diff --git a/BUILD.gn b/BUILD.gn
index 51480ed..cbf6fa0 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -804,6 +804,8 @@
 static_library("fxcrt") {
   sources = [
     "core/fxcrt/cfx_autorestorer.h",
+    "core/fxcrt/cfx_binarybuf.cpp",
+    "core/fxcrt/cfx_binarybuf.h",
     "core/fxcrt/cfx_bitstream.cpp",
     "core/fxcrt/cfx_bitstream.h",
     "core/fxcrt/cfx_bytestring.cpp",
diff --git a/core/fpdfapi/parser/cpdf_crypto_handler.h b/core/fpdfapi/parser/cpdf_crypto_handler.h
index 9d76e67..14a5743 100644
--- a/core/fpdfapi/parser/cpdf_crypto_handler.h
+++ b/core/fpdfapi/parser/cpdf_crypto_handler.h
@@ -10,8 +10,8 @@
 #include <memory>
 
 #include "core/fdrm/crypto/fx_crypt.h"
+#include "core/fxcrt/cfx_binarybuf.h"
 #include "core/fxcrt/cfx_retain_ptr.h"
-#include "core/fxcrt/fx_basic.h"
 #include "core/fxcrt/fx_memory.h"
 #include "core/fxcrt/fx_string.h"
 #include "core/fxcrt/fx_system.h"
diff --git a/core/fpdfapi/parser/cpdf_syntax_parser.cpp b/core/fpdfapi/parser/cpdf_syntax_parser.cpp
index c0d2121..e3a23cf 100644
--- a/core/fpdfapi/parser/cpdf_syntax_parser.cpp
+++ b/core/fpdfapi/parser/cpdf_syntax_parser.cpp
@@ -26,6 +26,7 @@
 #include "core/fpdfapi/parser/fpdf_parser_decode.h"
 #include "core/fpdfapi/parser/fpdf_parser_utility.h"
 #include "core/fxcrt/cfx_autorestorer.h"
+#include "core/fxcrt/cfx_binarybuf.h"
 #include "core/fxcrt/fx_extension.h"
 #include "third_party/base/numerics/safe_math.h"
 #include "third_party/base/ptr_util.h"
diff --git a/core/fxcodec/codec/fx_codec_fax.cpp b/core/fxcodec/codec/fx_codec_fax.cpp
index 641e0fd..20aada9 100644
--- a/core/fxcodec/codec/fx_codec_fax.cpp
+++ b/core/fxcodec/codec/fx_codec_fax.cpp
@@ -10,6 +10,7 @@
 
 #include "core/fxcodec/codec/codec_int.h"
 #include "core/fxcodec/fx_codec.h"
+#include "core/fxcrt/cfx_binarybuf.h"
 #include "core/fxcrt/fx_memory.h"
 #include "third_party/base/ptr_util.h"
 #include "third_party/base/stl_util.h"
diff --git a/core/fxcrt/cfx_binarybuf.cpp b/core/fxcrt/cfx_binarybuf.cpp
new file mode 100644
index 0000000..a1388b8
--- /dev/null
+++ b/core/fxcrt/cfx_binarybuf.cpp
@@ -0,0 +1,92 @@
+// 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_binarybuf.h"
+
+#include <algorithm>
+#include <utility>
+
+CFX_BinaryBuf::CFX_BinaryBuf()
+    : m_AllocStep(0), m_AllocSize(0), m_DataSize(0) {}
+
+CFX_BinaryBuf::CFX_BinaryBuf(FX_STRSIZE size)
+    : m_AllocStep(0), m_AllocSize(size), m_DataSize(size) {
+  m_pBuffer.reset(FX_Alloc(uint8_t, size));
+}
+
+CFX_BinaryBuf::~CFX_BinaryBuf() {}
+
+void CFX_BinaryBuf::Delete(FX_STRSIZE start_index, FX_STRSIZE count) {
+  if (!m_pBuffer || start_index < 0 || count < 0 || count > m_DataSize ||
+      start_index > m_DataSize - count) {
+    return;
+  }
+  memmove(m_pBuffer.get() + start_index, m_pBuffer.get() + start_index + count,
+          m_DataSize - start_index - count);
+  m_DataSize -= count;
+}
+
+void CFX_BinaryBuf::Clear() {
+  m_DataSize = 0;
+}
+
+std::unique_ptr<uint8_t, FxFreeDeleter> CFX_BinaryBuf::DetachBuffer() {
+  m_DataSize = 0;
+  m_AllocSize = 0;
+  return std::move(m_pBuffer);
+}
+
+void CFX_BinaryBuf::EstimateSize(FX_STRSIZE size, FX_STRSIZE step) {
+  m_AllocStep = step;
+  if (m_AllocSize < size)
+    ExpandBuf(size - m_DataSize);
+}
+
+void CFX_BinaryBuf::ExpandBuf(FX_STRSIZE add_size) {
+  FX_SAFE_STRSIZE new_size = m_DataSize;
+  new_size += add_size;
+  if (m_AllocSize >= new_size.ValueOrDie())
+    return;
+
+  int alloc_step = std::max(128, m_AllocStep ? m_AllocStep : m_AllocSize / 4);
+  new_size += alloc_step - 1;  // Quantize, don't combine these lines.
+  new_size /= alloc_step;
+  new_size *= alloc_step;
+  m_AllocSize = new_size.ValueOrDie();
+  m_pBuffer.reset(m_pBuffer
+                      ? FX_Realloc(uint8_t, m_pBuffer.release(), m_AllocSize)
+                      : FX_Alloc(uint8_t, m_AllocSize));
+}
+
+void CFX_BinaryBuf::AppendBlock(const void* pBuf, FX_STRSIZE size) {
+  if (size <= 0)
+    return;
+
+  ExpandBuf(size);
+  if (pBuf) {
+    memcpy(m_pBuffer.get() + m_DataSize, pBuf, size);
+  } else {
+    memset(m_pBuffer.get() + m_DataSize, 0, size);
+  }
+  m_DataSize += size;
+}
+
+void CFX_BinaryBuf::InsertBlock(FX_STRSIZE pos,
+                                const void* pBuf,
+                                FX_STRSIZE size) {
+  if (size <= 0)
+    return;
+
+  ExpandBuf(size);
+  memmove(m_pBuffer.get() + pos + size, m_pBuffer.get() + pos,
+          m_DataSize - pos);
+  if (pBuf) {
+    memcpy(m_pBuffer.get() + pos, pBuf, size);
+  } else {
+    memset(m_pBuffer.get() + pos, 0, size);
+  }
+  m_DataSize += size;
+}
diff --git a/core/fxcrt/cfx_binarybuf.h b/core/fxcrt/cfx_binarybuf.h
new file mode 100644
index 0000000..3081d02
--- /dev/null
+++ b/core/fxcrt/cfx_binarybuf.h
@@ -0,0 +1,52 @@
+// 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_BINARYBUF_H_
+#define CORE_FXCRT_CFX_BINARYBUF_H_
+
+#include <memory>
+
+#include "core/fxcrt/fx_memory.h"
+#include "core/fxcrt/fx_string.h"
+#include "core/fxcrt/fx_system.h"
+
+class CFX_BinaryBuf {
+ public:
+  CFX_BinaryBuf();
+  explicit CFX_BinaryBuf(FX_STRSIZE size);
+  ~CFX_BinaryBuf();
+
+  uint8_t* GetBuffer() const { return m_pBuffer.get(); }
+  FX_STRSIZE GetSize() const { return m_DataSize; }
+
+  void Clear();
+  void EstimateSize(FX_STRSIZE size, FX_STRSIZE alloc_step = 0);
+  void AppendBlock(const void* pBuf, FX_STRSIZE size);
+  void AppendString(const CFX_ByteString& str) {
+    AppendBlock(str.c_str(), str.GetLength());
+  }
+
+  void AppendByte(uint8_t byte) {
+    ExpandBuf(1);
+    m_pBuffer.get()[m_DataSize++] = byte;
+  }
+
+  void InsertBlock(FX_STRSIZE pos, const void* pBuf, FX_STRSIZE size);
+  void Delete(FX_STRSIZE start_index, FX_STRSIZE count);
+
+  // Releases ownership of |m_pBuffer| and returns it.
+  std::unique_ptr<uint8_t, FxFreeDeleter> DetachBuffer();
+
+ protected:
+  void ExpandBuf(FX_STRSIZE size);
+
+  FX_STRSIZE m_AllocStep;
+  FX_STRSIZE m_AllocSize;
+  FX_STRSIZE m_DataSize;
+  std::unique_ptr<uint8_t, FxFreeDeleter> m_pBuffer;
+};
+
+#endif  // CORE_FXCRT_CFX_BINARYBUF_H_
diff --git a/core/fxcrt/fx_basic.h b/core/fxcrt/fx_basic.h
index 6f67669..6052cc8 100644
--- a/core/fxcrt/fx_basic.h
+++ b/core/fxcrt/fx_basic.h
@@ -11,6 +11,7 @@
 #include <memory>
 #include <vector>
 
+#include "core/fxcrt/cfx_binarybuf.h"
 #include "core/fxcrt/cfx_retain_ptr.h"
 #include "core/fxcrt/fx_memory.h"
 #include "core/fxcrt/fx_stream.h"
@@ -21,42 +22,6 @@
 #define FX_IsOdd(a) ((a)&1)
 #endif  // PDF_ENABLE_XFA
 
-class CFX_BinaryBuf {
- public:
-  CFX_BinaryBuf();
-  explicit CFX_BinaryBuf(FX_STRSIZE size);
-  ~CFX_BinaryBuf();
-
-  uint8_t* GetBuffer() const { return m_pBuffer.get(); }
-  FX_STRSIZE GetSize() const { return m_DataSize; }
-
-  void Clear();
-  void EstimateSize(FX_STRSIZE size, FX_STRSIZE alloc_step = 0);
-  void AppendBlock(const void* pBuf, FX_STRSIZE size);
-  void AppendString(const CFX_ByteString& str) {
-    AppendBlock(str.c_str(), str.GetLength());
-  }
-
-  void AppendByte(uint8_t byte) {
-    ExpandBuf(1);
-    m_pBuffer.get()[m_DataSize++] = byte;
-  }
-
-  void InsertBlock(FX_STRSIZE pos, const void* pBuf, FX_STRSIZE size);
-  void Delete(FX_STRSIZE start_index, FX_STRSIZE count);
-
-  // Releases ownership of |m_pBuffer| and returns it.
-  std::unique_ptr<uint8_t, FxFreeDeleter> DetachBuffer();
-
- protected:
-  void ExpandBuf(FX_STRSIZE size);
-
-  FX_STRSIZE m_AllocStep;
-  FX_STRSIZE m_AllocSize;
-  FX_STRSIZE m_DataSize;
-  std::unique_ptr<uint8_t, FxFreeDeleter> m_pBuffer;
-};
-
 class CFX_WideTextBuf : public CFX_BinaryBuf {
  public:
   void AppendChar(wchar_t wch);
diff --git a/core/fxcrt/fx_basic_buffer.cpp b/core/fxcrt/fx_basic_buffer.cpp
index b93c1bc..e282aa4 100644
--- a/core/fxcrt/fx_basic_buffer.cpp
+++ b/core/fxcrt/fx_basic_buffer.cpp
@@ -13,88 +13,6 @@
 #include "core/fxcrt/fx_safe_types.h"
 #include "third_party/base/numerics/safe_conversions.h"
 
-CFX_BinaryBuf::CFX_BinaryBuf()
-    : m_AllocStep(0), m_AllocSize(0), m_DataSize(0) {}
-
-CFX_BinaryBuf::CFX_BinaryBuf(FX_STRSIZE size)
-    : m_AllocStep(0), m_AllocSize(size), m_DataSize(size) {
-  m_pBuffer.reset(FX_Alloc(uint8_t, size));
-}
-
-CFX_BinaryBuf::~CFX_BinaryBuf() {}
-
-void CFX_BinaryBuf::Delete(FX_STRSIZE start_index, FX_STRSIZE count) {
-  if (!m_pBuffer || start_index < 0 || count < 0 || count > m_DataSize ||
-      start_index > m_DataSize - count) {
-    return;
-  }
-  memmove(m_pBuffer.get() + start_index, m_pBuffer.get() + start_index + count,
-          m_DataSize - start_index - count);
-  m_DataSize -= count;
-}
-
-void CFX_BinaryBuf::Clear() {
-  m_DataSize = 0;
-}
-
-std::unique_ptr<uint8_t, FxFreeDeleter> CFX_BinaryBuf::DetachBuffer() {
-  m_DataSize = 0;
-  m_AllocSize = 0;
-  return std::move(m_pBuffer);
-}
-
-void CFX_BinaryBuf::EstimateSize(FX_STRSIZE size, FX_STRSIZE step) {
-  m_AllocStep = step;
-  if (m_AllocSize < size)
-    ExpandBuf(size - m_DataSize);
-}
-
-void CFX_BinaryBuf::ExpandBuf(FX_STRSIZE add_size) {
-  FX_SAFE_STRSIZE new_size = m_DataSize;
-  new_size += add_size;
-  if (m_AllocSize >= new_size.ValueOrDie())
-    return;
-
-  int alloc_step = std::max(128, m_AllocStep ? m_AllocStep : m_AllocSize / 4);
-  new_size += alloc_step - 1;  // Quantize, don't combine these lines.
-  new_size /= alloc_step;
-  new_size *= alloc_step;
-  m_AllocSize = new_size.ValueOrDie();
-  m_pBuffer.reset(m_pBuffer
-                      ? FX_Realloc(uint8_t, m_pBuffer.release(), m_AllocSize)
-                      : FX_Alloc(uint8_t, m_AllocSize));
-}
-
-void CFX_BinaryBuf::AppendBlock(const void* pBuf, FX_STRSIZE size) {
-  if (size <= 0)
-    return;
-
-  ExpandBuf(size);
-  if (pBuf) {
-    memcpy(m_pBuffer.get() + m_DataSize, pBuf, size);
-  } else {
-    memset(m_pBuffer.get() + m_DataSize, 0, size);
-  }
-  m_DataSize += size;
-}
-
-void CFX_BinaryBuf::InsertBlock(FX_STRSIZE pos,
-                                const void* pBuf,
-                                FX_STRSIZE size) {
-  if (size <= 0)
-    return;
-
-  ExpandBuf(size);
-  memmove(m_pBuffer.get() + pos + size, m_pBuffer.get() + pos,
-          m_DataSize - pos);
-  if (pBuf) {
-    memcpy(m_pBuffer.get() + pos, pBuf, size);
-  } else {
-    memset(m_pBuffer.get() + pos, 0, size);
-  }
-  m_DataSize += size;
-}
-
 void CFX_WideTextBuf::AppendChar(wchar_t ch) {
   ExpandBuf(sizeof(wchar_t));
   *(wchar_t*)(m_pBuffer.get() + m_DataSize) = ch;
diff --git a/fpdfsdk/javascript/JS_GlobalData.h b/fpdfsdk/javascript/JS_GlobalData.h
index c4e8e48..24e68c2 100644
--- a/fpdfsdk/javascript/JS_GlobalData.h
+++ b/fpdfsdk/javascript/JS_GlobalData.h
@@ -10,7 +10,7 @@
 #include <memory>
 #include <vector>
 
-#include "core/fxcrt/fx_basic.h"
+#include "core/fxcrt/cfx_binarybuf.h"
 #include "fpdfsdk/javascript/JS_KeyValue.h"
 
 class CPDFSDK_FormFillEnvironment;