字元函式和字串函式的模擬實現

strlen(算字串的長度)

size_t strlen

(const
char
*str)
;

//1.模擬實現strlen

#include
#include
intmy_strlen
(const
char
*p)return count;
}int
main()

char

*strcpy
(char
*destination,
const
char
*source)

//strcpy的模擬實現

#include
#include
char
*my_strcap
(char
* dest,
const
char
* src)
intmain()
;char arr2=
"hello bit"
;my_strcap
(arr1, arr2)
;printf
("%s\n"
, arr1)
;return0;
}

char

*strcat
(char
*destination,
const
char
*source)

#include

#include
char
*my_strcat
(char
*dest,
const
char
*src)
while
(*dest++
=*src++
)return ret;
}int
main()

#include

#include
intmy_strcmp
(const
char
*str1,
const
char
*str2)
str1++
; str2++;}
return
*str1 -
*str2;
}int
main()
printf
("%d\n"
, ret)
;return0;
}

strncpy

char

*strncpy
(char
*destination,
const
char
*source,size_t num)
;

#include

#include
char
*my_strncap
(char
*dest,
const
char
*src,size_t num)
return ret;
}int
main()

char

*strncat
(char
*destination,
const
char
*source,size_t num)
;

#include

#include
#include
char
*my_strncat
(char
* dest,
const
char
* src,size_t num)
while
(num--
)*dest =
'\0'
;return ret;
}int
main()

int

strncmp
(const
char
*str1,
const
char
*str2,size_t num)

#include

#include
intmy_strncmp
(const
char
* str1,
const
char
*str2,size_t num)if(
*str1 >
*str2)
return1;
else
return-1
;}intmain()

char

*strstr
(const
char
*str1,
const
char
*str2)
;

#include

#include
char
*my_strstr
(const
char
*str1,
const
char
*str2)if(
*s2 ==
'\0'
)return cp;
cp++;}
return
null;}
intmain()

char

*strchr
(const
char
*str,
char c)

#include

#include
char
*my_strchr
(const
char
*str,
char c)if(
(char
)c ==
*str)
return
(char
*)str;
return
null;}
intmain()

void

*memcpy
(void
*dest,
const
void
*src,size_t num)
;

#include

#include
void
*my_memcpy
(void
* dest,
const
void
*src,
int count)
return ret;
}int
main()
;int arr2[20]
=;my_memcpy
(arr2, arr1,
sizeof
(arr1));
return0;
}

void

*memcpy
(void
*dest,
const
void
*src,size_t num)
;

#include

#include
void
*my_memmove
(void
*dest,
const
void
*src,
int count)
}else
}return ret;
}int
main()
;int arr2[20]
=;my_memmove
(arr2, arr1,
sizeof
(arr1));
return0;
}

字元轉換函式：tolower(轉小寫)，toupper(轉大寫)。

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