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, 4 deletions

diff --git a/xfa/fxfa/parser/cxfa_layoutpagemgr.cpp b/xfa/fxfa/parser/cxfa_layoutpagemgr.cpp
index e643bc502f..b02efbb45d 100644
--- a/xfa/fxfa/parser/cxfa_layoutpagemgr.cpp
+++ b/xfa/fxfa/parser/cxfa_layoutpagemgr.cpp
@@ -148,11 +148,13 @@ CXFA_Node* ResolveBreakTarget(CXFA_Node* pPageSetRoot,
   bool bTargetAllFind = true;
   while (iSplitIndex != -1) {
     CFX_WideString wsExpr;
-    FX_STRSIZE iSplitNextIndex = 0;
+    pdfium::Optional<FX_STRSIZE> iSplitNextIndex = 0;
     if (!bTargetAllFind) {
       iSplitNextIndex = wsTargetAll.Find(' ', iSplitIndex);
-      ASSERT(iSplitNextIndex != FX_STRNPOS);
-      wsExpr = wsTargetAll.Mid(iSplitIndex, iSplitNextIndex - iSplitIndex);
+      if (!iSplitNextIndex.has_value())
+        return nullptr;
+      wsExpr =
+          wsTargetAll.Mid(iSplitIndex, iSplitNextIndex.value() - iSplitIndex);
     } else {
       wsExpr = wsTargetAll;
     }
@@ -180,7 +182,7 @@ CXFA_Node* ResolveBreakTarget(CXFA_Node* pPageSetRoot,
       if (iCount > 0 && rs.objects.front()->IsNode())
         return rs.objects.front()->AsNode();
     }
-    iSplitIndex = iSplitNextIndex;
+    iSplitIndex = iSplitNextIndex.value();
   }
   return nullptr;
 }