底层如何操作字符串

来源：互联网发布：知误会前番书语编辑：程序博客网时间：2024/06/05 02:46
char *strcpy(char *strDes, const char *strSrc) {     assert((strDes != NULL) && (strSrc != NULL));     char *address = strDes;     while ((*strDes ++ = *strSrc ++) != '\0')         NULL;     return address; }char *strchr_(char *str, int c) {     assert(str != NULL);     while ((*str != (char) c) && (*str != '\0'))         str ++;     if (*str != '\0')         return str;     return NULL; }char *strchr(const char *str, int c) {     assert(str != NULL);     for (; *str != (char) c; ++ str)         if (*str == '\0')             return NULL;     return (char *) str; }int strcmp(const char *s, const char *t) {     assert(s != NULL && t != NULL);     while (*s && *t && *s == *t)     {         ++ s;         ++ t;     }     return (*s - *t); }char *strcat(char *strDes, const char *strSrc) {     assert((strDes != NULL) && (strSrc != NULL));     char *address = strDes;     while (*strDes != '\0')         ++ strDes;     while ((*strDes ++ = *strSrc ++) != '\0')         NULL;     return address; }int strlen(const char *str) {     assert(str != NULL);     int len = 0;     while (*str ++ != '\0')         ++ len;     return len; }char *strdup(const char *strSrc) {     assert(strSrc != NULL);     int len = 0;     while (*strSrc ++ != '\0')         ++ len;     char *strDes = (char *) malloc (len + 1);     while ((*strDes ++ = *strSrc ++) != '\0')         NULL;     return strDes; }char *strstr(const char *strSrc, const char *str) {     assert(strSrc != NULL && str != NULL);     const char *s = strSrc;     const char *t = str;     for (; *t != '\0'; ++ strSrc)     {         for (s = strSrc, t = str; *t != '\0' && *s == *t; ++s, ++t)             NULL;         if (*t == '\0')             return (char *) strSrc;     }     return NULL; }char *strncpy(char *strDes, const char *strSrc, int count) {     assert(strDes != NULL && strSrc != NULL);     char *address = strDes;     while (count -- && *strSrc != '\0')         *strDes ++ = *strSrc ++;     return address; }char *strncat(char *strDes, const char *strSrc, int count) {     assert((strDes != NULL) && (strSrc != NULL));     char *address = strDes;     while (*strDes != '\0')         ++ strDes;     while (count -- && *strSrc != '\0' )         *strDes ++ = *strSrc ++;     *strDes = '\0';     return address; }int strncmp(const char *s, const char *t, int count) {     assert((s != NULL) && (t != NULL));     while (*s && *t && *s == *t && count --)     {         ++ s;         ++ t;     }     return (*s - *t); }char *strpbrk(const char *strSrc, const char *str) {     assert((strSrc != NULL) && (str != NULL));     const char *s;     while (*strSrc != '\0')     {         s = str;         while (*s != '\0')         {             if (*strSrc == *s)                 return (char *) strSrc;             ++ s;         }         ++ strSrc;     }     return NULL; }int strcspn(const char *strSrc, const char *str) {     assert((strSrc != NULL) && (str != NULL));     const char *s;     const char *t = strSrc;     while (*t != '\0')     {         s = str;         while (*s != '\0')         {             if (*t == *s)                 return t - strSrc;             ++ s;         }         ++ t;     }     return 0; }int strspn(const char *strSrc, const char *str) {     assert((strSrc != NULL) && (str != NULL));     const char *s;     const char *t = strSrc;     while (*t != '\0')     {         s = str;         while (*s != '\0')         {             if (*t == *s)                 break;             ++ s;         }         if (*s == '\0')             return t - strSrc;         ++ t;     }     return 0; }char *strrchr(const char *str, int c) {     assert(str != NULL);     const char *s = str;     while (*s != '\0')         ++ s;     for (-- s; *s != (char) c; -- s)         if (s == str)             return NULL;     return (char *) s; }char* strrev(char *str) {     assert(str != NULL);     char *s = str, *t = str, c;     while (*t != '\0')         ++ t;     for (-- t; s < t; ++ s, -- t)     {         c = *s;         *s = *t;         *t = c;     }     return str; }char *strnset(char *str, int c, int count) {     assert(str != NULL);     char *s = str;     for (; *s != '\0' && s - str < count; ++ s)         *s = (char) c;     return str; }char *strset(char *str, int c) {     assert(str != NULL);     char *s = str;     for (; *s != '\0'; ++ s)         *s = (char) c;     return str; }char *strtok(char *strToken, const char *str) {     assert(strToken != NULL && str != NULL);     char *s = strToken;     const char *t = str;     while (*s != '\0')     {         t = str;         while (*t != '\0')         {             if (*s == *t)             {                 *(strToken + (s - strToken)) = '\0';                 return strToken;             }             ++ t;         }         ++ s;     }     return NULL; }char *strupr(char *str) {     assert(str != NULL);     char *s = str;     while (*s != '\0')     {         if (*s >= 'a' && *s <= 'z')             *s -= 0x20;         s ++;     }     return str; }char *strlwr(char *str) {     assert(str != NULL);     char *s = str;     while (*s != '\0')     {         if (*s >= 'A' && *s <= 'Z')             *s += 0x20;         s ++;     }     return str; }void *memcpy(void *dest, const void *src, int count) {     assert((dest != NULL) && (src != NULL));     void *address = dest;     while (count --)     {         *(char *) dest = *(char *) src;         dest = (char *) dest + 1;         src = (char *) src + 1;     }     return address; }void *memccpy(void *dest, const void *src, int c, unsigned int count) {     assert((dest != NULL) && (src != NULL));     while (count --)     {         *(char *) dest = *(char *) src;         if (* (char *) src == (char) c)             return ((char *)dest + 1);         dest = (char *) dest + 1;         src = (char *) src + 1;     }     return NULL; }void *memchr(const void *buf, int c, int count) {     assert(buf != NULL);     while (count --)     {         if (*(char *) buf == c)             return (void *) buf;         buf = (char *) buf + 1;     }     return NULL; }int memcmp(const void *s, const void *t, int count) {     assert((s != NULL) && (t != NULL));     while (*(char *) s && *(char *) t && *(char *) s == *(char *) t && count --)     {         s = (char *) s + 1;         t = (char *) t + 1;     }     return (*(char *) s - *(char *) t); }void *memmove(void *dest, const void *src, int count) {     assert(dest != NULL && src != NULL);     void *address = dest;     while (count --)     {         *(char *) dest = *(char *) src;         dest = (char *) dest + 1;         src = (const char *)src + 1;     }     return address; }void *memset(void *str, int c, int count) {     assert(str != NULL);     void *s = str;     while (count --)     {         *(char *) s = (char) c;         s = (char *) s + 1;     }     return str; }
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