From a28780e994692f2494d8d54fb4539003a212dd6b Mon Sep 17 00:00:00 2001
From: danilchap <danilchap@webrtc.org>
Date: Fri, 18 Nov 2016 01:46:23 -0800
Subject: [PATCH] Introduce ArrayView::subview function to return portion of
 the original view

BUG=None

Review-Url: https://codereview.webrtc.org/2502383004
Cr-Commit-Position: refs/heads/master@{#15149}
---
 webrtc/base/array_view.h           |  7 +++++++
 webrtc/base/array_view_unittest.cc | 21 +++++++++++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/webrtc/base/array_view.h b/webrtc/base/array_view.h
index 5c1ffe2489..aa73ef72f6 100644
--- a/webrtc/base/array_view.h
+++ b/webrtc/base/array_view.h
@@ -120,6 +120,13 @@ class ArrayView final {
   const T* cbegin() const { return data_; }
   const T* cend() const { return data_ + size_; }
 
+  ArrayView subview(size_t offset, size_t size) const {
+    if (offset >= size_)
+      return ArrayView();
+    return ArrayView(data_ + offset, std::min(size, size_ - offset));
+  }
+  ArrayView subview(size_t offset) const { return subview(offset, size_); }
+
   // Comparing two ArrayViews compares their (pointer,size) pairs; it does
   // *not* dereference the pointers.
   friend bool operator==(const ArrayView& a, const ArrayView& b) {
diff --git a/webrtc/base/array_view_unittest.cc b/webrtc/base/array_view_unittest.cc
index 91facb0043..f7fe9fa36b 100644
--- a/webrtc/base/array_view_unittest.cc
+++ b/webrtc/base/array_view_unittest.cc
@@ -16,11 +16,15 @@
 #include "webrtc/base/buffer.h"
 #include "webrtc/base/checks.h"
 #include "webrtc/base/gunit.h"
+#include "webrtc/test/gmock.h"
 
 namespace rtc {
 
 namespace {
 
+using ::testing::ElementsAre;
+using ::testing::IsEmpty;
+
 template <typename T>
 void Call(ArrayView<T>) {}
 
@@ -232,4 +236,21 @@ TEST(ArrayViewTest, TestCompare) {
   EXPECT_NE(ArrayView<int>(a), ArrayView<int>(a, 2));
 }
 
+TEST(ArrayViewTest, TestSubView) {
+  int a[] = {1, 2, 3};
+  ArrayView<int> av(a);
+
+  EXPECT_EQ(av.subview(0), av);
+
+  EXPECT_THAT(av.subview(1), ElementsAre(2, 3));
+  EXPECT_THAT(av.subview(2), ElementsAre(3));
+  EXPECT_THAT(av.subview(3), IsEmpty());
+  EXPECT_THAT(av.subview(4), IsEmpty());
+
+  EXPECT_THAT(av.subview(1, 0), IsEmpty());
+  EXPECT_THAT(av.subview(1, 1), ElementsAre(2));
+  EXPECT_THAT(av.subview(1, 2), ElementsAre(2, 3));
+  EXPECT_THAT(av.subview(1, 3), ElementsAre(2, 3));
+}
+
 }  // namespace rtc