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std::memmove(3) C++ Standard Libary std::memmove(3) NAME std::memmove - std::memmove Synopsis Defined in header <cstring> void* memmove( void* dest, const void* src, std::size_t count ); Copies count characters from the object pointed to by src to the ob- ject pointed to by dest. Both objects are reinterpreted as arrays of unsigned char. The objects may overlap: copying takes place as if the characters were copied to a temporary character array and then the characters were copied from the array to dest. If either dest or src is an invalid or null pointer, the behavior is undefined, even if count is zero. If the objects are potentially-overlapping or not TriviallyCopyable, the behavior of memmove is not specified and may be undefined. Parameters dest - pointer to the memory location to copy to src - pointer to the memory location to copy from count - number of bytes to copy Return value dest Notes std::memmove may be used to implicitly create objects in the desti- nation buffer. Despite being specified "as if" a temporary buffer is used, actual implementations of this function do not incur the overhead of double copying or ex- tra memory. For small count, it may load up and write out registers; for larger blocks, a common approach (glibc and bsd libc) is to copy bytes forwards from the be- ginning of the buffer if the destination starts before the source, and backwards from the end otherwise, with a fall back to std::memcpy when there is no overlap at all. Where strict aliasing prohibits examining the same memory as values of two different types, std::memmove may be used to convert the values. Example // Run this code #include <iostream> #include <cstring> int main() { char str[] = "1234567890"; std::cout << str << '\n'; std::memmove(str + 4, str + 3, 3); // copies from [4, 5, 6] to [5, 6, 7] std::cout << str << '\n'; } Output: 1234567890 1234456890 See also memcpy copies one buffer to another (function) memset fills a buffer with a character (function) copies a certain amount of wide characters be- tween two, wmemmove possibly overlapping, arrays (function) copy copies a range of elements to a new location copy_if (function template) (C++11) copy_backward copies a range of elements in backwards order (function template) is_trivially_copyable checks if a type is trivially copyable (C++11) (class template) http://cppreference.com 2022.07.31 std::memmove(3)
NAME | Synopsis | Parameters | Return value | Notes | Example | Output: | See also
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