Add JBig2_BitStream ReadNBits unittests

Add test for reading past end of buffer and successful read of bits.

Bug: chromium:672176
Change-Id: Ibe2d818185cdb2260011d3fc8cad94ebb16984b7
Reviewed-on: https://pdfium-review.googlesource.com/3233
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>

2 files changed, 120 insertions, 0 deletions

diff --git a/BUILD.gn b/BUILD.gn
index e4bf45ddfa..5de9d19914 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1782,6 +1782,7 @@ test("pdfium_unittests") {
     "core/fxcodec/codec/fx_codec_a85_unittest.cpp",
     "core/fxcodec/codec/fx_codec_jpx_unittest.cpp",
     "core/fxcodec/codec/fx_codec_rle_unittest.cpp",
+    "core/fxcodec/jbig2/JBig2_BitStream_unittest.cpp",
     "core/fxcodec/jbig2/JBig2_Image_unittest.cpp",
     "core/fxcrt/cfx_maybe_owned_unittest.cpp",
     "core/fxcrt/cfx_observable_unittest.cpp",
diff --git a/core/fxcodec/jbig2/JBig2_BitStream_unittest.cpp b/core/fxcodec/jbig2/JBig2_BitStream_unittest.cpp
new file mode 100644
index 0000000000..f9d69b9c53
--- /dev/null
+++ b/core/fxcodec/jbig2/JBig2_BitStream_unittest.cpp
@@ -0,0 +1,119 @@
+// Copyright 2017 PDFium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/fxcodec/jbig2/JBig2_BitStream.h"
+
+#include <memory>
+#include <utility>
+
+#include "core/fpdfapi/parser/cpdf_stream_acc.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/base/ptr_util.h"
+
+TEST(JBig2_BitStream, ReadNBits) {
+  std::unique_ptr<uint8_t, FxFreeDeleter> data(FX_Alloc(uint8_t, 1));
+  data.get()[0] = 0xb1;  // 10110001
+
+  auto in_stream = pdfium::MakeUnique<CPDF_Stream>(std::move(data), 1, nullptr);
+  auto acc = pdfium::MakeUnique<CPDF_StreamAcc>();
+  acc->LoadAllData(in_stream.get());
+
+  CJBig2_BitStream stream(acc.get());
+
+  uint32_t val1;
+  EXPECT_EQ(0, stream.readNBits(1, &val1));
+  EXPECT_EQ(1U, val1);
+
+  int32_t val2;
+  EXPECT_EQ(0, stream.readNBits(1, &val2));
+  EXPECT_EQ(0, val2);
+
+  EXPECT_EQ(0, stream.readNBits(2, &val2));
+  EXPECT_EQ(3, val2);
+
+  EXPECT_EQ(0, stream.readNBits(4, &val2));
+  EXPECT_EQ(1, val2);
+}
+
+TEST(JBig2_BitStream, ReadNBitsLargerThenData) {
+  std::unique_ptr<uint8_t, FxFreeDeleter> data(FX_Alloc(uint8_t, 1));
+  data.get()[0] = 0xb1;
+
+  auto in_stream = pdfium::MakeUnique<CPDF_Stream>(std::move(data), 1, nullptr);
+  auto acc = pdfium::MakeUnique<CPDF_StreamAcc>();
+  acc->LoadAllData(in_stream.get());
+
+  CJBig2_BitStream stream(acc.get());
+
+  uint32_t val1;
+  EXPECT_EQ(0, stream.readNBits(10, &val1));
+  EXPECT_EQ(0xb1U, val1);
+}
+
+TEST(JBig2_BitStream, ReadNBitsNullStream) {
+  auto in_stream = pdfium::MakeUnique<CPDF_Stream>(nullptr, 0, nullptr);
+  auto acc = pdfium::MakeUnique<CPDF_StreamAcc>();
+  acc->LoadAllData(in_stream.get());
+
+  CJBig2_BitStream stream(acc.get());
+
+  uint32_t val1;
+  EXPECT_EQ(-1, stream.readNBits(1, &val1));
+
+  int32_t val2;
+  EXPECT_EQ(-1, stream.readNBits(2, &val2));
+}
+
+TEST(JBig2_BitStream, ReadNBitsEmptyStream) {
+  std::unique_ptr<uint8_t, FxFreeDeleter> data(FX_Alloc(uint8_t, 1));
+
+  auto in_stream = pdfium::MakeUnique<CPDF_Stream>(std::move(data), 0, nullptr);
+  auto acc = pdfium::MakeUnique<CPDF_StreamAcc>();
+  acc->LoadAllData(in_stream.get());
+
+  CJBig2_BitStream stream(acc.get());
+
+  uint32_t val1;
+  EXPECT_EQ(-1, stream.readNBits(1, &val1));
+
+  int32_t val2;
+  EXPECT_EQ(-1, stream.readNBits(2, &val2));
+}
+
+TEST(JBig2_BitStream, ReadNBitsOutOfBounds) {
+  std::unique_ptr<uint8_t, FxFreeDeleter> data(FX_Alloc(uint8_t, 1));
+  data.get()[0] = 0xb1;  // 10110001
+
+  auto in_stream = pdfium::MakeUnique<CPDF_Stream>(std::move(data), 1, nullptr);
+  auto acc = pdfium::MakeUnique<CPDF_StreamAcc>();
+  acc->LoadAllData(in_stream.get());
+
+  CJBig2_BitStream stream(acc.get());
+
+  uint32_t val1;
+  EXPECT_EQ(0, stream.readNBits(8, &val1));
+
+  int32_t val2;
+  EXPECT_EQ(-1, stream.readNBits(2, &val2));
+}
+
+TEST(JBig2_BitStream, ReadNBitsWhereNIs36) {
+  std::unique_ptr<uint8_t, FxFreeDeleter> data(FX_Alloc(uint8_t, 5));
+  data.get()[0] = 0xb0;
+  data.get()[1] = 0x01;
+  data.get()[2] = 0x00;
+  data.get()[3] = 0x00;
+  data.get()[4] = 0x40;
+
+  auto in_stream = pdfium::MakeUnique<CPDF_Stream>(std::move(data), 5, nullptr);
+  auto acc = pdfium::MakeUnique<CPDF_StreamAcc>();
+  acc->LoadAllData(in_stream.get());
+
+  CJBig2_BitStream stream(acc.get());
+
+  // This will shift off the top two bits and they end up lost.
+  uint32_t val1;
+  EXPECT_EQ(0, stream.readNBits(34, &val1));
+  EXPECT_EQ(0xc0040001U, val1);
+}