Convert string Find methods to return an Optional

The Find and ReverseFind methods for WideString, WideStringC,
ByteString, and ByteStringC have been converted from returning a raw
FX_STRSIZE, to returning Optional<FX_STRSIZE>, so that success/failure
can be indicated without using FX_STRNPOS.

This allows for removing FX_STRNPOS and by association makes the
conversion of FX_STRSIZE to size_t easier, since it forces checking
the return value of Find to be explictly done as well as taking the
error value out of the range of FX_STRSIZE.

New Contains methods have been added for cases where the success or
failure is all the call site to Find cared about, and the actual
position was ignored.

BUG=pdfium:828


Change-Id: Id827e508c8660affa68cc08a13d96121369364b7
Reviewed-on: https://pdfium-review.googlesource.com/11350
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

1 files changed, 6 insertions, 8 deletions

diff --git a/core/fxcrt/xml/cfx_xmlelement.cpp b/core/fxcrt/xml/cfx_xmlelement.cpp
index 75bf9ee593..eb60e68893 100644
--- a/core/fxcrt/xml/cfx_xmlelement.cpp
+++ b/core/fxcrt/xml/cfx_xmlelement.cpp
@@ -42,17 +42,15 @@ std::unique_ptr<CFX_XMLNode> CFX_XMLElement::Clone() {
 }
 
 CFX_WideString CFX_XMLElement::GetLocalTagName() const {
-  FX_STRSIZE iFind = GetName().Find(L':', 0);
-  if (iFind == FX_STRNPOS)
-    return GetName();
-  return GetName().Right(GetName().GetLength() - iFind - 1);
+  auto pos = GetName().Find(L':');
+  return pos.has_value()
+             ? GetName().Right(GetName().GetLength() - pos.value() - 1)
+             : GetName();
 }
 
 CFX_WideString CFX_XMLElement::GetNamespacePrefix() const {
-  FX_STRSIZE iFind = GetName().Find(L':', 0);
-  if (iFind == FX_STRNPOS)
-    return CFX_WideString();
-  return GetName().Left(iFind);
+  auto pos = GetName().Find(L':');
+  return pos.has_value() ? GetName().Left(pos.value()) : CFX_WideString();
 }
 
 CFX_WideString CFX_XMLElement::GetNamespaceURI() const {