C/C++指针数组

原创

JeaminThk 2022-11-10 14:12:58 博主文章分类：C/C++基本类型的掌握 ©著作权

©著作权归作者所有：来自51CTO博客作者JeaminThk的原创作品，请联系作者获取转载授权，否则将追究法律责任

Demo.cpp文件

#include <iostream>
#include <stdio.h>
#include <iomanip>
#include <ctime>

#include "headFile.h"
#include "Object.h"

using namespace std;

int main(int argc,char *argv[])
{
#ifdef X1 // 
  int i=7,j=8;
  printf("i==%d,&i==%p\n",i,&i);
  cout<<"j=="<<j<<" &j=="<<&j<<endl;
#endif
#ifdef X2 // 
  int i=7,j=8;
  int *ip=&i;
  int *jp=&j;
  cout<<"Address: "<<ip<<" contains: "<<*ip<<endl;
  cout<<"Adderss: "<<jp<<" contains: "<<*jp<<endl;
  *ip=9;
  *jp=10;
  cout<<"Now Address: "<<ip<<" contains: "<<*ip<<endl;
  cout<<"Now Adderss: "<<jp<<" contains: "<<*jp<<endl;

#endif
#ifdef X3 // 
  int i=7;
  int *ip=&i;
  int **ipp=&ip;
  cout<<"Address: "<<ip<<" constains: "<<*ip<<endl;
  cout<<"Address: "<<ipp<<" contains: "<<*ipp<<endl;
  cout<<"***ipp== "<<**ipp<<endl;
#endif
#ifdef X4 // 
  float a[]={1.0,2.0,3.0};
  cout<<"sizeof(float)=="<<sizeof(float)<<endl;
  float *p=&a[0];
  cout<<"p=="<<p<<" *p=="<<*p<<endl;
  ++p;
  cout<<"p=="<<p<<" *p=="<<*p<<endl;
  ptrdiff_t diff=(p+1)-p;
  cout<<"diff=="<<diff<<endl;
  diff=(char*)(p+1)-(char*)p;
  cout<<"diff=="<<diff<<endl;
#endif
#ifdef X5 // 
  int i=7;
  char *cp=(char*)&i;
  cout<<"The integer at "<<&i<<"=="<<i<<endl;
  for(int n=0;n<sizeof(i);++n)
    cout<<"The byte at"<<(void*)(cp+n)<<"=="<<int(*(cp+n))<<endl;
#endif
#ifdef X6 // 
  unsigned short date,year=92,mon=8,day=2;
  date= (year<<9) | (mon<<5) | day;
  cout<<hex<<date<<endl;
#endif
#ifdef X7 // 
  struct Date
  {
    unsigned day:5;
    unsigned mon:4;
    unsigned year:7;
  };
  
  unsigned short date,year=92,mon=8,day=2;
  Date *dp=(Date*)&date;
  dp->mon=mon;
  dp->day=day;
  dp->year=year;
  cout<<hex<<date<<endl;
  cout<<dec<<"year:"<<int(dp->year)<<" ";
  cout<<dec<<"mon:"<<int(dp->mon)<<" ";
  cout<<dec<<"day:"<<int(dp->day)<<endl;
#endif
#ifdef X8 // 
  int i=7,j=8;
  swap(&i,&j);
  cout<<"i=="<<i<<" j=="<<j<<endl;
#endif
#ifdef X9 //
  char source[]="1234";
  char tar[]="********";
  memcpy(tar,source,strlen(source));
  cout<<source<<" "<<" "<<tar<<endl;
#endif
#ifdef X10 // 
  char c='a';
  short i=100;
  long n=10000L;
  double pi=3.141529;// 40 *9 21 D9 F4 D3 7C 13
  char s[]="hello";
  char az[]="abcdefghijklmnopqrstuvwxyz";// 61~7A
  char AZ[]="ABCDEFGHIJKLMNOPQRSTUVWXYZ";// 41~5A
  inspect(&c,sizeof(c));    cout<<endl;
  inspect(&i,sizeof(i));    cout<<endl;
  inspect(&n,sizeof(n));    cout<<endl;
  inspect(&pi,sizeof(pi));  cout<<endl;
  inspect(s,sizeof(s));   cout<<endl;
  inspect(az,sizeof(az));   cout<<endl;
  inspect(AZ,sizeof(AZ));   cout<<endl;
#endif
#ifdef X11 // 
  int a[]={1,2,3,4,5};
  int *p=a;
  cout<<"sizeof(a)=="<<sizeof(a)<<endl;
  cout<<"sizeof(p)=="<<sizeof(p)<<endl;
  cout<<"p=="<<p<<" &a[0]=="<<&a[0]<<endl;
  cout<<"*p=="<<*p<<" a[0]=="<<a[0]<<endl;

  p=a+2;
  cout<<"p=="<<p<<" &a[2]=="<<&a[2]<<endl;
  cout<<"**p=="<<*p<<" a[2]=="<<a[2]<<endl;
#endif
#ifdef X12 // 
  int a[]={1,2,3,4,5};
  size_t n=sizeof(a)/sizeof(a[0]);

  for(int i=0;i<n;++i)
    cout<<a[i]<<' ';
  cout<<endl;

  for(i=0;i<n;++i)
    cout<<i[a]<<' ';
  cout<<endl;

  int* p=a;
  while(p<a+n)
    cout<<*p++<<' ';
  cout<<endl;

  p=a;
  for(i=0;i<n;++i)
    cout<<p[i]<<' ';
  cout<<endl;

  for(i=0;i<n;++i)
    cout<<*(a+i)<<' ';
  cout<<endl;

  p=a+n-1;
  while(p>=a)
    cout<<*p--<<' ';
  cout<<endl;

  p=a+n-1;
  for(i=0;i<n;++i)
    cout<<p[-i]<<' ';
  cout<<endl;
#endif
#ifdef X13 // 匿名数组
  char a[]="hello";
  char *p=a;
  cout<<"a=="<<&a<<" sizeof(a)=="<<sizeof(a)<<endl;
  cout<<"p=="<<(void*)p<<" sizeof(p)=="<<sizeof(p)<<endl;
  cout<<"sizeof\"hello\"=="<<sizeof("hello")<<endl;
  cout<<"address of \"hello\"=="<<(void*)"hello"<<endl;
  cout<<"address of \"hello\"=="<<(void*)"hello"<<endl;
#endif
#ifdef X14 //

  char c[]="0123456789";
  for(int i=0;i<10;i+=2)
    cout<<c[i]<<' ';

  cout<<endl;
  for(i=0;i<10;i+=2)
    cout<<"0123456789"[i]<<' '; // 经典
  cout<<endl;
#endif
#ifdef X15 // 
  int a[]={10,15,4,1,3,-4};
  int *p=&a[2];
  int *q=&a[2];
  cout<<*(p+1)<<endl;
  cout<<p[-1]<<endl;
  cout<<p-a<<endl;
  cout<<a[*p++]<<endl; // *p++ = 4 = a[2]
  cout<<a[*++q]<<endl; // *++q = 1 = a[3]
  cout<<*(a+a[2])<<endl;
#endif
#ifdef X16 // 
  int a[]={0,1,2,3,4};
  size_t n=sizeof(a)/sizeof(a[0]);
  cout<<"a=="<<a<<endl;
  cout<<"sizeof(a)=="<<sizeof(a)<<endl;
  func(a,n);
  for(int i=0;i<n;++i)
    cout<<a[i]<<' ';
  cout<<endl;
#endif
#ifdef X17 // Lincoln实验室 Chet Small 提供的这个聪明的例子
  char s[]="desolate",*p=s;
  cout<<*p++<<endl;
  cout<<*(p++)<<endl;
  cout<<(*p)++<<endl;
  cout<<*++p<<endl;
  cout<<++*p<<endl;
  cout<<++(*p)<<endl;
  //  StrCmp(s,?)==0     ?中 应该是什么 才能满足此表达式
#endif
#ifdef X18 // 指向字符串的指针数组 有个别名叫 “粗糙数组” 
  char* strings[]={"now","is","the","time"};
  size_t n=sizeof(strings)/sizeof(strings[0]);
  for(int i=0;i<n;++i)
    cout<<"string"<<i<<"==\""<<strings[i]
      <<"\"\tsize=="<<sizeof(strings[i])
      <<"\tlength=="<<strlen(strings[i])<<endl;
#endif
#ifdef X19 // 
  char strings[][5]={"now","is","the","time"};
  size_t n=sizeof(strings)/sizeof(strings[0]);
  for(int i=0;i<n;++i)
    cout<<"strings["<<i<<"]==\""<<strings[i]
    <<"\"\tsize=="<<sizeof(strings[i])
      <<"\tlength=="<<strlen(strings[i])<<endl;
#endif
#ifdef X20 // 
  int a[][4]={{0,1,2,3},{4,5,6,7},{8,9,0,1}};
  int (*p)[4]=a;
  size_t nrows=sizeof(a)/sizeof(a[0]);
  size_t ncols=sizeof(a[0])/sizeof(a[0][0]);
  cout<<"sizeof(*p)=="<<sizeof(*p)<<endl;
  for(int i=0;i<nrows;++i)
  {
    for(int j=0;j<ncols;++j)
      cout<<p[i][j]<<' ';
    cout<<endl;
  }
#endif
#ifdef X21 // 
  int a[][3][4]= {
            {
              {0,1,2,3},{4,5,6,7},{8,9,0,1}
            },
            {
              {2,3,4,5},{6,7,8,9},{0,1,2,3}
            }
          };
  int (*p)[3][4]=a;
  size_t ntables=sizeof(a)/sizeof(a[0]);
  size_t nrows=sizeof(a[0])/sizeof(a[0][0]);
  size_t ncols=sizeof(a[0][0])/sizeof(a[0][0][0]);
  cout<<"sizeof(*p)=="<<sizeof(*p)<<endl;
  cout<<"sizeof(a[0][0])=="<<sizeof(a[0][0])<<endl;
  for(int i=0;i<ntables;++i)
  {
    for(int j=0;j<nrows;++j)
    {
      for(int k=0;k<ncols;++k)
        cout<<p[i][j][k]<<' ';
      cout<<endl;
    }
    cout<<endl;
  }
#endif
#ifdef X22 // 
  int (*pFunc)(const char *, ...)=printf;
  pFunc("函数指针的应用\n");
#endif
#ifdef X23 // 
  qsort(argv+1,argc-1,sizeof(argv[0]),comp);
  while(--argc)
    cout<<*++argv<<endl;
#endif
#ifdef X24 //
  if(argc>=2&&argc<=4)
    for(int i=0;i<argc;i++)
      cout<<argv[i]<<endl;
    else 
      cout<<"输入有误"<<endl;

#endif
#ifdef X25 // 
  int i;
  for (i=0; i < argc; i++)
        printf("Argument %d is %s.\n", i, argv[i]);
#endif
#ifdef X26 // 
  extern void retrieve(void);
  extern void insert(void);
  extern void update(void);
  extern int show_menu(int c);
  
  void (*farray[])(void)={retrieve,insert,update}; // 数组元素是函数名字
  for(int choice=0;choice<show_menu(5);++choice)
  {
    farray[choice%3](); // choice%3 的可能值为 0、1、2 正好可以把farray数组下标覆盖全
  }
#endif
#ifdef X27 // 
  class C
  {
  public:
    void f(){ cout<<"C::f()\n";}
    void g(){ cout<<"C::g()\n";}
  };
  
  C cobject1;
  void (C::*pCF1)()=&C::f;// 未声明直接使用
  (cobject1.*pCF1)();
  pCF1=&C::g;
  (cobject1.*pCF1)();

  cout<<"上下两种风格的类成员函数指针"<<endl;// 上下两种风格

  void (C::*pCF2)();// 声明类的成员函数指针
  C cobject2;
  pCF2=&C::f;
  (cobject2.*pCF2)();
  pCF2=&C::g;
  (cobject2.*pCF2)();
#endif
#ifdef X28 // 
  int show_menu(int);
  srand((int)time(NULL));
  Object O;
  for(;;)
  {
    int choice=show_menu(rand()%100);
    if(0<=choice && choice <3)
      O.process(choice-1);
    else if(choice==4)
      break;
    else
      cout<<"No numbers contains"<<endl;
  }
#endif
#ifdef X29 // 
#endif
#ifdef X3 // 
#endif


  return 0;
}

headFile.h

#ifndef HEADFILE_H
#define HEADFILE_H
#include <iostream>
#include <cstdio>
#include <iomanip>
using namespace std;
#define X28

void swap(int* xp,int* yp);
void* memcpy(void* target,const void* source,size_t n);
void inspect(const void* ptr,size_t nbytes);
void func(int b[],size_t n);
int comp(const void* p1,const void* p2);



#endif

headFile.cpp

#include "headFile.h"


void swap(int* xp,int* yp)
{
  int temp=*xp;
  *xp=*yp;
  *yp=temp;
}

void* memcpy(void* target,const void* source,size_t n)
{
  char * targetp=(char*)target;
  const char* sourcep=(const char*)source;
  while(n--)
    *targetp++=*sourcep++;
  return target;
}

void inspect(const void* ptr,size_t nbytes)
{
  const unsigned char* p=(const unsigned char*)ptr;// 强制转换为const 类型的变量（只为读取不为改写）
  cout.setf(ios::hex,ios::basefield);
  for(int i=0;i<nbytes;++i)
    cout<<"byte"<<setw(2)<<setfill(' ')<<i<<":  "<<setw(2)<<setfill('*')<<int(p[i])<<endl;
}

void func(int b[],size_t n)
{
  cout<<"\n *** Entering function func() *** \n";
  cout<<"b=="<<b<<endl;
  cout<<"sizeof(b)=="<<sizeof(b)<<endl;
  for(int i=0;i<n;++i)
    cout<<b[i]<<' ';
  b[2]=99;
  cout<<"\n *** Leaveing function() ***\n\n";
}

int comp(const void* p1,const void* p2)
{
  const char *ps1=*(const char**)p1;
  const char *ps2=*(char**)p2;
  return strcmp(ps1,ps2);
}

void retrieve(void) { printf("1 retrieve\n"); }
void insert(void) { printf("2 insert\n");   }
void update(void) { printf("3 update\n");   }
int show_menu(int c){int i=c; return i;}

Object.h

#ifndef OBJECT_H
#define OBJECT_H
class Object
{
public:
  void retrieve(void) { printf(" Object::retrieve\n");  }
  void insert(void) { printf(" Object::insert\n");  }
  void update(void) { printf(" Object::update\n");  }
  void process(int choice);
private:
  typedef void (Object::*Omf)();
  static Omf farray[3];
};

Object::Omf Object::farray[3]=  { &Object::retrieve,
                  &Object::insert,
                  &Object::update
                };

void Object::process(int choice)
{
  if(0<= choice && choice <=2)
    (this->*farray[choice])();
}
#endif