Cleanup some numeric code.

This changes the various comparisons of char >= '0' && char <= '9' and
char < '0' || char > '9' to use std::isdigit checks. It also cleans up
a handful of hex to digit conversions to call one common method.

R=thestig@chromium.org

Review URL: https://codereview.chromium.org/1415933005 .

17 files changed, 163 insertions, 221 deletions

diff --git a/core/include/fxcrt/fx_ext.h b/core/include/fxcrt/fx_ext.h
index c24955fb7c..a31d10040a 100644
--- a/core/include/fxcrt/fx_ext.h
+++ b/core/include/fxcrt/fx_ext.h
@@ -13,6 +13,8 @@
 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,
@@ -45,13 +47,6 @@ 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);
@@ -66,6 +61,7 @@ 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 543816b03a..e5389f8c77 100644
--- a/core/src/fpdfapi/fpdf_font/fpdf_font.cpp
+++ b/core/src/fpdfapi/fpdf_font/fpdf_font.cpp
@@ -8,6 +8,7 @@
 #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"
@@ -511,32 +512,25 @@ 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++) {
-      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 {
+      if (!std::isxdigit(buf[i]))
         break;
-      }
-      result = result * 16 + digit;
+      result = result * 16 + HexCharToDigit(buf[i]);
     }
     return result;
   }
+
   for (int i = 0; i < len; i++) {
-    if (buf[i] < '0' || buf[i] > '9') {
+    if (!std::isdigit(buf[i]))
       break;
-    }
     result = result * 10 + buf[i] - '0';
   }
+
   return result;
 }
 static CFX_WideString _StringDataAdd(CFX_WideString str) {
@@ -560,25 +554,18 @@ 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++) {
-      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 {
+      if (!std::isxdigit(buf[i]))
         break;
-      }
-      ch = ch * 16 + digit;
+
+      ch = ch * 16 + HexCharToDigit(buf[i]);
       byte_pos++;
       if (byte_pos == 4) {
         result += ch;
@@ -588,8 +575,6 @@ 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 02f0933f36..165ef5bad5 100644
--- a/core/src/fpdfapi/fpdf_font/fpdf_font_cid.cpp
+++ b/core/src/fpdfapi/fpdf_font/fpdf_font_cid.cpp
@@ -7,6 +7,7 @@
 #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"
@@ -190,22 +191,15 @@ 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 (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 {
+      if (!std::isxdigit(digit))
         return num;
-      }
-      num = num * 16 + digit;
+      num = num * 16 + HexCharToDigit(digit);
     }
   } else {
     for (int i = 0; i < word.GetLength(); i++) {
-      if (word.GetAt(i) < '0' || word.GetAt(i) > '9') {
+      if (!std::isdigit(word.GetAt(i)))
         return num;
-      }
+
       num = num * 10 + word.GetAt(i) - '0';
     }
   }
@@ -231,13 +225,7 @@ 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);
-    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;
+    range.m_Lower[i] = HexCharToDigit(digit1) * 16 + HexCharToDigit(digit2);
   }
 
   FX_DWORD size = second.GetLength();
@@ -246,13 +234,7 @@ 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;
-    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;
+    range.m_Upper[i] = HexCharToDigit(digit1) * 16 + HexCharToDigit(digit2);
   }
   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 3057948959..cc9b0fcbe8 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 (ch >= '0' && ch <= '9') {
+    if (std::isdigit(ch)) {
       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 1fa27e3805..88e2269c7a 100644
--- a/core/src/fpdfapi/fpdf_page/fpdf_page_parser_old.cpp
+++ b/core/src/fpdfapi/fpdf_page/fpdf_page_parser_old.cpp
@@ -7,6 +7,7 @@
 #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>
 
@@ -875,34 +876,20 @@ CFX_ByteString CPDF_StreamParser::ReadHexString() {
   FX_BOOL bFirst = TRUE;
   int code = 0;
   while (1) {
-    if (ch == '>') {
+    if (ch == '>')
       break;
-    }
-    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 = (ch - 'A' + 10) * 16;
-      } else {
-        code += ch - 'A' + 10;
-        buf.AppendChar((char)code);
-      }
-      bFirst = !bFirst;
-    } else if (ch >= 'a' && ch <= 'f') {
+
+    if (std::isxdigit(ch)) {
+      int val = HexCharToDigit(ch);
       if (bFirst) {
-        code = (ch - 'a' + 10) * 16;
+        code = val * 16;
       } else {
-        code += ch - 'a' + 10;
-        buf.AppendChar((char)code);
+        code += val;
+        buf.AppendByte((uint8_t)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 255d0ce29c..eaff29d812 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp
@@ -8,6 +8,7 @@
 #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
 
@@ -135,23 +136,20 @@ FX_DWORD _HexDecode(const uint8_t* src_buf,
       continue;
 
     int digit;
-    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;
+    if (std::isxdigit(ch)) {
+      digit = HexCharToDigit(ch);
     } 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 4ce196e90d..fa114f9cfb 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
@@ -13,6 +13,7 @@
 #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"
 
@@ -162,85 +163,83 @@ 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 (ch >= '0' && ch <= '9') {
+  if (std::isdigit(ch))
     m_FileVersion = (ch - '0') * 10;
-  }
-  if (!m_Syntax.GetCharAt(7, ch)) {
+
+  if (!m_Syntax.GetCharAt(7, ch))
     return PDFPARSE_ERROR_FORMAT;
-  }
-  if (ch >= '0' && ch <= '9') {
+  if (std::isdigit(ch))
     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 == NULL) {
+    if (!pResult)
       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() == NULL || m_pDocument->GetPageCount() == 0) {
-    if (bXRefRebuilt) {
+  if (!m_pDocument->GetRoot() || 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() == NULL) {
+    if (!m_pDocument->GetRoot())
       return PDFPARSE_ERROR_FORMAT;
-    }
   }
   FXSYS_qsort(m_SortedOffset.GetData(), m_SortedOffset.GetSize(),
               sizeof(FX_FILESIZE), CompareFileSize);
@@ -249,13 +248,12 @@ 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 =
@@ -459,9 +457,8 @@ 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 (pEntry[c] < '0' || pEntry[c] > '9') {
+            if (!std::isdigit(pEntry[c]))
               return FALSE;
-            }
           }
         }
         m_CrossRef.SetAtGrow(objnum, offset);
@@ -560,9 +557,8 @@ 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 (pEntry[c] < '0' || pEntry[c] > '9') {
+                if (!std::isdigit(pEntry[c]))
                   return false;
-                }
               }
             }
             m_CrossRef.SetAtGrow(objnum, offset);
@@ -630,28 +626,32 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
       uint8_t byte = buffer[i];
       switch (status) {
         case 0:
-          if (PDFCharIsWhitespace(byte)) {
+          if (PDFCharIsWhitespace(byte))
             status = 1;
-          }
-          if (byte <= '9' && byte >= '0') {
+
+          if (std::isdigit(byte)) {
             --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 (byte <= '9' && byte >= '0') {
+          } else if (std::isdigit(byte)) {
             start_pos = pos + i;
             status = 2;
             objnum = byte - '0';
@@ -676,7 +676,7 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
           }
           break;
         case 2:
-          if (byte <= '9' && byte >= '0') {
+          if (std::isdigit(byte)) {
             objnum = objnum * 10 + byte - '0';
             break;
           } else if (PDFCharIsWhitespace(byte)) {
@@ -688,7 +688,7 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
           }
           break;
         case 3:
-          if (byte <= '9' && byte >= '0') {
+          if (std::isdigit(byte)) {
             start_pos1 = pos + i;
             status = 4;
             gennum = byte - '0';
@@ -703,7 +703,7 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
           }
           break;
         case 4:
-          if (byte <= '9' && byte >= '0') {
+          if (std::isdigit(byte)) {
             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 (byte <= '9' && byte >= '0') {
+          } else if (std::isdigit(byte)) {
             objnum = gennum;
             gennum = byte - '0';
             start_pos = start_pos1;
@@ -1922,48 +1922,33 @@ 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 (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 = (ch - 'A' + 10) * 16;
-      } else {
-        code += ch - 'A' + 10;
-        buf.AppendByte((uint8_t)code);
-      }
-      bFirst = !bFirst;
-    } else if (ch >= 'a' && ch <= 'f') {
+
+    if (std::isxdigit(ch)) {
+      int val = HexCharToDigit(ch);
       if (bFirst) {
-        code = (ch - 'a' + 10) * 16;
+        code = val * 16;
       } else {
-        code += ch - 'a' + 10;
+        code += val;
         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 335101e85b..d7c4136447 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
@@ -5,6 +5,7 @@
 // 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
@@ -279,18 +280,7 @@ 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();
@@ -302,7 +292,7 @@ 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++ = _hex2dec(pSrc[i + 1]) * 16 + _hex2dec(pSrc[i + 2]);
+      *pDest++ = HexCharToDigit(pSrc[i + 1]) * 16 + HexCharToDigit(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 9ecbc21bda..e9ad338025 100644
--- a/core/src/fpdftext/fpdf_text.cpp
+++ b/core/src/fpdftext/fpdf_text.cpp
@@ -436,10 +436,8 @@ 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 ((ch < '0' || ch > '9') && ch != '-' && ch != '+' && ch != '.' &&
-        ch != ' ') {
+    if (!std::isdigit(ch) && 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 9ab09e19e4..4459552c84 100644
--- a/core/src/fpdftext/fpdf_text_int.cpp
+++ b/core/src/fpdftext/fpdf_text_int.cpp
@@ -2433,12 +2433,11 @@ 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) ||
-      (char_left >= '0' && char_left <= '9') ||
+      (char_left > 0xfb00 && char_left < 0xfb06) || std::isdigit(char_left) ||
       (char_right > 'A' && char_right < 'a') ||
       (char_right > 'a' && char_right < 'z') ||
       (char_right > 0xfb00 && char_right < 0xfb06) ||
-      (char_right >= '0' && char_right <= '9')) {
+      std::isdigit(char_right)) {
     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 46f479e0b1..eca6505d12 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 (*ptr >= '0' && *ptr <= '9') {
-      if (!e_number) {
+
+    if (std::isdigit(*ptr)) {
+      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 (*ptr < '0' || *ptr > '9') { \
-      if (endptr)                   \
-        *endptr = (char*)ptr;       \
-      break;                        \
-    } else {                        \
-      exp_ret *= 10;                \
-      exp_ret += (*ptr - '0');      \
-      continue;                     \
-    }                               \
+#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;                \
+    }                          \
   }
       exp_ptr = ptr++;
       if (*ptr == '+' || *ptr == '-') {
         exp_sig = (*ptr++ == '+') ? 1 : -1;
-        if (*ptr < '0' || *ptr > '9') {
+        if (!std::isdigit(*ptr)) {
           if (endptr) {
             *endptr = (char*)exp_ptr;
           }
           break;
         }
         EXPONENT_DETECT(ptr);
-      } else if (*ptr >= '0' && *ptr <= '9') {
+      } else if (std::isdigit(*ptr)) {
         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 c706912d9d..d5ffcddb6d 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 (; (*lpsz) >= '0' && (*lpsz) <= '9'; lpsz++)
+      for (; std::isdigit(*lpsz); 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 (; (*lpsz) >= '0' && (*lpsz) <= '9'; lpsz++)
+        for (; std::isdigit(*lpsz); lpsz++)
           ;
       }
     }
diff --git a/core/src/fxcrt/fx_basic_gcc.cpp b/core/src/fxcrt/fx_basic_gcc.cpp
index 6f17482156..71f5fe322f 100644
--- a/core/src/fxcrt/fx_basic_gcc.cpp
+++ b/core/src/fxcrt/fx_basic_gcc.cpp
@@ -12,21 +12,20 @@
 template <class T, class STR_T>
 T FXSYS_StrToInt(STR_T str) {
   FX_BOOL neg = FALSE;
-  if (str == NULL) {
+  if (!str)
     return 0;
-  }
+
   if (*str == '-') {
     neg = TRUE;
     str++;
   }
   T num = 0;
   while (*str) {
-    if ((*str) < '0' || (*str) > '9') {
+    if (!std::isdigit(*str))
       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 46a0dec1e5..71119082a2 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 (str[cc] < '0' || str[cc] > '9') {
+      if (!std::isdigit(str[cc]))
         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 c097e1fc09..3310df7062 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 && (*lpsz) <= '9' && (*lpsz) >= '0'; lpsz++)
+      for (; *lpsz != 0 && std::isdigit(*lpsz); 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 && (*lpsz) >= '0' && (*lpsz) <= '9'; lpsz++)
+        for (; *lpsz != 0 && std::isdigit(*lpsz); lpsz++)
           ;
       }
     }
diff --git a/core/src/fxcrt/fx_extension.cpp b/core/src/fxcrt/fx_extension.cpp
index d64a06d08b..a75cfb48df 100644
--- a/core/src/fxcrt/fx_extension.cpp
+++ b/core/src/fxcrt/fx_extension.cpp
@@ -13,6 +13,15 @@
 #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
new file mode 100644
index 0000000000..e2017fc3ed
--- /dev/null
+++ b/core/src/fxcrt/fx_extension_unittest.cpp
@@ -0,0 +1,14 @@
+// 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'));
+}