一些小型的函数

strcpy()

strncpy()

strcmp()

strlen()

atoi()

itoa()

memset()

memset

<cstring>

void * memset ( void * ptr, int value, size_t num );

Fill block of memory

Sets the first  num bytes of the block of memory pointed by  ptr to the specified  value (interpreted as an  unsigned char).

Parameters

ptr

Pointer to the block of memory to fill.

value

Value to be set. The value is passed as an  int, but the function fills the block of memory using the  unsigned char conversion of this  value.

num

Number of bytes to be set to the value.

Return Value

ptr is returned.

Example

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/* memset example */ #include <stdio.h> #include <string.h> int main () { char str[] = "almost every programmer should know memset!"; memset (str,'-',6); puts (str); return 0; }

Output:

------ every programmer should know memset!

memcpy()

memcpy

<cstring>

void * memcpy ( void * destination, const void * source, size_t num );

Copy block of memory

Copies the values of  num bytes from the location pointed by  source directly to the memory block pointed by destination.

The underlying type of the objects pointed by both the  source and  destination pointers are irrelevant for this function; The result is a binary copy of the data.

The function does not check for any terminating null character in  source - it always copies exactly  num bytes.

To avoid overflows, the size of the arrays pointed by both the  destination and  source parameters, shall be at least num bytes, and should not overlap (for overlapping memory blocks,  memmove is a safer approach).

Parameters

destination

Pointer to the destination array where the content is to be copied, type-casted to a pointer of type  void*.

source

Pointer to the source of data to be copied, type-casted to a pointer of type  void*.

num

Number of bytes to copy.

Return Value

destination is returned.

Example

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/* memcpy example */ #include <stdio.h> #include <string.h> int main () { char str1[]="Sample string"; char str2[40]; char str3[40]; memcpy (str2,str1,strlen(str1)+1); memcpy (str3,"copy successful",16); printf ("str1: %s\nstr2: %s\nstr3: %s\n",str1,str2,str3); return 0; }

Output:

str1: Sample string str2: Sample string str3: copy successful

strcat()

strncat()

等