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>

2 files changed, 8 insertions, 5 deletions

diff --git a/core/fpdfapi/font/cpdf_simplefont.cpp b/core/fpdfapi/font/cpdf_simplefont.cpp
index a6c3ba0547..8c8520f0c4 100644
--- a/core/fpdfapi/font/cpdf_simplefont.cpp
+++ b/core/fpdfapi/font/cpdf_simplefont.cpp
@@ -130,7 +130,7 @@ bool CPDF_SimpleFont::LoadCommon() {
   }
   if (m_pFontFile) {
     if (m_BaseFont.GetLength() > 8 && m_BaseFont[7] == '+')
-      m_BaseFont = m_BaseFont.Mid(8);
+      m_BaseFont = m_BaseFont.Mid(8, m_BaseFont.GetLength() - 8);
   } else {
     LoadSubstFont();
   }
diff --git a/core/fpdfapi/page/cpdf_streamcontentparser.cpp b/core/fpdfapi/page/cpdf_streamcontentparser.cpp
index e00dbc54fd..5f571aa8d6 100644
--- a/core/fpdfapi/page/cpdf_streamcontentparser.cpp
+++ b/core/fpdfapi/page/cpdf_streamcontentparser.cpp
@@ -619,7 +619,8 @@ void CPDF_StreamContentParser::Handle_BeginImage() {
     if (type != CPDF_StreamParser::Name) {
       break;
     }
-    CFX_ByteString key(m_pSyntax->GetWord().Mid(1));
+    auto word = m_pSyntax->GetWord();
+    CFX_ByteString key(word.Mid(1, word.GetLength() - 1));
     auto pObj = m_pSyntax->ReadNextObject(false, false, 0);
     if (!key.IsEmpty()) {
       uint32_t dwObjNum = pObj ? pObj->GetObjNum() : 0;
@@ -1185,7 +1186,7 @@ CPDF_ColorSpace* CPDF_StreamContentParser::FindColorSpace(
   }
   if (name == "DeviceGray" || name == "DeviceCMYK" || name == "DeviceRGB") {
     CFX_ByteString defname = "Default";
-    defname += name.Mid(7);
+    defname += name.Mid(7, name.GetLength() - 7);
     CPDF_Object* pDefObj = FindResourceObj("ColorSpace", defname);
     if (!pDefObj) {
       if (name == "DeviceGray") {
@@ -1522,9 +1523,11 @@ uint32_t CPDF_StreamContentParser::Parse(const uint8_t* pData,
       case CPDF_StreamParser::Number:
         AddNumberParam(syntax.GetWord());
         break;
-      case CPDF_StreamParser::Name:
-        AddNameParam(syntax.GetWord().Mid(1));
+      case CPDF_StreamParser::Name: {
+        auto word = syntax.GetWord();
+        AddNameParam(word.Mid(1, word.GetLength() - 1));
         break;
+      }
       default:
         AddObjectParam(syntax.GetObject());
     }