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git/prio-queue.c

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prio-queue: priority queue of pointers to structs Traditionally we used a singly linked list of commits to hold a set of in-flight commits while traversing history. The most typical use of the list is to add commits that are newly discovered to it, keep the list sorted by commit timestamp, pick up the newest one from the list, and keep digging. The cost of keeping the singly linked list sorted is nontrivial, and this typical use pattern better matches a priority queue. Introduce a prio-queue structure, that can be used either as a LIFO stack, or a priority queue. This will be used in the next patch to hold in-flight commits during sort-in-topological-order. Tests and the idea to make it usable for any "void *" pointers to "things" are by Jeff King. Bugs are mine. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-07 02:13:50 +00:00
#include "cache.h"
#include "prio-queue.h"
prio-queue: factor out compare and swap operations When manipulating the priority queue's heap, we frequently have to compare and swap heap entries. As we are storing only void pointers right now, this is quite easy to do inline in a few lines. However, when we start using a more complicated heap entry in a future patch, that will get longer. Factoring out these operations lets us make future changes in one place. It also makes the code a little shorter and more readable. Note that we actually accept indices into the queue array instead of pointers. This is slightly less flexible than passing pointers-to-pointers (we could not swap items from unrelated arrays, but we would not want to), but will make further refactoring simpler (and lets us avoid repeating "queue->array" at each callsite, which led to some long lines). And finally, note that we are cleaning up an accidental use of a "struct commit" pointer to hold a temporary entry during swap. Even though we currently only use this code for commits, it is supposed to be type-agnostic. In practice this didn't matter anyway because we never dereferenced the commit pointer (and on most systems, the pointer values themselves are interchangeable between types). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-14 05:42:50 +00:00
static inline int compare(struct prio_queue *queue, int i, int j)
{
int cmp = queue->compare(queue->array[i], queue->array[j],
queue->cb_data);
return cmp;
}
static inline void swap(struct prio_queue *queue, int i, int j)
{
void *tmp = queue->array[i];
queue->array[i] = queue->array[j];
queue->array[j] = tmp;
}
sort-in-topological-order: use prio-queue Use the prio-queue data structure to implement a priority queue of commits sorted by committer date, when handling --date-order. The structure can also be used as a simple LIFO stack, which is a good match for --topo-order processing. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-07 04:58:12 +00:00
void prio_queue_reverse(struct prio_queue *queue)
{
int i, j;
if (queue->compare != NULL)
die("BUG: prio_queue_reverse() on non-LIFO queue");
prio-queue: factor out compare and swap operations When manipulating the priority queue's heap, we frequently have to compare and swap heap entries. As we are storing only void pointers right now, this is quite easy to do inline in a few lines. However, when we start using a more complicated heap entry in a future patch, that will get longer. Factoring out these operations lets us make future changes in one place. It also makes the code a little shorter and more readable. Note that we actually accept indices into the queue array instead of pointers. This is slightly less flexible than passing pointers-to-pointers (we could not swap items from unrelated arrays, but we would not want to), but will make further refactoring simpler (and lets us avoid repeating "queue->array" at each callsite, which led to some long lines). And finally, note that we are cleaning up an accidental use of a "struct commit" pointer to hold a temporary entry during swap. Even though we currently only use this code for commits, it is supposed to be type-agnostic. In practice this didn't matter anyway because we never dereferenced the commit pointer (and on most systems, the pointer values themselves are interchangeable between types). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-14 05:42:50 +00:00
for (i = 0; i <= (j = (queue->nr - 1) - i); i++)
swap(queue, i, j);
sort-in-topological-order: use prio-queue Use the prio-queue data structure to implement a priority queue of commits sorted by committer date, when handling --date-order. The structure can also be used as a simple LIFO stack, which is a good match for --topo-order processing. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-07 04:58:12 +00:00
}
prio-queue: priority queue of pointers to structs Traditionally we used a singly linked list of commits to hold a set of in-flight commits while traversing history. The most typical use of the list is to add commits that are newly discovered to it, keep the list sorted by commit timestamp, pick up the newest one from the list, and keep digging. The cost of keeping the singly linked list sorted is nontrivial, and this typical use pattern better matches a priority queue. Introduce a prio-queue structure, that can be used either as a LIFO stack, or a priority queue. This will be used in the next patch to hold in-flight commits during sort-in-topological-order. Tests and the idea to make it usable for any "void *" pointers to "things" are by Jeff King. Bugs are mine. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-07 02:13:50 +00:00
void clear_prio_queue(struct prio_queue *queue)
{
free(queue->array);
queue->nr = 0;
queue->alloc = 0;
queue->array = NULL;
}
void prio_queue_put(struct prio_queue *queue, void *thing)
{
int ix, parent;
/* Append at the end */
ALLOC_GROW(queue->array, queue->nr + 1, queue->alloc);
queue->array[queue->nr++] = thing;
prio-queue: factor out compare and swap operations When manipulating the priority queue's heap, we frequently have to compare and swap heap entries. As we are storing only void pointers right now, this is quite easy to do inline in a few lines. However, when we start using a more complicated heap entry in a future patch, that will get longer. Factoring out these operations lets us make future changes in one place. It also makes the code a little shorter and more readable. Note that we actually accept indices into the queue array instead of pointers. This is slightly less flexible than passing pointers-to-pointers (we could not swap items from unrelated arrays, but we would not want to), but will make further refactoring simpler (and lets us avoid repeating "queue->array" at each callsite, which led to some long lines). And finally, note that we are cleaning up an accidental use of a "struct commit" pointer to hold a temporary entry during swap. Even though we currently only use this code for commits, it is supposed to be type-agnostic. In practice this didn't matter anyway because we never dereferenced the commit pointer (and on most systems, the pointer values themselves are interchangeable between types). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-14 05:42:50 +00:00
if (!queue->compare)
prio-queue: priority queue of pointers to structs Traditionally we used a singly linked list of commits to hold a set of in-flight commits while traversing history. The most typical use of the list is to add commits that are newly discovered to it, keep the list sorted by commit timestamp, pick up the newest one from the list, and keep digging. The cost of keeping the singly linked list sorted is nontrivial, and this typical use pattern better matches a priority queue. Introduce a prio-queue structure, that can be used either as a LIFO stack, or a priority queue. This will be used in the next patch to hold in-flight commits during sort-in-topological-order. Tests and the idea to make it usable for any "void *" pointers to "things" are by Jeff King. Bugs are mine. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-07 02:13:50 +00:00
return; /* LIFO */
/* Bubble up the new one */
for (ix = queue->nr - 1; ix; ix = parent) {
parent = (ix - 1) / 2;
prio-queue: factor out compare and swap operations When manipulating the priority queue's heap, we frequently have to compare and swap heap entries. As we are storing only void pointers right now, this is quite easy to do inline in a few lines. However, when we start using a more complicated heap entry in a future patch, that will get longer. Factoring out these operations lets us make future changes in one place. It also makes the code a little shorter and more readable. Note that we actually accept indices into the queue array instead of pointers. This is slightly less flexible than passing pointers-to-pointers (we could not swap items from unrelated arrays, but we would not want to), but will make further refactoring simpler (and lets us avoid repeating "queue->array" at each callsite, which led to some long lines). And finally, note that we are cleaning up an accidental use of a "struct commit" pointer to hold a temporary entry during swap. Even though we currently only use this code for commits, it is supposed to be type-agnostic. In practice this didn't matter anyway because we never dereferenced the commit pointer (and on most systems, the pointer values themselves are interchangeable between types). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-14 05:42:50 +00:00
if (compare(queue, parent, ix) <= 0)
prio-queue: priority queue of pointers to structs Traditionally we used a singly linked list of commits to hold a set of in-flight commits while traversing history. The most typical use of the list is to add commits that are newly discovered to it, keep the list sorted by commit timestamp, pick up the newest one from the list, and keep digging. The cost of keeping the singly linked list sorted is nontrivial, and this typical use pattern better matches a priority queue. Introduce a prio-queue structure, that can be used either as a LIFO stack, or a priority queue. This will be used in the next patch to hold in-flight commits during sort-in-topological-order. Tests and the idea to make it usable for any "void *" pointers to "things" are by Jeff King. Bugs are mine. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-07 02:13:50 +00:00
break;
prio-queue: factor out compare and swap operations When manipulating the priority queue's heap, we frequently have to compare and swap heap entries. As we are storing only void pointers right now, this is quite easy to do inline in a few lines. However, when we start using a more complicated heap entry in a future patch, that will get longer. Factoring out these operations lets us make future changes in one place. It also makes the code a little shorter and more readable. Note that we actually accept indices into the queue array instead of pointers. This is slightly less flexible than passing pointers-to-pointers (we could not swap items from unrelated arrays, but we would not want to), but will make further refactoring simpler (and lets us avoid repeating "queue->array" at each callsite, which led to some long lines). And finally, note that we are cleaning up an accidental use of a "struct commit" pointer to hold a temporary entry during swap. Even though we currently only use this code for commits, it is supposed to be type-agnostic. In practice this didn't matter anyway because we never dereferenced the commit pointer (and on most systems, the pointer values themselves are interchangeable between types). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-14 05:42:50 +00:00
swap(queue, parent, ix);
prio-queue: priority queue of pointers to structs Traditionally we used a singly linked list of commits to hold a set of in-flight commits while traversing history. The most typical use of the list is to add commits that are newly discovered to it, keep the list sorted by commit timestamp, pick up the newest one from the list, and keep digging. The cost of keeping the singly linked list sorted is nontrivial, and this typical use pattern better matches a priority queue. Introduce a prio-queue structure, that can be used either as a LIFO stack, or a priority queue. This will be used in the next patch to hold in-flight commits during sort-in-topological-order. Tests and the idea to make it usable for any "void *" pointers to "things" are by Jeff King. Bugs are mine. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-07 02:13:50 +00:00
}
}
void *prio_queue_get(struct prio_queue *queue)
{
prio-queue: factor out compare and swap operations When manipulating the priority queue's heap, we frequently have to compare and swap heap entries. As we are storing only void pointers right now, this is quite easy to do inline in a few lines. However, when we start using a more complicated heap entry in a future patch, that will get longer. Factoring out these operations lets us make future changes in one place. It also makes the code a little shorter and more readable. Note that we actually accept indices into the queue array instead of pointers. This is slightly less flexible than passing pointers-to-pointers (we could not swap items from unrelated arrays, but we would not want to), but will make further refactoring simpler (and lets us avoid repeating "queue->array" at each callsite, which led to some long lines). And finally, note that we are cleaning up an accidental use of a "struct commit" pointer to hold a temporary entry during swap. Even though we currently only use this code for commits, it is supposed to be type-agnostic. In practice this didn't matter anyway because we never dereferenced the commit pointer (and on most systems, the pointer values themselves are interchangeable between types). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-14 05:42:50 +00:00
void *result;
prio-queue: priority queue of pointers to structs Traditionally we used a singly linked list of commits to hold a set of in-flight commits while traversing history. The most typical use of the list is to add commits that are newly discovered to it, keep the list sorted by commit timestamp, pick up the newest one from the list, and keep digging. The cost of keeping the singly linked list sorted is nontrivial, and this typical use pattern better matches a priority queue. Introduce a prio-queue structure, that can be used either as a LIFO stack, or a priority queue. This will be used in the next patch to hold in-flight commits during sort-in-topological-order. Tests and the idea to make it usable for any "void *" pointers to "things" are by Jeff King. Bugs are mine. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-07 02:13:50 +00:00
int ix, child;
if (!queue->nr)
return NULL;
prio-queue: factor out compare and swap operations When manipulating the priority queue's heap, we frequently have to compare and swap heap entries. As we are storing only void pointers right now, this is quite easy to do inline in a few lines. However, when we start using a more complicated heap entry in a future patch, that will get longer. Factoring out these operations lets us make future changes in one place. It also makes the code a little shorter and more readable. Note that we actually accept indices into the queue array instead of pointers. This is slightly less flexible than passing pointers-to-pointers (we could not swap items from unrelated arrays, but we would not want to), but will make further refactoring simpler (and lets us avoid repeating "queue->array" at each callsite, which led to some long lines). And finally, note that we are cleaning up an accidental use of a "struct commit" pointer to hold a temporary entry during swap. Even though we currently only use this code for commits, it is supposed to be type-agnostic. In practice this didn't matter anyway because we never dereferenced the commit pointer (and on most systems, the pointer values themselves are interchangeable between types). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-14 05:42:50 +00:00
if (!queue->compare)
prio-queue: priority queue of pointers to structs Traditionally we used a singly linked list of commits to hold a set of in-flight commits while traversing history. The most typical use of the list is to add commits that are newly discovered to it, keep the list sorted by commit timestamp, pick up the newest one from the list, and keep digging. The cost of keeping the singly linked list sorted is nontrivial, and this typical use pattern better matches a priority queue. Introduce a prio-queue structure, that can be used either as a LIFO stack, or a priority queue. This will be used in the next patch to hold in-flight commits during sort-in-topological-order. Tests and the idea to make it usable for any "void *" pointers to "things" are by Jeff King. Bugs are mine. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-07 02:13:50 +00:00
return queue->array[--queue->nr]; /* LIFO */
result = queue->array[0];
if (!--queue->nr)
return result;
queue->array[0] = queue->array[queue->nr];
/* Push down the one at the root */
for (ix = 0; ix * 2 + 1 < queue->nr; ix = child) {
child = ix * 2 + 1; /* left */
prio-queue: factor out compare and swap operations When manipulating the priority queue's heap, we frequently have to compare and swap heap entries. As we are storing only void pointers right now, this is quite easy to do inline in a few lines. However, when we start using a more complicated heap entry in a future patch, that will get longer. Factoring out these operations lets us make future changes in one place. It also makes the code a little shorter and more readable. Note that we actually accept indices into the queue array instead of pointers. This is slightly less flexible than passing pointers-to-pointers (we could not swap items from unrelated arrays, but we would not want to), but will make further refactoring simpler (and lets us avoid repeating "queue->array" at each callsite, which led to some long lines). And finally, note that we are cleaning up an accidental use of a "struct commit" pointer to hold a temporary entry during swap. Even though we currently only use this code for commits, it is supposed to be type-agnostic. In practice this didn't matter anyway because we never dereferenced the commit pointer (and on most systems, the pointer values themselves are interchangeable between types). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-14 05:42:50 +00:00
if (child + 1 < queue->nr &&
compare(queue, child, child + 1) >= 0)
prio-queue: priority queue of pointers to structs Traditionally we used a singly linked list of commits to hold a set of in-flight commits while traversing history. The most typical use of the list is to add commits that are newly discovered to it, keep the list sorted by commit timestamp, pick up the newest one from the list, and keep digging. The cost of keeping the singly linked list sorted is nontrivial, and this typical use pattern better matches a priority queue. Introduce a prio-queue structure, that can be used either as a LIFO stack, or a priority queue. This will be used in the next patch to hold in-flight commits during sort-in-topological-order. Tests and the idea to make it usable for any "void *" pointers to "things" are by Jeff King. Bugs are mine. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-07 02:13:50 +00:00
child++; /* use right child */
prio-queue: factor out compare and swap operations When manipulating the priority queue's heap, we frequently have to compare and swap heap entries. As we are storing only void pointers right now, this is quite easy to do inline in a few lines. However, when we start using a more complicated heap entry in a future patch, that will get longer. Factoring out these operations lets us make future changes in one place. It also makes the code a little shorter and more readable. Note that we actually accept indices into the queue array instead of pointers. This is slightly less flexible than passing pointers-to-pointers (we could not swap items from unrelated arrays, but we would not want to), but will make further refactoring simpler (and lets us avoid repeating "queue->array" at each callsite, which led to some long lines). And finally, note that we are cleaning up an accidental use of a "struct commit" pointer to hold a temporary entry during swap. Even though we currently only use this code for commits, it is supposed to be type-agnostic. In practice this didn't matter anyway because we never dereferenced the commit pointer (and on most systems, the pointer values themselves are interchangeable between types). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-14 05:42:50 +00:00
if (compare(queue, ix, child) <= 0)
prio-queue: priority queue of pointers to structs Traditionally we used a singly linked list of commits to hold a set of in-flight commits while traversing history. The most typical use of the list is to add commits that are newly discovered to it, keep the list sorted by commit timestamp, pick up the newest one from the list, and keep digging. The cost of keeping the singly linked list sorted is nontrivial, and this typical use pattern better matches a priority queue. Introduce a prio-queue structure, that can be used either as a LIFO stack, or a priority queue. This will be used in the next patch to hold in-flight commits during sort-in-topological-order. Tests and the idea to make it usable for any "void *" pointers to "things" are by Jeff King. Bugs are mine. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-07 02:13:50 +00:00
break;
prio-queue: factor out compare and swap operations When manipulating the priority queue's heap, we frequently have to compare and swap heap entries. As we are storing only void pointers right now, this is quite easy to do inline in a few lines. However, when we start using a more complicated heap entry in a future patch, that will get longer. Factoring out these operations lets us make future changes in one place. It also makes the code a little shorter and more readable. Note that we actually accept indices into the queue array instead of pointers. This is slightly less flexible than passing pointers-to-pointers (we could not swap items from unrelated arrays, but we would not want to), but will make further refactoring simpler (and lets us avoid repeating "queue->array" at each callsite, which led to some long lines). And finally, note that we are cleaning up an accidental use of a "struct commit" pointer to hold a temporary entry during swap. Even though we currently only use this code for commits, it is supposed to be type-agnostic. In practice this didn't matter anyway because we never dereferenced the commit pointer (and on most systems, the pointer values themselves are interchangeable between types). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-14 05:42:50 +00:00
swap(queue, child, ix);
prio-queue: priority queue of pointers to structs Traditionally we used a singly linked list of commits to hold a set of in-flight commits while traversing history. The most typical use of the list is to add commits that are newly discovered to it, keep the list sorted by commit timestamp, pick up the newest one from the list, and keep digging. The cost of keeping the singly linked list sorted is nontrivial, and this typical use pattern better matches a priority queue. Introduce a prio-queue structure, that can be used either as a LIFO stack, or a priority queue. This will be used in the next patch to hold in-flight commits during sort-in-topological-order. Tests and the idea to make it usable for any "void *" pointers to "things" are by Jeff King. Bugs are mine. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-06-07 02:13:50 +00:00
}
return result;
}
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