memmove

memcpy函数原型 void * memcpy ( void * dest , const void * src , size_t n ) ; man手册描述：memcpy()函数从内存区域src复制n个字节到内存区域dest。内存区域不能重叠。如果内存区域重复使用memmove memcpy实现 void * memcpy ( void * dest , const void * src , size_t n ) { char * dp = dest ; const char * sp = src ; while ( n -- ) * dp ++ = * sp ++ ; return dest ; } memmove函数原型 void * memmove ( void * dest , const void * src , size_t n ) ; man手册描述：memmove()函数将n个字节从内存区域src复制到内存区域dest 首先将字节复制到不重叠的src或dest的临时数组中，然后将这些字节从临时数组复制到dest。 memmove实现 ```handlebars void * memmove ( void * dest , const void * src , size_t n ) { unsigned char tmp [ n ] ; memcpy ( tmp

memcpy和memmove均为内存拷贝函数，原型分别为： void * memcpy ( void *dest, const void *src, size_t n); void *memmove( void *dest, const void *src, size_t n); 当拷贝的内存存在重叠区域时，memcpy可能会发生错误，而memmove不会发生。 下图为重叠情况剖析【绿色代表重叠区域】： 重叠情况（1）： 重叠情况（2）： 两个函数具体实现如下： void * memcpy ( void *dst, const void *src, size_t n) /*将src 的 n 字节拷贝到dst 内存中*/ { char *su1; const char *su2; for (su1 = dst, su2 = src; 0 < n; ++su1, ++su2, --n) { *su1 = *su2; } return dst; } void *memmove( void *dst, const void *src, size_t n) /*将scr 的 n 字节拷贝到dst 内存中*/ { char *sc1; const char *sc2; sc1 = dst; sc2 = src; if (sc2 < sc1 && sc1 < sc2 + n) { for

memcpy与memmove函数异同 memcpy memmove memset memcpy 函数原型 void * memcpy ( void * destination , const void * source , size_t num ) 头文件 < string . h > 作用：从源src所指的内存地址的起始位置开始拷贝num个字节到目标dest所指的内存地址的起始位置中。 注意： （1）memcpy是内存拷贝函数； （2）此函数不考虑类型，以字节为单位进行拷贝； （3）这个函数在遇到’\0’时不会停下来； （4）memcpy与strcpy功能有所重叠，但拷贝字符串一般使用strcpy，因为strcpy以’\0’结尾，更加专业安全。 模拟实现： # include <stdio.h> # include <windows.h> # include <assert.h> void * My_Memcpy ( void * dst , const void * src , int num ) { assert ( dst ) ; assert ( src ) ; char * dst_ = ( char * ) dst ; char * src_ = ( char * ) src ; while ( num ) { * dst_ = * src_ ; * dst_ ++

I have two doubt about use of memmove() : When is preferable use this function instead of use another function (i.e. a created own function)? I’m not sure I have understood properly. The signature of the function is void *memmove(void *dest, const void *src, size_t n) . If I have a simple array arr[N] , how can I put it into the called function? arr[N] or &arr[N]? The difference is if the array is declared with an initial size or like a pointer? I have this doubt because I saw many example where is used both. I hope I explained my doubts in a good way. edit: I have to delete an element from

As pointed out in an answer to this question , the compiler (in this case gcc-4.1.2, yes it's old, no I can't change it) can replace struct assignments with memcpy where it thinks it is appropriate. I'm running some code under valgrind and got a warning about memcpy source/destination overlap. When I look at the code, I see this (paraphrasing): struct outer { struct inner i; // lots of other stuff }; struct inner { int x; // lots of other stuff }; void frob(struct inner* i, struct outer* o) { o->i = *i; } int main() { struct outer o; // assign a bunch of fields in o->i... frob(&o.i, o); return

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: std::uninitialized_copy copies into an uninitialized range of memory. This could be done using memmove for bitwise copyable types. I stepped through below example code in gdb (compiling with gcc 5.2.0). Thereby I observed that memmove isn't used at all. In the example __is_trivial(Bar) is used to determine whether memmove may be used. It (correctly) evaluates to false as Bar has a non-trivial default constructor (cf. call to std::__uninitialized_copy<false>::__uninit_copy(...) in bits/stl_uninitialized.h line 123 ff). But why is __is_trivial

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I got really strange behavior for my x64 multithreading application. The execution time in debug mode is faster than in release mode. I break the problem down and found the issue: The debug modus optimize (!Note optimition is off!) the memcpy to memmove, which peforms faster. The release mode use still memcpy (!note optimition is on). This problem slows down my multithreading app in release mode. :( Anyone any idea? #include <time.h> #include <iostream> #define T_SIZE 1024*1024*2 int main() { clock_t start, end; char data[T_SIZE]; char store

可以将文章内容翻译成中文,广告屏蔽插件可能会导致该功能失效(如失效，请关闭广告屏蔽插件后再试): 问题: I am using the code below: char filename[ 255 ]; strncpy( filename, getenv( "HOME" ), 235 ); strncat( filename, "/.config/stationlist.xml", 255 ); Get this message: (warning) Dangerous usage of strncat - 3rd parameter is the maximum number of characters to append. (error) Dangerous usage of 'filename' (strncpy doesn't always null-terminate it). 回答1: I typically avoid using str*cpy() and str*cat() . You have to contend with boundary conditions, arcane API definitions, and unintended performance consequences. You can use snprintf() instead.