Revert "Revert "Cleanup some numeric code.""

core/src/fpdfapi/fpdf_font/fpdf_font.cpp

Index: core/src/fpdfapi/fpdf_font/fpdf_font.cpp
diff --git a/core/src/fpdfapi/fpdf_font/fpdf_font.cpp b/core/src/fpdfapi/fpdf_font/fpdf_font.cpp
index 543816b03afa47f8d4dbca2eaddd1ce5934dbf4d..6239b20e0c3467c2a7a735a08c1f873a3a8953ec 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 +512,19 @@ 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 {
-        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) {
@@ -560,25 +548,15 @@ 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 {
-        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;
@@ -588,8 +566,6 @@ static CFX_WideString _StringToWideString(const CFX_ByteStringC& str) {
     }
     return result;
   }
-  if (buf[0] == '(') {
-  }
   return result;
 }
 void CPDF_ToUnicodeMap::Load(CPDF_Stream* pStream) {