# Directed edge mode

An H3 Directed Edge index (mode 2) represents a single directed edge between two cells (an "origin" cell and a neighboring "destination" cell). The components of the H3 Directed Edge index are packed into a 64-bit integer in order, highest bit first, as follows:

- 1 bit reserved and set to 0,
- 4 bits to indicate the H3 Unidirectional Edge index mode,
- 3 bits to indicate the edge (1-6) of the origin cell,
- Subsequent bits matching the index bits of the origin cell.

## Bit layout of H3Index for directed edges

The layout of an `H3Index`

is shown below in table form. The interpretation of the "Mode-Dependent" field differs depending on the mode of the index.

0x0F | 0x0E | 0x0D | 0x0C | 0x0B | 0x0A | 0x09 | 0x08 | 0x07 | 0x06 | 0x05 | 0x04 | 0x03 | 0x02 | 0x01 | 0x00 | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|

0x30 | Reserved (0) | Mode (2) | Edge | Resolution | Base cell | |||||||||||

0x20 | Base cell | Digit 1 | Digit 2 | Digit 3 | Digit 4 | Digit 5 | ||||||||||

0x10 | Digit 5 | Digit 6 | Digit 7 | Digit 8 | Digit 9 | Digit 10 | ||||||||||

0x00 | Digit 10 | Digit 11 | Digit 12 | Digit 13 | Digit 14 | Digit 15 |