C语言常用库函数实现
对于C语言来说远着许多的函数需要记住，因此是十分考验技巧的语言，但是也是学习编程的入门知识，下面是小编为大家搜集整理出来的有关于C常用库函数实现，希望可以帮助到大家!
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 | C常用库函数实现// ---------- strlen -------------int strlen(char *t){ int length = 0; if(t == NULL) return -1; while (*t != ' ') { t++; length++; } return length;}size_t strlen(const char *s){ const char *sc; for (sc = s; *sc != ' '; ++sc); return sc - s;}// ---------- trim -------------void ltrim ( char *s ){ char *p; p = s; while ( *p == ' ' || *p == ' ' ) {p++;} strcpy ( s,p );}void rtrim ( char *s ){ int i; i = strlen ( s )-1; while ( ( s[i] == ' ' || s[i] == ' ' ) && i >= 0 ) {i--;}; s[i+1] = ' ';}void trim ( char *s ){ ltrim ( s ); rtrim ( s );}// ---------- strcpy -------------char *strcpy(char *dest, const char *src){ char *tmp = dest; while ((*dest++ = *src++) != ' '); return tmp;}// ---------- strcat -------------char *strcat(char *dest, const char *src){ char *tmp = dest; while (*dest) dest++; while ((*dest++ = *src++) != ' '); return tmp;}// ---------- strstr -------------char *strstr(const char *s1, const char *s2){ int 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;}// ---------- memcmp -------------int memcmp(char *cs, char *ct, size_t count){ char *su1, *su2; int res = 0; for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--) if ((res = *su1 - *su2) != 0) break; return res;}// ---------- strcmp -------------int strcmp(const char *cs, const char *ct){ unsigned char c1, c2; while (1) { c1 = *cs++; c2 = *ct++; if (c1 != c2) return c1 < c2 ? -1 : 1; if (!c1) break; } return 0;} |
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