C Foundation--the use of function pointers

Before looking at the code, look at the use of function pointers, broadly divided into the following categories:

• A function list, called by the pointer Index, makes functions with similar functions look clearer;
• A function pointer is used as a callback for another function's argument;
• Linux is often used to achieve the same interface, the implementation of different, such as:

1 structPlatform_driver {2     int(*probe) (structPlatform_device *);3     int(*remove) (structPlatform_device *);4     void(*shutdown) (structPlatform_device *);5     int(*suspend) (structPlatform_device *, pm_message_t state);6     int(*resume) (structPlatform_device *);7     structDevice_driver driver;8     Const structPLATFORM_DEVICE_ID *id_table;9     BOOLPrevent_deferred_probe;Ten};

The implementation can be the serial port of the Freescale IMX series chip:

1 Static structPlatform_driver Serial_imx_driver = {2. Probe =Serial_imx_probe,3. remove =__devexit_p (serial_imx_remove),4 5. Suspend =Serial_imx_suspend,6. Resume =Serial_imx_resume,7. id_table =Imx_uart_devtype,8. Driver = {9. Name ="Imx-uart",Ten. Owner =This_module, One. of_match_table =Imx_uart_dt_ids, A     }, -};

Here is an excerpt from a blog:

Transferred from: http://blog.sina.com.cn/s/blog_4d48cc5d0100xnh9.html

Use:

Function pointers are often used to implement callbacks, or they can be used to optimize a module invocation in the form of a function table.

How to use:

1. Define function pointer type

more intuitive and easy to use with typedef

1 // A function pointer that defines a prototype as an int fun (int a); 2 int int Apara);

The function of a typedef is to define a new type. This defines a type of Ptrfun and defines the type as a pointer to a function that takes an int as a parameter and returns a char type. You can use the ptrfun in the same way as with Int,char .

2. Definition of function pointer variable

1 // Pfun is a function pointer variable name 2 int int // pFun2 is also a function pointer variable name

3. Function pointers are passed as parameters of functions

1 //Defining callback Functions2 intCallBack (inta)3 {4     return++A;5 }6 7 //defining a callback function8 voidCaller (Ptrfun CB)//void Caller (int (*CB) (int))//It can also be stated that9 {Ten     intNpara =1;  One     intNret =CB (Npara); A } -  -  the //using callbacks - voidMain () - { -Caller (CallBack);//using callback functions directly +Ptrfun cb = CallBack;//Int (*CB) (int); cb = CallBack; -     intNRet1 = CB ( About);//NRet1 = +; +}

4, pointer to function pointer use

1 //pointers for defining function pointers2typedefint(**ptrptrfun) (intApara);3 4 //pointer to function pointer as parameter5 //void Ptrcaller (ptrfun* cb)//Pointer Declaration6 //void Ptrcaller (int (**CB) (int))//Prototype Declaration7 voidPtrcaller (ptrptrfun CB)8 {9     intNret = (*CB) (999);//nret = +;Ten } One  A //using pointers to function pointers - voidMain () - { thePtrfun cb =CallBack; -Ptrcaller (&CB); -}

5. Use of array of function pointers

1 //definition of an array of function pointers2Ptrfun farray[Ten]3 //Int (*farray[10]) (int);//prototype Definition4  for(inti =0; I <Ten; i++ )5 {6Farray[i] =CallBack;7     intNret = Farray[i] (i);//nret = i+1;8}

6. The size of the function pointer

Since it's called a pointer, it's the same size as a normal pointer in a 4 -bit system.

1 int sizeof // nSz1 = 4; 2 int sizeof // nSz2 = 4;

Usage examples:

Here is a simple example of using a function pointer:

1 //------------------------------------------------------2#include <stdio.h>3 4typedefint(*ptrfun) (intApara,intBpara);5 6 intFunc1 (intPaintPb);7 intFunc2 (intPaintPb);8 intFUNC3 (intPaintPb);9 intFunc4 (intPaintPb);Ten  One voidMain () A { -     inti =0; -     intj =0; thePtrfun pfuncarray[4] ={func1, Func2, func3, func4}; - Ptrfun PFunc; -  -      for(i =3; I >=0; I--) +     { -PFunc =Pfuncarray[i]; +printf"Output is:%d \ n", (*PFunc) (I,i)); A     } at } -  - intFunc1 (intPaintPb) - { -printf"func1 with input para%d,%d \ n", Pa, Pb); -     returnPa +Pb; in } -  to intFunc2 (intPaintPb) + { -printf"FUNC2 with input para%d,%d \ n", Pa, Pb); the     returnPa-Pb; * } $ Panax Notoginseng intFUNC3 (intPaintPb) - { theprintf"func3 with input para%d,%d \ n", Pa, Pb); +     returnPa *Pb; A } the  + intFunc4 (intPaintPb) - { $printf"FUNC4 with input para%d,%d \ n", Pa, Pb); $     return(Pb = =0)?0xFFFF: (Pa/Pb); -}

The output is:

1Func4 with input para3,32Output is:13 4FUNC3 with input para2,25Output is:46 7Func2 with input para1,18Output is:09 TenFunc1 with input para0,0 OneOutput is:0

C Foundation--the use of function pointers