"Thinkinginc++" 38, select overload or Default parameter

Header file

/*** book: "thinkinginc++" * Function: Select overload or Default parameter, header file * Time: September 6, 2014 14:54:28* Author: cutter_point*/#ifndef  mem_h_included# Define  mem_h_includedtypedef unsigned char byte;class mem{    byte* MEM;    int size;    void ensureminsize (int minSize);    member functions to increase the size of the memory block public:    Mem ();    Mem (int sz);    The second constructor ensures that the Mem object has a SZ-sized storage area of    ~mem ();         destructor frees space    int msize ();    Tells us how many bytes are still in the current Mem object    byte* pointer ();    byte* pointer (int minSize); Point A pointer to a piece of memory. The memory is at least minsize large}; #endif//mem_h_included

Definition file

/*** book: "thinkinginc++" * Function: Select overload or Default parameter, declare file * Time: September 6, 2014 14:54:58* Author: cutter_point*/#include "Mem.h" #include <    Cstring>using namespace Std;/*class mem{byte* Mem;    int size;    void ensureminsize (int minSize);    member functions to increase the size of the memory block Public:mem ();    Mem (int sz);         The second constructor ensures that the Mem object has a SZ-sized storage area of ~mem ();    destructor Frees space int msize ();    Tells us how many bytes are still in the current Mem object byte* pointer (); byte* pointer (int minSize); Point A pointer to a piece of memory.    The memory has at least minSize large};*///void ensureminsize (int minSize);  The member function to increase the size of the memory block void mem::ensureminsize (int minSize) {if (Size < minSize)//determines that only the smallest size given will be re-applied for space {byte*     Newmem=new Byte[minsize]; Apply for a new space/* Today to do a problem card in the use of memset function, originally thought int a[100];        Memset (A, max,sizeof (a));    is to assign all the array A to max, and now we know that his fill is in bytes and is typically used to assign values to the initial value of a character variable.        *///starting from newmem+size, altogether minsize-size all resets to 0 memset (newmem+size, 0, minsize-size);        MEMCPY provides replication of general memory.        That is, memcpy has no limitations on what needs to be replicated and is therefore more widely used. memcpy (Newmem, mem, size);        The contents of the mem are copied to Newmem, and the length is size//Reclaim space memory Delete []mem; Mem=newmem;   The new address is assigned to the object size=minsize; The new size gives the object}}//mem ();    Mem::mem () {mem=0; size=0;}    Mem (int sz);    The second constructor ensures that the Mem object has a SZ-sized storage area of mem::mem (int sz) {mem=0;    size=0;  Ensureminsize (SZ);         The initial space is set to SZ length}//~mem (); destructor frees Space Mem::~mem () {delete []mem;}    int msize (); Tells us how many bytes in the current Mem object are still int mem::msize () {return size;}  byte* pointer (); Point A pointer to a piece of memory. The memory has at least minsize large byte* Mem::p ointer () {return Mem;}    byte* pointer (int minSize); byte* Mem::p ointer (int minSize) {ensureminsize (minSize); return mem;}

Test the main function

/*** book: "thinkinginc++" * Function: Select the overload or default parameter, test the file, create a string class * as a tool for other classes to simplify their memory management (for example, it can also hide the more complex memory management details provided by the operating system *) *    Date: September 6, 2014 14:55:32* Author: cutter_point*//*class mem{byte* Mem;    int size;    void ensureminsize (int minSize);    member functions to increase the size of the memory block Public:mem ();    Mem (int sz);         The second constructor ensures that the Mem object has a SZ-sized storage area of ~mem ();    destructor Frees space int msize ();    Tells us how many bytes are still in the current Mem object byte* pointer (); byte* pointer (int minSize); Point A pointer to a piece of memory. This memory has at least minsize large};*/#include "Mem.cpp" #include <cstring> #include <iostream>using namespace Std;class   mystring{mem* buf;    Simplifies memory management public:mystring ();    MyString (char* str);    Heavy-duty ~mystring ();    Link two string void concat (char* str); void print (ostream& os);};/ /mystring (); Mystring::mystring () {buf=0;}    MyString (char* str);    Overloaded mystring::mystring (char* str)//with STR constructs a string type {buf=new Mem (strlen (str) +1);//Create a memory space for STR//construct a string type with str strcpy ((char*) buf->pointer (), str); Copy the past}//~mystring (); MyString::~mystring () {delete buf;//Reclaim Space memory}//link two string//void concat (char* str); void Mystring::concat (char* str) {if (    !BUF)//If the memory of BUF (pointer to Mem) is 0, create a memory space for him buf=new Mem; The transverse link string, pointer returns a pointer to a memory block with at least Buf->mszie () +strlen (str) +1 strcat ((char*) Buf->pointer (buf->msize () + strlen (str) +1), str);} void print (ostream& os), void MyString::p rint (ostream& os) {if (!BUF) return;//when buf=0, direct end os<   <buf->pointer () <<endl;    Not 0, then the output content}int main () {MyString s ("My test string");    S.print (cout);    S.concat ("This is Cutter_point");    S.print (cout);    MyString S2;    S2.concat ("Use default construct by Cutter_point");    S2.print (cout); return 0;}

"Thinkinginc++" 38, select overload or Default parameter