Revert "Revert "Revert "Cleanup some numeric code."""

core/include/fxcrt/fx_ext.h

 // Copyright 2014 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_INCLUDE_FXCRT_FX_EXT_H_
 #define CORE_INCLUDE_FXCRT_FX_EXT_H_
 
-#include <cctype>
+#include "fx_system.h"
 
-#include "fx_system.h"
+#ifdef __cplusplus
+extern "C" {
+#endif
 
 FX_FLOAT FXSYS_tan(FX_FLOAT a);
 FX_FLOAT FXSYS_logb(FX_FLOAT b, FX_FLOAT x);
 FX_FLOAT FXSYS_strtof(const FX_CHAR* pcsStr,
                       int32_t iLength = -1,
                       int32_t* pUsedLen = NULL);
 FX_FLOAT FXSYS_wcstof(const FX_WCHAR* pwsStr,
                       int32_t iLength = -1,
                       int32_t* pUsedLen = NULL);
 FX_WCHAR* FXSYS_wcsncpy(FX_WCHAR* dstStr, const FX_WCHAR* srcStr, size_t count);
 int32_t FXSYS_wcsnicmp(const FX_WCHAR* s1, const FX_WCHAR* s2, size_t count);
 int32_t FXSYS_strnicmp(const FX_CHAR* s1, const FX_CHAR* s2, size_t count);
 
 inline FX_BOOL FXSYS_islower(int32_t ch) {
   return ch >= 'a' && ch <= 'z';
 }
 inline FX_BOOL FXSYS_isupper(int32_t ch) {
   return ch >= 'A' && ch <= 'Z';
 }
 inline int32_t FXSYS_tolower(int32_t ch) {
   return ch < 'A' || ch > 'Z' ? ch : (ch + 0x20);
 }
 inline int32_t FXSYS_toupper(int32_t ch) {
   return ch < 'a' || ch > 'z' ? ch : (ch - 0x20);
 }
 
-inline int FXSYS_toHexDigit(char c) {
-  if (!std::isxdigit(c))
-    return 0;
-  char upchar = std::toupper(c);
-  return upchar > '9' ? upchar - 'A' + 10 : upchar - '0';
-}
-
-inline int FXSYS_toDecimalDigit(char c) {
-  if (!std::isdigit(c))
-    return 0;
-  return c - '0';
-}
-
 FX_DWORD FX_HashCode_String_GetA(const FX_CHAR* pStr,
                                  int32_t iLength,
                                  FX_BOOL bIgnoreCase = FALSE);
 FX_DWORD FX_HashCode_String_GetW(const FX_WCHAR* pStr,
                                  int32_t iLength,
                                  FX_BOOL bIgnoreCase = FALSE);
 
+#ifdef __cplusplus
+}
+#endif
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 void* FX_Random_MT_Start(FX_DWORD dwSeed);
 
 FX_DWORD FX_Random_MT_Generate(void* pContext);
 
 void FX_Random_MT_Close(void* pContext);
 
 void FX_Random_GenerateBase(FX_DWORD* pBuffer, int32_t iCount);
 
 void FX_Random_GenerateMT(FX_DWORD* pBuffer, int32_t iCount);
 
 void FX_Random_GenerateCrypto(FX_DWORD* pBuffer, int32_t iCount);
-
+#ifdef __cplusplus
+}
+#endif
 template <class baseType>
 class CFX_SSortTemplate {
  public:
   void ShellSort(baseType* pArray, int32_t iCount) {
     FXSYS_assert(pArray != NULL && iCount > 0);
     int32_t i, j, gap;
     baseType v1, v2;
     gap = iCount >> 1;
     while (gap > 0) {
       for (i = gap; i < iCount; i++) {
         j = i - gap;
         v1 = pArray[i];
         while (j > -1 && (v2 = pArray[j]) > v1) {
           pArray[j + gap] = v2;
           j -= gap;
         }
         pArray[j + gap] = v1;
       }
       gap >>= 1;
     }
   }
 };
 
 #endif  // CORE_INCLUDE_FXCRT_FX_EXT_H_