Revert "Revert "Cleanup some numeric code.""

core/src/fpdfapi/fpdf_page/fpdf_page_parser.cpp

 // 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
 
 #include "../../../include/fpdfapi/fpdf_page.h"
 #include "../../../include/fpdfapi/fpdf_module.h"
 #include "../../../include/fpdfapi/fpdf_serial.h"
+#include "../../../include/fxcrt/fx_ext.h"
 #include "pageint.h"
 
 #define REQUIRE_PARAMS(count)  \
   if (m_ParamCount != count) { \
     return;                    \
   }
 
 CPDF_StreamContentParser::CPDF_StreamContentParser(
     CPDF_Document* pDocument,
     CPDF_Dictionary* pPageResources,
@@ skipping 1507 matching lines @@
   if (PathClipType) {
     if (!matrix.IsIdentity()) {
       Path.Transform(&matrix);
       matrix.SetIdentity();
     }
     m_pCurStates->m_ClipPath.AppendPath(Path, PathClipType, TRUE);
   }
 }
 CFX_ByteString _FPDF_ByteStringFromHex(CFX_BinaryBuf& src_buf) {
   CFX_ByteTextBuf buf;
-  FX_BOOL bFirst = TRUE;
+  bool bFirst = true;
   int code = 0;
   const uint8_t* str = src_buf.GetBuffer();
   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::isxdigit(ch)) {
+      int val = FXSYS_toHexDigit(ch);
       if (bFirst) {
-        code = (ch - '0') * 16;
+        code = val * 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;
+        code += val;
         buf.AppendChar((char)code);
       }
       bFirst = !bFirst;
     }
   }
-  if (!bFirst) {
+  if (!bFirst)
     buf.AppendChar((char)code);
-  }
+
   return buf.GetByteString();
 }