[PATCH 15/26] reftable: add a heap-based priority queue for reftable records
From: Han-Wen Nienhuys <hanwen@google.com>
This is needed to create a merged view multiple reftables
Signed-off-by: Han-Wen Nienhuys <hanwen@google.com>
---
Makefile | 2 +
reftable/pq.c | 115 ++++++++++++++++++++++++++++++++++++++
reftable/pq.h | 32 +++++++++++
reftable/pq_test.c | 72 ++++++++++++++++++++++++
reftable/reftable-tests.h | 1 +
t/helper/test-reftable.c | 1 +
6 files changed, 223 insertions(+)
create mode 100644 reftable/pq.c
create mode 100644 reftable/pq.h
create mode 100644 reftable/pq_test.c
diff --git a/Makefile b/Makefile
index 235d30b55d6..2123aa782c9 100644
--- a/Makefile
+++ b/Makefile
@@ -2454,6 +2454,7 @@ REFTABLE_OBJS += reftable/block.o
REFTABLE_OBJS += reftable/blocksource.o
REFTABLE_OBJS += reftable/iter.o
REFTABLE_OBJS += reftable/publicbasics.o
+REFTABLE_OBJS += reftable/pq.o
REFTABLE_OBJS += reftable/reader.o
REFTABLE_OBJS += reftable/record.o
REFTABLE_OBJS += reftable/refname.o
@@ -2464,6 +2465,7 @@ REFTABLE_OBJS += reftable/writer.o
REFTABLE_TEST_OBJS += reftable/basics_test.o
REFTABLE_TEST_OBJS += reftable/block_test.o
+REFTABLE_TEST_OBJS += reftable/pq_test.o
REFTABLE_TEST_OBJS += reftable/record_test.o
REFTABLE_TEST_OBJS += reftable/readwrite_test.o
REFTABLE_TEST_OBJS += reftable/test_framework.o
diff --git a/reftable/pq.c b/reftable/pq.c
new file mode 100644
index 00000000000..8918d158e2d
--- /dev/null
+++ b/reftable/pq.c
@@ -0,0 +1,115 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#include "pq.h"
+
+#include "reftable-record.h"
+#include "system.h"
+#include "basics.h"
+
+static int pq_less(struct pq_entry a, struct pq_entry b)
+{
+ struct strbuf ak = STRBUF_INIT;
+ struct strbuf bk = STRBUF_INIT;
+ int cmp = 0;
+ reftable_record_key(&a.rec, &ak);
+ reftable_record_key(&b.rec, &bk);
+
+ cmp = strbuf_cmp(&ak, &bk);
+
+ strbuf_release(&ak);
+ strbuf_release(&bk);
+
+ if (cmp == 0)
+ return a.index > b.index;
+
+ return cmp < 0;
+}
+
+struct pq_entry merged_iter_pqueue_top(struct merged_iter_pqueue pq)
+{
+ return pq.heap[0];
+}
+
+int merged_iter_pqueue_is_empty(struct merged_iter_pqueue pq)
+{
+ return pq.len == 0;
+}
+
+void merged_iter_pqueue_check(struct merged_iter_pqueue pq)
+{
+ int i = 0;
+ for (i = 1; i < pq.len; i++) {
+ int parent = (i - 1) / 2;
+
+ assert(pq_less(pq.heap[parent], pq.heap[i]));
+ }
+}
+
+struct pq_entry merged_iter_pqueue_remove(struct merged_iter_pqueue *pq)
+{
+ int i = 0;
+ struct pq_entry e = pq->heap[0];
+ pq->heap[0] = pq->heap[pq->len - 1];
+ pq->len--;
+
+ i = 0;
+ while (i < pq->len) {
+ int min = i;
+ int j = 2 * i + 1;
+ int k = 2 * i + 2;
+ if (j < pq->len && pq_less(pq->heap[j], pq->heap[i])) {
+ min = j;
+ }
+ if (k < pq->len && pq_less(pq->heap[k], pq->heap[min])) {
+ min = k;
+ }
+
+ if (min == i) {
+ break;
+ }
+
+ SWAP(pq->heap[i], pq->heap[min]);
+ i = min;
+ }
+
+ return e;
+}
+
+void merged_iter_pqueue_add(struct merged_iter_pqueue *pq, struct pq_entry e)
+{
+ int i = 0;
+ if (pq->len == pq->cap) {
+ pq->cap = 2 * pq->cap + 1;
+ pq->heap = reftable_realloc(pq->heap,
+ pq->cap * sizeof(struct pq_entry));
+ }
+
+ pq->heap[pq->len++] = e;
+ i = pq->len - 1;
+ while (i > 0) {
+ int j = (i - 1) / 2;
+ if (pq_less(pq->heap[j], pq->heap[i])) {
+ break;
+ }
+
+ SWAP(pq->heap[j], pq->heap[i]);
+
+ i = j;
+ }
+}
+
+void merged_iter_pqueue_release(struct merged_iter_pqueue *pq)
+{
+ int i = 0;
+ for (i = 0; i < pq->len; i++) {
+ reftable_record_destroy(&pq->heap[i].rec);
+ }
+ FREE_AND_NULL(pq->heap);
+ pq->len = pq->cap = 0;
+}
diff --git a/reftable/pq.h b/reftable/pq.h
new file mode 100644
index 00000000000..385d2fb139a
--- /dev/null
+++ b/reftable/pq.h
@@ -0,0 +1,32 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#ifndef PQ_H
+#define PQ_H
+
+#include "record.h"
+
+struct pq_entry {
+ int index;
+ struct reftable_record rec;
+};
+
+struct merged_iter_pqueue {
+ struct pq_entry *heap;
+ size_t len;
+ size_t cap;
+};
+
+struct pq_entry merged_iter_pqueue_top(struct merged_iter_pqueue pq);
+int merged_iter_pqueue_is_empty(struct merged_iter_pqueue pq);
+void merged_iter_pqueue_check(struct merged_iter_pqueue pq);
+struct pq_entry merged_iter_pqueue_remove(struct merged_iter_pqueue *pq);
+void merged_iter_pqueue_add(struct merged_iter_pqueue *pq, struct pq_entry e);
+void merged_iter_pqueue_release(struct merged_iter_pqueue *pq);
+
+#endif
diff --git a/reftable/pq_test.c b/reftable/pq_test.c
new file mode 100644
index 00000000000..ad21673e854
--- /dev/null
+++ b/reftable/pq_test.c
@@ -0,0 +1,72 @@
+/*
+Copyright 2020 Google LLC
+
+Use of this source code is governed by a BSD-style
+license that can be found in the LICENSE file or at
+https://developers.google.com/open-source/licenses/bsd
+*/
+
+#include "system.h"
+
+#include "basics.h"
+#include "constants.h"
+#include "pq.h"
+#include "record.h"
+#include "reftable-tests.h"
+#include "test_framework.h"
+
+static void test_pq(void)
+{
+ char *names[54] = { NULL };
+ int N = ARRAY_SIZE(names) - 1;
+
+ struct merged_iter_pqueue pq = { NULL };
+ const char *last = NULL;
+
+ int i = 0;
+ for (i = 0; i < N; i++) {
+ char name[100];
+ snprintf(name, sizeof(name), "%02d", i);
+ names[i] = xstrdup(name);
+ }
+
+ i = 1;
+ do {
+ struct reftable_record rec =
+ reftable_new_record(BLOCK_TYPE_REF);
+ struct pq_entry e = { 0 };
+
+ reftable_record_as_ref(&rec)->refname = names[i];
+ e.rec = rec;
+ merged_iter_pqueue_add(&pq, e);
+ merged_iter_pqueue_check(pq);
+ i = (i * 7) % N;
+ } while (i != 1);
+
+ while (!merged_iter_pqueue_is_empty(pq)) {
+ struct pq_entry e = merged_iter_pqueue_remove(&pq);
+ struct reftable_ref_record *ref =
+ reftable_record_as_ref(&e.rec);
+
+ merged_iter_pqueue_check(pq);
+
+ if (last) {
+ assert(strcmp(last, ref->refname) < 0);
+ }
+ last = ref->refname;
+ ref->refname = NULL;
+ reftable_free(ref);
+ }
+
+ for (i = 0; i < N; i++) {
+ reftable_free(names[i]);
+ }
+
+ merged_iter_pqueue_release(&pq);
+}
+
+int pq_test_main(int argc, const char *argv[])
+{
+ RUN_TEST(test_pq);
+ return 0;
+}
diff --git a/reftable/reftable-tests.h b/reftable/reftable-tests.h
index 3d541fa5c0c..0019cbcfa49 100644
--- a/reftable/reftable-tests.h
+++ b/reftable/reftable-tests.h
@@ -12,6 +12,7 @@ https://developers.google.com/open-source/licenses/bsd
int basics_test_main(int argc, const char **argv);
int block_test_main(int argc, const char **argv);
int merged_test_main(int argc, const char **argv);
+int pq_test_main(int argc, const char **argv);
int record_test_main(int argc, const char **argv);
int refname_test_main(int argc, const char **argv);
int readwrite_test_main(int argc, const char **argv);
diff --git a/t/helper/test-reftable.c b/t/helper/test-reftable.c
index 898aba836fd..0b5a1701df1 100644
--- a/t/helper/test-reftable.c
+++ b/t/helper/test-reftable.c
@@ -5,6 +5,7 @@ int cmd__reftable(int argc, const char **argv)
{
basics_test_main(argc, argv);
block_test_main(argc, argv);
+ pq_test_main(argc, argv);
record_test_main(argc, argv);
readwrite_test_main(argc, argv);
tree_test_main(argc, argv);
--
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Han-Wen Nienhuys via GitGitGadget <gitgitgadget@gmail.com>