١٢ - سلسلة تعلم سي بلس بلس: Unions

ahmedeldeep · 2 يوليو 2022، 10:11م

يحتوي الفيديو على شرح للقاط الاتية

00:00 - Intro
00:07 - Unions
02:03 - Wasting Memory
04:36 - Using Unions
06:10 - Misusing Unions
10:54 - Outro

تحميل ملف العرض
12 Unions.pdf (393.6% u)

الأمثلة

ahmedeldeep/cpp-course/blob/master/05-user-types/06-without-unions.cc


// Better handling of arrays with structures
// From: The C++ Programming Language (4th Edition), Bjarne Stroustrup

#include <iostream>

enum Type { str, num };
struct Entry {
  char const* name;
  Type t;
  char const* s;  // use s if t==str
  int i;          // use i if t==num
};

void print_entry(Entry& p) {
  std::cout << p.name << " = ";

  if (p.t == str) {
    std::cout << p.s << "\n";
  } else {

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github.com

ahmedeldeep/cpp-course/blob/master/05-user-types/07-with-unions.cc


// Better handling of arrays with structures
// From: The C++ Programming Language (4th Edition), Bjarne Stroustrup

#include <iostream>

union Status {
  unsigned int reg;
  struct {
    unsigned int TXE : 1;   // Transmit data register empty
    unsigned int TC : 1;    // Transmission complete
    unsigned int RXNE : 1;  // Read data register not empty
    unsigned int ERR : 3;   // Error
    unsigned int : 26;      // Reserved
  } bitfields;
};

enum Type { str, num };
struct Entry {
  char const* name;

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github.com

ahmedeldeep/cpp-course/blob/master/05-user-types/08-misusing-unions.cc


// Better handling of arrays with structures
// From: The C++ Programming Language (4th Edition), Bjarne Stroustrup

#include <iostream>

union dirty_stuff {
  long int i;
  long int* p;
};

int main() {
  long int x{0x10};

  dirty_stuff bad{.p = &x};
  std::cout << "bad.i = " << std::hex << bad.i << std::endl;

  dirty_stuff dangerous{.i = bad.i};
  std::cout << "*dangerous.p = " << *dangerous.p << std::endl;

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