Add CFX_ByteStringC::CharAt() to avoid c_str() and casts

core/fxcrt/fx_extension.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 "core/fxcrt/extension.h"
 #include "core/fxcrt/include/fx_basic.h"
 #include "core/fxcrt/include/fx_ext.h"
 
@@ skipping 201 matching lines @@
     ch1 = (FX_CHAR)FXSYS_tolower(*s1++);
     ch2 = (FX_CHAR)FXSYS_tolower(*s2++);
     if (ch1 != ch2) {
       break;
     }
   }
   return ch1 - ch2;
 }
 
 uint32_t FX_HashCode_GetA(const CFX_ByteStringC& str, bool bIgnoreCase) {
-  const FX_CHAR* pStr = str.c_str();
-  const FX_CHAR* pStrEnd = pStr + str.GetLength();
   uint32_t dwHashCode = 0;
   if (bIgnoreCase) {
-    while (pStr < pStrEnd) {
-      dwHashCode = 31 * dwHashCode + FXSYS_tolower(*pStr++);
-    }
+    for (FX_STRSIZE i = 0; i < str.GetLength(); ++i)
+      dwHashCode = 31 * dwHashCode + FXSYS_tolower(str.CharAt(i));
   } else {
-    while (pStr < pStrEnd) {
-      dwHashCode = 31 * dwHashCode + *pStr++;
-    }
+    for (FX_STRSIZE i = 0; i < str.GetLength(); ++i)
+      dwHashCode = 31 * dwHashCode + str.CharAt(i);
   }
   return dwHashCode;
 }
 
 uint32_t FX_HashCode_GetW(const CFX_WideStringC& str, bool bIgnoreCase) {
   const FX_WCHAR* pStr = str.c_str();
   const FX_WCHAR* pStrEnd = pStr + str.GetLength();
   uint32_t dwHashCode = 0;
   if (bIgnoreCase) {
     while (pStr < pStrEnd) {
@@ skipping 128 matching lines @@
     b = ((const uint8_t*)pGUID)[i];
     *pBuf++ = gs_FX_pHexChars[b >> 4];
     *pBuf++ = gs_FX_pHexChars[b & 0x0F];
     if (bSeparator && (i == 3 || i == 5 || i == 7 || i == 9)) {
       *pBuf++ = L'-';
     }
   }
   bsStr.ReleaseBuffer(bSeparator ? 36 : 32);
 }
 #endif  // PDF_ENABLE_XFA