c++ - Replace std::vector's buffer with a malloc'ed char array -

-

i have following class holding std::vector resizable "buffer" data.

class packet { public:     struct packetheader     {         size_t datasize = 0;         size_t paddeddatasize = 0;     } header_;      const unsigned char* data() const     {         return &data_[0];     }      unsigned char* data()     {         return &data_[0];     }      /// changes size of data vector     void resize(size_t sz)     {        header_.datasize = sz;          // check if padding needed         if (sz % aes_block_size != 0){             auto padding = aes_block_size - (sz % aes_block_size);                   data_.resize(sz + padding);             (int = 1; <= padding; i++)             {                                data_[(sz + padding) - i] = '\0';             }             header_.paddeddatasize = sz + padding;         } else{                      data_.resize(sz);         }     }  private:         std::vector<unsigned char> data_;    };

then i'm performing aes encryption on data before transfering them on network, requires temporary buffer of same size generate ciphertext, has copied vector.

void tcpconnection::send_packet(packet& pkg) {     // cut out unrelevant lines of code      // need temporary buffer encryption     unsigned char* enc_out = (unsigned char*)malloc(pkg.header_.paddeddatasize);      // aes-128 bit cbc encryption     aes_cbc_encrypt(pkg.data(), enc_out, pkg.header_.paddeddatasize);      // need copy data temporary buffer objects vector      memcpy(pkg.data(), enc_out, pkg.header_.paddeddatasize);          free(enc_out);      io_service_.post([this, pkg]() { transmit(pkg); }); }

this seems rather expensive task. isn't there better way, kind of let vector take ownership of temporary buffer (did understand correctly these new std::move , rvalue move semantics used kind of stuff?)

move semantics can avoid copy.

however instead of malloc'ing buffer encrypted data, use vector. can use std::move replace contents of packet's data_ member.


Comments

Post a Comment

Popular posts from this blog

ios - Memory not freeing up after popping viewcontroller using ARC -

-
hi project arc based, using uinavigationcontroller make transition between viewcontroller. using profiler analyse happening behind scene memory. noticed when push viewcontroller allocate memory components , when pop not freeing allocated memory. since using arc unable implement dealloc or release component. have analysed in detail , there no memory leak in project. i not using strong property push viewcontroller. here how pushing viewcontroller. viewcontroller *obj = [[viewcontroller alloc] init]; [self.navigationcontroller pushviewcontroller:obj animated:no]; any clue whats going on? should free memory have consumed. please advise your description indicates have retain cycle, leads objects not being deallocated. typical source of retain cycles properties assigned loading nib files (usually declared iboutlet ). two strategies break them , release objects: declare property weak : @property (nonatomic, weak) iboutlet uilabel *statuslabel; set property nil in...
Read more

Django REST Framework perform_create: You cannot call `.save()` after accessing `serializer.data` -

-
i have following viewset: class artistprofileviewset(viewsets.modelviewset): queryset = artistprofile.objects.all() serializer_class = artistprofileserializer def perform_create(self, serializer): if serializer.is_valid(): serializer.save() with following serializers: class simpleartisttrackserializer(serializers.hyperlinkedmodelserializer): class meta: model = artisttrack fields = (...my fields...) class artistprofileserializer(serializers.hyperlinkedmodelserializer): owners = userserializer(many=true, required=false) tracks = simpleartisttrackserializer(many=true, required=false) class meta: model = artistprofile fields = (...my fields...) i getting following error: assertionerror: cannot call `.save()` after accessing `serializer.data`.if need access data before committing database inspect 'serializer.validated_data' instead. i don't see editing serializer.data object. th...
Read more

Why does Go error when trying to marshal this JSON? -

-
i'm trying rather simple example of trying decode json file structs using golang. however, when attempting error that json: cannot unmarshal object go value of type []main.track which don't understand. here's code in question, , json can found here . package main import ( "encoding/json" "fmt" "net/http" "os" ) // tracks group of track types type tracks struct { tracks []track } // track represents singular track type track struct { name string url string artist artist } // artist represents single artist type artist struct { name string mbid string url string } func main() { url := "http://ws.audioscrobbler.com/2.0/?method=geo.gettoptracks&api_key=c1572082105bd40d247836b5c1819623&format=json&country=netherlands" response, err := http.get(url) if err != nil { fmt.printf("%s\n", err) os.exit(1) } de...
Read more