C Code Examples: Array Rotations

Rotate an Array of Bytes to the Left

void array_rotl(uint8_t *array, const size_t len, const uint32_t num_shifts) {
    // Rotate an array to the left in-place
    if ((len > 0x02) && (num_shifts != 0x00)) {
        register uint32_t i, j;
        register uint8_t first;
        for (i = num_shifts; i != 0x00; --i) {
            first = array[0x00];
            for (j = 0x00; j < (uint32_t)(len - 0x01); ++j) array[j] = array[j + 0x01];
            array[j] = first;
        }
    }
}

Rotate an Array of Bytes to the Right

void array_rotr(uint8_t *array, const size_t len, const uint32_t num_shifts) {
    // Rotate an array to the right in-place
    if ((len > 0x02) && (num_shifts != 0x00)) {
        register uint32_t i, j;
        register uint8_t last;
        for (i = num_shifts; i != 0x00; --i) {
            last = array[len - 0x01];
            for (j = (uint32_t)len; --j;) array[j] = array[j - 0x01];
            array[0x00] = last;
        }
    }
}

Rotate Char Array of Bytes to the Left

void chararray_rotl(char *array, const size_t len, const uint32_t num_shifts) {
    // Rotate a char array to the left in-place
    if ((len > 0x02) && (num_shifts != 0x00)) {
        register uint32_t i, j;
        register char first;
        for (i = num_shifts; i != 0x00; --i) {
            first = array[0x00];
            for (j = 0x00; j < (uint32_t)(len - 0x01); ++j) array[j] = array[j + 0x01];
            array[j] = first;
        }
    }
}

Rotate Char Array of Bytes to the Right

void chararray_rotr(char *array, const size_t len, const uint32_t num_shifts) {
    // Rotate a char array to the right in-place
    if ((len > 0x02) && (num_shifts != 0x00)) {
        register uint32_t i, j;
        register char last;
        for (i = num_shifts; i != 0x00; --i) {
            last = array[len - 0x01];
            for (j = (uint32_t)len; --j;) array[j] = array[j - 0x01];
            array[0x00] = last;
        }
    }
}

Further Reading

• Programming and Development - https://dcjtech.info/topic/programming-and-development/
• C Programming Article Forum - https://dcjtech.info/forum/articles/programming/c-c-and-c/