软总线源码分析6：发现模块（一）

软总线主要包括四大模块：发现，连接，组网，传输。今天我们主要详细介绍一下发现模块。之前我们已经介绍过软总线的PublishService接口和StartDiscovery接口。接下来我们分别详细介绍这些接口的实现细节。

PublishService接口

之前我们介绍软总线的接口的时候，发现PublishService会调用DiscInterfaceByMedium来完成对应的业务处理，DiscInterfaceByMedium的源码如下所示：

static int32_t DiscInterfaceByMedium(const DiscInfo *info, const InterfaceFuncType type)
{
    switch (info->medium) {
        case BLE:
            return DiscInterfaceProcess(&(info->option), g_discBleInterface, info->mode, type);
        case COAP:
            return DiscInterfaceProcess(&(info->option), g_discCoapInterface, info->mode, type);
        case AUTO: {
            int32_t ret1 = DiscInterfaceProcess(&(info->option), g_discBleInterface, info->mode, type);
            int32_t ret2 = DiscInterfaceProcess(&(info->option), g_discCoapInterface, info->mode, type);
            if ((ret1 == SOFTBUS_OK) || (ret2 == SOFTBUS_OK)) {
                return SOFTBUS_OK;
            }
            return SOFTBUS_DISCOVER_MANAGER_INNERFUNCTION_FAIL;
        }
        default:
            return SOFTBUS_DISCOVER_MANAGER_INNERFUNCTION_FAIL;
    }
}

即DiscInterfaceByMedium函数根据info的媒介类型，选择不同的接口变量来进行相应的处理。以COAP类型为例，DiscInterfaceProcess的源码如下：

static int32_t DiscInterfaceProcess(const InnerOption *option, const DiscoveryFuncInterface *interface,
    const DiscoverMode mode, InterfaceFuncType type)
{
    if (interface == NULL) {
        return SOFTBUS_DISCOVER_MANAGER_INNERFUNCTION_FAIL;
    }

    switch (type) {
        case PUBLISH_FUNC:
            return ((mode == DISCOVER_MODE_ACTIVE) ? (interface->Publish(&(option->publishOption))) :
                (interface->StartScan(&(option->publishOption))));
        case UNPUBLISH_FUNC:
            return ((mode == DISCOVER_MODE_ACTIVE) ? (interface->Unpublish(&(option->publishOption))) :
                (interface->StopScan(&(option->publishOption))));
        case STARTDISCOVERTY_FUNC:
            return ((mode == DISCOVER_MODE_ACTIVE) ? (interface->StartAdvertise(&(option->subscribeOption))) :
                (interface->Subscribe(&(option->subscribeOption))));
        case STOPDISCOVERY_FUNC:
            return ((mode == DISCOVER_MODE_ACTIVE) ? (interface->StopAdvertise(&(option->subscribeOption))) :
                (interface->Unsubscribe(&(option->subscribeOption))));
        default:
            return SOFTBUS_DISCOVER_MANAGER_INNERFUNCTION_FAIL;
    }
}

可以看到，当处理类型为PUBLISH_FUNC的时候，如果为主动发现，则调用接口变量的Publish函数处理。如果是被动发现的话，则调用接口变量的StartScan函数处理。

而g_discCoapInterface在DiscMgrInit中初始化，其指向g_discCoapFuncInterface接口，源码如下：

static DiscoveryFuncInterface g_discCoapFuncInterface = {
    .Publish = CoapPublish,
    .StartScan = CoapStartScan,
    .Unpublish = CoapUnPublish,
    .StopScan = CoapStoptScan,
    .StartAdvertise = CoapStartAdvertise,
    .Subscribe = CoapSubscribe,
    .StopAdvertise = CoapStopAdvertise,
    .Unsubscribe = CoapUnsubscribe
};

因此，在COAP下，如果为主动发现，则相应的处理函数为CoapPublish。如果为被动发现，则相应的处理函数为CoapStartScan，接下来我们介绍这两个对应的处理。

CoapPublish

CoapPublish的源码如下所示：

static int32_t CoapPublish(const PublishOption *option)
{
    if (option == NULL || g_publishMgr == NULL) {
        return SOFTBUS_INVALID_PARAM;
    }
    if (pthread_mutex_lock(&(g_publishMgr->lock)) != 0) {
        LOG_ERR("pthread mutex lock failed.");
        return SOFTBUS_LOCK_ERR;
    }
    if (RegisterAllCapBitmap(CAPABILITY_NUM, option->capabilityBitmap, g_publishMgr, MAX_CAP_NUM) != SOFTBUS_OK) {
        (void)pthread_mutex_unlock(&(g_publishMgr->lock));
        LOG_ERR("merge publish capability failed.");
        return SOFTBUS_DISCOVER_COAP_MERGE_CAP_FAIL;
    }
    if (g_publishMgr->isUpdate) {
        if (DiscCoapRegisterCapability(CAPABILITY_NUM, g_publishMgr->allCap) != SOFTBUS_OK) {
            (void)pthread_mutex_unlock(&(g_publishMgr->lock));
            LOG_ERR("register all capability to dfinder failed.");
            return SOFTBUS_DISCOVER_COAP_REGISTER_CAP_FAIL;
        }
    }
    if (DiscCoapRegisterServiceData(option->capabilityData, option->dataLen) != SOFTBUS_OK) {
        (void)pthread_mutex_unlock(&(g_publishMgr->lock));
        LOG_ERR("register service data to dfinder failed.");
        return SOFTBUS_ERR;
    }
    if (DiscCoapStartDiscovery(ACTIVE_PUBLISH) != SOFTBUS_OK) {
        (void)pthread_mutex_unlock(&(g_publishMgr->lock));
        LOG_ERR("coap start publish failed.");
        return SOFTBUS_DISCOVER_COAP_START_DISCOVER_FAIL;
    }