String.h C Source Code implementation

int isspace (char c) {char comp[] = {"', ' \ t ', ' \ R ', ' \ n ', ' \v ', ' \f '};const int len = 6;for (int i=0; i<len; ++i) {if (c = = Comp[i]) return 1;} return 0;} Char ToLower (char c) {if (c >= ' A ' && C <= ' Z ') return (c + +); return C;} Finds the position of the first occurrence of C in the string S. Find: Returns the pointer position; Not found: Returns NULLCHAR * STRCHR (const char * s, int c) {for (; *s! = (char) c; ++s) {if (*s = = ') ') return NULL;//If s has reached the tail, Find, return Null}return (char *) s; Returns C at the pointer position of S}//in the string s from the end to find the character C, found returns the string pointer position, not found return Nullchar * STRRCHR (const char * s, int c) {const char * p = s + St Rlen (s); P points to the end of S do {if (*p = = (char) c) return (char *) p;//} while (--p >= s); return NULL;} Finds the character C within the specified length in the string s. char * STRNCHR (const char * s, size_t count, int c) {for (; count--&& *s! = '); ++s) {if (*s = = (char) c) RET Urn (char *) s;} return NULL;}  Search for a string S2 in another string S1 the first occurrence of char * STRSTR (const char * s1, const char * s2) {size_t L1, l2;l2 = strlen (s2); if (!l2 ) return (char *) S1;L1 = strlen (S1); while (L1 >= L2) {l1--;if (!memcmp (S1, S2, L2)) return (char *) s1;s1++;} return NULL;} Finds the number of characters from the beginning of the string s that conform to the accept character and returns the string s beginning with the string accept. If n is returned, it represents the character in the string accept that has n characters at the beginning of the string s. Char *str= "Linux is first developed for 386/486-based PCs."; /printf ("%d\n", strspn (str, "Linux")); The output is 5//printf ("%d\n", strspn (str, "/-")); The output is 0//printf ("%d\n", strspn (str, "1234567890")); The output is 0size_t strspn (const char * s, const char * accept) {const char * p;const char * a;size_t count = 0;for (p = s; * P! = ' + '; ++p) {for (a = accept; *a! = '); ++a)//*p one-by-one with the string alignment allowed by accept. {if (*p = = *a)//As long as the accept, jump out of the accept loop, count+1break;} if (*a = = ')//If the accept is at the end, the first character position that does not conform to accept is present. return count;++count;} return count;}  Find the reject character from the beginning of the string s, return string s at the beginning of the string reject the number of characters//if return n, which means that the string s starts with n characters without characters within the string reject.//char *str = "Linux was first developed for 386/486-based PCs. ";//printf ("%d\n ", strcspn (str," ")); Output 5, only the "" appears, so return the "Linux" Length//printf ("%d\n", strCSPN (str, "/-")); Output 33; Calculated to appear "/" or "-", so return to "6" of length//printf ("%d\n", strcspn (str, "1234567890")); Output 30;  Evaluates to a number character, so returns the length of "3" before it appears size_t strcspn (const char * s, const char * reject) {const char * p;const char * r;size_t count = 0;for (p = s; *p = ' *r '; ++p) {for (R = Reject; ++r! = '); *p) {if (*r = =)//If *p equals *r, returns the length return count ;} ++count; 2 are unequal, count+1}return count;} In the string S1, the S2 string is examined, and when the S2 character is in S1, the test is stopped and the character position is returned//char *s = "12,3a,45"//char *ptr = STRPBRK (S, ","); PTR =, 3a,45char * STRPBRK (const char * s1, const char * s2) {const char * SC1, * sc2;for (SC1 = S1; *sc1! = '); + + SC1) {for (SC2 = s2; ++sc2) {if (*SC1 = *SC2)//If the S1 character return (char *) S2 is found in SC1;//returns the character position}} return NULL; Not found returns Null}char * STRSEP (char **s, const char *ct) {char * sbegin = *s;char * END;IF (*sbegin = = NULL) return null;e nd = STRPBRK (sbegin, CT); Find the position of CT first outlet in Sbegin. if (end)//found *end++ = ' + '; Add terminator ' *s ' = end; s points to a new openStart position return sbegin;} Skip whitespace character char * skip_spaces (const char * str) {while (Isspace (*STR)) ++str;return (char *) str;} Skip end-to-end whitespace char * Strim (char * s) {size_t Size;char * end;s = skip_spaces (s);//skip whitespace character size = strlen (s);//calculate s character length I F (!size)//Length 0, then return s directly; s = ' + ' end = s + size-1; End points at the end of the S string while (end >= s && isspace (*end))//Skip the end of the white space character end--;* (end + 1) = ' + '; Set the next one to return s;} Calculates the length of the string s. End With ' size_t ' strlen (const char * s) {const char * SC;FOR (sc = s; *SC! = ' + '; ++sc);//Nothingreturn sc-s;}  Compares 2 strings of a specified length, case-insensitive int strnicmp (const char * s1, const char * s2, size_t len) {unsigned char C1, c2;if (!len) return 0;do {c1 = *S1++;C2 = *s2++;if (!c1 | |!c2)//If one is empty break;if (c1 = = C2)//equal, continue to compare next CONTINUE;C1 = ToLower (C1); C2 = ToLower (C2); are converted to lowercase if (c1! = C2)//unequal break;} while (--len); Compares return (int) c1-(int) c2 within a specified length; Compares characters for equality after jumping out of the loop. }//compares 2 strings, not case sensitive. int strcasecmp (const char * s1, const CHar * s2) {int C1, C2;do {c1 = ToLower (*s1++); c2 = ToLower (*s2++);} while (C1 = C2 && C1! = ' 0 ');//return C1-C2;} Compares 2 strings of a specified length, case-insensitive int strncasecmp (const char * s1, const char * s2, size_t n) {int C1, C2;do {c1 = ToLower (*s1++); C2 = ToLower (*s2++);} while ((--n > 0) && c1 = = C2 && C1! = ' 0 '); return C1-C2;} A copy of the string. Copy the SRC content into the dest. There is no length, the src length is greater than dest length, it will exceed the storage range. char * strcpy (char * dest, const char * src) {char * begin = dest;//point at the beginning of the destination storage space. while ((*dest++ = *src++)! = ' + ')//character save content. S Nothingreturn begin;} A copy of the string. Copies the contents of the src specified length to dest.  char * strncpy (char * dest, const char * src, size_t count) {char * move = Dest;while (count) {if (*move = *src)! = ' src++;move++;count--'); return dest;} string concatenation, copy the SRC content to the back of the Dest char * strcat (char * dest, const char * src) {char * begin = Dest;while (*dest) dest++; while ((*dest++ = *src++)! = ' + '); do Nothingreturn begin;} string concatenation, specifying SRCThe contents of the length are copied to the back of the Dest char * strncat (char * dest, const char * src, size_t count) {char * begin = Dest;while (*dest) dest++ ; while ((*dest++ = *src++)! = ' + ') {if (--count = = 0) {*dest= ' + '; break;}}; do Nothingreturn begin;} Comparison of 2 strings.  Return value: 0,-1, 1int strcmp (const char * s1, const char * s2) {unsigned char C1, C2;while (1) {c1 = *S1++;C2 = *s2++;if (c1 ! = C2) Return (C1 < C2)? -1:1; Unequal return-1 1if (!C1)//If C1 has reached the end of break;} return 0; Equal returns 0}//a specified length of 2 string comparisons. Returns 0-1 1int strncmp (const char * s1, const char * s2, size_t count) {unsigned char C1, C2;while (count) {c1 = *S1++;C2 = *s2++;if (C1! = C2) Return (C1 < C2)? -1:1; Unequal return-1 1if (!C1) break;count--; Length minus 1}return 0;  Equal returns 0}//the contents of the length count in s in C to initialize svoid * memset (void *s, int c, size_t count) {char * xs = (char *) s;while (count-- ) *xs++ = C;return s;}  Copy the contents of count length in src to dest void * memcpy (void * dest, const void * src, size_t count) {char * tmp = (char *) dest;const char * s = (const char *) src;while (count--) *tmp++ = *s++;return dest;} Compares S1 s2 size, returns an integer int memcmp (const void * S1, const void *S2, size_t count) {const unsigned char * SU1 = (const unsign  Ed char *) s1;const unsigned char * su2 = (const unsigned char *) s2;int res = 0;for (; count > 0; ++su1, ++SU2,--count {if (res = *su1-*SU2) = 0)//is not equal, then jumps out of the loop. break;} return res;}

　　

String.h C Source Code implementation