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>

8 files changed, 25 insertions, 39 deletions

diff --git a/core/fxcrt/cfx_bytestring.cpp b/core/fxcrt/cfx_bytestring.cpp
index c88ad51ab3..e7e55de8e3 100644
--- a/core/fxcrt/cfx_bytestring.cpp
+++ b/core/fxcrt/cfx_bytestring.cpp
@@ -121,6 +121,7 @@ static_assert(sizeof(CFX_ByteString) <= sizeof(char*),
               "Strings must not require more space than pointers");
 
 CFX_ByteString::CFX_ByteString(const char* pStr, FX_STRSIZE nLen) {
+  ASSERT(nLen >= 0);
   if (nLen < 0)
     nLen = pStr ? FXSYS_strlen(pStr) : 0;
 
@@ -129,6 +130,7 @@ CFX_ByteString::CFX_ByteString(const char* pStr, FX_STRSIZE nLen) {
 }
 
 CFX_ByteString::CFX_ByteString(const uint8_t* pStr, FX_STRSIZE nLen) {
+  ASSERT(nLen >= 0);
   if (nLen > 0) {
     m_pData.Reset(
         StringData::Create(reinterpret_cast<const char*>(pStr), nLen));
@@ -456,14 +458,8 @@ void CFX_ByteString::Concat(const char* pSrcData, FX_STRSIZE nSrcLen) {
   m_pData.Swap(pNewData);
 }
 
-CFX_ByteString CFX_ByteString::Mid(FX_STRSIZE nFirst) const {
-  if (!m_pData)
-    return CFX_ByteString();
-
-  return Mid(nFirst, m_pData->m_nDataLength - nFirst);
-}
-
 CFX_ByteString CFX_ByteString::Mid(FX_STRSIZE nFirst, FX_STRSIZE nCount) const {
+  ASSERT(nCount >= 0);
   if (!m_pData)
     return CFX_ByteString();
 
diff --git a/core/fxcrt/cfx_bytestring.h b/core/fxcrt/cfx_bytestring.h
index abf8ac80c8..519cee39d4 100644
--- a/core/fxcrt/cfx_bytestring.h
+++ b/core/fxcrt/cfx_bytestring.h
@@ -124,7 +124,6 @@ class CFX_ByteString {
   char* GetBuffer(FX_STRSIZE len);
   void ReleaseBuffer(FX_STRSIZE len = -1);
 
-  CFX_ByteString Mid(FX_STRSIZE first) const;
   CFX_ByteString Mid(FX_STRSIZE first, FX_STRSIZE count) const;
   CFX_ByteString Left(FX_STRSIZE count) const;
   CFX_ByteString Right(FX_STRSIZE count) const;
diff --git a/core/fxcrt/cfx_bytestring_unittest.cpp b/core/fxcrt/cfx_bytestring_unittest.cpp
index f5d9413b7d..bcf6f7495e 100644
--- a/core/fxcrt/cfx_bytestring_unittest.cpp
+++ b/core/fxcrt/cfx_bytestring_unittest.cpp
@@ -440,10 +440,10 @@ TEST(fxcrt, ByteStringMid) {
   CFX_ByteString fred("FRED");
   EXPECT_EQ("", fred.Mid(0, 0));
   EXPECT_EQ("", fred.Mid(3, 0));
-  EXPECT_EQ("FRED", fred.Mid(0));
-  EXPECT_EQ("RED", fred.Mid(1));
-  EXPECT_EQ("ED", fred.Mid(2));
-  EXPECT_EQ("D", fred.Mid(3));
+  EXPECT_EQ("FRED", fred.Mid(0, 4));
+  EXPECT_EQ("RED", fred.Mid(1, 3));
+  EXPECT_EQ("ED", fred.Mid(2, 2));
+  EXPECT_EQ("D", fred.Mid(3, 1));
   EXPECT_EQ("F", fred.Mid(0, 1));
   EXPECT_EQ("R", fred.Mid(1, 1));
   EXPECT_EQ("E", fred.Mid(2, 1));
@@ -458,9 +458,6 @@ TEST(fxcrt, ByteStringMid) {
 
   CFX_ByteString empty;
   EXPECT_EQ("", empty.Mid(0, 0));
-  EXPECT_EQ("", empty.Mid(0));
-  EXPECT_EQ("", empty.Mid(1));
-  EXPECT_EQ("", empty.Mid(-1));
 }
 
 TEST(fxcrt, ByteStringLeft) {
diff --git a/core/fxcrt/cfx_string_c_template.h b/core/fxcrt/cfx_string_c_template.h
index cd3cd27e75..77f34f638e 100644
--- a/core/fxcrt/cfx_string_c_template.h
+++ b/core/fxcrt/cfx_string_c_template.h
@@ -130,29 +130,32 @@ class CFX_StringCTemplate {
     return found ? found - m_Ptr.Get() : -1;
   }
 
-  CFX_StringCTemplate Mid(FX_STRSIZE index, FX_STRSIZE count = -1) const {
-    index = std::max(0, index);
+  CFX_StringCTemplate Mid(FX_STRSIZE index, FX_STRSIZE count) const {
+    ASSERT(count >= 0);
     if (index > m_Length)
       return CFX_StringCTemplate();
 
-    if (count < 0 || count > m_Length - index)
-      count = m_Length - index;
+    index = pdfium::clamp(index, 0, m_Length);
+    count = pdfium::clamp(count, 0, m_Length - index);
+    if (count == 0)
+      return CFX_StringCTemplate();
 
     return CFX_StringCTemplate(m_Ptr.Get() + index, count);
   }
 
   CFX_StringCTemplate Left(FX_STRSIZE count) const {
-    if (count <= 0)
+    count = pdfium::clamp(count, 0, m_Length);
+    if (count == 0)
       return CFX_StringCTemplate();
 
-    return CFX_StringCTemplate(m_Ptr.Get(), std::min(count, m_Length));
+    return CFX_StringCTemplate(m_Ptr.Get(), count);
   }
 
   CFX_StringCTemplate Right(FX_STRSIZE count) const {
-    if (count <= 0)
+    count = pdfium::clamp(count, 0, m_Length);
+    if (count == 0)
       return CFX_StringCTemplate();
 
-    count = std::min(count, m_Length);
     return CFX_StringCTemplate(m_Ptr.Get() + m_Length - count, count);
   }
 
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();
 
diff --git a/core/fxcrt/cfx_widestring.h b/core/fxcrt/cfx_widestring.h
index 0e477bfc8b..938b1e7958 100644
--- a/core/fxcrt/cfx_widestring.h
+++ b/core/fxcrt/cfx_widestring.h
@@ -112,7 +112,6 @@ class CFX_WideString {
   int Compare(const CFX_WideString& str) const;
   int CompareNoCase(const wchar_t* str) const;
 
-  CFX_WideString Mid(FX_STRSIZE first) const;
   CFX_WideString Mid(FX_STRSIZE first, FX_STRSIZE count) const;
   CFX_WideString Left(FX_STRSIZE count) const;
   CFX_WideString Right(FX_STRSIZE count) const;
diff --git a/core/fxcrt/cfx_widestring_unittest.cpp b/core/fxcrt/cfx_widestring_unittest.cpp
index 4cd71d9997..1d6d110497 100644
--- a/core/fxcrt/cfx_widestring_unittest.cpp
+++ b/core/fxcrt/cfx_widestring_unittest.cpp
@@ -406,10 +406,10 @@ TEST(fxcrt, WideStringMid) {
   CFX_WideString fred(L"FRED");
   EXPECT_EQ(L"", fred.Mid(0, 0));
   EXPECT_EQ(L"", fred.Mid(3, 0));
-  EXPECT_EQ(L"FRED", fred.Mid(0));
-  EXPECT_EQ(L"RED", fred.Mid(1));
-  EXPECT_EQ(L"ED", fred.Mid(2));
-  EXPECT_EQ(L"D", fred.Mid(3));
+  EXPECT_EQ(L"FRED", fred.Mid(0, 4));
+  EXPECT_EQ(L"RED", fred.Mid(1, 3));
+  EXPECT_EQ(L"ED", fred.Mid(2, 2));
+  EXPECT_EQ(L"D", fred.Mid(3, 1));
   EXPECT_EQ(L"F", fred.Mid(0, 1));
   EXPECT_EQ(L"R", fred.Mid(1, 1));
   EXPECT_EQ(L"E", fred.Mid(2, 1));
@@ -424,9 +424,6 @@ TEST(fxcrt, WideStringMid) {
 
   CFX_WideString empty;
   EXPECT_EQ(L"", empty.Mid(0, 0));
-  EXPECT_EQ(L"", empty.Mid(0));
-  EXPECT_EQ(L"", empty.Mid(1));
-  EXPECT_EQ(L"", empty.Mid(-1));
 }
 
 TEST(fxcrt, WideStringLeft) {
diff --git a/core/fxcrt/xml/cxml_parser.cpp b/core/fxcrt/xml/cxml_parser.cpp
index a741d8409e..0166ea8490 100644
--- a/core/fxcrt/xml/cxml_parser.cpp
+++ b/core/fxcrt/xml/cxml_parser.cpp
@@ -87,7 +87,7 @@ void FX_XML_SplitQualifiedName(const CFX_ByteStringC& bsFullName,
     bsName = bsFullName;
   } else {
     bsSpace = bsFullName.Mid(0, iStart);
-    bsName = bsFullName.Mid(iStart + 1);
+    bsName = bsFullName.Mid(iStart + 1, bsFullName.GetLength() - (iStart + 1));
   }
 }