Add help IsValid* methods to string classeschromium/3198chromium/3197

The various string classes, CFX_ByteString, CFX_ByteStringC,
CFX_WideString, and CFX_WideStringC, have many conditionals that are
effectively determining if a value is a valid index or length. This CL
refactors the logic into one place per class, so it only needs to be
changed once if its behaviour needs to change. It also make the some
of the methods stricter on the inputs they will accept.

BUG=pdfium:828

Change-Id: Iadcdaa34a6d862a2804485770027179c89dc6956
Reviewed-on: https://pdfium-review.googlesource.com/12030
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/fxbarcode/oned/BC_OnedCode128Writer.cpp b/fxbarcode/oned/BC_OnedCode128Writer.cpp
index 95a95b69e2..a6dc749a76 100644
--- a/fxbarcode/oned/BC_OnedCode128Writer.cpp
+++ b/fxbarcode/oned/BC_OnedCode128Writer.cpp
@@ -193,7 +193,9 @@ int32_t CBC_OnedCode128Writer::Encode128C(const CFX_ByteString& contents,
     int32_t patternIndex;
     char ch = contents[position];
     if (std::isdigit(ch)) {
-      patternIndex = FXSYS_atoi(contents.Mid(position, 2).c_str());
+      patternIndex = FXSYS_atoi(
+          contents.Mid(position, position + 1 < contents.GetLength() ? 2 : 1)
+              .c_str());
       ++position;
       if (position < contents.GetLength() && std::isdigit(contents[position]))
         ++position;