path.c: clarify trie_find()'s in-code comment

A fairly long comment describes trie_find()'s behavior and shows examples, but it's slightly incomplete/inaccurate. Update this comment to specify how trie_find() handles a negative return value from the given match function. Furthermore, update the list of examples to include not only two but three levels of path components. This makes the examples slightly more complicated, but it can illustrate the behavior in more corner cases. Finally, basically everything refers to the data stored for a key as "value", with two confusing exceptions: - The type definition of the match function calls its corresponding parameter 'data'. Rename that parameter to 'value'. (check_common(), the only function of this type already calls it 'value'). - The table of examples above trie_find() has a "val from node" column, which has nothing to do with the value stored in the trie: it's a "prefix of the key for which the trie contains a value" that led to that node. Rename that column header to "prefix to node". Note that neither the original nor the updated description and examples correspond 100% to the current implementation, because the implementation is a bit buggy, but the comment describes the desired behavior. The bug will be fixed in the last patch of this series. Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>

SZEDER Gábor committed Oct 21, 2019 at 18:00 UTC 7cb8c929d76c12750fdece2e5da75d207938d3b9

1 file changed +28 -17

path.c

+28 -17

@@ -236,30 +236,41 @@ static void *add_to_trie(struct trie *root, const char *key, void *value)

236 return old;

237 }

238

239 -typedef int (*match_fn)(const char *unmatched, void *data, void *baton);

239 +typedef int (*match_fn)(const char *unmatched, void *value, void *baton);

240

241 /*

242 * Search a trie for some key. Find the longest /-or-\0-terminated

243 - * prefix of the key for which the trie contains a value. Call fn

244 - * with the unmatched portion of the key and the found value, and

245 - * return its return value. If there is no such prefix, return -1.

243 + * prefix of the key for which the trie contains a value. If there is

244 + * no such prefix, return -1. Otherwise call fn with the unmatched

245 + * portion of the key and the found value. If fn returns 0 or

246 + * positive, then return its return value. If fn returns negative,

247 + * then call fn with the next-longest /-terminated prefix of the key

248 + * (i.e. a parent directory) for which the trie contains a value, and

249 + * handle its return value the same way. If there is no shorter

250 + * /-terminated prefix with a value left, then return the negative

251 + * return value of the most recent fn invocation.

252 *

253 * The key is partially normalized: consecutive slashes are skipped.

254 *

249 - * For example, consider the trie containing only [refs,

250 - * refs/worktree] (both with values).

251 - *

253 - * |-----------------|------------|---------------|--------------|

254 - * | a | not called | n/a | -1 |

261 - * |-----------------|------------|---------------|--------------|

255 + * For example, consider the trie containing only [logs,

256 + * logs/refs/bisect], both with values, but not logs/refs.

257 *

259 + * |--------------------|----------------|------------------|--------------|

260 + * | a | not called | n/a | -1 |

261 + * | logstore | not called | n/a | -1 |

271 + * | (If fn in the previous line returns -1, then fn is called once more:) |

273 + * |--------------------|----------------|------------------|--------------|

274 */

275 static int trie_find(struct trie *root, const char *key, match_fn fn,

276 void *baton)