1. memcpy and memmove
1、memcpy
Function: Copy num bytes of data backward from the location of source to the memory location of destination.
Notice:
- The memcpy() function will not stop when it encounters '\0' (the strcpy string copy function will stop when it encounters '\0');
- The content pointed to by destination and source cannot overlap, otherwise the desired result cannot be obtained.
void* memcpy(void* destination,const void* source,size_t num);
2、memmove
2、memmove
Function: Copy num bytes of data backward from the position of source and move it to the memory location of destination.
Note: The difference from the memcpy() function is that the original memory block and the target memory block processed by the memmove() function can overlap.
void* memmove(void* destination,const void* source,size_t num);
3. The difference between memove and memcpy and the problem of overlapping memory
memmove is an upgraded version of memcpy , memmove is more secure.
For details, see: [C Language] Talking about the difference between memcpy and memmove_DanteIoVeYou's Blog-CSDN Blog
Two, memcmp
Function: Used to compare the contents of two memory areas.
int memcmp(const void * Buf1,const void * Buf2,size_t Size);
buf1: Pointer to the first memory area.
buf2: pointer to the second memory area.
size: The number of bytes to compare.
- If the return value < 0, it means that str1 is smaller than str2.
- If the return value > 0, it means that str1 is greater than str2.
- If the return value = 0, it means that str1 is equal to str2.
3. memset
Function: memory assignment function, used to assign a certain memory space; included in the < string.h > header file.
Detailed explanation : Set the value of the first n bytes of the allocated memory space s to the value c.
Note : This function assigns values to arrays or structures byte by byte.
void *memset(void *s, int v, size_t n)；
s is the name of the array, or a pointer to an internal space;
v is the value to be filled;
n is the number of bytes to be filled;
If it is a character type array, memset can be used casually, but for an int type array, it is generally only used to clear 0 or fill -1, if it is filled with other data, an error will occur.
4. Reference content
[C language] Talking about the difference between memcpy and memmove_DanteIoVeYou's Blog-CSDN Blog
C language memcpy, memmove, memcmp, memset functions_sheygshsi's Blog-CSDN Blog
Introduction to C/C++---memset, memcpy, memcmp functions_c/c++ memcpy with different array sizes