Add unit test for CFX_BitStream.

Change-Id: I764196b9cc1d437313aac18ee9d5dbed642c7119
Reviewed-on: https://pdfium-review.googlesource.com/32850
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

2 files changed, 120 insertions, 0 deletions

diff --git a/BUILD.gn b/BUILD.gn
index f761b896b8..0535423d8e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -2887,6 +2887,7 @@ test("pdfium_unittests") {
     "core/fxcodec/jbig2/JBig2_BitStream_unittest.cpp",
     "core/fxcodec/jbig2/JBig2_Image_unittest.cpp",
     "core/fxcrt/bytestring_unittest.cpp",
+    "core/fxcrt/cfx_bitstream_unittest.cpp",
     "core/fxcrt/cfx_seekablemultistream_unittest.cpp",
     "core/fxcrt/fx_bidi_unittest.cpp",
     "core/fxcrt/fx_coordinates_unittest.cpp",
diff --git a/core/fxcrt/cfx_bitstream_unittest.cpp b/core/fxcrt/cfx_bitstream_unittest.cpp
new file mode 100644
index 0000000000..991cd43147
--- /dev/null
+++ b/core/fxcrt/cfx_bitstream_unittest.cpp
@@ -0,0 +1,119 @@
+// Copyright 2018 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/fxcrt/cfx_bitstream.h"
+#include "core/fxcrt/fx_extension.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+TEST(fxcrt, BitStream) {
+  static const uint8_t kData[] = {0x00, 0x11, 0x22, 0x33,
+                                  0x44, 0x55, 0x66, 0x77};
+  CFX_BitStream bitstream(kData);
+
+  // Initial state.
+  EXPECT_FALSE(bitstream.IsEOF());
+  EXPECT_EQ(0U, bitstream.GetPos());
+  EXPECT_EQ(64U, bitstream.BitsRemaining());
+
+  // Read, read, read!
+  EXPECT_EQ(0x00U, bitstream.GetBits(8));
+  EXPECT_EQ(8U, bitstream.GetPos());
+  EXPECT_EQ(56U, bitstream.BitsRemaining());
+
+  EXPECT_EQ(0x00U, bitstream.GetBits(1));
+  EXPECT_EQ(9U, bitstream.GetPos());
+  EXPECT_EQ(55U, bitstream.BitsRemaining());
+
+  EXPECT_EQ(0x00U, bitstream.GetBits(2));
+  EXPECT_EQ(11U, bitstream.GetPos());
+  EXPECT_EQ(53U, bitstream.BitsRemaining());
+
+  EXPECT_EQ(0x04U, bitstream.GetBits(3));
+  EXPECT_EQ(14U, bitstream.GetPos());
+  EXPECT_EQ(50U, bitstream.BitsRemaining());
+
+  EXPECT_EQ(0x04U, bitstream.GetBits(4));
+  EXPECT_EQ(18U, bitstream.GetPos());
+  EXPECT_EQ(46U, bitstream.BitsRemaining());
+
+  EXPECT_EQ(0x44U, bitstream.GetBits(7));
+  EXPECT_EQ(25U, bitstream.GetPos());
+  EXPECT_EQ(39U, bitstream.BitsRemaining());
+
+  EXPECT_EQ(0xCDU, bitstream.GetBits(9));
+  EXPECT_EQ(34U, bitstream.GetPos());
+  EXPECT_EQ(30U, bitstream.BitsRemaining());
+
+  EXPECT_EQ(0x08AAU, bitstream.GetBits(15));
+  EXPECT_EQ(49U, bitstream.GetPos());
+  EXPECT_EQ(15U, bitstream.BitsRemaining());
+
+  // Cannot advance past the end.
+  EXPECT_EQ(0x00U, bitstream.GetBits(16));
+  EXPECT_EQ(49U, bitstream.GetPos());
+  EXPECT_EQ(15U, bitstream.BitsRemaining());
+
+  // Make sure SkipBits() works.
+  bitstream.SkipBits(14);
+  EXPECT_EQ(63U, bitstream.GetPos());
+  EXPECT_EQ(1U, bitstream.BitsRemaining());
+  bitstream.SkipBits(2);
+  EXPECT_EQ(65U, bitstream.GetPos());
+  EXPECT_EQ(0U, bitstream.BitsRemaining());
+  EXPECT_TRUE(bitstream.IsEOF());
+
+  // Make sure Rewind() works.
+  bitstream.Rewind();
+  EXPECT_FALSE(bitstream.IsEOF());
+  EXPECT_EQ(0U, bitstream.GetPos());
+  EXPECT_EQ(64U, bitstream.BitsRemaining());
+
+  // Read some more.
+  bitstream.SkipBits(5);
+  EXPECT_EQ(5U, bitstream.GetPos());
+  EXPECT_EQ(59U, bitstream.BitsRemaining());
+
+  EXPECT_EQ(0x0448U, bitstream.GetBits(17));
+  EXPECT_EQ(22U, bitstream.GetPos());
+  EXPECT_EQ(42U, bitstream.BitsRemaining());
+
+  // Make sure ByteAlign() works.
+  bitstream.ByteAlign();
+  EXPECT_EQ(24U, bitstream.GetPos());
+  EXPECT_EQ(40U, bitstream.BitsRemaining());
+
+  EXPECT_EQ(0x19A22AB3U, bitstream.GetBits(31));
+  EXPECT_EQ(55U, bitstream.GetPos());
+  EXPECT_EQ(9U, bitstream.BitsRemaining());
+
+  // Do some bigger reads.
+  bitstream.Rewind();
+  EXPECT_EQ(0x112233U, bitstream.GetBits(32));
+  EXPECT_EQ(32U, bitstream.GetPos());
+  EXPECT_EQ(32U, bitstream.BitsRemaining());
+
+  bitstream.Rewind();
+  bitstream.SkipBits(31);
+  EXPECT_EQ(0xA22AB33BU, bitstream.GetBits(32));
+  EXPECT_EQ(63U, bitstream.GetPos());
+  EXPECT_EQ(1U, bitstream.BitsRemaining());
+
+  // Skip past the end.
+  bitstream.SkipBits(1000);
+  EXPECT_TRUE(bitstream.IsEOF());
+  EXPECT_EQ(1063U, bitstream.GetPos());
+  EXPECT_EQ(0U, bitstream.BitsRemaining());
+}
+
+TEST(fxcrt, BitStreamSameAsGetBit32) {
+  unsigned char kData[] = {0xDE, 0x3F, 0xB1, 0x7C, 0x12, 0x9A, 0x04, 0x56};
+  CFX_BitStream bitstream(kData);
+  for (uint32_t nbits = 1; nbits <= 32; ++nbits) {
+    for (size_t bitpos = 0; bitpos < sizeof(kData) * 8 - nbits; ++bitpos) {
+      bitstream.Rewind();
+      bitstream.SkipBits(bitpos);
+      EXPECT_EQ(bitstream.GetBits(nbits), GetBits32(kData, bitpos, nbits));
+    }
+  }
+}