Revert "Cleanup some numeric code."

This reverts commit 589f7e0a57675efce9810c15a3e9b7c49bf0bc90.

Broke the build on Mac, unable to find std::isdigit.

TBR=thestig@chromium.org

Review URL: https://codereview.chromium.org/1428853002 .

22 files changed, 233 insertions, 177 deletions

diff --git a/BUILD.gn b/BUILD.gn
index 903e901046..abd189b8eb 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -757,7 +757,6 @@ test("pdfium_unittests") {
     "core/src/fxcrt/fx_basic_memmgr_unittest.cpp",
     "core/src/fxcrt/fx_basic_wstring_unittest.cpp",
     "core/src/fxcrt/fx_bidi_unittest.cpp",
-    "core/src/fxcrt/fx_extension_unittest.cpp",
     "core/src/fxcrt/fx_system_unittest.cpp",
     "third_party/base/nonstd_unique_ptr_unittest.cpp",
   ]
diff --git a/core/include/fxcrt/fx_ext.h b/core/include/fxcrt/fx_ext.h
index a31d10040a..c24955fb7c 100644
--- a/core/include/fxcrt/fx_ext.h
+++ b/core/include/fxcrt/fx_ext.h
@@ -13,8 +13,6 @@
 extern "C" {
 #endif
 
-int HexCharToDigit(char c);
-
 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,
@@ -47,6 +45,13 @@ 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);
@@ -61,7 +66,6 @@ void FX_Random_GenerateCrypto(FX_DWORD* pBuffer, int32_t iCount);
 #ifdef __cplusplus
 }
 #endif
-
 template <class baseType>
 class CFX_SSortTemplate {
  public:
diff --git a/core/src/fpdfapi/fpdf_font/fpdf_font.cpp b/core/src/fpdfapi/fpdf_font/fpdf_font.cpp
index e5389f8c77..543816b03a 100644
--- a/core/src/fpdfapi/fpdf_font/fpdf_font.cpp
+++ b/core/src/fpdfapi/fpdf_font/fpdf_font.cpp
@@ -8,7 +8,6 @@
 #include "../../../include/fpdfapi/fpdf_page.h"
 #include "../../../include/fpdfapi/fpdf_pageobj.h"
 #include "../../../include/fpdfapi/fpdf_resource.h"
-#include "../../../include/fxcrt/fx_ext.h"
 #include "../../../include/fxge/fx_freetype.h"
 #include "../fpdf_page/pageint.h"
 #include "font_int.h"
@@ -512,25 +511,32 @@ FX_DWORD CPDF_ToUnicodeMap::ReverseLookup(FX_WCHAR unicode) {
 static FX_DWORD _StringToCode(const CFX_ByteStringC& str) {
   const FX_CHAR* buf = str.GetCStr();
   int len = str.GetLength();
-  if (len == 0)
+  if (len == 0) {
     return 0;
-
+  }
   int result = 0;
   if (buf[0] == '<') {
     for (int i = 1; i < len; i++) {
-      if (!std::isxdigit(buf[i]))
+      int digit;
+      if (buf[i] >= '0' && buf[i] <= '9') {
+        digit = buf[i] - '0';
+      } else if (buf[i] >= 'a' && buf[i] <= 'f') {
+        digit = buf[i] - 'a' + 10;
+      } else if (buf[i] >= 'A' && buf[i] <= 'F') {
+        digit = buf[i] - 'A' + 10;
+      } else {
         break;
-      result = result * 16 + HexCharToDigit(buf[i]);
+      }
+      result = result * 16 + digit;
     }
     return result;
   }
-
   for (int i = 0; i < len; i++) {
-    if (!std::isdigit(buf[i]))
+    if (buf[i] < '0' || buf[i] > '9') {
       break;
+    }
     result = result * 10 + buf[i] - '0';
   }
-
   return result;
 }
 static CFX_WideString _StringDataAdd(CFX_WideString str) {
@@ -554,18 +560,25 @@ static CFX_WideString _StringDataAdd(CFX_WideString str) {
 static CFX_WideString _StringToWideString(const CFX_ByteStringC& str) {
   const FX_CHAR* buf = str.GetCStr();
   int len = str.GetLength();
-  if (len == 0)
+  if (len == 0) {
     return CFX_WideString();
-
+  }
   CFX_WideString result;
   if (buf[0] == '<') {
     int byte_pos = 0;
     FX_WCHAR ch = 0;
     for (int i = 1; i < len; i++) {
-      if (!std::isxdigit(buf[i]))
+      int digit;
+      if (buf[i] >= '0' && buf[i] <= '9') {
+        digit = buf[i] - '0';
+      } else if (buf[i] >= 'a' && buf[i] <= 'f') {
+        digit = buf[i] - 'a' + 10;
+      } else if (buf[i] >= 'A' && buf[i] <= 'F') {
+        digit = buf[i] - 'A' + 10;
+      } else {
         break;
-
-      ch = ch * 16 + HexCharToDigit(buf[i]);
+      }
+      ch = ch * 16 + digit;
       byte_pos++;
       if (byte_pos == 4) {
         result += ch;
@@ -575,6 +588,8 @@ static CFX_WideString _StringToWideString(const CFX_ByteStringC& str) {
     }
     return result;
   }
+  if (buf[0] == '(') {
+  }
   return result;
 }
 void CPDF_ToUnicodeMap::Load(CPDF_Stream* pStream) {
diff --git a/core/src/fpdfapi/fpdf_font/fpdf_font_cid.cpp b/core/src/fpdfapi/fpdf_font/fpdf_font_cid.cpp
index 165ef5bad5..02f0933f36 100644
--- a/core/src/fpdfapi/fpdf_font/fpdf_font_cid.cpp
+++ b/core/src/fpdfapi/fpdf_font/fpdf_font_cid.cpp
@@ -7,7 +7,6 @@
 #include "../../../include/fpdfapi/fpdf_module.h"
 #include "../../../include/fpdfapi/fpdf_page.h"
 #include "../../../include/fpdfapi/fpdf_resource.h"
-#include "../../../include/fxcrt/fx_ext.h"
 #include "../../../include/fxge/fx_freetype.h"
 #include "../../../include/fxge/fx_ge.h"
 #include "../fpdf_cmaps/cmap_int.h"
@@ -191,15 +190,22 @@ FX_DWORD CMap_GetCode(const CFX_ByteStringC& word) {
   if (word.GetAt(0) == '<') {
     for (int i = 1; i < word.GetLength(); i++) {
       uint8_t digit = word.GetAt(i);
-      if (!std::isxdigit(digit))
+      if (digit >= '0' && digit <= '9') {
+        digit = digit - '0';
+      } else if (digit >= 'a' && digit <= 'f') {
+        digit = digit - 'a' + 10;
+      } else if (digit >= 'A' && digit <= 'F') {
+        digit = digit - 'A' + 10;
+      } else {
         return num;
-      num = num * 16 + HexCharToDigit(digit);
+      }
+      num = num * 16 + digit;
     }
   } else {
     for (int i = 0; i < word.GetLength(); i++) {
-      if (!std::isdigit(word.GetAt(i)))
+      if (word.GetAt(i) < '0' || word.GetAt(i) > '9') {
         return num;
-
+      }
       num = num * 10 + word.GetAt(i) - '0';
     }
   }
@@ -225,7 +231,13 @@ bool CMap_GetCodeRange(CMap_CodeRange& range,
   for (i = 0; i < range.m_CharSize; ++i) {
     uint8_t digit1 = first.GetAt(i * 2 + 1);
     uint8_t digit2 = first.GetAt(i * 2 + 2);
-    range.m_Lower[i] = HexCharToDigit(digit1) * 16 + HexCharToDigit(digit2);
+    uint8_t byte = (digit1 >= '0' && digit1 <= '9')
+                       ? (digit1 - '0')
+                       : ((digit1 & 0xdf) - 'A' + 10);
+    byte = byte * 16 + ((digit2 >= '0' && digit2 <= '9')
+                            ? (digit2 - '0')
+                            : ((digit2 & 0xdf) - 'A' + 10));
+    range.m_Lower[i] = byte;
   }
 
   FX_DWORD size = second.GetLength();
@@ -234,7 +246,13 @@ bool CMap_GetCodeRange(CMap_CodeRange& range,
         ((FX_DWORD)i * 2 + 1 < size) ? second.GetAt((FX_STRSIZE)i * 2 + 1) : 0;
     uint8_t digit2 =
         ((FX_DWORD)i * 2 + 2 < size) ? second.GetAt((FX_STRSIZE)i * 2 + 2) : 0;
-    range.m_Upper[i] = HexCharToDigit(digit1) * 16 + HexCharToDigit(digit2);
+    uint8_t byte = (digit1 >= '0' && digit1 <= '9')
+                       ? (digit1 - '0')
+                       : ((digit1 & 0xdf) - 'A' + 10);
+    byte = byte * 16 + ((digit2 >= '0' && digit2 <= '9')
+                            ? (digit2 - '0')
+                            : ((digit2 & 0xdf) - 'A' + 10));
+    range.m_Upper[i] = byte;
   }
   return true;
 }
diff --git a/core/src/fpdfapi/fpdf_page/fpdf_page_parser.cpp b/core/src/fpdfapi/fpdf_page/fpdf_page_parser.cpp
index cc9b0fcbe8..3057948959 100644
--- a/core/src/fpdfapi/fpdf_page/fpdf_page_parser.cpp
+++ b/core/src/fpdfapi/fpdf_page/fpdf_page_parser.cpp
@@ -1540,7 +1540,7 @@ CFX_ByteString _FPDF_ByteStringFromHex(CFX_BinaryBuf& src_buf) {
   FX_DWORD size = src_buf.GetSize();
   for (FX_DWORD i = 0; i < size; i++) {
     uint8_t ch = str[i];
-    if (std::isdigit(ch)) {
+    if (ch >= '0' && ch <= '9') {
       if (bFirst) {
         code = (ch - '0') * 16;
       } else {
diff --git a/core/src/fpdfapi/fpdf_page/fpdf_page_parser_old.cpp b/core/src/fpdfapi/fpdf_page/fpdf_page_parser_old.cpp
index 88e2269c7a..1fa27e3805 100644
--- a/core/src/fpdfapi/fpdf_page/fpdf_page_parser_old.cpp
+++ b/core/src/fpdfapi/fpdf_page/fpdf_page_parser_old.cpp
@@ -7,7 +7,6 @@
 #include "../../../include/fpdfapi/fpdf_page.h"
 #include "../../../include/fpdfapi/fpdf_module.h"
 #include "../../../include/fxcodec/fx_codec.h"
-#include "../../../include/fxcrt/fx_ext.h"
 #include "pageint.h"
 #include <limits.h>
 
@@ -876,20 +875,34 @@ CFX_ByteString CPDF_StreamParser::ReadHexString() {
   FX_BOOL bFirst = TRUE;
   int code = 0;
   while (1) {
-    if (ch == '>')
+    if (ch == '>') {
       break;
-
-    if (std::isxdigit(ch)) {
-      int val = HexCharToDigit(ch);
+    }
+    if (ch >= '0' && ch <= '9') {
+      if (bFirst) {
+        code = (ch - '0') * 16;
+      } else {
+        code += ch - '0';
+        buf.AppendChar((char)code);
+      }
+      bFirst = !bFirst;
+    } else if (ch >= 'A' && ch <= 'F') {
       if (bFirst) {
-        code = val * 16;
+        code = (ch - 'A' + 10) * 16;
       } else {
-        code += val;
-        buf.AppendByte((uint8_t)code);
+        code += ch - 'A' + 10;
+        buf.AppendChar((char)code);
+      }
+      bFirst = !bFirst;
+    } else if (ch >= 'a' && ch <= 'f') {
+      if (bFirst) {
+        code = (ch - 'a' + 10) * 16;
+      } else {
+        code += ch - 'a' + 10;
+        buf.AppendChar((char)code);
       }
       bFirst = !bFirst;
     }
-
     if (!PositionIsInBounds())
       break;
 
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp
index eaff29d812..255d0ce29c 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp
@@ -8,7 +8,6 @@
 #include "../../../include/fpdfapi/fpdf_parser.h"
 #include "../../../include/fpdfapi/fpdf_module.h"
 #include "../../../include/fxcodec/fx_codec.h"
-#include "../../../include/fxcrt/fx_ext.h"
 
 #define _STREAM_MAX_SIZE_ 20 * 1024 * 1024
 
@@ -136,20 +135,23 @@ FX_DWORD _HexDecode(const uint8_t* src_buf,
       continue;
 
     int digit;
-    if (std::isxdigit(ch)) {
-      digit = HexCharToDigit(ch);
+    if (ch <= '9' && ch >= '0') {
+      digit = ch - '0';
+    } else if (ch <= 'f' && ch >= 'a') {
+      digit = ch - 'a' + 10;
+    } else if (ch <= 'F' && ch >= 'A') {
+      digit = ch - 'A' + 10;
     } else if (ch == '>') {
       i++;
       break;
     } else {
       continue;
     }
-
-    if (bFirstDigit)
+    if (bFirstDigit) {
       dest_buf[dest_size] = digit * 16;
-    else
+    } else {
       dest_buf[dest_size++] += digit;
-
+    }
     bFirstDigit = !bFirstDigit;
   }
   if (!bFirstDigit) {
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
index fa114f9cfb..4ce196e90d 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
@@ -13,7 +13,6 @@
 #include "../../../include/fpdfapi/fpdf_module.h"
 #include "../../../include/fpdfapi/fpdf_page.h"
 #include "../../../include/fpdfapi/fpdf_parser.h"
-#include "../../../include/fxcrt/fx_ext.h"
 #include "../../../include/fxcrt/fx_safe_types.h"
 #include "../fpdf_page/pageint.h"
 
@@ -163,83 +162,85 @@ FX_DWORD CPDF_Parser::StartParse(IFX_FileRead* pFileAccess,
   m_bXRefStream = FALSE;
   m_LastXRefOffset = 0;
   m_bOwnFileRead = bOwnFileRead;
-
   int32_t offset = GetHeaderOffset(pFileAccess);
   if (offset == -1) {
-    if (bOwnFileRead && pFileAccess)
+    if (bOwnFileRead && pFileAccess) {
       pFileAccess->Release();
+    }
     return PDFPARSE_ERROR_FORMAT;
   }
   m_Syntax.InitParser(pFileAccess, offset);
-
   uint8_t ch;
-  if (!m_Syntax.GetCharAt(5, ch))
+  if (!m_Syntax.GetCharAt(5, ch)) {
     return PDFPARSE_ERROR_FORMAT;
-  if (std::isdigit(ch))
+  }
+  if (ch >= '0' && ch <= '9') {
     m_FileVersion = (ch - '0') * 10;
-
-  if (!m_Syntax.GetCharAt(7, ch))
+  }
+  if (!m_Syntax.GetCharAt(7, ch)) {
     return PDFPARSE_ERROR_FORMAT;
-  if (std::isdigit(ch))
+  }
+  if (ch >= '0' && ch <= '9') {
     m_FileVersion += ch - '0';
-
-  if (m_Syntax.m_FileLen < m_Syntax.m_HeaderOffset + 9)
+  }
+  if (m_Syntax.m_FileLen < m_Syntax.m_HeaderOffset + 9) {
     return PDFPARSE_ERROR_FORMAT;
-
+  }
   m_Syntax.RestorePos(m_Syntax.m_FileLen - m_Syntax.m_HeaderOffset - 9);
-  if (!bReParse)
+  if (!bReParse) {
     m_pDocument = new CPDF_Document(this);
-
+  }
   FX_BOOL bXRefRebuilt = FALSE;
   if (m_Syntax.SearchWord(FX_BSTRC("startxref"), TRUE, FALSE, 4096)) {
     FX_FILESIZE startxref_offset = m_Syntax.SavePos();
     void* pResult = FXSYS_bsearch(&startxref_offset, m_SortedOffset.GetData(),
                                   m_SortedOffset.GetSize(), sizeof(FX_FILESIZE),
                                   CompareFileSize);
-    if (!pResult)
+    if (pResult == NULL) {
       m_SortedOffset.Add(startxref_offset);
-
+    }
     m_Syntax.GetKeyword();
     FX_BOOL bNumber;
     CFX_ByteString xrefpos_str = m_Syntax.GetNextWord(bNumber);
-    if (!bNumber)
+    if (!bNumber) {
       return PDFPARSE_ERROR_FORMAT;
-
+    }
     m_LastXRefOffset = (FX_FILESIZE)FXSYS_atoi64(xrefpos_str);
     if (!LoadAllCrossRefV4(m_LastXRefOffset) &&
         !LoadAllCrossRefV5(m_LastXRefOffset)) {
-      if (!RebuildCrossRef())
+      if (!RebuildCrossRef()) {
         return PDFPARSE_ERROR_FORMAT;
-
+      }
       bXRefRebuilt = TRUE;
       m_LastXRefOffset = 0;
     }
   } else {
-    if (!RebuildCrossRef())
+    if (!RebuildCrossRef()) {
       return PDFPARSE_ERROR_FORMAT;
-
+    }
     bXRefRebuilt = TRUE;
   }
   FX_DWORD dwRet = SetEncryptHandler();
-  if (dwRet != PDFPARSE_ERROR_SUCCESS)
+  if (dwRet != PDFPARSE_ERROR_SUCCESS) {
     return dwRet;
-
+  }
   m_pDocument->LoadDoc();
-  if (!m_pDocument->GetRoot() || m_pDocument->GetPageCount() == 0) {
-    if (bXRefRebuilt)
+  if (m_pDocument->GetRoot() == NULL || m_pDocument->GetPageCount() == 0) {
+    if (bXRefRebuilt) {
       return PDFPARSE_ERROR_FORMAT;
-
+    }
     ReleaseEncryptHandler();
-    if (!RebuildCrossRef())
+    if (!RebuildCrossRef()) {
       return PDFPARSE_ERROR_FORMAT;
-
+    }
     dwRet = SetEncryptHandler();
-    if (dwRet != PDFPARSE_ERROR_SUCCESS)
+    if (dwRet != PDFPARSE_ERROR_SUCCESS) {
       return dwRet;
-
+    }
     m_pDocument->LoadDoc();
-    if (!m_pDocument->GetRoot())
+    if (m_pDocument->GetRoot() == NULL) {
       return PDFPARSE_ERROR_FORMAT;
+    }
   }
   FXSYS_qsort(m_SortedOffset.GetData(), m_SortedOffset.GetSize(),
               sizeof(FX_FILESIZE), CompareFileSize);
@@ -248,12 +249,13 @@ FX_DWORD CPDF_Parser::StartParse(IFX_FileRead* pFileAccess,
     ReleaseEncryptHandler();
     RebuildCrossRef();
     RootObjNum = GetRootObjNum();
-    if (RootObjNum == 0)
+    if (RootObjNum == 0) {
       return PDFPARSE_ERROR_FORMAT;
-
+    }
     dwRet = SetEncryptHandler();
-    if (dwRet != PDFPARSE_ERROR_SUCCESS)
+    if (dwRet != PDFPARSE_ERROR_SUCCESS) {
       return dwRet;
+    }
   }
   if (m_pSecurityHandler && !m_pSecurityHandler->IsMetadataEncrypted()) {
     CPDF_Reference* pMetadata =
@@ -457,8 +459,9 @@ FX_BOOL CPDF_Parser::LoadLinearizedCrossRefV4(FX_FILESIZE pos,
         int32_t offset = FXSYS_atoi(pEntry);
         if (offset == 0) {
           for (int32_t c = 0; c < 10; c++) {
-            if (!std::isdigit(pEntry[c]))
+            if (pEntry[c] < '0' || pEntry[c] > '9') {
               return FALSE;
+            }
           }
         }
         m_CrossRef.SetAtGrow(objnum, offset);
@@ -557,8 +560,9 @@ bool CPDF_Parser::LoadCrossRefV4(FX_FILESIZE pos,
             FX_FILESIZE offset = (FX_FILESIZE)FXSYS_atoi64(pEntry);
             if (offset == 0) {
               for (int32_t c = 0; c < 10; c++) {
-                if (!std::isdigit(pEntry[c]))
+                if (pEntry[c] < '0' || pEntry[c] > '9') {
                   return false;
+                }
               }
             }
             m_CrossRef.SetAtGrow(objnum, offset);
@@ -626,32 +630,28 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
       uint8_t byte = buffer[i];
       switch (status) {
         case 0:
-          if (PDFCharIsWhitespace(byte))
+          if (PDFCharIsWhitespace(byte)) {
             status = 1;
-
-          if (std::isdigit(byte)) {
+          }
+          if (byte <= '9' && byte >= '0') {
             --i;
             status = 1;
           }
-
           if (byte == '%') {
             inside_index = 0;
             status = 9;
           }
-
           if (byte == '(') {
             status = 10;
             depth = 1;
           }
-
           if (byte == '<') {
             inside_index = 1;
             status = 11;
           }
-
-          if (byte == '\\')
+          if (byte == '\\') {
             status = 13;
-
+          }
           if (byte == 't') {
             status = 7;
             inside_index = 1;
@@ -660,7 +660,7 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
         case 1:
           if (PDFCharIsWhitespace(byte)) {
             break;
-          } else if (std::isdigit(byte)) {
+          } else if (byte <= '9' && byte >= '0') {
             start_pos = pos + i;
             status = 2;
             objnum = byte - '0';
@@ -676,7 +676,7 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
           }
           break;
         case 2:
-          if (std::isdigit(byte)) {
+          if (byte <= '9' && byte >= '0') {
             objnum = objnum * 10 + byte - '0';
             break;
           } else if (PDFCharIsWhitespace(byte)) {
@@ -688,7 +688,7 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
           }
           break;
         case 3:
-          if (std::isdigit(byte)) {
+          if (byte <= '9' && byte >= '0') {
             start_pos1 = pos + i;
             status = 4;
             gennum = byte - '0';
@@ -703,7 +703,7 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
           }
           break;
         case 4:
-          if (std::isdigit(byte)) {
+          if (byte <= '9' && byte >= '0') {
             gennum = gennum * 10 + byte - '0';
             break;
           } else if (PDFCharIsWhitespace(byte)) {
@@ -719,7 +719,7 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
             inside_index = 1;
           } else if (PDFCharIsWhitespace(byte)) {
             break;
-          } else if (std::isdigit(byte)) {
+          } else if (byte <= '9' && byte >= '0') {
             objnum = gennum;
             gennum = byte - '0';
             start_pos = start_pos1;
@@ -1922,33 +1922,48 @@ CFX_ByteString CPDF_SyntaxParser::ReadString() {
 }
 CFX_ByteString CPDF_SyntaxParser::ReadHexString() {
   uint8_t ch;
-  if (!GetNextChar(ch))
+  if (!GetNextChar(ch)) {
     return CFX_ByteString();
-
+  }
   CFX_BinaryBuf buf;
   FX_BOOL bFirst = TRUE;
   uint8_t code = 0;
   while (1) {
-    if (ch == '>')
+    if (ch == '>') {
       break;
-
-    if (std::isxdigit(ch)) {
-      int val = HexCharToDigit(ch);
+    }
+    if (ch >= '0' && ch <= '9') {
+      if (bFirst) {
+        code = (ch - '0') * 16;
+      } else {
+        code += ch - '0';
+        buf.AppendByte((uint8_t)code);
+      }
+      bFirst = !bFirst;
+    } else if (ch >= 'A' && ch <= 'F') {
       if (bFirst) {
-        code = val * 16;
+        code = (ch - 'A' + 10) * 16;
       } else {
-        code += val;
+        code += ch - 'A' + 10;
+        buf.AppendByte((uint8_t)code);
+      }
+      bFirst = !bFirst;
+    } else if (ch >= 'a' && ch <= 'f') {
+      if (bFirst) {
+        code = (ch - 'a' + 10) * 16;
+      } else {
+        code += ch - 'a' + 10;
         buf.AppendByte((uint8_t)code);
       }
       bFirst = !bFirst;
     }
-
-    if (!GetNextChar(ch))
+    if (!GetNextChar(ch)) {
       break;
+    }
   }
-  if (!bFirst)
+  if (!bFirst) {
     buf.AppendByte((uint8_t)code);
-
+  }
   return buf.GetByteString();
 }
 void CPDF_SyntaxParser::ToNextLine() {
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
index d7c4136447..335101e85b 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
@@ -5,7 +5,6 @@
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #include "../../../include/fpdfapi/fpdf_parser.h"
-#include "../../../include/fxcrt/fx_ext.h"
 
 // Indexed by 8-bit character code, contains either:
 //   'W' - for whitespace: NUL, TAB, CR, LF, FF, 0x80, 0xff
@@ -280,7 +279,18 @@ FX_BOOL CPDF_SimpleParser::FindTagParam(const CFX_ByteStringC& token,
   }
   return FALSE;
 }
-
+static int _hex2dec(char ch) {
+  if (ch >= '0' && ch <= '9') {
+    return ch - '0';
+  }
+  if (ch >= 'a' && ch <= 'f') {
+    return ch - 'a' + 10;
+  }
+  if (ch >= 'A' && ch <= 'F') {
+    return ch - 'A' + 10;
+  }
+  return 0;
+}
 CFX_ByteString PDF_NameDecode(const CFX_ByteStringC& bstr) {
   int size = bstr.GetLength();
   const FX_CHAR* pSrc = bstr.GetCStr();
@@ -292,7 +302,7 @@ CFX_ByteString PDF_NameDecode(const CFX_ByteStringC& bstr) {
   FX_CHAR* pDest = pDestStart;
   for (int i = 0; i < size; i++) {
     if (pSrc[i] == '#' && i < size - 2) {
-      *pDest++ = HexCharToDigit(pSrc[i + 1]) * 16 + HexCharToDigit(pSrc[i + 2]);
+      *pDest++ = _hex2dec(pSrc[i + 1]) * 16 + _hex2dec(pSrc[i + 2]);
       i += 2;
     } else {
       *pDest++ = pSrc[i];
diff --git a/core/src/fpdftext/fpdf_text.cpp b/core/src/fpdftext/fpdf_text.cpp
index e9ad338025..9ecbc21bda 100644
--- a/core/src/fpdftext/fpdf_text.cpp
+++ b/core/src/fpdftext/fpdf_text.cpp
@@ -436,8 +436,10 @@ void NormalizeString(CFX_WideString& str) {
 static FX_BOOL IsNumber(CFX_WideString& str) {
   for (int i = 0; i < str.GetLength(); i++) {
     FX_WCHAR ch = str[i];
-    if (!std::isdigit(ch) && ch != '-' && ch != '+' && ch != '.' && ch != ' ')
+    if ((ch < '0' || ch > '9') && ch != '-' && ch != '+' && ch != '.' &&
+        ch != ' ') {
       return FALSE;
+    }
   }
   return TRUE;
 }
diff --git a/core/src/fpdftext/fpdf_text_int.cpp b/core/src/fpdftext/fpdf_text_int.cpp
index 4459552c84..9ab09e19e4 100644
--- a/core/src/fpdftext/fpdf_text_int.cpp
+++ b/core/src/fpdftext/fpdf_text_int.cpp
@@ -2433,11 +2433,12 @@ FX_BOOL CPDF_TextPageFind::IsMatchWholeWord(const CFX_WideString& csPageText,
   }
   if ((char_left > 'A' && char_left < 'a') ||
       (char_left > 'a' && char_left < 'z') ||
-      (char_left > 0xfb00 && char_left < 0xfb06) || std::isdigit(char_left) ||
+      (char_left > 0xfb00 && char_left < 0xfb06) ||
+      (char_left >= '0' && char_left <= '9') ||
       (char_right > 'A' && char_right < 'a') ||
       (char_right > 'a' && char_right < 'z') ||
       (char_right > 0xfb00 && char_right < 0xfb06) ||
-      std::isdigit(char_right)) {
+      (char_right >= '0' && char_right <= '9')) {
     return FALSE;
   }
   if (!(('A' > char_left || char_left > 'Z') &&
diff --git a/core/src/fxcodec/codec/fx_codec.cpp b/core/src/fxcodec/codec/fx_codec.cpp
index eca6505d12..46f479e0b1 100644
--- a/core/src/fxcodec/codec/fx_codec.cpp
+++ b/core/src/fxcodec/codec/fx_codec.cpp
@@ -157,13 +157,13 @@ extern "C" double FXstrtod(const char* nptr, char** endptr) {
     return 0.0;
   }
   for (;; ptr++) {
-    if (!e_number && !e_point && (*ptr == '\t' || *ptr == ' '))
+    if (!e_number && !e_point && (*ptr == '\t' || *ptr == ' ')) {
       continue;
-
-    if (std::isdigit(*ptr)) {
-      if (!e_number)
+    }
+    if (*ptr >= '0' && *ptr <= '9') {
+      if (!e_number) {
         e_number = 1;
-
+      }
       if (!e_point) {
         ret *= 10;
         ret += (*ptr - '0');
@@ -188,29 +188,29 @@ extern "C" double FXstrtod(const char* nptr, char** endptr) {
       }
     }
     if (e_number && (*ptr == 'e' || *ptr == 'E')) {
-#define EXPONENT_DETECT(ptr)   \
-  for (;; ptr++) {             \
-    if (!std::isdigit(*ptr)) { \
-      if (endptr)              \
-        *endptr = (char*)ptr;  \
-      break;                   \
-    } else {                   \
-      exp_ret *= 10;           \
-      exp_ret += (*ptr - '0'); \
-      continue;                \
-    }                          \
+#define EXPONENT_DETECT(ptr)        \
+  for (;; ptr++) {                  \
+    if (*ptr < '0' || *ptr > '9') { \
+      if (endptr)                   \
+        *endptr = (char*)ptr;       \
+      break;                        \
+    } else {                        \
+      exp_ret *= 10;                \
+      exp_ret += (*ptr - '0');      \
+      continue;                     \
+    }                               \
   }
       exp_ptr = ptr++;
       if (*ptr == '+' || *ptr == '-') {
         exp_sig = (*ptr++ == '+') ? 1 : -1;
-        if (!std::isdigit(*ptr)) {
+        if (*ptr < '0' || *ptr > '9') {
           if (endptr) {
             *endptr = (char*)exp_ptr;
           }
           break;
         }
         EXPONENT_DETECT(ptr);
-      } else if (std::isdigit(*ptr)) {
+      } else if (*ptr >= '0' && *ptr <= '9') {
         EXPONENT_DETECT(ptr);
       } else {
         if (endptr) {
diff --git a/core/src/fxcrt/fx_basic_bstring.cpp b/core/src/fxcrt/fx_basic_bstring.cpp
index d5ffcddb6d..c706912d9d 100644
--- a/core/src/fxcrt/fx_basic_bstring.cpp
+++ b/core/src/fxcrt/fx_basic_bstring.cpp
@@ -493,7 +493,7 @@ void CFX_ByteString::FormatV(const FX_CHAR* lpszFormat, va_list argList) {
     }
     if (nWidth == 0) {
       nWidth = FXSYS_atoi(lpsz);
-      for (; std::isdigit(*lpsz); lpsz++)
+      for (; (*lpsz) >= '0' && (*lpsz) <= '9'; lpsz++)
         ;
     }
     if (nWidth < 0 || nWidth > 128 * 1024) {
@@ -509,7 +509,7 @@ void CFX_ByteString::FormatV(const FX_CHAR* lpszFormat, va_list argList) {
         lpsz++;
       } else {
         nPrecision = FXSYS_atoi(lpsz);
-        for (; std::isdigit(*lpsz); lpsz++)
+        for (; (*lpsz) >= '0' && (*lpsz) <= '9'; lpsz++)
           ;
       }
     }
diff --git a/core/src/fxcrt/fx_basic_gcc.cpp b/core/src/fxcrt/fx_basic_gcc.cpp
index 71f5fe322f..6f17482156 100644
--- a/core/src/fxcrt/fx_basic_gcc.cpp
+++ b/core/src/fxcrt/fx_basic_gcc.cpp
@@ -12,20 +12,21 @@
 template <class T, class STR_T>
 T FXSYS_StrToInt(STR_T str) {
   FX_BOOL neg = FALSE;
-  if (!str)
+  if (str == NULL) {
     return 0;
-
+  }
   if (*str == '-') {
     neg = TRUE;
     str++;
   }
   T num = 0;
   while (*str) {
-    if (!std::isdigit(*str))
+    if ((*str) < '0' || (*str) > '9') {
       break;
-    if (num > (std::numeric_limits<T>::max() - 9) / 10)
+    }
+    if (num > (std::numeric_limits<T>::max() - 9) / 10) {
       break;
-
+    }
     num = num * 10 + (*str) - '0';
     str++;
   }
diff --git a/core/src/fxcrt/fx_basic_util.cpp b/core/src/fxcrt/fx_basic_util.cpp
index 71119082a2..46a0dec1e5 100644
--- a/core/src/fxcrt/fx_basic_util.cpp
+++ b/core/src/fxcrt/fx_basic_util.cpp
@@ -101,13 +101,13 @@ void FX_atonum(const CFX_ByteStringC& strc, FX_BOOL& bInteger, void* pData) {
       cc++;
     }
     while (cc < len) {
-      if (!std::isdigit(str[cc]))
+      if (str[cc] < '0' || str[cc] > '9') {
         break;
-
+      }
       integer = integer * 10 + str[cc] - '0';
-      if (integer < 0)
+      if (integer < 0) {
         break;
-
+      }
       cc++;
     }
     if (bNegative) {
diff --git a/core/src/fxcrt/fx_basic_wstring.cpp b/core/src/fxcrt/fx_basic_wstring.cpp
index 3310df7062..c097e1fc09 100644
--- a/core/src/fxcrt/fx_basic_wstring.cpp
+++ b/core/src/fxcrt/fx_basic_wstring.cpp
@@ -765,7 +765,7 @@ void CFX_WideString::FormatV(const FX_WCHAR* lpszFormat, va_list argList) {
     }
     if (nWidth == 0) {
       nWidth = FXSYS_wtoi(lpsz);
-      for (; *lpsz != 0 && std::isdigit(*lpsz); lpsz++)
+      for (; *lpsz != 0 && (*lpsz) <= '9' && (*lpsz) >= '0'; lpsz++)
         ;
     }
     if (nWidth < 0 || nWidth > 128 * 1024) {
@@ -781,7 +781,7 @@ void CFX_WideString::FormatV(const FX_WCHAR* lpszFormat, va_list argList) {
         lpsz++;
       } else {
         nPrecision = FXSYS_wtoi(lpsz);
-        for (; *lpsz != 0 && std::isdigit(*lpsz); lpsz++)
+        for (; *lpsz != 0 && (*lpsz) >= '0' && (*lpsz) <= '9'; lpsz++)
           ;
       }
     }
diff --git a/core/src/fxcrt/fx_extension.cpp b/core/src/fxcrt/fx_extension.cpp
index a75cfb48df..d64a06d08b 100644
--- a/core/src/fxcrt/fx_extension.cpp
+++ b/core/src/fxcrt/fx_extension.cpp
@@ -13,15 +13,6 @@
 #include <ctime>
 #endif
 
-#include <cctype>
-
-int HexCharToDigit(char c) {
-  if (!std::isxdigit(c))
-    return 0;
-  char upchar = std::toupper(c);
-  return upchar > '9' ? upchar - 'A' + 10 : upchar - '0';
-}
-
 IFX_FileStream* FX_CreateFileStream(const FX_CHAR* filename, FX_DWORD dwModes) {
   IFXCRT_FileAccess* pFA = FXCRT_FileAccess_Create();
   if (!pFA) {
diff --git a/core/src/fxcrt/fx_extension_unittest.cpp b/core/src/fxcrt/fx_extension_unittest.cpp
deleted file mode 100644
index e2017fc3ed..0000000000
--- a/core/src/fxcrt/fx_extension_unittest.cpp
+++ /dev/null
@@ -1,14 +0,0 @@
-// Copyright 2015 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 "testing/gtest/include/gtest/gtest.h"
-
-#include "../../include/fxcrt/fx_ext.h"
-
-TEST(fxcrt, HexCharToDigit) {
-  EXPECT_EQ(10, HexCharToDigit('a'));
-  EXPECT_EQ(10, HexCharToDigit('A'));
-  EXPECT_EQ(7, HexCharToDigit('7'));
-  EXPECT_EQ(0, HexCharToDigit('i'));
-}
diff --git a/fpdfsdk/src/fsdk_baseannot.cpp b/fpdfsdk/src/fsdk_baseannot.cpp
index ebf56ad293..c6731e6f56 100644
--- a/fpdfsdk/src/fsdk_baseannot.cpp
+++ b/fpdfsdk/src/fsdk_baseannot.cpp
@@ -221,7 +221,7 @@ CPDFSDK_DateTime& CPDFSDK_DateTime::FromPDFDateTimeString(
     FX_CHAR ch;
     while (i < strLength) {
       ch = dtStr[i];
-      if (std::isdigit(ch))
+      if (ch >= '0' && ch <= '9')
         break;
       i++;
     }
@@ -234,7 +234,7 @@ CPDFSDK_DateTime& CPDFSDK_DateTime::FromPDFDateTimeString(
       ch = dtStr[i];
       k = k * 10 + ch - '0';
       j++;
-      if (!std::isdigit(ch))
+      if (ch < '0' || ch > '9')
         break;
       i++;
     }
@@ -248,7 +248,7 @@ CPDFSDK_DateTime& CPDFSDK_DateTime::FromPDFDateTimeString(
       ch = dtStr[i];
       k = k * 10 + ch - '0';
       j++;
-      if (!std::isdigit(ch))
+      if (ch < '0' || ch > '9')
         break;
       i++;
     }
@@ -262,7 +262,7 @@ CPDFSDK_DateTime& CPDFSDK_DateTime::FromPDFDateTimeString(
       ch = dtStr[i];
       k = k * 10 + ch - '0';
       j++;
-      if (!std::isdigit(ch))
+      if (ch < '0' || ch > '9')
         break;
       i++;
     }
@@ -276,7 +276,7 @@ CPDFSDK_DateTime& CPDFSDK_DateTime::FromPDFDateTimeString(
       ch = dtStr[i];
       k = k * 10 + ch - '0';
       j++;
-      if (!std::isdigit(ch))
+      if (ch < '0' || ch > '9')
         break;
       i++;
     }
@@ -290,7 +290,7 @@ CPDFSDK_DateTime& CPDFSDK_DateTime::FromPDFDateTimeString(
       ch = dtStr[i];
       k = k * 10 + ch - '0';
       j++;
-      if (!std::isdigit(ch))
+      if (ch < '0' || ch > '9')
         break;
       i++;
     }
@@ -304,7 +304,7 @@ CPDFSDK_DateTime& CPDFSDK_DateTime::FromPDFDateTimeString(
       ch = dtStr[i];
       k = k * 10 + ch - '0';
       j++;
-      if (!std::isdigit(ch))
+      if (ch < '0' || ch > '9')
         break;
       i++;
     }
@@ -325,7 +325,7 @@ CPDFSDK_DateTime& CPDFSDK_DateTime::FromPDFDateTimeString(
       ch = dtStr[i];
       k = k * 10 + ch - '0';
       j++;
-      if (!std::isdigit(ch))
+      if (ch < '0' || ch > '9')
         break;
       i++;
     }
@@ -342,7 +342,7 @@ CPDFSDK_DateTime& CPDFSDK_DateTime::FromPDFDateTimeString(
       ch = dtStr[i];
       k = k * 10 + ch - '0';
       j++;
-      if (!std::isdigit(ch))
+      if (ch < '0' || ch > '9')
         break;
       i++;
     }
diff --git a/fpdfsdk/src/javascript/PublicMethods.cpp b/fpdfsdk/src/javascript/PublicMethods.cpp
index 13239aeb1d..e898214cd8 100644
--- a/fpdfsdk/src/javascript/PublicMethods.cpp
+++ b/fpdfsdk/src/javascript/PublicMethods.cpp
@@ -116,7 +116,7 @@ FX_BOOL CJS_PublicMethods::IsDigit(wchar_t ch) {
 }
 
 FX_BOOL CJS_PublicMethods::IsDigit(char ch) {
-  return std::isdigit(ch);
+  return (ch >= '0' && ch <= '9');
 }
 
 FX_BOOL CJS_PublicMethods::IsAlphabetic(wchar_t ch) {
diff --git a/fpdfsdk/src/javascript/util.cpp b/fpdfsdk/src/javascript/util.cpp
index cf10bbd7b4..14e15c1b6f 100644
--- a/fpdfsdk/src/javascript/util.cpp
+++ b/fpdfsdk/src/javascript/util.cpp
@@ -425,7 +425,7 @@ void util::printx(const std::string& cFormat,
         break;
       case 'X': {
         while (itSource < iSize) {
-          if (std::isdigit(cSource[itSource]) ||
+          if ((cSource[itSource] >= '0' && cSource[itSource] <= '9') ||
               (cSource[itSource] >= 'a' && cSource[itSource] <= 'z') ||
               (cSource[itSource] >= 'A' && cSource[itSource] <= 'Z')) {
             cPurpose += cSource[itSource];
@@ -450,7 +450,7 @@ void util::printx(const std::string& cFormat,
       } break;
       case '9': {
         while (itSource < iSize) {
-          if (std::isdigit(cSource[itSource])) {
+          if (cSource[itSource] >= '0' && cSource[itSource] <= '9') {
             cPurpose += cSource[itSource];
             itSource++;
             break;
diff --git a/pdfium.gyp b/pdfium.gyp
index 250e4e2584..e98a4eee33 100644
--- a/pdfium.gyp
+++ b/pdfium.gyp
@@ -721,7 +721,6 @@
         'core/src/fxcrt/fx_basic_memmgr_unittest.cpp',
         'core/src/fxcrt/fx_basic_wstring_unittest.cpp',
         'core/src/fxcrt/fx_bidi_unittest.cpp',
-        'core/src/fxcrt/fx_extension_unittest.cpp',
         'core/src/fxcrt/fx_system_unittest.cpp',
         'testing/fx_string_testhelpers.h',
         'testing/fx_string_testhelpers.cpp',