Cleanup usages of Mid(foo, 1), Right(1), and Left(1)chromium/3203

Mid(foo, 1) is equivalent to [foo], if all you want is the character. Similarly
Left(1) is [0]. It is faster also, since it does not need to create intermediate
strings.

Right(1) is a touch more tricky, since it requires something like GetLength() ?
[GetLength() - 1] : 0;. A new method, Last() has been added to perform this
character extraction.

Multiple call sites have been updated to use more efficient/simpler
syntax. There are a number of call sites that use on these patterns, but based
on the surrounding context we actually need/want a string, so they have not been
modified.

Change-Id: I485a7f9c7b34c9bdacecada610158f996816afdd
Reviewed-on: https://pdfium-review.googlesource.com/12890
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

4 files changed, 14 insertions, 2 deletions

diff --git a/core/fpdfapi/font/cpdf_cmap.cpp b/core/fpdfapi/font/cpdf_cmap.cpp
index 659139f687..0d3745e44a 100644
--- a/core/fpdfapi/font/cpdf_cmap.cpp
+++ b/core/fpdfapi/font/cpdf_cmap.cpp
@@ -253,12 +253,12 @@ void CPDF_CMap::LoadPredefined(CPDF_CMapManager* pMgr,
   m_PredefinedCMap = bsName;
   if (m_PredefinedCMap == "Identity-H" || m_PredefinedCMap == "Identity-V") {
     m_Coding = CIDCODING_CID;
-    m_bVertical = bsName[9] == 'V';
+    m_bVertical = bsName.Last() == 'V';
     m_bLoaded = true;
     return;
   }
   CFX_ByteString cmapid = m_PredefinedCMap;
-  m_bVertical = cmapid.Right(1) == "V";
+  m_bVertical = cmapid.Last() == 'V';
   if (cmapid.GetLength() > 2) {
     cmapid = cmapid.Left(cmapid.GetLength() - 2);
   }
diff --git a/core/fxcrt/cfx_bytestring.h b/core/fxcrt/cfx_bytestring.h
index a47b5f89ab..261060bda0 100644
--- a/core/fxcrt/cfx_bytestring.h
+++ b/core/fxcrt/cfx_bytestring.h
@@ -120,6 +120,9 @@ class CFX_ByteString {
     return m_pData ? m_pData->m_String[index] : 0;
   }
 
+  CharType First() const { return GetLength() ? (*this)[0] : 0; }
+  CharType Last() const { return GetLength() ? (*this)[GetLength() - 1] : 0; }
+
   void SetAt(FX_STRSIZE index, char c);
 
   FX_STRSIZE Insert(FX_STRSIZE index, char ch);
diff --git a/core/fxcrt/cfx_string_c_template.h b/core/fxcrt/cfx_string_c_template.h
index c46b0c4671..6bc71d853d 100644
--- a/core/fxcrt/cfx_string_c_template.h
+++ b/core/fxcrt/cfx_string_c_template.h
@@ -135,6 +135,12 @@ class CFX_StringCTemplate {
     return m_Ptr.Get()[index];
   }
 
+  UnsignedType First() const { return GetLength() ? (*this)[0] : 0; }
+
+  UnsignedType Last() const {
+    return GetLength() ? (*this)[GetLength() - 1] : 0;
+  }
+
   const CharType CharAt(const FX_STRSIZE index) const {
     ASSERT(IsValidIndex(index));
     return static_cast<CharType>(m_Ptr.Get()[index]);
diff --git a/core/fxcrt/cfx_widestring.h b/core/fxcrt/cfx_widestring.h
index 242138853b..100fec6706 100644
--- a/core/fxcrt/cfx_widestring.h
+++ b/core/fxcrt/cfx_widestring.h
@@ -115,6 +115,9 @@ class CFX_WideString {
     return m_pData ? m_pData->m_String[index] : 0;
   }
 
+  CharType First() const { return GetLength() ? (*this)[0] : 0; }
+  CharType Last() const { return GetLength() ? (*this)[GetLength() - 1] : 0; }
+
   void SetAt(FX_STRSIZE index, wchar_t c);
 
   int Compare(const wchar_t* str) const;