Move ASCII string operations to string_view_template.h

Allows interoperability with both Strings and StringViews of
either kind.

Test: tested by widestring wrapper.
Change-Id: Ifd11f1985ec758143ed4a6f5e9e813262684513f
Reviewed-on: https://pdfium-review.googlesource.com/c/46210
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>

core/fxcrt/string_view_template.h

diff --git a/core/fxcrt/string_view_template.h b/core/fxcrt/string_view_template.h
index e1924fe..adedbdc 100644
--- a/core/fxcrt/string_view_template.h
+++ b/core/fxcrt/string_view_template.h
@@ -109,6 +109,40 @@
     return !(*this == other);
   }
 
+  bool IsASCII() const {
+    for (auto c : *this) {
+      if (c <= 0 || c > 127)  // Questionable signedness of |c|.
+        return false;
+    }
+    return true;
+  }
+
+  bool EqualsASCII(const StringViewTemplate<char>& that) const {
+    size_t length = GetLength();
+    if (length != that.GetLength())
+      return false;
+
+    for (size_t i = 0; i < length; ++i) {
+      auto c = (*this)[i];
+      if (c <= 0 || c > 127 || c != that[i])  // Questionable signedness of |c|.
+        return false;
+    }
+    return true;
+  }
+
+  bool EqualsASCIINoCase(const StringViewTemplate<char>& that) const {
+    size_t length = GetLength();
+    if (length != that.GetLength())
+      return false;
+
+    for (size_t i = 0; i < length; ++i) {
+      auto c = (*this)[i];
+      if (c <= 0 || c > 127 || tolower(c) != tolower(that[i]))
+        return false;
+    }
+    return true;
+  }
+
   uint32_t GetID() const {
     if (m_Span.size() == 0)
       return 0;

core/fxcrt/widestring.cpp

diff --git a/core/fxcrt/widestring.cpp b/core/fxcrt/widestring.cpp
index bda34e1..0ddbcd9 100644
--- a/core/fxcrt/widestring.cpp
+++ b/core/fxcrt/widestring.cpp
@@ -635,40 +635,6 @@
   return m_pData ? m_pData->m_nRefs : 0;
 }
 
-bool WideString::IsASCII() const {
-  for (wchar_t wc : *this) {
-    if (wc <= 0 || wc > 127)  // Questionable signedness of wchar_t.
-      return false;
-  }
-  return true;
-}
-
-bool WideString::EqualsASCII(const ByteStringView& that) const {
-  size_t length = GetLength();
-  if (length != that.GetLength())
-    return false;
-
-  for (size_t i = 0; i < length; ++i) {
-    wchar_t wc = (*this)[i];
-    if (wc <= 0 || wc > 127 || wc != that[i])
-      return false;
-  }
-  return true;
-}
-
-bool WideString::EqualsASCIINoCase(const ByteStringView& that) const {
-  size_t length = GetLength();
-  if (length != that.GetLength())
-    return false;
-
-  for (size_t i = 0; i < length; ++i) {
-    wchar_t wc = (*this)[i];
-    if (wc <= 0 || wc > 127 || tolower(wc) != tolower(that[i]))
-      return false;
-  }
-  return true;
-}
-
 ByteString WideString::ToASCII() const {
   ByteString result;
   result.Reserve(GetLength());

core/fxcrt/widestring.h

diff --git a/core/fxcrt/widestring.h b/core/fxcrt/widestring.h
index be03731..f918bca 100644
--- a/core/fxcrt/widestring.h
+++ b/core/fxcrt/widestring.h
@@ -192,9 +192,13 @@
   size_t Replace(const WideStringView& pOld, const WideStringView& pNew);
   size_t Remove(wchar_t ch);
 
-  bool IsASCII() const;
-  bool EqualsASCII(const ByteStringView& that) const;
-  bool EqualsASCIINoCase(const ByteStringView& that) const;
+  bool IsASCII() const { return AsStringView().IsASCII(); }
+  bool EqualsASCII(const ByteStringView& that) const {
+    return AsStringView().EqualsASCII(that);
+  }
+  bool EqualsASCIINoCase(const ByteStringView& that) const {
+    return AsStringView().EqualsASCIINoCase(that);
+  }
 
   ByteString ToASCII() const;
   ByteString ToDefANSI() const;