git-commit-vandalism/object.h

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#ifndef OBJECT_H
#define OBJECT_H
#include "cache.h"
struct buffer_slab;
struct parsed_object_pool {
struct object **obj_hash;
int nr_objs, obj_hash_size;
/* TODO: migrate alloc_states to mem-pool? */
struct alloc_state *blob_state;
struct alloc_state *tree_state;
struct alloc_state *commit_state;
struct alloc_state *tag_state;
struct alloc_state *object_state;
unsigned commit_count;
/* parent substitutions from .git/info/grafts and .git/shallow */
struct commit_graft **grafts;
int grafts_alloc, grafts_nr;
int is_shallow;
struct stat_validity *shallow_stat;
char *alternate_shallow_file;
int commit_graft_prepared;
struct buffer_slab *buffer_slab;
};
struct parsed_object_pool *parsed_object_pool_new(void);
void parsed_object_pool_clear(struct parsed_object_pool *o);
struct object_list {
struct object *item;
struct object_list *next;
};
Add "named object array" concept We've had this notion of a "object_list" for a long time, which eventually grew a "name" member because some users (notably git-rev-list) wanted to name each object as it is generated. That object_list is great for some things, but it isn't all that wonderful for others, and the "name" member is generally not used by everybody. This patch splits the users of the object_list array up into two: the traditional list users, who want the list-like format, and who don't actually use or want the name. And another class of users that really used the list as an extensible array, and generally wanted to name the objects. The patch is fairly straightforward, but it's also biggish. Most of it really just cleans things up: switching the revision parsing and listing over to the array makes things like the builtin-diff usage much simpler (we now see exactly how many members the array has, and we don't get the objects reversed from the order they were on the command line). One of the main reasons for doing this at all is that the malloc overhead of the simple object list was actually pretty high, and the array is just a lot denser. So this patch brings down memory usage by git-rev-list by just under 3% (on top of all the other memory use optimizations) on the mozilla archive. It does add more lines than it removes, and more importantly, it adds a whole new infrastructure for maintaining lists of objects, but on the other hand, the new dynamic array code is pretty obvious. The change to builtin-diff-tree.c shows a fairly good example of why an array interface is sometimes more natural, and just much simpler for everybody. Signed-off-by: Linus Torvalds <torvalds@osdl.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
2006-06-20 02:42:35 +02:00
struct object_array {
unsigned int nr;
unsigned int alloc;
struct object_array_entry {
struct object *item;
object_array_entry: fix memory handling of the name field Previously, the memory management of the object_array_entry::name field was inconsistent and undocumented. object_array_entries are ultimately created by a single function, add_object_array_with_mode(), which has an argument "const char *name". This function used to simply set the name field to reference the string pointed to by the name parameter, and nobody on the object_array side ever freed the memory. Thus, it assumed that the memory for the name field would be managed by the caller, and that the lifetime of that string would be at least as long as the lifetime of the object_array_entry. But callers were inconsistent: * Some passed pointers to constant strings or argv entries, which was OK. * Some passed pointers to newly-allocated memory, but didn't arrange for the memory ever to be freed. * Some passed the return value of sha1_to_hex(), which is a pointer to a statically-allocated buffer that can be overwritten at any time. * Some passed pointers to refnames that they received from a for_each_ref()-type iteration, but the lifetimes of such refnames is not guaranteed by the refs API. Bring consistency to this mess by changing object_array to make its own copy for the object_array_entry::name field and free this memory when an object_array_entry is deleted from the array. Many callers were passing the empty string as the name parameter, so as a performance optimization, treat the empty string specially. Instead of making a copy, store a pointer to a statically-allocated empty string to object_array_entry::name. When deleting such an entry, skip the free(). Change the callers that were already passing copies to add_object_array_with_mode() to either skip the copy, or (if the memory needed to be allocated anyway) freeing the memory itself. A part of this commit effectively reverts 70d26c6e76 read_revisions_from_stdin: make copies for handle_revision_arg because the copying introduced by that commit (which is still necessary) is now done at a deeper level. Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-05-25 11:08:14 +02:00
/*
* name or NULL. If non-NULL, the memory pointed to
* is owned by this object *except* if it points at
* object_array_slopbuf, which is a static copy of the
* empty string.
*/
char *name;
char *path;
unsigned mode;
Add "named object array" concept We've had this notion of a "object_list" for a long time, which eventually grew a "name" member because some users (notably git-rev-list) wanted to name each object as it is generated. That object_list is great for some things, but it isn't all that wonderful for others, and the "name" member is generally not used by everybody. This patch splits the users of the object_list array up into two: the traditional list users, who want the list-like format, and who don't actually use or want the name. And another class of users that really used the list as an extensible array, and generally wanted to name the objects. The patch is fairly straightforward, but it's also biggish. Most of it really just cleans things up: switching the revision parsing and listing over to the array makes things like the builtin-diff usage much simpler (we now see exactly how many members the array has, and we don't get the objects reversed from the order they were on the command line). One of the main reasons for doing this at all is that the malloc overhead of the simple object list was actually pretty high, and the array is just a lot denser. So this patch brings down memory usage by git-rev-list by just under 3% (on top of all the other memory use optimizations) on the mozilla archive. It does add more lines than it removes, and more importantly, it adds a whole new infrastructure for maintaining lists of objects, but on the other hand, the new dynamic array code is pretty obvious. The change to builtin-diff-tree.c shows a fairly good example of why an array interface is sometimes more natural, and just much simpler for everybody. Signed-off-by: Linus Torvalds <torvalds@osdl.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
2006-06-20 02:42:35 +02:00
} *objects;
};
#define OBJECT_ARRAY_INIT { 0, 0, NULL }
/*
* object flag allocation:
revision: --show-pulls adds helpful merges The default file history simplification of "git log -- <path>" or "git rev-list -- <path>" focuses on providing the smallest set of commits that first contributed a change. The revision walk greatly restricts the set of walked commits by visiting only the first TREESAME parent of a merge commit, when one exists. This means that portions of the commit-graph are not walked, which can be a performance benefit, but can also "hide" commits that added changes but were ignored by a merge resolution. The --full-history option modifies this by walking all commits and reporting a merge commit as "interesting" if it has _any_ parent that is not TREESAME. This tends to be an over-representation of important commits, especially in an environment where most merge commits are created by pull request completion. Suppose we have a commit A and we create a commit B on top that changes our file. When we merge the pull request, we create a merge commit M. If no one else changed the file in the first-parent history between M and A, then M will not be TREESAME to its first parent, but will be TREESAME to B. Thus, the simplified history will be "B". However, M will appear in the --full-history mode. However, suppose that a number of topics T1, T2, ..., Tn were created based on commits C1, C2, ..., Cn between A and M as follows: A----C1----C2--- ... ---Cn----M------P1---P2--- ... ---Pn \ \ \ \ / / / / \ \__.. \ \/ ..__T1 / Tn \ \__.. /\ ..__T2 / \_____________________B \____________________/ If the commits T1, T2, ... Tn did not change the file, then all of P1 through Pn will be TREESAME to their first parent, but not TREESAME to their second. This means that all of those merge commits appear in the --full-history view, with edges that immediately collapse into the lower history without introducing interesting single-parent commits. The --simplify-merges option was introduced to remove these extra merge commits. By noticing that the rewritten parents are reachable from their first parents, those edges can be simplified away. Finally, the commits now look like single-parent commits that are TREESAME to their "only" parent. Thus, they are removed and this issue does not cause issues anymore. However, this also ends up removing the commit M from the history view! Even worse, the --simplify-merges option requires walking the entire history before returning a single result. Many Git users are using Git alongside a Git service that provides code storage alongside a code review tool commonly called "Pull Requests" or "Merge Requests" against a target branch. When these requests are accepted and merged, they typically create a merge commit whose first parent is the previous branch tip and the second parent is the tip of the topic branch used for the request. This presents a valuable order to the parents, but also makes that merge commit slightly special. Users may want to see not only which commits changed a file, but which pull requests merged those commits into their branch. In the previous example, this would mean the users want to see the merge commit "M" in addition to the single- parent commit "C". Users are even more likely to want these merge commits when they use pull requests to merge into a feature branch before merging that feature branch into their trunk. In some sense, users are asking for the "first" merge commit to bring in the change to their branch. As long as the parent order is consistent, this can be handled with the following rule: Include a merge commit if it is not TREESAME to its first parent, but is TREESAME to a later parent. These merges look like the merge commits that would result from running "git pull <topic>" on a main branch. Thus, the option to show these commits is called "--show-pulls". This has the added benefit of showing the commits created by closing a pull request or merge request on any of the Git hosting and code review platforms. To test these options, extend the standard test example to include a merge commit that is not TREESAME to its first parent. It is surprising that that option was not already in the example, as it is instructive. In particular, this extension demonstrates a common issue with file history simplification. When a user resolves a merge conflict using "-Xours" or otherwise ignoring one side of the conflict, they create a TREESAME edge that probably should not be TREESAME. This leads users to become frustrated and complain that "my change disappeared!" In my experience, showing them history with --full-history and --simplify-merges quickly reveals the problematic merge. As mentioned, this option is expensive to compute. The --show-pulls option _might_ show the merge commit (usually titled "resolving conflicts") more quickly. Of course, this depends on the user having the correct parent order, which is backwards when using "git pull master" from a topic branch. There are some special considerations when combining the --show-pulls option with --simplify-merges. This requires adding a new PULL_MERGE object flag to store the information from the initial TREESAME comparisons. This helps avoid dropping those commits in later filters. This is covered by a test, including how the parents can be simplified. Since "struct object" has already ruined its 32-bit alignment by using 33 bits across parsed, type, and flags member, let's not make it worse. PULL_MERGE is used in revision.c with the same value (1u<<15) as REACHABLE in commit-graph.c. The REACHABLE flag is only used when writing a commit-graph file, and a revision walk using --show-pulls does not happen in the same process. Care must be taken in the future to ensure this remains the case. Update Documentation/rev-list-options.txt with significant details around this option. This requires updating the example in the History Simplification section to demonstrate some of the problems with TREESAME second parents. Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2020-04-10 14:19:43 +02:00
* revision.h: 0---------10 15 25----28
* fetch-pack.c: 01
* negotiator/default.c: 2--5
* walker.c: 0-2
* upload-pack.c: 4 11-----14 16-----19
* builtin/blame.c: 12-13
* bisect.c: 16
* bundle.c: 16
* http-push.c: 16-----19
commit-graph: fix writing first commit-graph during fetch The previous commit includes a failing test for an issue around fetch.writeCommitGraph and fetching in a repo with a submodule. Here, we fix that bug and set the test to "test_expect_success". The problem arises with this set of commands when the remote repo at <url> has a submodule. Note that --recurse-submodules is not needed to demonstrate the bug. $ git clone <url> test $ cd test $ git -c fetch.writeCommitGraph=true fetch origin Computing commit graph generation numbers: 100% (12/12), done. BUG: commit-graph.c:886: missing parent <hash1> for commit <hash2> Aborted (core dumped) As an initial fix, I converted the code in builtin/fetch.c that calls write_commit_graph_reachable() to instead launch a "git commit-graph write --reachable --split" process. That code worked, but is not how we want the feature to work long-term. That test did demonstrate that the issue must be something to do with internal state of the 'git fetch' process. The write_commit_graph() method in commit-graph.c ensures the commits we plan to write are "closed under reachability" using close_reachable(). This method walks from the input commits, and uses the UNINTERESTING flag to mark which commits have already been visited. This allows the walk to take O(N) time, where N is the number of commits, instead of O(P) time, where P is the number of paths. (The number of paths can be exponential in the number of commits.) However, the UNINTERESTING flag is used in lots of places in the codebase. This flag usually means some barrier to stop a commit walk, such as in revision-walking to compare histories. It is not often cleared after the walk completes because the starting points of those walks do not have the UNINTERESTING flag, and clear_commit_marks() would stop immediately. This is happening during a 'git fetch' call with a remote. The fetch negotiation is comparing the remote refs with the local refs and marking some commits as UNINTERESTING. I tested running clear_commit_marks_many() to clear the UNINTERESTING flag inside close_reachable(), but the tips did not have the flag, so that did nothing. It turns out that the calculate_changed_submodule_paths() method is at fault. Thanks, Peff, for pointing out this detail! More specifically, for each submodule, the collect_changed_submodules() runs a revision walk to essentially do file-history on the list of submodules. That revision walk marks commits UNININTERESTING if they are simplified away by not changing the submodule. Instead, I finally arrived on the conclusion that I should use a flag that is not used in any other part of the code. In commit-reach.c, a number of flags were defined for commit walk algorithms. The REACHABLE flag seemed like it made the most sense, and it seems it was not actually used in the file. The REACHABLE flag was used in early versions of commit-reach.c, but was removed by 4fbcca4 (commit-reach: make can_all_from_reach... linear, 2018-07-20). Add the REACHABLE flag to commit-graph.c and use it instead of UNINTERESTING in close_reachable(). This fixes the bug in manual testing. Reported-by: Johannes Schindelin <johannes.schindelin@gmx.de> Helped-by: Jeff King <peff@peff.net> Helped-by: Szeder Gábor <szeder.dev@gmail.com> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2019-10-24 15:40:42 +02:00
* commit-graph.c: 15
* commit-reach.c: 16-----19
* sha1-name.c: 20
* list-objects-filter.c: 21
* builtin/fsck.c: 0--3
* builtin/index-pack.c: 2021
* builtin/pack-objects.c: 20
* builtin/reflog.c: 10--12
* builtin/show-branch.c: 0-------------------------------------------26
* builtin/unpack-objects.c: 2021
*/
revision.c: generation-based topo-order algorithm The current --topo-order algorithm requires walking all reachable commits up front, topo-sorting them, all before outputting the first value. This patch introduces a new algorithm which uses stored generation numbers to incrementally walk in topo-order, outputting commits as we go. This can dramatically reduce the computation time to write a fixed number of commits, such as when limiting with "-n <N>" or filling the first page of a pager. When running a command like 'git rev-list --topo-order HEAD', Git performed the following steps: 1. Run limit_list(), which parses all reachable commits, adds them to a linked list, and distributes UNINTERESTING flags. If all unprocessed commits are UNINTERESTING, then it may terminate without walking all reachable commits. This does not occur if we do not specify UNINTERESTING commits. 2. Run sort_in_topological_order(), which is an implementation of Kahn's algorithm. It first iterates through the entire set of important commits and computes the in-degree of each (plus one, as we use 'zero' as a special value here). Then, we walk the commits in priority order, adding them to the priority queue if and only if their in-degree is one. As we remove commits from this priority queue, we decrement the in-degree of their parents. 3. While we are peeling commits for output, get_revision_1() uses pop_commit on the full list of commits computed by sort_in_topological_order(). In the new algorithm, these three steps correspond to three different commit walks. We run these walks simultaneously, and advance each only as far as necessary to satisfy the requirements of the 'higher order' walk. We know when we can pause each walk by using generation numbers from the commit- graph feature. Recall that the generation number of a commit satisfies: * If the commit has at least one parent, then the generation number is one more than the maximum generation number among its parents. * If the commit has no parent, then the generation number is one. There are two special generation numbers: * GENERATION_NUMBER_INFINITY: this value is 0xffffffff and indicates that the commit is not stored in the commit-graph and the generation number was not previously calculated. * GENERATION_NUMBER_ZERO: this value (0) is a special indicator to say that the commit-graph was generated by a version of Git that does not compute generation numbers (such as v2.18.0). Since we use generation_numbers_enabled() before using the new algorithm, we do not need to worry about GENERATION_NUMBER_ZERO. However, the existence of GENERATION_NUMBER_INFINITY implies the following weaker statement than the usual we expect from generation numbers: If A and B are commits with generation numbers gen(A) and gen(B) and gen(A) < gen(B), then A cannot reach B. Thus, we will walk in each of our stages until the "maximum unexpanded generation number" is strictly lower than the generation number of a commit we are about to use. The walks are as follows: 1. EXPLORE: using the explore_queue priority queue (ordered by maximizing the generation number), parse each reachable commit until all commits in the queue have generation number strictly lower than needed. During this walk, update the UNINTERESTING flags as necessary. 2. INDEGREE: using the indegree_queue priority queue (ordered by maximizing the generation number), add one to the in- degree of each parent for each commit that is walked. Since we walk in order of decreasing generation number, we know that discovering an in-degree value of 0 means the value for that commit was not initialized, so should be initialized to two. (Recall that in-degree value "1" is what we use to say a commit is ready for output.) As we iterate the parents of a commit during this walk, ensure the EXPLORE walk has walked beyond their generation numbers. 3. TOPO: using the topo_queue priority queue (ordered based on the sort_order given, which could be commit-date, author- date, or typical topo-order which treats the queue as a LIFO stack), remove a commit from the queue and decrement the in-degree of each parent. If a parent has an in-degree of one, then we add it to the topo_queue. Before we decrement the in-degree, however, ensure the INDEGREE walk has walked beyond that generation number. The implementations of these walks are in the following methods: * explore_walk_step and explore_to_depth * indegree_walk_step and compute_indegrees_to_depth * next_topo_commit and expand_topo_walk These methods have some patterns that may seem strange at first, but they are probably carry-overs from their equivalents in limit_list and sort_in_topological_order. One thing that is missing from this implementation is a proper way to stop walking when the entire queue is UNINTERESTING, so this implementation is not enabled by comparisions, such as in 'git rev-list --topo-order A..B'. This can be updated in the future. In my local testing, I used the following Git commands on the Linux repository in three modes: HEAD~1 with no commit-graph, HEAD~1 with a commit-graph, and HEAD with a commit-graph. This allows comparing the benefits we get from parsing commits from the commit-graph and then again the benefits we get by restricting the set of commits we walk. Test: git rev-list --topo-order -100 HEAD HEAD~1, no commit-graph: 6.80 s HEAD~1, w/ commit-graph: 0.77 s HEAD, w/ commit-graph: 0.02 s Test: git rev-list --topo-order -100 HEAD -- tools HEAD~1, no commit-graph: 9.63 s HEAD~1, w/ commit-graph: 6.06 s HEAD, w/ commit-graph: 0.06 s This speedup is due to a few things. First, the new generation- number-enabled algorithm walks commits on order of the number of results output (subject to some branching structure expectations). Since we limit to 100 results, we are running a query similar to filling a single page of results. Second, when specifying a path, we must parse the root tree object for each commit we walk. The previous benefits from the commit-graph are entirely from reading the commit-graph instead of parsing commits. Since we need to parse trees for the same number of commits as before, we slow down significantly from the non-path-based query. For the test above, I specifically selected a path that is changed frequently, including by merge commits. A less-frequently-changed path (such as 'README') has similar end-to-end time since we need to walk the same number of commits (before determining we do not have 100 hits). However, get the benefit that the output is presented to the user as it is discovered, much the same as a normal 'git log' command (no '--topo-order'). This is an improved user experience, even if the command has the same runtime. Helped-by: Jeff King <peff@peff.net> Signed-off-by: Derrick Stolee <dstolee@microsoft.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-11-01 14:46:22 +01:00
#define FLAG_BITS 29
/*
* The object type is stored in 3 bits.
*/
struct object {
unsigned parsed : 1;
unsigned type : TYPE_BITS;
unsigned flags : FLAG_BITS;
struct object_id oid;
};
const char *type_name(unsigned int type);
int type_from_string_gently(const char *str, ssize_t, int gentle);
#define type_from_string(str) type_from_string_gently(str, -1, 0)
/*
* Return the current number of buckets in the object hashmap.
*/
unsigned int get_max_object_index(void);
/*
* Return the object from the specified bucket in the object hashmap.
*/
struct object *get_indexed_object(unsigned int);
/*
* This can be used to see if we have heard of the object before, but
* it can return "yes we have, and here is a half-initialised object"
* for an object that we haven't loaded/parsed yet.
*
* When parsing a commit to create an in-core commit object, its
* parents list holds commit objects that represent its parents, but
* they are expected to be lazily initialized and do not know what
* their trees or parents are yet. When this function returns such a
* half-initialised objects, the caller is expected to initialize them
* by calling parse_object() on them.
*/
struct object *lookup_object(struct repository *r, const struct object_id *oid);
void *create_object(struct repository *r, const struct object_id *oid, void *obj);
void *object_as_type(struct repository *r, struct object *obj, enum object_type type, int quiet);
add object_as_type helper for casting objects When we call lookup_commit, lookup_tree, etc, the logic goes something like: 1. Look for an existing object struct. If we don't have one, allocate and return a new one. 2. Double check that any object we have is the expected type (and complain and return NULL otherwise). 3. Convert an object with type OBJ_NONE (from a prior call to lookup_unknown_object) to the expected type. We can encapsulate steps 2 and 3 in a helper function which checks whether we have the expected object type, converts OBJ_NONE as appropriate, and returns the object. Not only does this shorten the code, but it also provides one central location for converting OBJ_NONE objects into objects of other types. Future patches will use that to enforce type-specific invariants. Since this is a refactoring, we would want it to behave exactly as the current code. It takes a little reasoning to see that this is the case: - for lookup_{commit,tree,etc} functions, we are just pulling steps 2 and 3 into a function that does the same thing. - for the call in peel_object, we currently only do step 3 (but we want to consolidate it with the others, as mentioned above). However, step 2 is a noop here, as the surrounding conditional makes sure we have OBJ_NONE (which we want to keep to avoid an extraneous call to sha1_object_info). - for the call in lookup_commit_reference_gently, we are currently doing step 2 but not step 3. However, step 3 is a noop here. The object we got will have just come from deref_tag, which must have figured out the type for each object in order to know when to stop peeling. Therefore the type will never be OBJ_NONE. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-13 08:42:03 +02:00
/*
* Returns the object, having parsed it to find out what it is.
*
* Returns NULL if the object is missing or corrupt.
*/
struct object *parse_object(struct repository *r, const struct object_id *oid);
/*
* Like parse_object, but will die() instead of returning NULL. If the
* "name" parameter is not NULL, it is included in the error message
* (otherwise, the hex object ID is given).
*/
struct object *parse_object_or_die(const struct object_id *oid, const char *name);
/* Given the result of read_sha1_file(), returns the object after
* parsing it. eaten_p indicates if the object has a borrowed copy
* of buffer and the caller should not free() it.
*/
struct object *parse_object_buffer(struct repository *r, const struct object_id *oid, enum object_type type, unsigned long size, void *buffer, int *eaten_p);
/** Returns the object, with potentially excess memory allocated. **/
struct object *lookup_unknown_object(const struct object_id *oid);
struct object_list *object_list_insert(struct object *item,
struct object_list **list_p);
int object_list_contains(struct object_list *list, struct object *obj);
void object_list_free(struct object_list **list);
Add "named object array" concept We've had this notion of a "object_list" for a long time, which eventually grew a "name" member because some users (notably git-rev-list) wanted to name each object as it is generated. That object_list is great for some things, but it isn't all that wonderful for others, and the "name" member is generally not used by everybody. This patch splits the users of the object_list array up into two: the traditional list users, who want the list-like format, and who don't actually use or want the name. And another class of users that really used the list as an extensible array, and generally wanted to name the objects. The patch is fairly straightforward, but it's also biggish. Most of it really just cleans things up: switching the revision parsing and listing over to the array makes things like the builtin-diff usage much simpler (we now see exactly how many members the array has, and we don't get the objects reversed from the order they were on the command line). One of the main reasons for doing this at all is that the malloc overhead of the simple object list was actually pretty high, and the array is just a lot denser. So this patch brings down memory usage by git-rev-list by just under 3% (on top of all the other memory use optimizations) on the mozilla archive. It does add more lines than it removes, and more importantly, it adds a whole new infrastructure for maintaining lists of objects, but on the other hand, the new dynamic array code is pretty obvious. The change to builtin-diff-tree.c shows a fairly good example of why an array interface is sometimes more natural, and just much simpler for everybody. Signed-off-by: Linus Torvalds <torvalds@osdl.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
2006-06-20 02:42:35 +02:00
/* Object array handling .. */
void add_object_array(struct object *obj, const char *name, struct object_array *array);
void add_object_array_with_path(struct object *obj, const char *name, struct object_array *array, unsigned mode, const char *path);
object_array: add and use `object_array_pop()` In a couple of places, we pop objects off an object array `foo` by decreasing `foo.nr`. We access `foo.nr` in many places, but most if not all other times we do so read-only, e.g., as we iterate over the array. But when we change `foo.nr` behind the array's back, it feels a bit nasty and looks like it might leak memory. Leaks happen if the popped element has an allocated `name` or `path`. At the moment, that is not the case. Still, 1) the object array might gain more fields that want to be freed, 2) a code path where we pop might start using names or paths, 3) one of these code paths might be copied to somewhere where we do, and 4) using a dedicated function for popping is conceptually cleaner. Introduce and use `object_array_pop()` instead. Release memory in the new function. Document that popping an object leaves the associated elements in limbo. The converted places were identified by grepping for "\.nr\>" and looking for "--". Make the new function return NULL on an empty array. This is consistent with `pop_commit()` and allows the following: while ((o = object_array_pop(&foo)) != NULL) { // do something } But as noted above, we don't need to go out of our way to avoid reading `foo.nr`. This is probably more readable: while (foo.nr) { ... o = object_array_pop(&foo); // do something } The name of `object_array_pop()` does not quite align with `add_object_array()`. That is unfortunate. On the other hand, it matches `object_array_clear()`. Arguably it's `add_...` that is the odd one out, since it reads like it's used to "add" an "object array". For that reason, side with `object_array_clear()`. Signed-off-by: Martin Ågren <martin.agren@gmail.com> Reviewed-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-09-23 01:34:53 +02:00
/*
* Returns NULL if the array is empty. Otherwise, returns the last object
* after removing its entry from the array. Other resources associated
* with that object are left in an unspecified state and should not be
* examined.
*/
struct object *object_array_pop(struct object_array *array);
typedef int (*object_array_each_func_t)(struct object_array_entry *, void *);
/*
* Apply want to each entry in array, retaining only the entries for
* which the function returns true. Preserve the order of the entries
* that are retained.
*/
void object_array_filter(struct object_array *array,
object_array_each_func_t want, void *cb_data);
/*
* Remove from array all but the first entry with a given name.
* Warning: this function uses an O(N^2) algorithm.
*/
void object_array_remove_duplicates(struct object_array *array);
Add "named object array" concept We've had this notion of a "object_list" for a long time, which eventually grew a "name" member because some users (notably git-rev-list) wanted to name each object as it is generated. That object_list is great for some things, but it isn't all that wonderful for others, and the "name" member is generally not used by everybody. This patch splits the users of the object_list array up into two: the traditional list users, who want the list-like format, and who don't actually use or want the name. And another class of users that really used the list as an extensible array, and generally wanted to name the objects. The patch is fairly straightforward, but it's also biggish. Most of it really just cleans things up: switching the revision parsing and listing over to the array makes things like the builtin-diff usage much simpler (we now see exactly how many members the array has, and we don't get the objects reversed from the order they were on the command line). One of the main reasons for doing this at all is that the malloc overhead of the simple object list was actually pretty high, and the array is just a lot denser. So this patch brings down memory usage by git-rev-list by just under 3% (on top of all the other memory use optimizations) on the mozilla archive. It does add more lines than it removes, and more importantly, it adds a whole new infrastructure for maintaining lists of objects, but on the other hand, the new dynamic array code is pretty obvious. The change to builtin-diff-tree.c shows a fairly good example of why an array interface is sometimes more natural, and just much simpler for everybody. Signed-off-by: Linus Torvalds <torvalds@osdl.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
2006-06-20 02:42:35 +02:00
/*
* Remove any objects from the array, freeing all used memory; afterwards
* the array is ready to store more objects with add_object_array().
*/
void object_array_clear(struct object_array *array);
void clear_object_flags(unsigned flags);
/*
* Clear the specified object flags from all in-core commit objects.
*/
void clear_commit_marks_all(unsigned int flags);
#endif /* OBJECT_H */