Derrick Stolee <sto...@gmail.com> writes:
> On 4/11/2018 4:58 PM, Jakub Narebski wrote:
>> Derrick Stolee <sto...@gmail.com> writes:
>>
>>> +CHUNK DATA:
>>> +
>>> + OID Fanout (ID: {'O', 'I', 'D', 'F'}) (256 * 4 bytes)
>>> + The ith entry, F[i], stores the number of OIDs with first
>>> + byte at most i. Thus F[255] stores the total
>>> + number of commits (N).
>>> +
>>> + OID Lookup (ID: {'O', 'I', 'D', 'L'}) (N * H bytes)
>>> + The OIDs for all commits in the graph, sorted in ascending order.
>>> +
>>> + Commit Data (ID: {'C', 'G', 'E', 'T' }) (N * (H + 16) bytes)
>> I think it is a typo, and it should be CDAT, not CGET
>> (CDAT seem to me to stand for Commit DATa):
>>
>> + Commit Data (ID: {'C', 'D', 'A', 'T' }) (N * (H + 16) bytes)
>>
>> This is what you use in actual implementation, in PATCH v8 06/14
>>
>> DS> +#define GRAPH_SIGNATURE 0x43475048 /* "CGPH" */
>> DS> +#define GRAPH_CHUNKID_OIDFANOUT 0x4f494446 /* "OIDF" */
>> DS> +#define GRAPH_CHUNKID_OIDLOOKUP 0x4f49444c /* "OIDL" */
>> DS> +#define GRAPH_CHUNKID_DATA 0x43444154 /* "CDAT" */
>> DS> +#define GRAPH_CHUNKID_LARGEEDGES 0x45444745 /* "EDGE" */
>>
>
> Documentation bugs are hard to diagnose. Thanks for finding this. I
> double checked that the hex int "0x43444154" matches "CDAT".
Another possible way of checking the correctness would be to run
`hexdump -C` or equivalent on generated commit-graph file. File and
chunk headers should be visible in its output.
> Here is a diff to make it match.
>
> diff --git a/Documentation/technical/commit-graph-format.txt
> b/Documentation/technical/commit-graph-format.txt
> index ad6af8105c..af03501834 100644
> --- a/Documentation/technical/commit-graph-format.txt
> +++ b/Documentation/technical/commit-graph-format.txt
> @@ -70,7 +70,7 @@ CHUNK DATA:
> OID Lookup (ID: {'O', 'I', 'D', 'L'}) (N * H bytes)
> The OIDs for all commits in the graph, sorted in ascending order.
>
> - Commit Data (ID: {'C', 'G', 'E', 'T' }) (N * (H + 16) bytes)
> + Commit Data (ID: {'C', 'D', 'A', 'T' }) (N * (H + 16) bytes)
> * The first H bytes are for the OID of the root tree.
> * The next 8 bytes are for the positions of the first two parents
> of the ith commit. Stores value 0xffffffff if no parent in that
