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2020-11-02hashmap: provide deallocation function namesLibravatar Elijah Newren1-17/+27
hashmap_free(), hashmap_free_entries(), and hashmap_free_() have existed for a while, but aren't necessarily the clearest names, especially with hashmap_partial_clear() being added to the mix and lazy-initialization now being supported. Peff suggested we adopt the following names[1]: - hashmap_clear() - remove all entries and de-allocate any hashmap-specific data, but be ready for reuse - hashmap_clear_and_free() - ditto, but free the entries themselves - hashmap_partial_clear() - remove all entries but don't deallocate table - hashmap_partial_clear_and_free() - ditto, but free the entries This patch provides the new names and converts all existing callers over to the new naming scheme. [1] https://lore.kernel.org/git/20201030125059.GA3277724@coredump.intra.peff.net/ Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-11-02hashmap: introduce a new hashmap_partial_clear()Libravatar Elijah Newren1-1/+12
merge-ort is a heavy user of strmaps, which are built on hashmap.[ch]. clear_or_reinit_internal_opts() in merge-ort was taking about 12% of overall runtime in my testcase involving rebasing 35 patches of linux.git across a big rename. clear_or_reinit_internal_opts() was calling hashmap_free() followed by hashmap_init(), meaning that not only was it freeing all the memory associated with each of the strmaps just to immediately allocate a new array again, it was allocating a new array that was likely smaller than needed (thus resulting in later need to rehash things). The ending size of the map table on the previous commit was likely almost perfectly sized for the next commit we wanted to pick, and not dropping and reallocating the table immediately is a win. Add some new API to hashmap to clear a hashmap of entries without freeing map->table (and instead only zeroing it out like alloc_table() would do, along with zeroing the count of items in the table and the shrink_at field). Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-11-02hashmap: allow re-use after hashmap_free()Libravatar Elijah Newren1-0/+3
Previously, once map->table had been freed, any calls to hashmap_put(), hashmap_get(), or hashmap_remove() would cause a NULL pointer dereference (since hashmap_free_() also zeros the memory; without that zeroing, calling these functions would cause a use-after-free problem). Modify these functions to check for a NULL table and automatically allocate as needed. Also add a HASHMAP_INIT(fn, data) macro for initializing hashmaps on the stack without calling hashmap_init(). Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-11-02hashmap: adjust spacing to fix argument alignmentLibravatar Elijah Newren1-11/+11
No actual code changes; just whitespace adjustments. Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-10-13hashmap: add usage documentation explaining hashmap_free[_entries]()Libravatar Elijah Newren1-2/+29
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> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-09-30hashmap_for_each_entry(): workaround MSVC's runtime check failure #3Libravatar Junio C Hamano1-1/+2
The OFFSETOF_VAR(var, member) macro is implemented in terms of offsetof(typeof(*var), member) with compilers that know typeof(), but its fallback implemenation compares &(var->member) and (var) and count the distance in bytes, i.e. ((uintptr_t)&(var)->member - (uintptr_t)(var)) MSVC's runtime check, when fed an uninitialized 'var', flags this as a use of an uninitialized variable (and that is legit---uninitialized contents of 'var' is subtracted) in a debug build. After auditing all 6 uses of OFFSETOF_VAR(), 1 of them does feed a potentially uninitialized 'var' to the macro in the beginning of the for() loop: #define hashmap_for_each_entry(map, iter, var, member) \ for (var = hashmap_iter_first_entry_offset(map, iter, \ OFFSETOF_VAR(var, member)); \ var; \ var = hashmap_iter_next_entry_offset(iter, \ OFFSETOF_VAR(var, member))) We can work around this by making sure that var has _some_ value when OFFSETOF_VAR() is called. Strictly speaking, it invites undefined behaviour to use NULL here if we end up with pointer comparison, but MSVC runtime seems to be happy with it, and most other systems have typeof() and don't even need pointer comparison fallback code. Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-07-28hashmap: fix typo in usage docsLibravatar Elijah Newren1-1/+1
Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-12-01Merge branch 'en/doc-typofix'Libravatar Junio C Hamano1-1/+1
Docfix. * en/doc-typofix: Fix spelling errors in no-longer-updated-from-upstream modules multimail: fix a few simple spelling errors sha1dc: fix trivial comment spelling error Fix spelling errors in test commands Fix spelling errors in messages shown to users Fix spelling errors in names of tests Fix spelling errors in comments of testcases Fix spelling errors in code comments Fix spelling errors in documentation outside of Documentation/ Documentation: fix a bunch of typos, both old and new
2019-11-10Fix spelling errors in code commentsLibravatar Elijah Newren1-1/+1
Reported-by: Jens Schleusener <Jens.Schleusener@fossies.org> Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-11-07hashmap: fix documentation misuses of -> versus .Libravatar Elijah Newren1-3/+3
Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_entry: remove first member requirement from docsLibravatar Eric Wong1-2/+2
Comments stating that "struct hashmap_entry" must be the first member in a struct are no longer valid. Suggested-by: Phillip Wood <phillip.wood123@gmail.com> Signed-off-by: Eric Wong <e@80x24.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap: remove type arg from hashmap_{get,put,remove}_entryLibravatar Eric Wong1-12/+33
Since these macros already take a `keyvar' pointer of a known type, we can rely on OFFSETOF_VAR to get the correct offset without relying on non-portable `__typeof__' and `offsetof'. Argument order is also rearranged, so `keyvar' and `member' are sequential as they are used as: `keyvar->member' Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07OFFSETOF_VAR macro to simplify hashmap iteratorsLibravatar Eric Wong1-14/+30
While we cannot rely on a `__typeof__' operator being portable to use with `offsetof'; we can calculate the pointer offset using an existing pointer and the address of a member using pointer arithmetic for compilers without `__typeof__'. This allows us to simplify usage of hashmap iterator macros by not having to specify a type when a pointer of that type is already given. In the future, list iterator macros (e.g. list_for_each_entry) may also be implemented using OFFSETOF_VAR to save hackers the trouble of using container_of/list_entry macros and without relying on non-portable `__typeof__'. v3: use `__typeof__' to avoid clang warnings Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap: introduce hashmap_free_entriesLibravatar Eric Wong1-6/+13
`hashmap_free_entries' behaves like `container_of' and passes the offset of the hashmap_entry struct to the internal `hashmap_free_' function, allowing the function to free any struct pointer regardless of where the hashmap_entry field is located. `hashmap_free' no longer takes any arguments aside from the hashmap itself. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap: hashmap_{put,remove} return hashmap_entry *Libravatar Eric Wong1-3/+12
And add *_entry variants to perform container_of as necessary to simplify most callers. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap: use *_entry APIs for iterationLibravatar Eric Wong1-2/+13
Inspired by list_for_each_entry in the Linux kernel. Once again, these are somewhat compromised usability-wise by compilers lacking __typeof__ support. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_cmp_fn takes hashmap_entry paramsLibravatar Eric Wong1-4/+9
Another step in eliminating the requirement of hashmap_entry being the first member of a struct. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_get{,_from_hash} return "struct hashmap_entry *"Libravatar Eric Wong1-5/+7
Update callers to use hashmap_get_entry, hashmap_get_entry_from_hash or container_of as appropriate. This is another step towards eliminating the requirement of hashmap_entry being the first field in a struct. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap: use *_entry APIs to wrap container_ofLibravatar Eric Wong1-6/+34
Using `container_of' can be verbose and choosing names for intermediate "struct hashmap_entry" pointers is a hard problem. So introduce "*_entry" APIs inspired by similar linked-list APIs in the Linux kernel. Unfortunately, `__typeof__' is not portable C, so we need an extra parameter to specify the type. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_get_next returns "struct hashmap_entry *"Libravatar Eric Wong1-4/+8
This is a step towards removing the requirement for hashmap_entry being the first field of a struct. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_put takes "struct hashmap_entry *"Libravatar Eric Wong1-1/+1
This is less error-prone than "void *" as the compiler now detects invalid types being passed. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_remove takes "const struct hashmap_entry *"Libravatar Eric Wong1-1/+1
This is less error-prone than "const void *" as the compiler now detects invalid types being passed. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_get takes "const struct hashmap_entry *"Libravatar Eric Wong1-3/+5
This is less error-prone than "const void *" as the compiler now detects invalid types being passed. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_add takes "struct hashmap_entry *"Libravatar Eric Wong1-2/+2
This is less error-prone than "void *" as the compiler now detects invalid types being passed. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_get_next takes "const struct hashmap_entry *"Libravatar Eric Wong1-1/+2
This is less error-prone than "const void *" as the compiler now detects invalid types being passed. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-07hashmap_entry_init takes "struct hashmap_entry *"Libravatar Eric Wong1-6/+6
C compilers do type checking to make life easier for us. So rely on that and update all hashmap_entry_init callers to take "struct hashmap_entry *" to avoid future bugs while improving safety and readability. Signed-off-by: Eric Wong <e@80x24.org> Reviewed-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-06-20hashmap: convert sha1hash() to oidhash()Libravatar Jeff King1-3/+5
There are no callers left of sha1hash() that do not simply pass the "hash" member of a "struct object_id". Let's get rid of the outdated sha1-specific function and provide one that operates on the whole struct (even though the technique, taking the first few bytes of the hash, will remain the same). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-05-05*.[ch]: remove extern from function declarations using spatchLibravatar Denton Liu1-15/+15
There has been a push to remove extern from function declarations. Remove some instances of "extern" for function declarations which are caught by Coccinelle. Note that Coccinelle has some difficulty with processing functions with `__attribute__` or varargs so some `extern` declarations are left behind to be dealt with in a future patch. This was the Coccinelle patch used: @@ type T; identifier f; @@ - extern T f(...); and it was run with: $ git ls-files \*.{c,h} | grep -v ^compat/ | xargs spatch --sp-file contrib/coccinelle/noextern.cocci --in-place Files under `compat/` are intentionally excluded as some are directly copied from external sources and we should avoid churning them as much as possible. Signed-off-by: Denton Liu <liu.denton@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-02-13Merge branch 'rb/hashmap-h-compilation-fix'Libravatar Junio C Hamano1-2/+1
Code clean-up. * rb/hashmap-h-compilation-fix: hashmap.h: remove unused variable
2018-01-16hashmap.h: remove unused variableLibravatar Randall S. Becker1-2/+1
In 'hashmap_enable_item_counting()', item is assigned but never used. This causes a warning on HP NonStop. As the variable is never used, fix this by just removing it. Signed-off-by: Randall S. Becker <rsbecker@nexbridge.com> Helped-by: Thomas Gummerer <t.gummerer@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-12-05hashmap: adjust documentation to reflect realityLibravatar Johannes Schindelin1-31/+29
The hashmap API is just complicated enough that even at least one long-time Git contributor has to look up how to use it every time he finds a new use case. When that happens, it is really useful if the provided example code is correct... While at it, "fix a memory leak", avoid statements before variable declarations, fix a const -> no-const cast, several %l specifiers (which want to be %ld), avoid using an undefined constant, call scanf() correctly, use FLEX_ALLOC_STR() where appropriate, and adjust the style here and there. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Reviewed-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-07hashmap: add API to disable item counting when threadedLibravatar Jeff Hostetler1-21/+51
This is to address concerns raised by ThreadSanitizer on the mailing list about threaded unprotected R/W access to map.size with my previous "disallow rehash" change (0607e10009ee4e37cb49b4cec8d28a9dda1656a4). See: https://public-inbox.org/git/adb37b70139fd1e2bac18bfd22c8b96683ae18eb.1502780344.git.martin.agren@gmail.com/ Add API to hashmap to disable item counting and thus automatic rehashing. Also include API to later re-enable them. When item counting is disabled, the map.size field is invalid. So to prevent accidents, the field has been renamed and an accessor function hashmap_get_size() has been added. All direct references to this field have been been updated. And the name of the field changed to map.private_size to communicate this. Here is the relevant output from ThreadSanitizer showing the problem: WARNING: ThreadSanitizer: data race (pid=10554) Read of size 4 at 0x00000082d488 by thread T2 (mutexes: write M16): #0 hashmap_add hashmap.c:209 #1 hash_dir_entry_with_parent_and_prefix name-hash.c:302 #2 handle_range_dir name-hash.c:347 #3 handle_range_1 name-hash.c:415 #4 lazy_dir_thread_proc name-hash.c:471 #5 <null> <null> Previous write of size 4 at 0x00000082d488 by thread T1 (mutexes: write M31): #0 hashmap_add hashmap.c:209 #1 hash_dir_entry_with_parent_and_prefix name-hash.c:302 #2 handle_range_dir name-hash.c:347 #3 handle_range_1 name-hash.c:415 #4 handle_range_dir name-hash.c:380 #5 handle_range_1 name-hash.c:415 #6 lazy_dir_thread_proc name-hash.c:471 #7 <null> <null> Martin gives instructions for running TSan on test t3008 in this post: https://public-inbox.org/git/CAN0heSoJDL9pWELD6ciLTmWf-a=oyxe4EXXOmCKvsG5MSuzxsA@mail.gmail.com/ Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-30hashmap: migrate documentation from Documentation/technical into headerLibravatar Stefan Beller1-32/+316
While at it, clarify the use of `key`, `keydata`, `entry_or_key` as well as documenting the new data pointer for the compare function. Rework the example. Signed-off-by: Stefan Beller <sbeller@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-06-30hashmap.h: compare function has access to a data fieldLibravatar Stefan Beller1-4/+8
When using the hashmap a common need is to have access to caller provided data in the compare function. A couple of times we abuse the keydata field to pass in the data needed. This happens for example in patch-ids.c. This patch changes the function signature of the compare function to have one more void pointer available. The pointer given for each invocation of the compare function must be defined in the init function of the hashmap and is just passed through. Documentation of this new feature is deferred to a later patch. This is a rather mechanical conversion, just adding the new pass-through parameter. However while at it improve the naming of the fields of all compare functions used by hashmaps by ensuring unused parameters are prefixed with 'unused_' and naming the parameters what they are (instead of 'unused' make it 'unused_keydata'). Signed-off-by: Stefan Beller <sbeller@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-03-22hashmap: add disallow_rehash settingLibravatar Jeff Hostetler1-0/+24
Teach hashmap to allow rehashes to be suppressed. This is useful when hashmaps are accessed by multiple threads. It still requires the caller to properly manage their locking. This just prevents unexpected rehashing during inserts and deletes. Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-03-22hashmap: allow memihash computation to be continuedLibravatar Jeff Hostetler1-0/+1
Add variant of memihash() to allow the hash computation to be continued. There are times when we compute the hash on a full path and then the hash on just the path to the parent directory. This can be expensive on large repositories. With this, we can hash the parent directory first. And then continue the computation to include the "/filename". Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-07hashmap: add string interning APILibravatar Karsten Blees1-0/+8
Interning short strings with high probability of duplicates can reduce the memory footprint and speed up comparisons. Add strintern() and memintern() APIs that use a hashmap to manage the pool of unique, interned strings. Note: strintern(getenv()) could be used to sanitize git's use of getenv(), in case we ever encounter a platform where a call to getenv() invalidates previous getenv() results (which is allowed by POSIX). Signed-off-by: Karsten Blees <blees@dcon.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-07hashmap: add simplified hashmap_get_from_hash() APILibravatar Karsten Blees1-0/+8
Hashmap entries are typically looked up by just a key. The hashmap_get() API expects an initialized entry structure instead, to support compound keys. This flexibility is currently only needed by find_dir_entry() in name-hash.c (and compat/win32/fscache.c in the msysgit fork). All other (currently five) call sites of hashmap_get() have to set up a near emtpy entry structure, resulting in duplicate code like this: struct hashmap_entry keyentry; hashmap_entry_init(&keyentry, hash(key)); return hashmap_get(map, &keyentry, key); Add a hashmap_get_from_hash() API that allows hashmap lookups by just specifying the key and its hash code, i.e.: return hashmap_get_from_hash(map, hash(key), key); Signed-off-by: Karsten Blees <blees@dcon.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-07hashmap: factor out getting a hash code from a SHA1Libravatar Karsten Blees1-0/+11
Copying the first bytes of a SHA1 is duplicated in six places, however, the implications (the actual value would depend on the endianness of the platform) is documented only once. Add a properly documented API for this. Signed-off-by: Karsten Blees <blees@dcon.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-02-24hashmap.h: use 'unsigned int' for hash-codes everywhereLibravatar Karsten Blees1-1/+1
Signed-off-by: Karsten Blees <blees@dcon.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-11-18add a hashtable implementation that supports O(1) removalLibravatar Karsten Blees1-0/+71
The existing hashtable implementation (in hash.[ch]) uses open addressing (i.e. resolve hash collisions by distributing entries across the table). Thus, removal is difficult to implement with less than O(n) complexity. Resolving collisions of entries with identical hashes (e.g. via chaining) is left to the client code. Add a hashtable implementation that supports O(1) removal and is slightly easier to use due to builtin entry chaining. Supports all basic operations init, free, get, add, remove and iteration. Also includes ready-to-use hash functions based on the public domain FNV-1 algorithm (http://www.isthe.com/chongo/tech/comp/fnv). The per-entry data structure (hashmap_entry) is piggybacked in front of the client's data structure to save memory. See test-hashmap.c for usage examples. The hashtable is resized by a factor of four when 80% full. With these settings, average memory consumption is about 2/3 of hash.[ch], and insertion is about twice as fast due to less frequent resizing. Lookups are also slightly faster, because entries are strictly confined to their bucket (i.e. no data of other buckets needs to be traversed). Signed-off-by: Karsten Blees <blees@dcon.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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