How to use the memcpy function

The memcpy function is one of the most commonly used functions in C language. It is used to copy the contents of one memory block to another memory block. In this article, we will introduce the use of memcpy function in detail.

First, let us take a look at the function prototype of the memcpy function:

void *memcpy(void *dest, const void *src, size_t n);

Among them, `dest` is the pointer of the target memory block, `src` is the pointer of the source memory block, `n ` is the number of bytes to copy.

The following are some notes on the use of the memcpy function:

1. The target memory block and the source memory block cannot overlap. If the target memory block overlaps the source memory block, the result of the copy will be undefined.

2. The destination memory block must have enough space to store the contents of the source memory block. Otherwise, a memory overflow error will occur.

3. If the length of the source memory block is less than the number of bytes to be copied, the result of the copy will be undefined. Therefore, before using the memcpy function, you should ensure that the source memory block is of sufficient length.

The following is a sample code that demonstrates how to use the memcpy function:

#include
#include
int main() {
char src[] = "Hello, World!";
char dest[20];
// 复制src到dest
memcpy(dest, src, strlen(src) + 1);
printf("复制后的字符串：%s\n", dest);
return 0;
}

In the above example, we first define a source memory block `src` and initialize it to a string" Hello, World!". Then, we define a target memory block `dest` with a length of 20 bytes. Next, we use the memcpy function to copy the contents of the source memory block `src` to the target memory block `dest`. Finally, we print out the copied string.

It should be noted that when we call the memcpy function, we replace `strlen(src) 1` as the number of bytes to copy. This is because in C language, the string ends with a null character ('\0'), so we need to copy the null character together into the target memory block.

To summarize, the memcpy function is a very useful function in C language, which can copy the contents of one memory block to another memory block. When using the memcpy function, we need to note that the target memory block and the source memory block cannot overlap. The target memory block must have enough space to store the contents of the source memory block, and ensure that the source memory block is of sufficient length. I hope this article will help you understand how to use the memcpy function. .

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