zoukankan      html  css  js  c++  java
  • c++ using Handle Class Pattern to accomplish implementation hiding

    Reference material:

    • Thinking In C++ 2nd eidition chapter 5 section "Handle classes"

    If there's something need to be hidden from clients of the class (such as an encryption algorithm, etc), you can use this pattern to hide the detail of your implementation (however, it can not be used on class templetes, see http://www.cnblogs.com/qrlozte/p/4108807.html). This trick is like the one used in C programming language to define a struct pointer of the implementation (See "C Programming: A Modern Approach, Second Edition. Section 19.4").

    As an example, see code snippets 'main.cpp', 'Encryption.h', 'Encryption.cpp'

    main.cpp

     1 #include "Encryption.h"
     2 
     3 typedef Encryption::byte byte;
     4 
     5 byte getByteFromSocket() {
     6     byte b = 0;
     7     // assign 'b' with a byte from the socket..
     8     return b;
     9 }
    10 
    11 void sendEncrpytedByte(const byte& encrpted) {
    12     // send encrypted message...
    13 }
    14 
    15 int main()
    16 {
    17     Encryption obj;
    18     byte encypted = obj.encrypt(getByteFromSocket());
    19     sendEncrpytedByte(encypted);
    20     return 0;
    21 }

    Encryption.h

     1 #ifndef ENCRYPTION_H
     2 #define ENCRYPTION_H
     3 
     4 class EncryptionImpl; // Encryption Implementation
     5 
     6 class Encryption // Handle class
     7 {
     8     public:
     9         typedef unsigned char byte;
    10         Encryption();
    11         byte encrypt(const byte &src);
    12         ~Encryption();
    13 
    14     private:
    15         /*
    16             Implementation (detail) of the algorithm is wrapped
    17             in an incomplete type here, internal data structures
    18             or helper classes or other functions needed to be
    19             protect cannot be seen or used by clients even in
    20             this header
    21         */
    22         EncryptionImpl *impl;
    23 };
    24 
    25 #endif // ENCRYPTION_H

    Encryption.cpp

     1 #include "Encryption.h"
     2 
     3 #include <iostream>
     4 
     5 using namespace std;
     6 
     7 class EncryptionImpl {
     8     public:
     9         /*
    10             Internal data structures:
    11 
    12             Normally, they can be public for ease
    13             of use, because the data structure
    14             is totally under your control.
    15             If you do need encapsulation for
    16             some reason, then use it.
    17         */
    18 };
    19 
    20 class HelperClass1 {
    21     // ...
    22     public:
    23         void dosomething() { cout << "HelperClass1 object is doing something.." << endl; }
    24 };
    25 
    26 
    27 class HelperClass2 {
    28     // ...
    29     public:
    30         void dosomething() { cout << "HelperClass2 object is doing something.." << endl; }
    31 };
    32 
    33 void helperFunction1() {
    34     //...
    35     cout << "helperFunction1 is doing something.." << endl;
    36 }
    37 
    38 void helperFunction2() {
    39     //...
    40     cout << "helperFunction2 is doing something.." << endl;
    41 }
    42 
    43 /**
    44     do any initialization as you need
    45 */
    46 Encryption::Encryption(): impl(new EncryptionImpl())
    47 {
    48     // do any initialization as you need
    49 }
    50 
    51 /**
    52     do any cleanup as you need
    53 */
    54 Encryption::~Encryption()
    55 {
    56     // do any cleanup as you need
    57     if (impl != NULL) delete impl;
    58 }
    59 
    60 Encryption::byte Encryption::encrypt(const byte& src)
    61 {
    62     byte encrypted = src;
    63     // algorithm detail...
    64     HelperClass1 obj1;
    65     HelperClass2 obj2;
    66     obj1.dosomething();
    67     obj2.dosomething();
    68     helperFunction1();
    69     helperFunction2();
    70     // etc...
    71     return encrypted;
    72 }
  • 相关阅读:
    Alpha项目冲刺_博客链接合集
    项目系统设计
    项目需求分析
    项目选题
    项目展示
    原型设计 + 用户规格说明书
    测试与优化
    结对作业1
    MathExam6317
    js入门基础
  • 原文地址:https://www.cnblogs.com/qrlozte/p/4107277.html
Copyright © 2011-2022 走看看