Remove single param Mid() method from string classes

This support is being removed from CFX_ByteString, CFX_ByteStringC,
CFX_WideString, and CFX_WideStringC. This standardizes all of these
classes to only have one Mid method that takes in 2 params, offset and
count. Count now must be positive. The old behaviour of calculating
the length for the user if -1 is passed in for the count has been
removed. This work is in preperation for converting these classes to
not accept negative lengths anywhere and thus make the underlying size
type unsigned.

BUG=pdfium:828

Change-Id: I5f15e7b7b00b264231817f143e2da88ee6f69e7b
Reviewed-on: https://pdfium-review.googlesource.com/9430
Reviewed-by: (OOO Jul 28 - Aug 8) dsinclair <dsinclair@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>

1 files changed, 2 insertions, 7 deletions

diff --git a/core/fxcrt/cfx_widestring.cpp b/core/fxcrt/cfx_widestring.cpp
index 6a4fbb9846..d7c1ef23ea 100644
--- a/core/fxcrt/cfx_widestring.cpp
+++ b/core/fxcrt/cfx_widestring.cpp
@@ -291,6 +291,7 @@ CFX_WideString::CFX_WideString(CFX_WideString&& other) noexcept {
 }
 
 CFX_WideString::CFX_WideString(const wchar_t* pStr, FX_STRSIZE nLen) {
+  ASSERT(nLen >= 0);
   if (nLen < 0)
     nLen = pStr ? FXSYS_wcslen(pStr) : 0;
 
@@ -605,14 +606,8 @@ CFX_ByteString CFX_WideString::UTF16LE_Encode() const {
   return result;
 }
 
-CFX_WideString CFX_WideString::Mid(FX_STRSIZE nFirst) const {
-  if (!m_pData)
-    return CFX_WideString();
-
-  return Mid(nFirst, m_pData->m_nDataLength - nFirst);
-}
-
 CFX_WideString CFX_WideString::Mid(FX_STRSIZE nFirst, FX_STRSIZE nCount) const {
+  ASSERT(nCount >= 0);
   if (!m_pData)
     return CFX_WideString();