#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <stdio.h>

int strrev(uint8_t* source, uint8_t* destination){
    uint8_t *end, *dst;

    destination += strlen(source);

    while (*source) {
        end = source;

        do {
            destination--;
            end++;
        } while (*end && 0x80 == (*end & 0xC0));

        for (dst = destination; source < end; ++dst, ++source) {
            *dst = *source;
        }
    }
}

int main() {
    char text[] = "Тест перевернутой строки!";
    char result[sizeof(text)];

    result[strlen(text)] = 0;

    for (int i = 0; i<1000000; i++) {
        strrev(text, result);
    }

    printf("Result: %s", result);
}