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From: "Elijah Newren via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: Jeff King <peff@peff.net>, Elijah Newren <newren@gmail.com>,
	Elijah Newren <newren@gmail.com>,
	Elijah Newren <newren@gmail.com>
Subject: [PATCH v3 01/13] hashmap: add usage documentation explaining hashmap_free[_entries]()
Date: Mon, 02 Nov 2020 18:55:01 +0000
Message-ID: <af6b6fcb460be900d3fffeb743a42f3f87ce6b7f.1604343314.git.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.835.v3.git.git.1604343313.gitgitgadget@gmail.com>

From: Elijah Newren <newren@gmail.com>

The existence of hashmap_free() and hashmap_free_entries() confused me,
and the docs weren't clear enough.  We are dealing with a map table,
entries in that table, and possibly also things each of those entries
point to.  I had to consult other source code examples and the
implementation.  Add a brief note to clarify the differences.  This will
become even more important once we introduce a new
hashmap_partial_clear() function which will add the question of whether
the table itself has been freed.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 hashmap.h | 31 +++++++++++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/hashmap.h b/hashmap.h
index b011b394fe..2994dc7a9c 100644
--- a/hashmap.h
+++ b/hashmap.h
@@ -236,13 +236,40 @@ void hashmap_init(struct hashmap *map,
 void hashmap_free_(struct hashmap *map, ssize_t offset);
 
 /*
- * Frees a hashmap structure and allocated memory, leaves entries undisturbed
+ * Frees a hashmap structure and allocated memory for the table, but does not
+ * free the entries nor anything they point to.
+ *
+ * Usage note:
+ *
+ * Many callers will need to iterate over all entries and free the data each
+ * entry points to; in such a case, they can free the entry itself while at it.
+ * Thus, you might see:
+ *
+ *    hashmap_for_each_entry(map, hashmap_iter, e, hashmap_entry_name) {
+ *      free(e->somefield);
+ *      free(e);
+ *    }
+ *    hashmap_free(map);
+ *
+ * instead of
+ *
+ *    hashmap_for_each_entry(map, hashmap_iter, e, hashmap_entry_name) {
+ *      free(e->somefield);
+ *    }
+ *    hashmap_free_entries(map, struct my_entry_struct, hashmap_entry_name);
+ *
+ * to avoid the implicit extra loop over the entries.  However, if there are
+ * no special fields in your entry that need to be freed beyond the entry
+ * itself, it is probably simpler to avoid the explicit loop and just call
+ * hashmap_free_entries().
  */
 #define hashmap_free(map) hashmap_free_(map, -1)
 
 /*
  * Frees @map and all entries.  @type is the struct type of the entry
- * where @member is the hashmap_entry struct used to associate with @map
+ * where @member is the hashmap_entry struct used to associate with @map.
+ *
+ * See usage note above hashmap_free().
  */
 #define hashmap_free_entries(map, type, member) \
 	hashmap_free_(map, offsetof(type, member));
-- 
gitgitgadget


  reply index

Thread overview: 144+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-21 18:52 [PATCH 0/5] Add struct strmap and associated utility functions Elijah Newren via GitGitGadget
2020-08-21 18:52 ` [PATCH 1/5] hashmap: add usage documentation explaining hashmap_free[_entries]() Elijah Newren via GitGitGadget
2020-08-21 19:22   ` Jeff King
2020-08-21 18:52 ` [PATCH 2/5] strmap: new utility functions Elijah Newren via GitGitGadget
2020-08-21 19:48   ` Jeff King
2020-08-21 18:52 ` [PATCH 3/5] strmap: add more " Elijah Newren via GitGitGadget
2020-08-21 19:58   ` Jeff King
2020-08-21 18:52 ` [PATCH 4/5] strmap: add strdup_strings option Elijah Newren via GitGitGadget
2020-08-21 20:01   ` Jeff King
2020-08-21 20:41     ` Elijah Newren
2020-08-21 21:03       ` Jeff King
2020-08-21 22:25         ` Elijah Newren
2020-08-28  7:08           ` Jeff King
2020-08-28 17:20             ` Elijah Newren
2020-08-21 18:52 ` [PATCH 5/5] strmap: add functions facilitating use as a string->int map Elijah Newren via GitGitGadget
2020-08-21 20:10   ` Jeff King
2020-08-21 20:51     ` Elijah Newren
2020-08-21 21:05       ` Jeff King
2020-08-21 20:16 ` [PATCH 0/5] Add struct strmap and associated utility functions Jeff King
2020-08-21 21:33   ` Elijah Newren
2020-08-21 22:28     ` Elijah Newren
2020-08-28  7:03     ` Jeff King
2020-08-28 15:29       ` Elijah Newren
2020-09-01  9:27         ` Jeff King
2020-10-13  0:40 ` [PATCH v2 00/10] " Elijah Newren via GitGitGadget
2020-10-13  0:40   ` [PATCH v2 01/10] hashmap: add usage documentation explaining hashmap_free[_entries]() Elijah Newren via GitGitGadget
2020-10-30 12:50     ` Jeff King
2020-10-30 19:55       ` Elijah Newren
2020-11-03 16:26         ` Jeff King
2020-11-03 16:48           ` Elijah Newren
2020-10-13  0:40   ` [PATCH v2 02/10] hashmap: adjust spacing to fix argument alignment Elijah Newren via GitGitGadget
2020-10-30 12:51     ` Jeff King
2020-10-13  0:40   ` [PATCH v2 03/10] hashmap: allow re-use after hashmap_free() Elijah Newren via GitGitGadget
2020-10-30 13:35     ` Jeff King
2020-10-30 15:37       ` Elijah Newren
2020-11-03 16:08         ` Jeff King
2020-11-03 16:16           ` Elijah Newren
2020-10-13  0:40   ` [PATCH v2 04/10] hashmap: introduce a new hashmap_partial_clear() Elijah Newren via GitGitGadget
2020-10-30 13:41     ` Jeff King
2020-10-30 16:03       ` Elijah Newren
2020-11-03 16:10         ` Jeff King
2020-10-13  0:40   ` [PATCH v2 05/10] strmap: new utility functions Elijah Newren via GitGitGadget
2020-10-30 14:12     ` Jeff King
2020-10-30 16:26       ` Elijah Newren
2020-10-13  0:40   ` [PATCH v2 06/10] strmap: add more " Elijah Newren via GitGitGadget
2020-10-30 14:23     ` Jeff King
2020-10-30 16:43       ` Elijah Newren
2020-11-03 16:12         ` Jeff King
2020-10-13  0:40   ` [PATCH v2 07/10] strmap: enable faster clearing and reusing of strmaps Elijah Newren via GitGitGadget
2020-10-30 14:27     ` Jeff King
2020-10-13  0:40   ` [PATCH v2 08/10] strmap: add functions facilitating use as a string->int map Elijah Newren via GitGitGadget
2020-10-30 14:39     ` Jeff King
2020-10-30 17:28       ` Elijah Newren
2020-11-03 16:20         ` Jeff King
2020-11-03 16:46           ` Elijah Newren
2020-10-13  0:40   ` [PATCH v2 09/10] strmap: add a strset sub-type Elijah Newren via GitGitGadget
2020-10-30 14:44     ` Jeff King
2020-10-30 18:02       ` Elijah Newren
2020-10-13  0:40   ` [PATCH v2 10/10] strmap: enable allocations to come from a mem_pool Elijah Newren via GitGitGadget
2020-10-30 14:56     ` Jeff King
2020-10-30 19:31       ` Elijah Newren
2020-11-03 16:24         ` Jeff King
2020-11-02 18:55   ` [PATCH v3 00/13] Add struct strmap and associated utility functions Elijah Newren via GitGitGadget
2020-11-02 18:55     ` Elijah Newren via GitGitGadget [this message]
2020-11-02 18:55     ` [PATCH v3 02/13] hashmap: adjust spacing to fix argument alignment Elijah Newren via GitGitGadget
2020-11-02 18:55     ` [PATCH v3 03/13] hashmap: allow re-use after hashmap_free() Elijah Newren via GitGitGadget
2020-11-02 18:55     ` [PATCH v3 04/13] hashmap: introduce a new hashmap_partial_clear() Elijah Newren via GitGitGadget
2020-11-02 18:55     ` [PATCH v3 05/13] hashmap: provide deallocation function names Elijah Newren via GitGitGadget
2020-11-02 18:55     ` [PATCH v3 06/13] strmap: new utility functions Elijah Newren via GitGitGadget
2020-11-02 18:55     ` [PATCH v3 07/13] strmap: add more " Elijah Newren via GitGitGadget
2020-11-04 20:13       ` Jeff King
2020-11-04 20:24         ` Elijah Newren
2020-11-02 18:55     ` [PATCH v3 08/13] strmap: enable faster clearing and reusing of strmaps Elijah Newren via GitGitGadget
2020-11-02 18:55     ` [PATCH v3 09/13] strmap: add functions facilitating use as a string->int map Elijah Newren via GitGitGadget
2020-11-04 20:21       ` Jeff King
2020-11-02 18:55     ` [PATCH v3 10/13] strmap: add a strset sub-type Elijah Newren via GitGitGadget
2020-11-04 20:31       ` Jeff King
2020-11-02 18:55     ` [PATCH v3 11/13] strmap: enable allocations to come from a mem_pool Elijah Newren via GitGitGadget
2020-11-02 18:55     ` [PATCH v3 12/13] strmap: take advantage of FLEXPTR_ALLOC_STR when relevant Elijah Newren via GitGitGadget
2020-11-04 20:43       ` Jeff King
2020-11-02 18:55     ` [PATCH v3 13/13] Use new HASHMAP_INIT macro to simplify hashmap initialization Elijah Newren via GitGitGadget
2020-11-04 20:48       ` Jeff King
2020-11-04 20:52     ` [PATCH v3 00/13] Add struct strmap and associated utility functions Jeff King
2020-11-04 22:20       ` Elijah Newren
2020-11-05  0:22     ` [PATCH v4 " Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 01/13] hashmap: add usage documentation explaining hashmap_free[_entries]() Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 02/13] hashmap: adjust spacing to fix argument alignment Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 03/13] hashmap: allow re-use after hashmap_free() Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 04/13] hashmap: introduce a new hashmap_partial_clear() Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 05/13] hashmap: provide deallocation function names Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 06/13] strmap: new utility functions Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 07/13] strmap: add more " Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 08/13] strmap: enable faster clearing and reusing of strmaps Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 09/13] strmap: add functions facilitating use as a string->int map Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 10/13] strmap: add a strset sub-type Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 11/13] strmap: enable allocations to come from a mem_pool Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 12/13] strmap: take advantage of FLEXPTR_ALLOC_STR when relevant Elijah Newren via GitGitGadget
2020-11-05  0:22       ` [PATCH v4 13/13] Use new HASHMAP_INIT macro to simplify hashmap initialization Elijah Newren via GitGitGadget
2020-11-05 13:29       ` [PATCH v4 00/13] Add struct strmap and associated utility functions Jeff King
2020-11-05 20:25         ` Junio C Hamano
2020-11-05 21:17           ` Jeff King
2020-11-05 21:22           ` Elijah Newren
2020-11-05 22:15             ` Junio C Hamano
2020-11-06  0:24       ` [PATCH v5 00/15] " Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 01/15] hashmap: add usage documentation explaining hashmap_free[_entries]() Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 02/15] hashmap: adjust spacing to fix argument alignment Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 03/15] hashmap: allow re-use after hashmap_free() Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 04/15] hashmap: introduce a new hashmap_partial_clear() Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 05/15] hashmap: provide deallocation function names Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 06/15] strmap: new utility functions Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 07/15] strmap: add more " Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 08/15] strmap: enable faster clearing and reusing of strmaps Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 09/15] strmap: add functions facilitating use as a string->int map Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 10/15] strmap: split create_entry() out of strmap_put() Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 11/15] strmap: add a strset sub-type Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 12/15] strmap: enable allocations to come from a mem_pool Elijah Newren via GitGitGadget
2020-11-11 17:33           ` Phillip Wood
2020-11-11 18:49             ` Elijah Newren
2020-11-11 19:01             ` Jeff King
2020-11-11 20:34               ` Chris Torek
2020-11-06  0:24         ` [PATCH v5 13/15] strmap: take advantage of FLEXPTR_ALLOC_STR when relevant Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 14/15] Use new HASHMAP_INIT macro to simplify hashmap initialization Elijah Newren via GitGitGadget
2020-11-06  0:24         ` [PATCH v5 15/15] shortlog: use strset from strmap.h Elijah Newren via GitGitGadget
2020-11-06  2:00         ` [PATCH v5 00/15] Add struct strmap and associated utility functions Junio C Hamano
2020-11-06  2:42           ` Elijah Newren
2020-11-06  2:48             ` Jeff King
2020-11-06 17:32               ` Junio C Hamano
2020-11-11 20:02         ` [PATCH v6 " Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 01/15] hashmap: add usage documentation explaining hashmap_free[_entries]() Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 02/15] hashmap: adjust spacing to fix argument alignment Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 03/15] hashmap: allow re-use after hashmap_free() Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 04/15] hashmap: introduce a new hashmap_partial_clear() Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 05/15] hashmap: provide deallocation function names Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 06/15] strmap: new utility functions Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 07/15] strmap: add more " Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 08/15] strmap: enable faster clearing and reusing of strmaps Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 09/15] strmap: add functions facilitating use as a string->int map Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 10/15] strmap: split create_entry() out of strmap_put() Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 11/15] strmap: add a strset sub-type Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 12/15] strmap: enable allocations to come from a mem_pool Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 13/15] strmap: take advantage of FLEXPTR_ALLOC_STR when relevant Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 14/15] Use new HASHMAP_INIT macro to simplify hashmap initialization Elijah Newren via GitGitGadget
2020-11-11 20:02           ` [PATCH v6 15/15] shortlog: use strset from strmap.h Elijah Newren via GitGitGadget
2020-11-11 20:07           ` [PATCH v6 00/15] Add struct strmap and associated utility functions Jeff King

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