C language of Cocos2d-x Series 2

1. macro definition
<1>. Constant Definition

# Define MATH_PI 3.14 void defineH () {// The macro replaces the constant corresponding to the macro in the compilation phase, so it is very fast; printf ("% f", MATH_PI );}

<2>. method definition

// Define the macro method. The macro method does not have A specific return type. When multiple rows exist, add A backslash; # define MAX (A, B) {\ A> B? A: B \}

Call: MAX (12, 30 );

2. struct
<1>. struct Definition

struct People {    int age;    char *name;};

Usage:

    struct People p;    p.age = 12;    printf("%d", p.age);

<2>. struct pointer

/*** Stdlib needs to be introduced. h */void structpointer () {// declare a People pointer (requires initialization) and allocate a memory address, the size of the memory is the size of the struct People * p = malloc (sizeof (struct People); p-> age = 20; p-> name = "ls "; struct People * p1 = p; p1-> name = "ls1"; printf ("hello struct People % s", p-> name ); // The output result is ls1 // the pointer allocated with malloc needs to be released free (p) after it is not needed );}

3. function pointer

/*** Function pointer */void functionpointer (int I) {printf ("hello functionpointer % d \ n", I );}
Int functionpointer1 () {printf ("hello functionpointer1 \ n"); return 0 ;}
Void functionpointerexe () {void (* p) (int); p = functionpointer; p (34); int (* a) (); a = functionpointer1; ();}

4. typedef keyword
<1>. Define struct

typedef struct {    int age;} P1;

After being defined by typedef, you no longer need to add the struct keyword before declaring P1 struct;

    P1 p;    p.age = 12;    printf("%d", p.age);

<2>. Define the function pointer

typedef int (*Void)();

Void v = functionpointer1; v (); // output functionpointer1

5. Introduce custom header files

Hello. h

// If HELLO_H _ is not defined, HELLO_H _ is defined to prevent repeated header files; # ifndef HELLO_H _ # define HELLO_H_void sayHello (); # endif/* HELLO_H _*/

Hello. c

# Include <stdio. h> // the specific implementation of sayHello in hello. h void sayHello () {printf ("hello c ");}

Main. c

#include "hello.h"int main(int argc, const char * argv[]) {    sayHello();}

6. File Operations

Read:

Void fileRead1 () {FILE * f = fopen ("xx.txt", "r"); fseek (f, 0, SEEK_END); // seek to the end of the FILE: obtain the file size long size = ftell (f); // returns the file size char buf [size + 1]; fseek (f, 0, SEEK_SET ); // return to the file and start fread (buf, sizeof (unsigned char), size, f); buf [size] = '\ 0'; fclose (f ); printf ("% s", buf );}

Write:

Void fileWrite1 () {// f may be null and must be determined! FILE * f = fopen ("xx.txt", "w"); fprintf (f, "hello c"); fclose (f );}

7. Others

<1>. Generate a random number:

    srand((int) time(NULL ));    int randNum = rand();    printf("%d,", randNum);    return 0;

<2>. String operation:

    char buf[100];    memset(buf, 0, 100); //     sprintf(buf, "hello c %d s%f,", 12, 23.2);    printf("%s", buf);

<3>. Input and Output:

Void getput () {char buf [100]; gets (buf); // wait for the user to enter puts (buf);} int scanprint () {int; scanf ("% d", & a); printf ("% d", a); return 0 ;}