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

Most of the time, we want to operate on chars as if they
were unsigned, but there are a few places where we need
the default (questionably signed) values. Consolidate
the casting in a single place rather than forcing callers
to get a char* ptr.

BUG=pdfium:493

Review-Url: https://codereview.chromium.org/1972053003

2 files changed, 3 insertions, 3 deletions

diff --git a/core/fpdfapi/fpdf_font/cpdf_font.cpp b/core/fpdfapi/fpdf_font/cpdf_font.cpp
index f143bed541..9fb54a828b 100644
--- a/core/fpdfapi/fpdf_font/cpdf_font.cpp
+++ b/core/fpdfapi/fpdf_font/cpdf_font.cpp
@@ -149,7 +149,7 @@ FX_BOOL CPDF_Font::IsVertWriting() const {
 }
 
 int CPDF_Font::AppendChar(FX_CHAR* buf, uint32_t charcode) const {
-  *buf = (FX_CHAR)charcode;
+  *buf = static_cast<FX_CHAR>(charcode);
   return 1;
 }
 
diff --git a/core/fpdfapi/fpdf_font/fpdf_font.cpp b/core/fpdfapi/fpdf_font/fpdf_font.cpp
index dccce5656b..9f7b127d60 100644
--- a/core/fpdfapi/fpdf_font/fpdf_font.cpp
+++ b/core/fpdfapi/fpdf_font/fpdf_font.cpp
@@ -139,12 +139,12 @@ uint32_t CPDF_ToUnicodeMap::StringToCode(const CFX_ByteStringC& str) {
   int result = 0;
   if (str[0] == '<') {
     for (int i = 1; i < len && std::isxdigit(str[i]); ++i)
-      result = result * 16 + FXSYS_toHexDigit(str[i]);
+      result = result * 16 + FXSYS_toHexDigit(str.CharAt(i));
     return result;
   }
 
   for (int i = 0; i < len && std::isdigit(str[i]); ++i)
-    result = result * 10 + FXSYS_toDecimalDigit(static_cast<FX_CHAR>(str[i]));
+    result = result * 10 + FXSYS_toDecimalDigit(str.CharAt(i));
 
   return result;
 }