int H3_EXPORT()

in h3_h3Index.c [263:300]

• 10 lines of code
• 6 McCabe index (conditional complexity)

int H3_EXPORT(isValidCell)(H3Index h) {
    /*
    Look for bit patterns that would disqualify an H3Index from
    being valid. If identified, exit early.

    For reference the H3 index bit layout:

    |   Region   | # bits |
    |------------|--------|
    | High       |      1 |
    | Mode       |      4 |
    | Reserved   |      3 |
    | Resolution |      4 |
    | Base Cell  |      7 |
    | Digit 1    |      3 |
    | Digit 2    |      3 |
    | ...        |    ... |
    | Digit 15   |      3 |

    Speed benefits come from using bit manipulation instead of loops,
    whenever possible.
    */
    if (!_hasGoodTopBits(h)) return false;

    // No need to check resolution; any 4 bits give a valid resolution.
    const int res = H3_GET_RESOLUTION(h);

    // Get base cell number and check that it is valid.
    const int bc = H3_GET_BASE_CELL(h);
    if (bc >= NUM_BASE_CELLS) return false;

    if (_hasAny7UptoRes(h, res)) return false;
    if (!_hasAll7AfterRes(h, res)) return false;
    if (_hasDeletedSubsequence(h, bc)) return false;

    // If no disqualifications were identified, the index is a valid H3 cell.
    return true;
}