Why can the defined pointer be used as an array?

shijizai

Why can the defined pointer be used as an array? [Copy link]

 

/*Clear screen function--clear the entire screen to the same color*/
void lcd_clear(unsigned int color)
{
unsigned int num;
unsigned int i = 0;
unsigned int *startaddr = (unsigned int*)tftlcd_dev.framebuffer;
num = (unsigned int)tftlcd_dev.width * tftlcd_dev.heigh;
for(i = 0; i < num; i++)
{
startaddr[i] = color;
}

}

This is the program I encountered when learning the Linux development board.

What I don't understand is that the program defines unsigned int *startaddr as a pointer, so why is it used directly as an array when it is used later? startaddr[ i ] is clearly the way to use an array, so how can a pointer and an array be used together? What is this syntax?

shijizai

I think I found the answer myself. This link says https://blog.csdn.net/qq_25814297/article/details/87445481?spm=1001.2101.3001.6650.1&utm_medium=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7Edefault-1-87445481-blog-102632978.pc_relevant_default&depth_1-utm_source=distribute.pc_relevant.none-task-blog-2%7Edefault%7ECTRLIST%7Edefault-1-87445481-blog-102632978.pc_relevant_default&utm_relevant_index=2

jimtien

An array is a continuous storage unit in memory. The pointer points to the head of this memory data block to access data, which is no different from array operations. Be careful when using pointers to avoid crossing the boundary.

freebsder

Equivalent in a certain sense

vincentc543

I have discovered this, it is quite special, and I often use it interchangeably.

azhangxingweia

The array name is the address

damiaa

shijizai published on 2022-5-19 10:41 I seem to have found the answer myself. This link says https://blog.csdn.net/qq_25814297/article/details ...

Data exchange between arrays or memory often uses pointers. C language pointers are very flexible. They can hit whatever you point to. If you point to the wrong place, it will still hit. But that will cause trouble.

lizd

Array names and pointers are essentially memory addresses and are equivalent.

starcat123

Take a look at the disassembled code and you will know what it is doing behind the scenes.

heleijunjie72

The array name is the first address of the data in the memory. The array data is a continuous storage unit in the memory. The pointer can point to the first address of the array.

fjdeepblue

The internal array name of the C compiler is treated as a pointer, that is, the first address.

heleijunjie72

Array names and pointers are related but also different. Array names are constant types, while pointers are variable types. You cannot assign a pointer to an array name.

LitchiCheng

Print the pointer address and you will know. There is also a simple way to verify it, * (ptr + x * sizeof (type)) to see if it is equal to ptr [x]

heleijunjie72

This knowledge is worth further study and I hope to provide information on this topic for further study.

LewisBlake

Because the data stored in the array is continuous in memory, the pointer index group refers to the address of the first element of the array, so adding 1+1 to the pointer can read or write to the array.