On Mon, Apr 9, 2018 at 9:42 AM, Derrick Stolee <dsto...@microsoft.com> wrote: > The generation number of a commit is defined recursively as follows: > > * If a commit A has no parents, then the generation number of A is one. > * If a commit A has parents, then the generation number of A is one > more than the maximum generation number among the parents of A. > > Add a uint32_t generation field to struct commit so we can pass this > information to revision walks. We use two special values to signal > the generation number is invalid: > > GENERATION_NUMBER_ININITY 0xFFFFFFFF
GENERATION_NUMBER_INFINITY On disk we currently only store up to 2^30-1, (2 bits fewer than MAX_UINT_32), but here we just take the maximum value of what a uint32_t can store. That miss match should not be a problem albeit aesthetically. Once we run into scaling problems, we can just up to uint64_t in the code, and defer the solution on disk to a new file format. With both ZERO and _INFINITY we are at the border of uint wrap-around, so we have to be very careful to not add/subtract one and then compare. Just to watch out for when reviewing.
