reftable: a generic binary tree implementation
The reftable format includes support for an (OID => ref) map. This map can speed up visibility and reachability checks. In particular, various operations along the fetch/push path within Gerrit have ben sped up by using this structure. The map is constructed with help of a binary tree. Object IDs are hashes, so they are uniformly distributed. Hence, the tree does not attempt forced rebalancing. Signed-off-by: Han-Wen Nienhuys <hanwen@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Han-Wen Nienhuys committed
Oct 7, 2021 at 20:25 UTC
35425d1034f2a98d438da21c68334056af7033ca
5 files changed
+162
-1
Makefile
+3
-1
@@ -2462,11 +2462,13 @@ REFTABLE_OBJS += reftable/block.o
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REFTABLE_OBJS += reftable/blocksource.o
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REFTABLE_OBJS += reftable/publicbasics.o
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REFTABLE_OBJS += reftable/record.o
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+REFTABLE_OBJS += reftable/tree.o
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+REFTABLE_TEST_OBJS += reftable/basics_test.o
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REFTABLE_TEST_OBJS += reftable/block_test.o
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REFTABLE_TEST_OBJS += reftable/record_test.o
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REFTABLE_TEST_OBJS += reftable/test_framework.o
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-REFTABLE_TEST_OBJS += reftable/basics_test.o
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+REFTABLE_TEST_OBJS += reftable/tree_test.o
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TEST_OBJS := $(patsubst %$X,%.o,$(TEST_PROGRAMS)) $(patsubst %,t/helper/%,$(TEST_BUILTINS_OBJS))
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reftable/tree.c
new
+63
@@ -0,0 +1,63 @@
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+/*
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+Copyright 2020 Google LLC
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+
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+Use of this source code is governed by a BSD-style
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+license that can be found in the LICENSE file or at
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+https://developers.google.com/open-source/licenses/bsd
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+*/
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+
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+#include "tree.h"
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+
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+#include "basics.h"
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+#include "system.h"
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+
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+struct tree_node *tree_search(void *key, struct tree_node **rootp,
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+ int (*compare)(const void *, const void *),
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+ int insert)
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+{
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+ int res;
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+ if (*rootp == NULL) {
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+ if (!insert) {
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+ return NULL;
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+ } else {
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+ struct tree_node *n =
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+ reftable_calloc(sizeof(struct tree_node));
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+ n->key = key;
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+ *rootp = n;
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+ return *rootp;
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+ }
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+ }
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+
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+ res = compare(key, (*rootp)->key);
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+ if (res < 0)
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+ return tree_search(key, &(*rootp)->left, compare, insert);
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+ else if (res > 0)
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+ return tree_search(key, &(*rootp)->right, compare, insert);
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+ return *rootp;
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+}
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+
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+void infix_walk(struct tree_node *t, void (*action)(void *arg, void *key),
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+ void *arg)
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+{
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+ if (t->left) {
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+ infix_walk(t->left, action, arg);
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+ }
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+ action(arg, t->key);
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+ if (t->right) {
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+ infix_walk(t->right, action, arg);
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+ }
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+}
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+
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+void tree_free(struct tree_node *t)
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+{
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+ if (t == NULL) {
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+ return;
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+ }
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+ if (t->left) {
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+ tree_free(t->left);
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+ }
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+ if (t->right) {
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+ tree_free(t->right);
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+ }
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+ reftable_free(t);
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+}
reftable/tree.h
new
+34
@@ -0,0 +1,34 @@
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+/*
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+Copyright 2020 Google LLC
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+
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+Use of this source code is governed by a BSD-style
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+license that can be found in the LICENSE file or at
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+https://developers.google.com/open-source/licenses/bsd
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+*/
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+
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+#ifndef TREE_H
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+#define TREE_H
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+
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+/* tree_node is a generic binary search tree. */
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+struct tree_node {
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+ void *key;
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+ struct tree_node *left, *right;
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+};
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+
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+/* looks for `key` in `rootp` using `compare` as comparison function. If insert
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+ * is set, insert the key if it's not found. Else, return NULL.
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+ */
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+struct tree_node *tree_search(void *key, struct tree_node **rootp,
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+ int (*compare)(const void *, const void *),
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+ int insert);
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+
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+/* performs an infix walk of the tree. */
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+void infix_walk(struct tree_node *t, void (*action)(void *arg, void *key),
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+ void *arg);
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+
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+/*
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+ * deallocates the tree nodes recursively. Keys should be deallocated separately
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+ * by walking over the tree. */
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+void tree_free(struct tree_node *t);
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+
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+#endif
reftable/tree_test.c
new
+61
@@ -0,0 +1,61 @@
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+/*
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+Copyright 2020 Google LLC
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+
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+Use of this source code is governed by a BSD-style
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+license that can be found in the LICENSE file or at
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+https://developers.google.com/open-source/licenses/bsd
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+*/
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+
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+#include "tree.h"
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+
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+#include "basics.h"
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+#include "record.h"
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+#include "test_framework.h"
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+#include "reftable-tests.h"
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+
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+static int test_compare(const void *a, const void *b)
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+{
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+ return (char *)a - (char *)b;
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+}
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+
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+struct curry {
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+ void *last;
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+};
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+
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+static void check_increasing(void *arg, void *key)
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+{
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+ struct curry *c = arg;
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+ if (c->last) {
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+ EXPECT(test_compare(c->last, key) < 0);
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+ }
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+ c->last = key;
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+}
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+
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+static void test_tree(void)
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+{
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+ struct tree_node *root = NULL;
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+
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+ void *values[11] = { NULL };
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+ struct tree_node *nodes[11] = { NULL };
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+ int i = 1;
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+ struct curry c = { NULL };
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+ do {
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+ nodes[i] = tree_search(values + i, &root, &test_compare, 1);
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+ i = (i * 7) % 11;
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+ } while (i != 1);
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+
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+ for (i = 1; i < ARRAY_SIZE(nodes); i++) {
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+ EXPECT(values + i == nodes[i]->key);
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+ EXPECT(nodes[i] ==
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+ tree_search(values + i, &root, &test_compare, 0));
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+ }
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+
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+ infix_walk(root, check_increasing, &c);
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+ tree_free(root);
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+}
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+
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+int tree_test_main(int argc, const char *argv[])
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+{
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+ RUN_TEST(test_tree);
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+ return 0;
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+}
t/helper/test-reftable.c
+1
@@ -6,5 +6,6 @@ int cmd__reftable(int argc, const char **argv)
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basics_test_main(argc, argv);
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block_test_main(argc, argv);
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record_test_main(argc, argv);
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+ tree_test_main(argc, argv);
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return 0;
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}