Convert calls to Mid() to Left() or Right() if possible

The various string/byte classes support Mid(), Left(), and Right() for
extracting substrings. Mid() can handle all possible cases, but Left()
and Right() are useful for common cases and  more explicit about what
is going on.

Calls like Mid(offset, length - offset) can be converted to
Right(length - offset). Calls like Mid(0, length) can be converted to
Left(length).

If the substring being extracted does not extend all the way to one of
the edges of the string, then Mid() still needs to be used.

BUG=pdfium:828

Change-Id: I2ec46ad3d71aac0f7b513e103c69cbe8c854cf62
Reviewed-on: https://pdfium-review.googlesource.com/9510
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

1 files changed, 3 insertions, 5 deletions

diff --git a/xfa/fxfa/fm2js/cxfa_fm2jscontext.cpp b/xfa/fxfa/fm2js/cxfa_fm2jscontext.cpp
index 1910e60e3e..84064efb45 100644
--- a/xfa/fxfa/fm2js/cxfa_fm2jscontext.cpp
+++ b/xfa/fxfa/fm2js/cxfa_fm2jscontext.cpp
@@ -1139,7 +1139,7 @@ void CXFA_FM2JSContext::IsoTime2Num(CFXJSE_Value* pThis,
   CXFA_LocaleMgr* pMgr = pDoc->GetLocalMgr();
   CFX_ByteString szArgString = ValueToUTF8String(argOne.get());
   FX_STRSIZE pos = szArgString.Find('T', 0);
-  szArgString = szArgString.Mid(pos + 1, szArgString.GetLength() - (pos + 1));
+  szArgString = szArgString.Right(szArgString.GetLength() - (pos + 1));
   if (szArgString.IsEmpty()) {
     args.GetReturnValue()->SetInteger(0);
     return;
@@ -3694,8 +3694,7 @@ void CXFA_FM2JSContext::Format(CFXJSE_Value* pThis,
 
         CFX_WideString wsTimePattern(L"time{");
         wsTimePattern +=
-            wsPattern.Mid(iTChar + 1, wsPattern.GetLength() - (iTChar + 1)) +
-            L"}";
+            wsPattern.Right(wsPattern.GetLength() - (iTChar + 1)) + L"}";
         wsPattern = wsDatePattern + wsTimePattern;
       } break;
       case XFA_VT_DATE: {
@@ -3881,8 +3880,7 @@ void CXFA_FM2JSContext::Parse(CFXJSE_Value* pThis,
       FX_STRSIZE iTChar = wsPattern.Find(L'T');
       CFX_WideString wsDatePattern(L"date{" + wsPattern.Left(iTChar) + L"} ");
       CFX_WideString wsTimePattern(
-          L"time{" +
-          wsPattern.Mid(iTChar + 1, wsPattern.GetLength() - (iTChar + 1)) +
+          L"time{" + wsPattern.Right(wsPattern.GetLength() - (iTChar + 1)) +
           L"}");
       wsPattern = wsDatePattern + wsTimePattern;
       CXFA_LocaleValue localeValue(patternType, wsValue, wsPattern, pLocale,