Merge to XFA: Reland "Cleanup some numeric code.""

This reverts commit 0569ab0b11b723d9bca4ddd642b0cf8828c4bdd1.

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=tsepez@chromium.org

Review URL: https://codereview.chromium.org/1449873003 .

(cherry picked from commit 3f148915d12f54a946a0c0bf526162b79c39d650)

Review URL: https://codereview.chromium.org/1452673002 .

6 files changed, 139 insertions, 232 deletions

diff --git a/core/src/fpdfapi/fpdf_font/fpdf_font.cpp b/core/src/fpdfapi/fpdf_font/fpdf_font.cpp
index 9f83da062c..64d6cdce92 100644
--- a/core/src/fpdfapi/fpdf_font/fpdf_font.cpp
+++ b/core/src/fpdfapi/fpdf_font/fpdf_font.cpp
@@ -11,6 +11,7 @@
 #include "core/include/fpdfapi/fpdf_page.h"
 #include "core/include/fpdfapi/fpdf_pageobj.h"
 #include "core/include/fpdfapi/fpdf_resource.h"
+#include "core/include/fxcrt/fx_ext.h"
 #include "core/include/fxge/fx_freetype.h"
 
 #if _FXM_PLATFORM_ == _FXM_PLATFORM_APPLE_
@@ -518,32 +519,19 @@ FX_DWORD CPDF_ToUnicodeMap::ReverseLookup(FX_WCHAR unicode) {
 FX_DWORD CPDF_ToUnicodeMap::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 {
-        break;
-      }
-      result = result * 16 + digit;
-    }
+    for (int i = 1; i < len && std::isxdigit(buf[i]); ++i)
+      result = result * 16 + FXSYS_toHexDigit(buf[i]);
     return result;
   }
-  for (int i = 0; i < len; i++) {
-    if (buf[i] < '0' || buf[i] > '9') {
-      break;
-    }
-    result = result * 10 + buf[i] - '0';
-  }
+
+  for (int i = 0; i < len && std::isdigit(buf[i]); ++i)
+    result = result * 10 + FXSYS_toDecimalDigit(buf[i]);
+
   return result;
 }
 static CFX_WideString StringDataAdd(CFX_WideString str) {
@@ -570,26 +558,15 @@ CFX_WideString CPDF_ToUnicodeMap::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 {
-        break;
-      }
-      ch = ch * 16 + digit;
-
+    for (int i = 1; i < len && std::isxdigit(buf[i]); ++i) {
+      ch = ch * 16 + FXSYS_toHexDigit(buf[i]);
       byte_pos++;
       if (byte_pos == 4) {
         result += ch;
@@ -599,8 +576,6 @@ CFX_WideString CPDF_ToUnicodeMap::StringToWideString(
     }
     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 65b4b781b1..d4c71085a1 100644
--- a/core/src/fpdfapi/fpdf_font/fpdf_font_cid.cpp
+++ b/core/src/fpdfapi/fpdf_font/fpdf_font_cid.cpp
@@ -9,6 +9,7 @@
 #include "core/include/fpdfapi/fpdf_module.h"
 #include "core/include/fpdfapi/fpdf_page.h"
 #include "core/include/fpdfapi/fpdf_resource.h"
+#include "core/include/fxcrt/fx_ext.h"
 #include "core/include/fxge/fx_freetype.h"
 #include "core/include/fxge/fx_ge.h"
 #include "core/src/fpdfapi/fpdf_cmaps/cmap_int.h"
@@ -699,30 +700,17 @@ void CPDF_CMapParser::ParseWord(const CFX_ByteStringC& word) {
   m_LastWord = word;
 }
 
+// Static.
 FX_DWORD CPDF_CMapParser::CMap_GetCode(const CFX_ByteStringC& word) {
   int num = 0;
   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 {
-        return num;
-      }
-      num = num * 16 + digit;
-    }
-  } else {
-    for (int i = 0; i < word.GetLength(); i++) {
-      if (word.GetAt(i) < '0' || word.GetAt(i) > '9') {
-        return num;
-      }
-      num = num * 10 + word.GetAt(i) - '0';
-    }
+    for (int i = 1; i < word.GetLength() && std::isxdigit(word.GetAt(i)); ++i)
+      num = num * 16 + FXSYS_toHexDigit(word.GetAt(i));
+    return num;
   }
+
+  for (int i = 0; i < word.GetLength() && std::isdigit(word.GetAt(i)); ++i)
+    num = num * 10 + FXSYS_toDecimalDigit(word.GetAt(i));
   return num;
 }
 
@@ -746,13 +734,7 @@ bool CPDF_CMapParser::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] = FXSYS_toHexDigit(digit1) * 16 + FXSYS_toHexDigit(digit2);
   }
 
   FX_DWORD size = second.GetLength();
@@ -763,13 +745,7 @@ bool CPDF_CMapParser::CMap_GetCodeRange(CMap_CodeRange& range,
     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] = FXSYS_toHexDigit(digit1) * 16 + FXSYS_toHexDigit(digit2);
   }
   return true;
 }
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 8d155e787b..a1aa686248 100644
--- a/core/src/fpdfapi/fpdf_page/fpdf_page_parser_old.cpp
+++ b/core/src/fpdfapi/fpdf_page/fpdf_page_parser_old.cpp
@@ -11,6 +11,7 @@
 #include "core/include/fpdfapi/fpdf_module.h"
 #include "core/include/fpdfapi/fpdf_page.h"
 #include "core/include/fxcodec/fx_codec.h"
+#include "core/include/fxcrt/fx_ext.h"
 
 namespace {
 
@@ -791,7 +792,7 @@ CFX_ByteString CPDF_StreamParser::ReadString() {
         break;
       case 1:
         if (ch >= '0' && ch <= '7') {
-          iEscCode = ch - '0';
+          iEscCode = FXSYS_toDecimalDigit(ch);
           status = 2;
           break;
         }
@@ -816,7 +817,7 @@ CFX_ByteString CPDF_StreamParser::ReadString() {
         break;
       case 2:
         if (ch >= '0' && ch <= '7') {
-          iEscCode = iEscCode * 8 + ch - '0';
+          iEscCode = iEscCode * 8 + FXSYS_toDecimalDigit(ch);
           status = 3;
         } else {
           buf.AppendChar(iEscCode);
@@ -826,7 +827,7 @@ CFX_ByteString CPDF_StreamParser::ReadString() {
         break;
       case 3:
         if (ch >= '0' && ch <= '7') {
-          iEscCode = iEscCode * 8 + ch - '0';
+          iEscCode = iEscCode * 8 + FXSYS_toDecimalDigit(ch);
           buf.AppendChar(iEscCode);
           status = 0;
         } else {
@@ -859,50 +860,33 @@ CFX_ByteString CPDF_StreamParser::ReadHexString() {
   if (!PositionIsInBounds())
     return CFX_ByteString();
 
-  int ch = m_pBuf[m_Pos++];
   CFX_ByteTextBuf buf;
-  FX_BOOL bFirst = TRUE;
+  bool bFirst = true;
   int code = 0;
-  while (1) {
-    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 (bFirst) {
-        code = (ch - 'a' + 10) * 16;
-      } else {
-        code += ch - 'a' + 10;
-        buf.AppendChar((char)code);
-      }
-      bFirst = !bFirst;
-    }
-    if (!PositionIsInBounds())
+  while (PositionIsInBounds()) {
+    int ch = m_pBuf[m_Pos++];
+
+    if (ch == '>')
       break;
 
-    ch = m_pBuf[m_Pos++];
+    if (!std::isxdigit(ch))
+      continue;
+
+    int val = FXSYS_toHexDigit(ch);
+    if (bFirst) {
+      code = val * 16;
+    } else {
+      code += val;
+      buf.AppendByte((uint8_t)code);
+    }
+    bFirst = !bFirst;
   }
-  if (!bFirst) {
+  if (!bFirst)
     buf.AppendChar((char)code);
-  }
-  if (buf.GetLength() > MAX_STRING_LENGTH) {
+
+  if (buf.GetLength() > MAX_STRING_LENGTH)
     return CFX_ByteString(buf.GetBuffer(), MAX_STRING_LENGTH);
-  }
+
   return buf.GetByteString();
 }
 
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp
index 588ab5dff6..57d1971889 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_decode.cpp
@@ -9,6 +9,7 @@
 #include "core/include/fpdfapi/fpdf_module.h"
 #include "core/include/fpdfapi/fpdf_parser.h"
 #include "core/include/fxcodec/fx_codec.h"
+#include "core/include/fxcrt/fx_ext.h"
 
 #define _STREAM_MAX_SIZE_ 20 * 1024 * 1024
 
@@ -129,37 +130,32 @@ FX_DWORD HexDecode(const uint8_t* src_buf,
     }
   dest_buf = FX_Alloc(uint8_t, i / 2 + 1);
   dest_size = 0;
-  FX_BOOL bFirstDigit = TRUE;
+  bool bFirst = true;
   for (i = 0; i < src_size; i++) {
     uint8_t ch = src_buf[i];
     if (PDFCharIsLineEnding(ch) || ch == ' ' || ch == '\t')
       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;
-    } else if (ch == '>') {
-      i++;
+    if (ch == '>') {
+      ++i;
       break;
-    } else {
-      continue;
     }
-    if (bFirstDigit) {
+    if (!std::isxdigit(ch))
+      continue;
+
+    int digit = FXSYS_toHexDigit(ch);
+    if (bFirst)
       dest_buf[dest_size] = digit * 16;
-    } else {
+    else
       dest_buf[dest_size++] += digit;
-    }
-    bFirstDigit = !bFirstDigit;
+
+    bFirst = !bFirst;
   }
-  if (!bFirstDigit) {
+  if (!bFirst)
     dest_size++;
-  }
   return i;
 }
+
 FX_DWORD RunLengthDecode(const uint8_t* src_buf,
                          FX_DWORD src_size,
                          uint8_t*& dest_buf,
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
index 543f8f6323..9318403766 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 "core/include/fpdfapi/fpdf_module.h"
 #include "core/include/fpdfapi/fpdf_page.h"
 #include "core/include/fpdfapi/fpdf_parser.h"
+#include "core/include/fxcrt/fx_ext.h"
 #include "core/include/fxcrt/fx_safe_types.h"
 #include "core/src/fpdfapi/fpdf_page/pageint.h"
 #include "third_party/base/nonstd_unique_ptr.h"
@@ -164,85 +165,83 @@ 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') {
-    m_FileVersion = (ch - '0') * 10;
-  }
-  if (!m_Syntax.GetCharAt(7, ch)) {
+  if (std::isdigit(ch))
+    m_FileVersion = FXSYS_toDecimalDigit(ch) * 10;
+
+  if (!m_Syntax.GetCharAt(7, ch))
     return PDFPARSE_ERROR_FORMAT;
-  }
-  if (ch >= '0' && ch <= '9') {
-    m_FileVersion += ch - '0';
-  }
-  if (m_Syntax.m_FileLen < m_Syntax.m_HeaderOffset + 9) {
+  if (std::isdigit(ch))
+    m_FileVersion += FXSYS_toDecimalDigit(ch);
+
+  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);
@@ -251,13 +250,12 @@ 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 =
@@ -461,9 +459,8 @@ 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);
@@ -562,9 +559,8 @@ 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);
@@ -632,28 +628,32 @@ 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;
@@ -662,10 +662,10 @@ 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';
+            objnum = FXSYS_toDecimalDigit(byte);
           } else if (byte == 't') {
             status = 7;
             inside_index = 1;
@@ -678,8 +678,8 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
           }
           break;
         case 2:
-          if (byte <= '9' && byte >= '0') {
-            objnum = objnum * 10 + byte - '0';
+          if (std::isdigit(byte)) {
+            objnum = objnum * 10 + FXSYS_toDecimalDigit(byte);
             break;
           } else if (PDFCharIsWhitespace(byte)) {
             status = 3;
@@ -690,10 +690,10 @@ 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';
+            gennum = FXSYS_toDecimalDigit(byte);
           } else if (PDFCharIsWhitespace(byte)) {
             break;
           } else if (byte == 't') {
@@ -705,8 +705,8 @@ FX_BOOL CPDF_Parser::RebuildCrossRef() {
           }
           break;
         case 4:
-          if (byte <= '9' && byte >= '0') {
-            gennum = gennum * 10 + byte - '0';
+          if (std::isdigit(byte)) {
+            gennum = gennum * 10 + FXSYS_toDecimalDigit(byte);
             break;
           } else if (PDFCharIsWhitespace(byte)) {
             status = 5;
@@ -721,9 +721,9 @@ 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';
+            gennum = FXSYS_toDecimalDigit(byte);
             start_pos = start_pos1;
             start_pos1 = pos + i;
             status = 4;
@@ -1858,7 +1858,7 @@ CFX_ByteString CPDF_SyntaxParser::ReadString() {
         break;
       case 1:
         if (ch >= '0' && ch <= '7') {
-          iEscCode = ch - '0';
+          iEscCode = FXSYS_toDecimalDigit(ch);
           status = 2;
           break;
         }
@@ -1883,7 +1883,7 @@ CFX_ByteString CPDF_SyntaxParser::ReadString() {
         break;
       case 2:
         if (ch >= '0' && ch <= '7') {
-          iEscCode = iEscCode * 8 + ch - '0';
+          iEscCode = iEscCode * 8 + FXSYS_toDecimalDigit(ch);
           status = 3;
         } else {
           buf.AppendChar(iEscCode);
@@ -1893,7 +1893,7 @@ CFX_ByteString CPDF_SyntaxParser::ReadString() {
         break;
       case 3:
         if (ch >= '0' && ch <= '7') {
-          iEscCode = iEscCode * 8 + ch - '0';
+          iEscCode = iEscCode * 8 + FXSYS_toDecimalDigit(ch);
           buf.AppendChar(iEscCode);
           status = 0;
         } else {
@@ -1918,48 +1918,33 @@ 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;
+  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 = FXSYS_toHexDigit(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 89a5deb62d..9729bab942 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 "core/include/fpdfapi/fpdf_parser.h"
+#include "core/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 +292,8 @@ 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++ =
+          FXSYS_toHexDigit(pSrc[i + 1]) * 16 + FXSYS_toHexDigit(pSrc[i + 2]);
       i += 2;
     } else {
       *pDest++ = pSrc[i];