strrot.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

void stlrot(char* str, int n);

void strrot(char* str, int n);

const char* strstrn(const char* orig, const char* pat, int n);

char* cutoff(const char *str, int from , int to);

const char* cuttoff2(const char* str, int from, int to);

int main(int argc, char* argv[])
{
    (void)argc;
    (void)argv;
    char srev1[] = "123456789A";
    char srev2[] = "123456789A";

    char s1[] = "123456789A123456789B123456789C";
    int i = 0;
//    const char* p = strstrn(s1, "123", 2);
    for(i=0; i < 5; i++) {
        stlrot(srev1, 1);
        strrot(srev2, 1);
    }
}

void stlrot(char* str, int n)
{ //    return s[1:] + s[:1]
    char* it = str;
    char* s1=cutoff(str, n, strlen(str));
    char* s2=cutoff(str, 0, n);
    char* t1 = s1;
    char* t2 = s2;
    if (!s1 || !s2) return;

    while (*s1 != '\0')
        *it++ = *s1++;
    while(*s2 != '\0')
        *it++ = *s2++;

    free(t1); free(t2);
    printf("%s\r\n", str);
}

void strrot(char* str, int n)
{
    //    return s[strlen(str)-n:strlen(str)] + s[0:strlen(str)-n]
    char* it = str;
    char* s1=cutoff(str, 0, strlen(str)-n);
    char* s2=cutoff(str, strlen(str)-n, strlen(str));
    char* t1 = s1;
    char* t2 = s2;
    if (!s1 || !s2) return;

    while (*s2 != '\0')
        *it++ = *s2++;
    while(*s1 != '\0')
        *it++ = *s1++;
    free(t1); free(t2);

    printf("%s\r\n", str);
}

const char* cuttoff2(const char* str, int from, int to)
{
    return NULL;
}

char* cutoff(const char* str, int from , int to)
{
    if (from >= to)
        return  NULL;

    char* cut = calloc(sizeof(char), (to - from) + 1);
    char* begin = cut;
    if (!cut)
        return  NULL;

    const char* fromit = str+from;
    const char* toit = str+to;
    (void)toit;
    memcpy(cut, fromit, to);
    return begin;
}


const char* strstrn(const char* orig, const char* pat, int n)
{
    const char* it = orig;
    do
    {
        const char* tmp = it;
        const char* tmp2 = pat;
        if (*tmp == *tmp2) {
            while (*tmp == *tmp2 && *tmp != '\0') {
                tmp++;
                tmp2++;
            }
            if (n-- == 0)
                return it;
        }
        tmp = it;
        tmp2 = pat;
    } while (*it++ != '\0');
    return  NULL;
}