Add InputStream::ReadExactly

Read() can return fewer bytes than requested.
ReadExactly() will call Read() repeatedly until we
have read as many bytes as we need.

PiperOrigin-RevId: 518719418

internal/platform/input_stream_test.cc

@@ -0,0 +1,119 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "internal/platform/input_stream.h"
+
+#include <string>
+
+#include "gmock/gmock.h"
+#include "protobuf-matchers/protocol-buffer-matchers.h"
+#include "gtest/gtest.h"
+#include "internal/platform/byte_array.h"
+#include "internal/platform/exception.h"
+
+namespace nearby {
+namespace {
+
+using ::testing::_;
+using ::testing::InSequence;
+using ::testing::NiceMock;
+using ::testing::Return;
+
+class TestInputStream : public InputStream {
+ public:
+  MOCK_METHOD(ExceptionOr<ByteArray>, Read, (std::int64_t), (override));
+  MOCK_METHOD(Exception, Close, (), (override));
+};
+
+// Returns a ByteArray with values: a, a + 1, a + 2, ..., b - 1.
+ExceptionOr<ByteArray> Range(char a, char b) {
+  std::string s;
+  for (char c = a; c < b; c++) {
+    s.push_back(c);
+  }
+  return ExceptionOr<ByteArray>(ByteArray(s));
+}
+
+TEST(InputStreamTest, Skip) {
+  NiceMock<TestInputStream> stream;
+  InSequence seq;
+  EXPECT_CALL(stream, Read(50)).WillOnce(Return(Range(0, 10)));
+  EXPECT_CALL(stream, Read(40)).WillOnce(Return(Range(0, 10)));
+  EXPECT_CALL(stream, Read(30)).WillOnce(Return(Range(0, 30)));
+
+  ExceptionOr<std::size_t> skipped = stream.Skip(50);
+
+  EXPECT_EQ(skipped.result(), 50);
+}
+
+TEST(InputStreamTest, SkipsLessOnEof) {
+  NiceMock<TestInputStream> stream;
+  InSequence seq;
+  EXPECT_CALL(stream, Read(50)).WillOnce(Return(Range(0, 10)));
+  EXPECT_CALL(stream, Read(40)).WillOnce(Return(Range(0, 10)));
+  // Returns EOF
+  EXPECT_CALL(stream, Read(30)).WillOnce(Return(Range(0, 0)));
+
+  ExceptionOr<std::size_t> skipped = stream.Skip(50);
+
+  EXPECT_EQ(skipped.result(), 20);
+}
+
+TEST(InputStreamTest, SkipFailsOnError) {
+  NiceMock<TestInputStream> stream;
+  InSequence seq;
+  EXPECT_CALL(stream, Read(50)).WillOnce(Return(Range(0, 10)));
+  EXPECT_CALL(stream, Read(40))
+      .WillOnce(Return(ExceptionOr<ByteArray>(Exception::kIo)));
+
+  ExceptionOr<std::size_t> skipped = stream.Skip(50);
+
+  EXPECT_EQ(skipped.exception(), Exception::kIo);
+}
+
+TEST(InputStreamTest, ReadExactlyOneChunk) {
+  NiceMock<TestInputStream> stream;
+  EXPECT_CALL(stream, Read(10)).WillOnce(Return(Range(0, 10)));
+
+  ExceptionOr<ByteArray> result = stream.ReadExactly(10);
+
+  EXPECT_EQ(result, Range(0, 10));
+}
+
+TEST(InputStreamTest, ReadExactlyMultipleChunks) {
+  NiceMock<TestInputStream> stream;
+  InSequence seq;
+  EXPECT_CALL(stream, Read(30)).WillOnce(Return(Range(0, 10)));
+  EXPECT_CALL(stream, Read(20)).WillOnce(Return(Range(10, 20)));
+  EXPECT_CALL(stream, Read(10)).WillOnce(Return(Range(20, 30)));
+
+  ExceptionOr<ByteArray> result = stream.ReadExactly(30);
+
+  EXPECT_EQ(result, Range(0, 30));
+}
+
+TEST(InputStreamTest, ReadExactlyFailsOnError) {
+  NiceMock<TestInputStream> stream;
+  InSequence seq;
+  EXPECT_CALL(stream, Read(30)).WillOnce(Return(Range(0, 10)));
+  EXPECT_CALL(stream, Read(20))
+      .WillOnce(Return(ExceptionOr<ByteArray>(Exception::kIo)));
+
+  ExceptionOr<ByteArray> result = stream.ReadExactly(30);
+
+  EXPECT_EQ(result.exception(), Exception::kIo);
+}
+
+}  // namespace
+}  // namespace nearby