transport/include/hidl/HidlTransportSupport.h

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * 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.
 */

#ifndef ANDROID_HIDL_TRANSPORT_SUPPORT_H
#define ANDROID_HIDL_TRANSPORT_SUPPORT_H

#include <android/hidl/base/1.0/IBase.h>
#include <hidl/HidlBinderSupport.h>
#include <hidl/HidlPassthroughSupport.h>
#include <hidl/HidlSupport.h>
#include <hidl/HidlTransportUtils.h>
#include <hidl/ServiceManagement.h>

namespace android {
namespace hardware {

/* Configures the threadpool used for handling incoming RPC calls in this process.
 *
 * This method MUST be called before interacting with any HIDL interfaces,
 * including the IFoo::getService and IFoo::registerAsService methods.
 *
 * @param maxThreads maximum number of threads in this process
 * @param callerWillJoin whether the caller will join the threadpool later.
 *
 * Note that maxThreads must include the caller thread if callerWillJoin is true;
 *
 * If you want to create a threadpool of 5 threads, without the caller ever joining:
 *   configureRpcThreadPool(5, false);
 * If you want to create a threadpool of 1 thread, with the caller joining:
 *   configureRpcThreadPool(1, true); // transport won't launch any threads by itself
 *
 */
void configureRpcThreadpool(size_t maxThreads, bool callerWillJoin);

/* Joins a threadpool that you configured earlier with
 * configureRpcThreadPool(x, true);
 */
void joinRpcThreadpool();

/**
 * Sets up the transport for use with (e)poll.
 *
 * Note that all currently supported transports can only be polled
 * from a single thread. When poll() on the returned fd returns,
 * the caller must call handleTransportPoll() to handle the result.
 *
 * @return the file descriptor to be used with (e)poll, or -1 in case of error.
 */
int setupTransportPolling();

/**
 * Handles transport work after poll() returns.
 *
 * @param fd returned from setupTransportPolling()
 *
 * @return OK when successful
 */
status_t handleTransportPoll(int fd);

/**
 * Sets a minimum scheduler policy for all transactions coming into this
 * service.
 *
 * This method MUST be called before passing this service to another process
 * and/or registering it with registerAsService().
 *
 * @param service the service to set the policy for
 * @param policy scheduler policy as defined in linux UAPI
 * @param priority priority. [-20..19] for SCHED_NORMAL, [1..99] for RT
 */
bool setMinSchedulerPolicy(const sp<::android::hidl::base::V1_0::IBase>& service,
                           int policy, int priority);

struct SchedPrio {
    int sched_policy;
    int prio;
};

SchedPrio getMinSchedulerPolicy(const sp<::android::hidl::base::V1_0::IBase>& service);

/**
 * Sets whether or not this object should request security contexts to be populatd for incoming
 * calls (e.g. with getCallingSid).
 *
 * This method MUST be called before passing this service to another process
 * and/or registering it with registerAsService().
 *
 * @param service the service to set the policy for
 * @param requesting whether or not to request sid (default is false)
 */
bool setRequestingSid(const sp<::android::hidl::base::V1_0::IBase>& service, bool requesting);

/**
 * Says whether or not this service is requesting a SID. If this was set after the service was
 * sent to another process, then it will not take effect.
 */
bool getRequestingSid(const sp<::android::hidl::base::V1_0::IBase>& service);

/**
 * Returns whether two interfaces represent the same interface. References to interfaces in the same
 * process will always be equivalent. However, in order to compare a service that is a proxy to a
 * different process, its underlying structure may have to be checked.
 */
bool interfacesEqual(const sp<::android::hidl::base::V1_0::IBase>& left,
                     const sp<::android::hidl::base::V1_0::IBase>& right);

namespace details {

// Return PID on userdebug / eng builds and IServiceManager::PidConstant::NO_PID on user builds.
int32_t getPidIfSharable();

// cast the interface IParent to IChild.
// Return nonnull if cast successful.
// Return nullptr if:
// 1. parent is null
// 2. cast failed because IChild is not a child type of IParent.
// 3. !emitError, calling into parent fails.
// Return an error Return object if:
// 1. emitError, calling into parent fails.
template <typename IChild, typename IParent, typename BpChild>
Return<sp<IChild>> castInterface(sp<IParent> parent, const char* childIndicator, bool emitError) {
    if (parent.get() == nullptr) {
        // casts always succeed with nullptrs.
        return nullptr;
    }
    Return<bool> canCastRet = details::canCastInterface(parent.get(), childIndicator, emitError);
    if (!canCastRet.isOk()) {
        // call fails, propagate the error if emitError
        return emitError
                ? details::StatusOf<bool, sp<IChild>>(canCastRet)
                : Return<sp<IChild>>(sp<IChild>(nullptr));
    }

    if (!canCastRet) {
        return sp<IChild>(nullptr); // cast failed.
    }
    // TODO b/32001926 Needs to be fixed for socket mode.
    if (parent->isRemote()) {
        // binderized mode. Got BpChild. grab the remote and wrap it.
        return sp<IChild>(new BpChild(getOrCreateCachedBinder(parent.get())));
    }
    // Passthrough mode. Got BnChild or BsChild.
    return sp<IChild>(static_cast<IChild *>(parent.get()));
}

template <typename BpType, typename IType = typename BpType::Pure,
          typename = std::enable_if_t<std::is_same<i_tag, typename IType::_hidl_tag>::value>,
          typename = std::enable_if_t<std::is_same<bphw_tag, typename BpType::_hidl_tag>::value>>
sp<IType> getServiceInternal(const std::string& instance, bool retry, bool getStub) {
    using ::android::hidl::base::V1_0::IBase;

    sp<IBase> base = getRawServiceInternal(IType::descriptor, instance, retry, getStub);

    if (base == nullptr) {
        return nullptr;
    }

    if (base->isRemote()) {
        // getRawServiceInternal guarantees we get the proper class
        return sp<IType>(new BpType(getOrCreateCachedBinder(base.get())));
    }

    return IType::castFrom(base);
}

}  // namespace details

}  // namespace hardware
}  // namespace android


#endif  // ANDROID_HIDL_TRANSPORT_SUPPORT_H