std::memcpy
STD：：Memcpy
| Defined in header | | |
|---|---|---|
| void* memcpy( void* dest, const void* src, std::size_t count | | |
复制件count指向的对象的字节。src指向的对象dest两个对象都被重新解释为unsigned char...
如果对象重叠，则行为未定义。
如果dest或src为空指针，则行为未定义，即使count是零。
如果对象不是TriviallyCopyable的行为memcpy未指定，并且可能没有定义...
参数
| dest | - | pointer to the memory location to copy to |
|---|---|---|
| src | - | pointer to the memory location to copy from |
| count | - | number of bytes to copy |
返回值
dest...
注记
std::memcpy是内存到内存复制最快的库例程。它通常比std::strcpy，它必须扫描它复制的数据，或者std::memmove，它必须采取预防措施来处理重叠的输入。
几个C++编译器将适当的内存复制循环转换为std::memcpy打电话。
何地严格混叠禁止检查作为两种不同类型的值的相同内存，std::memcpy可用于转换值。
例
二次
#include <iostream>
#include <cstdint>
#include <cstring>
int main()
{
// simple usage
char source[] = "once upon a midnight dreary...", dest[4];
std::memcpy(dest, source, sizeof dest
for (char c : dest)
std::cout << c << '\n';
// reinterpreting
double d = 0.1;
// std::int64_t n = *reinterpret_cast<std::int64_t*>(&d // aliasing violation
std::int64_t n;
std::memcpy(&n, &d, sizeof d // OK
std::cout << std::hexfloat << d << " is " << std::hex << n
<< " as an std::int64_t\n";
}
二次
产出：
二次
o
n
c
e
0x1.999999999999ap-4 is 3fb999999999999a as an std::int64_t
二次
另见
| memmove | moves one buffer to another (function) |
|---|---|
| memset | fills a buffer with a character (function) |
| wmemcpy | copies a certain amount of wide characters between two non-overlapping arrays (function) |
| copycopy_if (C++11) | copies a range of elements to a new location (function template) |
| copy_backward | copies a range of elements in backwards order (function template) |
| is_trivially_copyable (C++11) | checks if a type is trivially copyable (class template) |
C.Memcpy文档
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