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  1. /** Oliveri Dario's article code for
  2.     gameprog.it
  3. */
  4. #include <iostream>
  5. #include <exception>
  6.  
  7. #define IMAGE_MOVE_SEMANTICS 1
  8.  
  9. class MismatchingSize: public std::exception{
  10. public:
  11.  
  12. };
  13.  
  14. class Image{
  15.  
  16.     unsigned char * buffer = nullptr;
  17.     std::size_t     size = 0;
  18.  
  19.     void copyFrom( const Image & o){
  20.         for( std::size_t i = 0; i<size; i++)
  21.             buffer[i] = o.buffer[i];
  22.         std::cout<<"Copia eseguita"<<std::endl;
  23.     }
  24.  
  25.     void realloc(std::size_t s){
  26.         if(buffer)
  27.             delete buffer;
  28.  
  29.         if(s>0){
  30.             buffer = new unsigned char[s];
  31.             std::cout<<"Allocazione eseguita"<<std::endl;
  32.         }
  33.     }
  34.  
  35. public:
  36.  
  37.     Image(){  }
  38.  
  39.     Image( std::size_t s):size(s) {
  40.         realloc(s); // allocazione
  41.     }
  42.  
  43. #ifdef IMAGE_MOVE_SEMANTICS
  44.     Image( Image &&o){
  45.         std::cout<<"Move Constructor chiamato!"<<std::endl;
  46.         buffer = o.buffer; //copio i dati da "o"
  47.         size = o.size;
  48.  
  49.         o.buffer = nullptr; //resetto "o"
  50.         o.size = 0;
  51.     }
  52.  
  53.     Image& operator = ( Image &&o){
  54.         std::cout<<"Move Assignment chiamato!"<<std::endl;
  55.         buffer = o.buffer; //copio i dati da "o"
  56.         size = o.size;
  57.  
  58.         o.buffer = nullptr;  //resetto "o"
  59.         o.size = 0;
  60.         return (*this);
  61.     }
  62. #endif
  63.     Image( const Image &o): Image(o.size){ // allocazione
  64.         copyFrom(o);
  65.     }
  66.  
  67.     Image& operator = ( const Image &o){
  68.         size = o.size;
  69.         realloc(size);
  70.         copyFrom(o);
  71.         return (*this);
  72.     }
  73.  
  74.     bool drawAColor( std::size_t s, unsigned char color ){
  75.         size = s;
  76.         realloc(s);
  77.         for( std::size_t i = 0; i<s; i++)
  78.             buffer[i] = color;
  79.  
  80.         return true;
  81.     }
  82.  
  83.     friend Image operator+( const Image &A, const Image &B){
  84.         if(A.size!=B.size)
  85.             throw MismatchingSize();
  86.  
  87.         Image image(A.size);
  88.         for( std::size_t i = 0; i<A.size; i++)
  89.             image.buffer[i] = A.buffer[i]+B.buffer[i];
  90.  
  91.         std::cout<<"Somma eseguita"<<std::endl;
  92.  
  93.         return image;
  94.     }
  95.  
  96.     void print() const{
  97.         for( std::size_t i = 0; i<size; i++)
  98.             std::cout<<(int)buffer[i]<<" ";
  99.         std::cout<<std::endl;
  100.     }
  101. };
  102.  
  103. void test1(){
  104.     std::cout<<"Test 1:"<<std::endl;
  105.     Image a,b;
  106.     a.drawAColor(5,10);
  107.     b.drawAColor(5,17);
  108.  
  109.     Image c;
  110.     c = a+b; //scrittura apparentemente innocua e "leggera"
  111.  
  112.     std::cout<<"\nImmagine a:"<<std::endl;
  113.     a.print();
  114.     std::cout<<"Immagine b:"<<std::endl;
  115.     b.print();
  116.     std::cout<<"Immagine c:"<<std::endl;
  117.     c.print();
  118. }
  119.  
  120. void test2(){
  121.     std::cout<<"\n\nTest 2:"<<std::endl;
  122.     Image a,b;
  123.     a.drawAColor(5,10);
  124.     b.drawAColor(5,17);
  125.  
  126.     Image c;
  127.     c = (a+b)+(a+b); //scrittura apparentemente innocua e "leggera"
  128.  
  129.     std::cout<<"\nImmagine a:"<<std::endl;
  130.     a.print();
  131.     std::cout<<"Immagine b:"<<std::endl;
  132.     b.print();
  133.     std::cout<<"Immagine c:"<<std::endl;
  134.     c.print();
  135. }
  136.  
  137. int main(){
  138.     test1();
  139.     test2();
  140.     return 0;
  141. }
Success #stdin #stdout 0s 3476KB
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stdin
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Standard input is empty
stdout
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Test 1:
Allocazione eseguita
Allocazione eseguita
Allocazione eseguita
Somma eseguita
Move Assignment chiamato!

Immagine a:
10 10 10 10 10 
Immagine b:
17 17 17 17 17 
Immagine c:
27 27 27 27 27 


Test 2:
Allocazione eseguita
Allocazione eseguita
Allocazione eseguita
Somma eseguita
Allocazione eseguita
Somma eseguita
Allocazione eseguita
Somma eseguita
Move Assignment chiamato!

Immagine a:
10 10 10 10 10 
Immagine b:
17 17 17 17 17 
Immagine c:
54 54 54 54 54
https://ideone.com/iJJowB
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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