Add td::vector_split.

2 files changed, 40 insertions, 0 deletions

diff --git a/tdutils/td/utils/algorithm.h b/tdutils/td/utils/algorithm.h
index 7046c8e65..7aea70d9b 100644
--- a/tdutils/td/utils/algorithm.h
+++ b/tdutils/td/utils/algorithm.h
@@ -46,6 +46,23 @@ auto transform(V &&v, const Func &f) {
   return detail::transform_helper<std::decay_t<V>>().transform(std::forward<V>(v), f);
 }
 
+template <class T>
+vector<vector<T>> vector_split(vector<T> &&v, std::size_t size) {
+  CHECK(size != 0);
+  vector<vector<T>> result((v.size() + size - 1) / size);
+  if (result.size() <= 1) {
+    if (!result.empty()) {
+      result[0] = std::move(v);
+    }
+    return result;
+  }
+  for (size_t i = 0; i + 1 < result.size(); i++) {
+    result[i] = vector<T>(v.begin() + i * size, v.begin() + (i + 1) * size);
+  }
+  result.back() = vector<T>(v.begin() + (result.size() - 1) * size, v.end());
+  return result;
+}
+
 template <class V, class Func>
 bool remove_if(V &v, const Func &f) {
   size_t i = 0;
diff --git a/tdutils/test/misc.cpp b/tdutils/test/misc.cpp
index cabd4e6ef..a3ae1b4e6 100644
--- a/tdutils/test/misc.cpp
+++ b/tdutils/test/misc.cpp
@@ -322,6 +322,29 @@ TEST(Misc, bench_zero_encode) {
   td::bench(ZeroEncodeBenchmark());
 }
 
+static void test_vector_split(td::vector<char> v, std::size_t size, const td::vector<td::vector<char>> &expected) {
+  auto split = td::vector_split(std::move(v), size);
+  if (expected != split) {
+    LOG(FATAL) << "Receive " << split << ", expected " << expected << " in vector_split";
+  }
+}
+
+TEST(Misc, vector_split) {
+  test_vector_split({}, 1, {});
+  test_vector_split({}, 2, {});
+  test_vector_split({'1'}, 1, {{'1'}});
+  test_vector_split({'1'}, 2, {{'1'}});
+  td::vector<char> v{'1', '2', '3', '4', '5', '6'};
+  test_vector_split(v, 1, {{'1'}, {'2'}, {'3'}, {'4'}, {'5'}, {'6'}});
+  test_vector_split(v, 2, {{'1', '2'}, {'3', '4'}, {'5', '6'}});
+  test_vector_split(v, 3, {{'1', '2', '3'}, {'4', '5', '6'}});
+  test_vector_split(v, 4, {{'1', '2', '3', '4'}, {'5', '6'}});
+  test_vector_split(v, 5, {{'1', '2', '3', '4', '5'}, {'6'}});
+  test_vector_split(v, 6, {v});
+  test_vector_split(v, 7, {v});
+  test_vector_split(v, 107, {v});
+}
+
 template <class T>
 static void test_remove_if(td::vector<int> v, const T &func, const td::vector<int> &expected) {
   td::remove_if(v, func);