autovector::resize

Summary: Resize the autovector!

Test Plan: test

Reviewers: sdong

Reviewed By: sdong

CC: leveldb

Differential Revision: https://reviews.facebook.net/D18543

util/autovector.h

@@ -24,7 +24,7 @@ class autovector : public std::vector<T> {};
 // full-fledged generic container.
 //
 // Currently we don't support:
-//  * reserve()/shrink_to_fit()/resize()
+//  * reserve()/shrink_to_fit()
 //     If used correctly, in most cases, people should not touch the
 //     underlying vector at all.
 //  * random insert()/erase(), please only use push_back()/pop_back().
@@ -176,6 +176,18 @@ class autovector {
 
   size_type size() const { return num_stack_items_ + vect_.size(); }
 
+  // resize does not guarantee anything about the contents of the newly
+  // available elements
+  void resize(size_type n) {
+    if (n > kSize) {
+      vect_.resize(n - kSize);
+      num_stack_items_ = kSize;
+    } else {
+      vect_.clear();
+      num_stack_items_ = n;
+    }
+  }
+
   bool empty() const { return size() == 0; }
 
   // will not check boundry

util/autovector_test.cc

@@ -70,6 +70,28 @@ TEST(AutoVectorTest, EmplaceBack) {
   ASSERT_TRUE(!vec.only_in_stack());
 }
 
+TEST(AutoVectorTest, Resize) {
+  autovector<size_t, kSize> vec;
+
+  vec.resize(kSize);
+  ASSERT_TRUE(vec.only_in_stack());
+  for (size_t i = 0; i < kSize; ++i) {
+    vec[i] = i;
+  }
+
+  vec.resize(kSize * 2);
+  ASSERT_TRUE(!vec.only_in_stack());
+  for (size_t i = 0; i < kSize; ++i) {
+    ASSERT_EQ(vec[i], i);
+  }
+  for (size_t i = 0; i < kSize; ++i) {
+    vec[i + kSize] = i;
+  }
+
+  vec.resize(1);
+  ASSERT_EQ(1U, vec.size());
+}
+
 namespace {
 void AssertEqual(
     const autovector<size_t, kSize>& a, const autovector<size_t, kSize>& b) {