Android 시작: ContentProvider 데이터 변경 수신

ServiceMananger android          ，   init        ，                    service。  ：InputMethodService、ActivityManagerService 。 ServiceManager           ：add_service、check_service。   service    add_service         ServiceManager ，      ，  check_service   service    。

   

          ：

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    int main(int argc, char **argv)  
    {  
        struct binder_state *bs;  
        void *svcmgr = BINDER_SERVICE_MANAGER;  
        bs = binder_open(128*1024);  
        if (binder_become_context_manager(bs)) {  
            LOGE("cannot become context manager (%s)
", strerror(errno));  
            return -1;  
        }  
        svcmgr_handle = svcmgr;  
        binder_loop(bs, svcmgr_handler);  
        return 0;  
    }  

 main       ，         ：
  /dev/binder  ，       128K   。
  Binder  ，     context_manager
    ，     Binder  ，     service   ，     ，    svcmgr_handler        。

    

    ServiceManager           。    ，   service    ，       svcmgr_handler：

[java] view plain copy

    int svcmgr_handler(struct binder_state *bs,  
                       struct binder_txn *txn,  
                       struct binder_io *msg,  
                       struct binder_io *reply)  
    {  
        struct svcinfo *si;  
        uint16_t *s;  
        unsigned len;  
        void *ptr;  
        uint32_t strict_policy;  
    //  LOGI("target=%p code=%d pid=%d uid=%d
",  
    //  txn->target, txn->code, txn->sender_pid, txn->sender_euid);  
        if (txn->target != svcmgr_handle)  
            return -1;  
        // Equivalent to Parcel::enforceInterface(), reading the RPC  
        // header with the strict mode policy mask and the interface name.  
        // Note that we ignore the strict_policy and don't propagate it  
        // further (since we do no outbound RPCs anyway).  
        strict_policy = bio_get_uint32(msg);  
        s = bio_get_string16(msg, &len);  
        if ((len != (sizeof(svcmgr_id) / 2)) ||  
            memcmp(svcmgr_id, s, sizeof(svcmgr_id))) {  
            fprintf(stderr,"invalid id %s
", str8(s));  
            return -1;  
        }  
        switch(txn->code) {  
        case SVC_MGR_GET_SERVICE:  
        case SVC_MGR_CHECK_SERVICE:  
            s = bio_get_string16(msg, &len);  
            ptr = do_find_service(bs, s, len);  
            if (!ptr)  
                break;  
            bio_put_ref(reply, ptr);  
            return 0;  
        case SVC_MGR_ADD_SERVICE:  
            s = bio_get_string16(msg, &len);  
            ptr = bio_get_ref(msg);  
            if (do_add_service(bs, s, len, ptr, txn->sender_euid))  
                return -1;  
            break；  
        case SVC_MGR_LIST_SERVICES: {  
            unsigned n = bio_get_uint32(msg);  
            si = svclist;  
            while ((n-- > 0) && si)  
                si = si->next;  
            if (si) {  
                bio_put_string16(reply, si->name);  
                return 0;  
            }  
            return -1;  
        }  
        default:  
            LOGE("unknown code %d
", txn->code);  
            return -1;  
        }  
        bio_put_uint32(reply, 0);  
        return 0;  
    }  

          Service     ，       service，     ：
[java] view plain copy

    case SVC_MGR_ADD_SERVICE:  
            s = bio_get_string16(msg, &len);  
            ptr = bio_get_ref(msg);  
            if (do_add_service(bs, s, len, ptr, txn->sender_euid))  
                return -1;  
            break;  

      do_add_service       ：

[java] view plain copy

    int do_add_service(struct binder_state *bs,  
                       uint16_t *s, unsigned len,  
                       void *ptr, unsigned uid)  
    {  
        struct svcinfo *si;  
    //    LOGI("add_service('%s',%p) uid=%d
", str8(s), ptr, uid);  
        if (!ptr || (len == 0) || (len > 127))  
            return -1；  
        if (!svc_can_register(uid, s)) {  
            LOGE("add_service('%s',%p) uid=%d - PERMISSION DENIED
",  
                 str8(s), ptr, uid);  
            return -1;  
        }  
        si = find_svc(s, len);  
        if (si) {  
            if (si->ptr) {  
                LOGE("add_service('%s',%p) uid=%d - ALREADY REGISTERED
",  
                     str8(s), ptr, uid);  
                return -1;  
            }  
            si->ptr = ptr;  
        } else {  
            si = malloc(sizeof(*si) + (len + 1) * sizeof(uint16_t));  
            if (!si) {  
                LOGE("add_service('%s',%p) uid=%d - OUT OF MEMORY
",  
                     str8(s), ptr, uid);  
                return -1;  
            }  
            si->ptr = ptr;  
            si->len = len;  
            memcpy(si->name, s, (len + 1) * sizeof(uint16_t));  
            si->name[len] = '\0';  
            si->death.func = svcinfo_death;  
            si->death.ptr = si;  
            si->next = svclist;  
            svclist = si;  
        }  
        binder_acquire(bs, ptr);  
        binder_link_to_death(bs, ptr, &si->death);  
        return 0;  
    }  

     ，             service，           ，    。
[java] view plain copy

    if (!svc_can_register(uid, s)) {  
            LOGE("add_service('%s',%p) uid=%d - PERMISSION DENIED
",  
                 str8(s), ptr, uid);  
            return -1;  
        }  

       service        ，       ，         ：

[java] view plain copy

    si = find_svc(s, len);  
    if (si) {  
          if (si->ptr) {  
              LOGE("add_service('%s',%p) uid=%d - ALREADY REGISTERED
",  
                   str8(s), ptr, uid);  
              return -1;  
          }  
          si->ptr = ptr;  
      }  

         ：

[java] view plain copy

    si = malloc(sizeof(*si) + (len + 1) * sizeof(uint16_t));  
            if (!si) {  
                LOGE("add_service('%s',%p) uid=%d - OUT OF MEMORY
",  
                     str8(s), ptr, uid);  
                return -1;  
            }  

        ，    service，   svcList  。  ， ServiceManager   service       svclist。    service name handler。

    

        ，service       。       service           。             ：
[java] view plain copy

    case SVC_MGR_CHECK_SERVICE:  
            s = bio_get_string16(msg, &len);  
            ptr = do_find_service(bs, s, len);  
            if (!ptr)  
                break;  
            bio_put_ref(reply, ptr);  
            return 0；  

     service，    SVC_MGR_CHECK_SERVICE，         reply，      。

do_find_service       service   。

[java] view plain copy

    void *do_find_service(struct binder_state *bs, uint16_t *s, unsigned len)  
    {  
        struct svcinfo *si;  
        si = find_svc(s, len);  
    //    LOGI("check_service('%s') ptr = %p
", str8(s), si ? si->ptr : 0);  
        if (si && si->ptr) {  
            return si->ptr;  
        } else {  
            return 0;  
        }  
    }  

   ServiceManager             。   ServiceManager    ：