C常用函数的实现

转载，直接贴代码

int strcmp2(const char *s1, const char*s2) {    int ret;    for (; *s1++ == *s2++; ret = *s1 - *s2) {        if (*s1 == '\0')            break;    }    if (ret < 0)        ret = -1;    else if (ret > 0)        ret = 1;    return ret;}int strcmp3(char *src, char *sub) {    int ret;    while (!(ret = *src - *sub) && *sub) {        ++src;        ++sub;    }    if (ret < 0)        ret = -1;    else if (ret > 0)        ret = 1;    return ret;}char *strncpy2(char *dest, const char *src, size_t count) {    char *str = dest;    for (; (count > 0)&&(*dest = *src); count--, dest++, src++)        ;    return str;}char * strncpy1(char *dest, const char *src, size_t count) {    char *address = dest;    assert((dest != NULL && src != NULL && count > 1));    while (count-- > 0 && (*dest++ = *src++) != '\0');    return address;}char * strcpy1(char *strDest, const char *strSrc) {    char *address = strDest;    assert((strDest != NULL) && (strSrc != NULL));    printf("1=%s 2=%s\n", strDest, strSrc);    while ((*strDest++ = *strSrc++) != '\0') {        printf("1=%s 2=%s\n", strDest, strSrc);    }    printf("function str=%s\n", address);    return address;}int strlen1(const char *str) //输入参数const {    int len = 0;    assert(str != NULL); //断言字符串地址非0    while ((*str++) != '\0') {        printf("len=%d str=%s\n", len, str);        len++;    }    printf("\n\nlen=%d str=%s\n", len, str);    return len;}int strlen2(const char *src) {    int len = 0;    assert(src != NULL);    while (*src++ != '\0') {        len++;    }    return len;}int mystrlen(const char *p) {    int t;    printf("p=[%s]\n", p);    if (*p) {        t = mystrlen(p + 1) + 1;        printf("t=%d\n", t);        return t;    }    printf("last!!!!!!!!\n");    return 0;}int mystrlen1(const char *p) {    printf("\nfirst=0x%x last=0x%x\n", p, strchr(p, '\0'));    return strchr(p, '\0') - p;}int mystrlen2(const char *p) {    return (printf("%s", p));}int mystrlen3(const char *p) {    if (0 == p[0]) return 0;    if (0 == p[1]) return 1;    if (0 == p[2]) return 2;    if (0 == p[3]) return 3;    for (*(int*) p = 4; '\0' != p[*(int*) p]; ++(*(int*) p)) {    }    return *(int*) p;}int x(int n) {    if (n <= 3) {        printf("laset n=%d\n", n);        return 1;    } else {        printf("n=%d \n", n);        return x(n - 2) + x(n - 4) + 1;    }}int calcone(unsigned char s) {    int ret = 0;    while (s) {        ret++;        s &= s - 1;    }    return ret;}size_t func(unsigned char x) {    printf("0x=0x%x >>1=0x%x\n", x, x >> 1);    x = (x & 0x55) + ((x >> 1) & 0x55);    printf("0x=0x%x >>2=0x%x\n", x, x >> 2);    x = (x & 0x33) + ((x >> 2) & 0x33);    printf("0x33=0x%x\n", x);    x = (x & 0x0f) + ((x >> 4) & 0x0f);    printf("0x0f=0x%x\n", x);    return x;}int MaxSub(const int A[], int N) {    int ThisSum = 0;    int MaxSum = 0;    int i;    for (i = 0; i < N; i++) {        ThisSum += A[i];        if (ThisSum > MaxSum)            MaxSum = ThisSum;        else if (ThisSum < 0)            ThisSum = 0;    }    return MaxSum;}void shuzu(int a[], int b[][2]) {    printf("a=%d b=%d!\n", a[0], b[0][0]);    return;}int count(int n) {    if (1 == n) {        printf("1\n");        return 1;    } else if (2 == n) {        printf("2\n");        return 2;    } else {        printf("%d%d%d\n", n, n, n);        return count(n - 1) + count(n - 2);    }}char * ReverseStringSlow(char * aStr) {    int i, j;    int len = strlen(aStr);    char * ptemp = (char*) malloc(len);    for (i = len - 1, j = 0; i >= 0; --i, ++j) {        ptemp[j] = aStr[i];    }    strncpy(aStr, ptemp, len);    free(ptemp);    return aStr;}char * ReverseStringFast(char * aStr) {    int i;    int len = strlen(aStr);    char temp = '\0';    for (i = 0; i < len / 2; ++i) {        printf("i=%d len-i-1=%d\n", i, len - i - 1);        temp = aStr[i];        aStr[i] = aStr[len - i - 1];        aStr[len - i - 1] = temp;    }    return aStr;}