闲着无聊，自己写了个几个string.h里的函数练手

1. strtok   没有考虑执行效率问题，代码质量也比较差，不过基本算是完成了任务

static bool check( char c, const char *token );char *strtok( char *str, const char *token ){int len;static char *cur = 0;static char *next = 0;if ( token == 0 )return str;if ( str == 0 ){if ( next == 0 )return 0;cur = next;len = xl::strlen( cur );}else {len = xl::strlen( str );cur = str;}for ( int i = 0; i < len; i++ ){if ( check( cur[i], token ) ){cur[i] = '\0';next = &cur[i+1];return cur;}}char * ret = next;next = 0;cur = 0;return ret;}static bool check( char c, const char *token ){int len = xl::strlen( token );for ( int i = 0; i < len; i++ ){if ( c == token[i] )return true;}return false;}

 

 

 

2. strncpy，模仿写的，不过感觉代码还有优化的空间，自己没太多的测试

主要是从2个角度进行的优化

(1) 32bit内存边界对齐

(2) 机器字长内容复制

ps. 也许写memcpy函数会更好

 

char * strncpy( char *dest, const char *src , int _len ){char *ret = dest;long n = (sizeof(long) - (long)dest % sizeof(long)) % sizeof(long); long len = _len - n; if ( len > 0 ) {for ( long i = 0; i < n; i++ ) *dest++ = *src++;} else if( len < 0 ){for ( long i = 0; i < _len; i++ )*dest++ = *src++;return ret;} while( len >= 4 ) {*((long *)dest) = *((long *)src);dest += sizeof(long);src += sizeof(long);len -= 4;}while( len > 0 ) {*dest++ = *src++;len--;}return ret;}

转载于:https://www.cnblogs.com/dickhead/archive/2010/11/15/1877343.html

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