Move CFX_BitStream to its own file

This CL moves the CFX_BitStream code out of fx_basic and into
cfx_bitstream.

Bug: pdfium:867
Change-Id: I5b7e6190a7db1fe1d24feb6bd676035a5c73ee92
Reviewed-on: https://pdfium-review.googlesource.com/12350
Commit-Queue: dsinclair <dsinclair@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

10 files changed, 122 insertions, 91 deletions

diff --git a/BUILD.gn b/BUILD.gn
index 1a08382bf6..969c917924 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -803,6 +803,8 @@ config("fxge_warnings") {
 
 static_library("fxcrt") {
   sources = [
+    "core/fxcrt/cfx_bitstream.cpp",
+    "core/fxcrt/cfx_bitstream.h",
     "core/fxcrt/cfx_bytestring.cpp",
     "core/fxcrt/cfx_bytestring.h",
     "core/fxcrt/cfx_datetime.cpp",
diff --git a/core/fpdfapi/page/cpdf_meshstream.cpp b/core/fpdfapi/page/cpdf_meshstream.cpp
index 8588734d95..1850efde9c 100644
--- a/core/fpdfapi/page/cpdf_meshstream.cpp
+++ b/core/fpdfapi/page/cpdf_meshstream.cpp
@@ -117,7 +117,8 @@ CPDF_MeshStream::~CPDF_MeshStream() {}
 
 bool CPDF_MeshStream::Load() {
   m_pStream->LoadAllData();
-  m_BitStream.Init(m_pStream->GetData(), m_pStream->GetSize());
+  m_BitStream = pdfium::MakeUnique<CFX_BitStream>(m_pStream->GetData(),
+                                                  m_pStream->GetSize());
   CPDF_Dictionary* pDict = m_pShadingStream->GetDict();
   m_nCoordBits = pDict->GetIntegerFor("BitsPerCoordinate");
   m_nComponentBits = pDict->GetIntegerFor("BitsPerComponent");
@@ -158,20 +159,20 @@ bool CPDF_MeshStream::Load() {
 }
 
 bool CPDF_MeshStream::CanReadFlag() const {
-  return m_BitStream.BitsRemaining() >= m_nFlagBits;
+  return m_BitStream->BitsRemaining() >= m_nFlagBits;
 }
 
 bool CPDF_MeshStream::CanReadCoords() const {
-  return m_BitStream.BitsRemaining() / 2 >= m_nCoordBits;
+  return m_BitStream->BitsRemaining() / 2 >= m_nCoordBits;
 }
 
 bool CPDF_MeshStream::CanReadColor() const {
-  return m_BitStream.BitsRemaining() / m_nComponentBits >= m_nComponents;
+  return m_BitStream->BitsRemaining() / m_nComponentBits >= m_nComponents;
 }
 
 uint32_t CPDF_MeshStream::ReadFlag() {
   ASSERT(ShouldCheckBitsPerFlag(m_type));
-  return m_BitStream.GetBits(m_nFlagBits) & 0x03;
+  return m_BitStream->GetBits(m_nFlagBits) & 0x03;
 }
 
 CFX_PointF CPDF_MeshStream::ReadCoords() {
@@ -179,17 +180,15 @@ CFX_PointF CPDF_MeshStream::ReadCoords() {
 
   CFX_PointF pos;
   if (m_nCoordBits == 32) {
-    pos.x = m_xmin +
-            m_BitStream.GetBits(m_nCoordBits) * (m_xmax - m_xmin) /
-                static_cast<double>(m_CoordMax);
-    pos.y = m_ymin +
-            m_BitStream.GetBits(m_nCoordBits) * (m_ymax - m_ymin) /
-                static_cast<double>(m_CoordMax);
+    pos.x = m_xmin + m_BitStream->GetBits(m_nCoordBits) * (m_xmax - m_xmin) /
+                         static_cast<double>(m_CoordMax);
+    pos.y = m_ymin + m_BitStream->GetBits(m_nCoordBits) * (m_ymax - m_ymin) /
+                         static_cast<double>(m_CoordMax);
   } else {
     pos.x = m_xmin +
-            m_BitStream.GetBits(m_nCoordBits) * (m_xmax - m_xmin) / m_CoordMax;
+            m_BitStream->GetBits(m_nCoordBits) * (m_xmax - m_xmin) / m_CoordMax;
     pos.y = m_ymin +
-            m_BitStream.GetBits(m_nCoordBits) * (m_ymax - m_ymin) / m_CoordMax;
+            m_BitStream->GetBits(m_nCoordBits) * (m_ymax - m_ymin) / m_CoordMax;
   }
   return pos;
 }
@@ -199,9 +198,9 @@ std::tuple<float, float, float> CPDF_MeshStream::ReadColor() {
 
   float color_value[kMaxComponents];
   for (uint32_t i = 0; i < m_nComponents; ++i) {
-    color_value[i] = m_ColorMin[i] +
-                     m_BitStream.GetBits(m_nComponentBits) *
-                         (m_ColorMax[i] - m_ColorMin[i]) / m_ComponentMax;
+    color_value[i] = m_ColorMin[i] + m_BitStream->GetBits(m_nComponentBits) *
+                                         (m_ColorMax[i] - m_ColorMin[i]) /
+                                         m_ComponentMax;
   }
 
   float r = 0.0;
@@ -238,7 +237,7 @@ bool CPDF_MeshStream::ReadVertex(const CFX_Matrix& pObject2Bitmap,
   if (!CanReadColor())
     return false;
   std::tie(vertex->r, vertex->g, vertex->b) = ReadColor();
-  m_BitStream.ByteAlign();
+  m_BitStream->ByteAlign();
   return true;
 }
 
@@ -247,7 +246,7 @@ std::vector<CPDF_MeshVertex> CPDF_MeshStream::ReadVertexRow(
     int count) {
   std::vector<CPDF_MeshVertex> vertices;
   for (int i = 0; i < count; ++i) {
-    if (m_BitStream.IsEOF() || !CanReadCoords())
+    if (m_BitStream->IsEOF() || !CanReadCoords())
       return std::vector<CPDF_MeshVertex>();
 
     vertices.push_back(CPDF_MeshVertex());
@@ -257,7 +256,7 @@ std::vector<CPDF_MeshVertex> CPDF_MeshStream::ReadVertexRow(
       return std::vector<CPDF_MeshVertex>();
 
     std::tie(vertex.r, vertex.g, vertex.b) = ReadColor();
-    m_BitStream.ByteAlign();
+    m_BitStream->ByteAlign();
   }
   return vertices;
 }
diff --git a/core/fpdfapi/page/cpdf_meshstream.h b/core/fpdfapi/page/cpdf_meshstream.h
index 60c47790a4..0a06381c68 100644
--- a/core/fpdfapi/page/cpdf_meshstream.h
+++ b/core/fpdfapi/page/cpdf_meshstream.h
@@ -13,7 +13,7 @@
 
 #include "core/fpdfapi/page/cpdf_shadingpattern.h"
 #include "core/fpdfapi/parser/cpdf_stream_acc.h"
-#include "core/fxcrt/fx_basic.h"
+#include "core/fxcrt/cfx_bitstream.h"
 #include "core/fxcrt/fx_system.h"
 
 class CPDF_MeshVertex {
@@ -57,7 +57,7 @@ class CPDF_MeshStream {
   std::vector<CPDF_MeshVertex> ReadVertexRow(const CFX_Matrix& pObject2Bitmap,
                                              int count);
 
-  CFX_BitStream* BitStream() { return &m_BitStream; }
+  CFX_BitStream* BitStream() { return m_BitStream.get(); }
   uint32_t ComponentBits() const { return m_nComponentBits; }
   uint32_t Components() const { return m_nComponents; }
 
@@ -81,7 +81,7 @@ class CPDF_MeshStream {
   float m_ColorMin[kMaxComponents];
   float m_ColorMax[kMaxComponents];
   CFX_RetainPtr<CPDF_StreamAcc> m_pStream;
-  CFX_BitStream m_BitStream;
+  std::unique_ptr<CFX_BitStream> m_BitStream;
 };
 
 #endif  // CORE_FPDFAPI_PAGE_CPDF_MESHSTREAM_H_
diff --git a/core/fpdfapi/parser/cpdf_hint_tables.cpp b/core/fpdfapi/parser/cpdf_hint_tables.cpp
index 6a84143f9e..deffe5cb38 100644
--- a/core/fpdfapi/parser/cpdf_hint_tables.cpp
+++ b/core/fpdfapi/parser/cpdf_hint_tables.cpp
@@ -15,6 +15,7 @@
 #include "core/fpdfapi/parser/cpdf_linearized_header.h"
 #include "core/fpdfapi/parser/cpdf_stream.h"
 #include "core/fpdfapi/parser/cpdf_stream_acc.h"
+#include "core/fxcrt/cfx_bitstream.h"
 #include "core/fxcrt/fx_safe_types.h"
 #include "third_party/base/numerics/safe_conversions.h"
 
@@ -486,8 +487,7 @@ bool CPDF_HintTables::LoadHintStream(CPDF_Stream* pHintStream) {
     return false;
   }
 
-  CFX_BitStream bs;
-  bs.Init(pAcc->GetData(), size);
+  CFX_BitStream bs(pAcc->GetData(), size);
   return ReadPageHintTable(&bs) &&
          ReadSharedObjHintTable(&bs, shared_hint_table_offset);
 }
diff --git a/core/fpdfapi/parser/cpdf_hint_tables.h b/core/fpdfapi/parser/cpdf_hint_tables.h
index 25f276ce55..2ab42a93cf 100644
--- a/core/fpdfapi/parser/cpdf_hint_tables.h
+++ b/core/fpdfapi/parser/cpdf_hint_tables.h
@@ -11,7 +11,6 @@
 
 #include "core/fpdfapi/parser/cpdf_data_avail.h"
 #include "core/fxcrt/cfx_unowned_ptr.h"
-#include "core/fxcrt/fx_basic.h"
 #include "core/fxcrt/fx_stream.h"
 
 class CFX_BitStream;
diff --git a/core/fxcrt/cfx_bitstream.cpp b/core/fxcrt/cfx_bitstream.cpp
new file mode 100644
index 0000000000..7cf6d36adf
--- /dev/null
+++ b/core/fxcrt/cfx_bitstream.cpp
@@ -0,0 +1,57 @@
+// 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.
+
+// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
+
+#include "core/fxcrt/cfx_bitstream.h"
+
+#include <limits>
+
+#include "core/fxcrt/fx_system.h"
+
+CFX_BitStream::CFX_BitStream(const uint8_t* pData, uint32_t dwSize)
+    : m_BitPos(0), m_BitSize(dwSize * 8), m_pData(pData) {
+  ASSERT(dwSize <= std::numeric_limits<uint32_t>::max() / 8);
+}
+
+CFX_BitStream::~CFX_BitStream() {}
+
+void CFX_BitStream::ByteAlign() {
+  m_BitPos = (m_BitPos + 7) & ~7;
+}
+
+uint32_t CFX_BitStream::GetBits(uint32_t nBits) {
+  if (nBits > m_BitSize || m_BitPos + nBits > m_BitSize)
+    return 0;
+
+  const uint8_t* data = m_pData.Get();
+
+  if (nBits == 1) {
+    int bit = (data[m_BitPos / 8] & (1 << (7 - m_BitPos % 8))) ? 1 : 0;
+    m_BitPos++;
+    return bit;
+  }
+
+  uint32_t byte_pos = m_BitPos / 8;
+  uint32_t bit_pos = m_BitPos % 8;
+  uint32_t bit_left = nBits;
+  uint32_t result = 0;
+  if (bit_pos) {
+    if (8 - bit_pos >= bit_left) {
+      result = (data[byte_pos] & (0xff >> bit_pos)) >> (8 - bit_pos - bit_left);
+      m_BitPos += bit_left;
+      return result;
+    }
+    bit_left -= 8 - bit_pos;
+    result = (data[byte_pos++] & ((1 << (8 - bit_pos)) - 1)) << bit_left;
+  }
+  while (bit_left >= 8) {
+    bit_left -= 8;
+    result |= data[byte_pos++] << bit_left;
+  }
+  if (bit_left)
+    result |= data[byte_pos] >> (8 - bit_left);
+  m_BitPos += nBits;
+  return result;
+}
diff --git a/core/fxcrt/cfx_bitstream.h b/core/fxcrt/cfx_bitstream.h
new file mode 100644
index 0000000000..1829f23b92
--- /dev/null
+++ b/core/fxcrt/cfx_bitstream.h
@@ -0,0 +1,38 @@
+// 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.
+
+// Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
+
+#ifndef CORE_FXCRT_CFX_BITSTREAM_H_
+#define CORE_FXCRT_CFX_BITSTREAM_H_
+
+#include <stdint.h>
+
+#include "core/fxcrt/cfx_unowned_ptr.h"
+
+class CFX_BitStream {
+ public:
+  CFX_BitStream(const uint8_t* pData, uint32_t dwSize);
+  ~CFX_BitStream();
+
+  void ByteAlign();
+
+  bool IsEOF() const { return m_BitPos >= m_BitSize; }
+  uint32_t GetPos() const { return m_BitPos; }
+  uint32_t GetBits(uint32_t nBits);
+
+  void SkipBits(uint32_t nBits) { m_BitPos += nBits; }
+  void Rewind() { m_BitPos = 0; }
+
+  uint32_t BitsRemaining() const {
+    return m_BitSize >= m_BitPos ? m_BitSize - m_BitPos : 0;
+  }
+
+ private:
+  uint32_t m_BitPos;
+  uint32_t m_BitSize;
+  CFX_UnownedPtr<const uint8_t> m_pData;
+};
+
+#endif  // CORE_FXCRT_CFX_BITSTREAM_H_
diff --git a/core/fxcrt/fx_basic.h b/core/fxcrt/fx_basic.h
index 1f05dfb627..167ef5ce70 100644
--- a/core/fxcrt/fx_basic.h
+++ b/core/fxcrt/fx_basic.h
@@ -136,26 +136,6 @@ class CFX_FixedBufGrow {
   std::unique_ptr<DataType, FxFreeDeleter> m_pGrowData;
 };
 
-class CFX_BitStream {
- public:
-  void Init(const uint8_t* pData, uint32_t dwSize);
-
-  void ByteAlign();
-  bool IsEOF() const { return m_BitPos >= m_BitSize; }
-  uint32_t GetBits(uint32_t nBits);
-  void SkipBits(uint32_t nBits) { m_BitPos += nBits; }
-  void Rewind() { m_BitPos = 0; }
-  uint32_t GetPos() const { return m_BitPos; }
-  uint32_t BitsRemaining() const {
-    return m_BitSize >= m_BitPos ? m_BitSize - m_BitPos : 0;
-  }
-
- private:
-  uint32_t m_BitPos;
-  uint32_t m_BitSize;
-  const uint8_t* m_pData;
-};
-
 class IFX_Pause {
  public:
   virtual ~IFX_Pause() {}
diff --git a/core/fxcrt/fx_basic_buffer.cpp b/core/fxcrt/fx_basic_buffer.cpp
index 310aec7faf..b93c1bc9da 100644
--- a/core/fxcrt/fx_basic_buffer.cpp
+++ b/core/fxcrt/fx_basic_buffer.cpp
@@ -145,47 +145,3 @@ CFX_WideTextBuf& CFX_WideTextBuf::operator<<(const CFX_WideTextBuf& buf) {
   AppendBlock(buf.m_pBuffer.get(), buf.m_DataSize);
   return *this;
 }
-
-void CFX_BitStream::Init(const uint8_t* pData, uint32_t dwSize) {
-  m_pData = pData;
-  m_BitSize = dwSize * 8;
-  m_BitPos = 0;
-}
-
-void CFX_BitStream::ByteAlign() {
-  m_BitPos = (m_BitPos + 7) & ~7;
-}
-
-uint32_t CFX_BitStream::GetBits(uint32_t nBits) {
-  if (nBits > m_BitSize || m_BitPos + nBits > m_BitSize)
-    return 0;
-
-  if (nBits == 1) {
-    int bit = (m_pData[m_BitPos / 8] & (1 << (7 - m_BitPos % 8))) ? 1 : 0;
-    m_BitPos++;
-    return bit;
-  }
-
-  uint32_t byte_pos = m_BitPos / 8;
-  uint32_t bit_pos = m_BitPos % 8;
-  uint32_t bit_left = nBits;
-  uint32_t result = 0;
-  if (bit_pos) {
-    if (8 - bit_pos >= bit_left) {
-      result =
-          (m_pData[byte_pos] & (0xff >> bit_pos)) >> (8 - bit_pos - bit_left);
-      m_BitPos += bit_left;
-      return result;
-    }
-    bit_left -= 8 - bit_pos;
-    result = (m_pData[byte_pos++] & ((1 << (8 - bit_pos)) - 1)) << bit_left;
-  }
-  while (bit_left >= 8) {
-    bit_left -= 8;
-    result |= m_pData[byte_pos++] << bit_left;
-  }
-  if (bit_left)
-    result |= m_pData[byte_pos] >> (8 - bit_left);
-  m_BitPos += nBits;
-  return result;
-}
diff --git a/testing/libfuzzer/pdf_hint_table_fuzzer.cc b/testing/libfuzzer/pdf_hint_table_fuzzer.cc
index b31d56eb8f..ac4229a5a9 100644
--- a/testing/libfuzzer/pdf_hint_table_fuzzer.cc
+++ b/testing/libfuzzer/pdf_hint_table_fuzzer.cc
@@ -10,6 +10,7 @@
 #include "core/fpdfapi/parser/cpdf_hint_tables.h"
 #include "core/fpdfapi/parser/cpdf_linearized_header.h"
 #include "core/fpdfapi/parser/cpdf_number.h"
+#include "core/fxcrt/cfx_bitstream.h"
 #include "third_party/base/ptr_util.h"
 
 int32_t GetData(const int32_t** data32, const uint8_t** data, size_t* size) {
@@ -35,8 +36,7 @@ class HintTableForFuzzing : public CPDF_HintTables {
     if (size < static_cast<size_t>(shared_hint_table_offset_))
       return;
 
-    CFX_BitStream bs;
-    bs.Init(data, size);
+    CFX_BitStream bs(data, size);
     if (!ReadPageHintTable(&bs))
       return;
     ReadSharedObjHintTable(&bs, shared_hint_table_offset_);