before the notification has actually occured. */
aws_condition_variable_notify_all(&promise->cv);
aws_mutex_unlock(&promise->mutex);
}
void aws_promise_fail(struct aws_promise *promise, int error_code) {
AWS_FATAL_ASSERT(error_code != 0 && "aws_promise_fail: cannot fail a promise with a 0 error_code");
aws_mutex_lock(&promise->mutex);
AWS_FATAL_ASSERT(!promise->complete && "aws_promise_fail: cannot complete a promise more than once");
promise->error_code = error_code;
promise->complete = true;
aws_condition_variable_notify_all(&promise->cv);
aws_mutex_unlock(&promise->mutex);
}
int aws_promise_error_code(struct aws_promise *promise) {
AWS_FATAL_ASSERT(aws_promise_is_complete(promise));
return promise->error_code;
}
void *aws_promise_value(struct aws_promise *promise) {
AWS_FATAL_ASSERT(aws_promise_is_complete(promise));
return promise->value;
}
void *aws_promise_take_value(struct aws_promise *promise) {
AWS_FATAL_ASSERT(aws_promise_is_complete(promise));
void *value = promise->value;
promise->value = NULL;
promise->dtor = NULL;
return value;
}
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