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new 2b3442c3 Provide an example of FlatMap that erases element during
iteration (#2178)
2b3442c3 is described below
commit 2b3442c3a7f7b3df474bf2a2346a81f9432f215e
Author: Bright Chen <[email protected]>
AuthorDate: Mon Mar 27 10:01:28 2023 +0800
Provide an example of FlatMap that erases element during iteration (#2178)
---
docs/cn/flatmap.md | 38 ++++++++++++++++++++++++++++++++++++++
1 file changed, 38 insertions(+)
diff --git a/docs/cn/flatmap.md b/docs/cn/flatmap.md
index 913e052b..c37ba31d 100644
--- a/docs/cn/flatmap.md
+++ b/docs/cn/flatmap.md
@@ -32,6 +32,44 @@ void flatmap_example() {
map.clear();
CHECK_EQ(0UL, map.size());
}
+
+void flatmap_erase_hinted_during_iteration_example() {
+ typedef butil::FlatMap<int, int> Map;
+ Map map;
+ // bucket_count: initial count of buckets, big enough to avoid resize.
+ // load_factor: element_count * 100 / bucket_count, 80 as default.
+ int bucket_count = 1000;
+ int load_factor = 80;
+ map.init(bucket_count, load_factor);
+ const int N = 10;
+ for (int i = 0; i < N; ++i) {
+ map[i] = i;
+ }
+
+ for (Map::const_iterator it = map.begin(); it != map.end(); ++it) {
+ // After `erase()', ++iterator may fail.
+ // We need to save iterator before `erase()'
+ // and restore iterator after `erase()'.
+ typename Map::PositionHint hint{};
+ map.save_iterator(it, &hint);
+ if (it->first % 2 == 0) {
+ CHECK_EQ(1UL, map.erase(it->first));
+ }
+ it = map.restore_iterator(hint);
+ if (it == map.end()) {
+ break;
+ }
+ }
+ CHECK_EQ((size_t)(N / 2), map.size());
+
+ LOG(INFO) << "All remaining elements of the map:";
+ for (Map::const_iterator it = map.begin(); it != map.end(); ++it) {
+ CHECK_EQ(1, it->first % 2);
+ LOG(INFO) << it->first << " : " << it->second;
+ }
+ map.clear();
+ CHECK_EQ(0UL, map.size());
+}
```
# DESCRIPTION
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