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>

4 files changed, 95 insertions, 64 deletions

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;
-}