Convert calls to Mid() to Left() or Right() if possible

The various string/byte classes support Mid(), Left(), and Right() for
extracting substrings. Mid() can handle all possible cases, but Left()
and Right() are useful for common cases and  more explicit about what
is going on.

Calls like Mid(offset, length - offset) can be converted to
Right(length - offset). Calls like Mid(0, length) can be converted to
Left(length).

If the substring being extracted does not extend all the way to one of
the edges of the string, then Mid() still needs to be used.

BUG=pdfium:828

Change-Id: I2ec46ad3d71aac0f7b513e103c69cbe8c854cf62
Reviewed-on: https://pdfium-review.googlesource.com/9510
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

8 files changed, 12 insertions, 13 deletions

diff --git a/fxbarcode/cbc_ean13.cpp b/fxbarcode/cbc_ean13.cpp
index 1c57a877f2..ac08a9d53e 100644
--- a/fxbarcode/cbc_ean13.cpp
+++ b/fxbarcode/cbc_ean13.cpp
@@ -45,7 +45,7 @@ CFX_WideString CBC_EAN13::Preprocess(const CFX_WideStringC& contents) {
     encodeContents = byteString.UTF8Decode();
   }
   if (length > 13)
-    encodeContents = encodeContents.Mid(0, 13);
+    encodeContents = encodeContents.Left(13);
 
   return encodeContents;
 }
diff --git a/fxbarcode/cbc_ean8.cpp b/fxbarcode/cbc_ean8.cpp
index 3b4369e80f..ce2cf2ba79 100644
--- a/fxbarcode/cbc_ean8.cpp
+++ b/fxbarcode/cbc_ean8.cpp
@@ -43,7 +43,7 @@ CFX_WideString CBC_EAN8::Preprocess(const CFX_WideStringC& contents) {
     encodeContents += wchar_t(checksum - 0 + '0');
   }
   if (length > 8)
-    encodeContents = encodeContents.Mid(0, 8);
+    encodeContents = encodeContents.Left(8);
 
   return encodeContents;
 }
diff --git a/fxbarcode/cbc_upca.cpp b/fxbarcode/cbc_upca.cpp
index 6c2e08a9fb..85b5d549ab 100644
--- a/fxbarcode/cbc_upca.cpp
+++ b/fxbarcode/cbc_upca.cpp
@@ -44,7 +44,7 @@ CFX_WideString CBC_UPCA::Preprocess(const CFX_WideStringC& contents) {
     encodeContents = byteString.UTF8Decode();
   }
   if (length > 12)
-    encodeContents = encodeContents.Mid(0, 12);
+    encodeContents = encodeContents.Left(12);
 
   return encodeContents;
 }
diff --git a/fxbarcode/datamatrix/BC_HighLevelEncoder.cpp b/fxbarcode/datamatrix/BC_HighLevelEncoder.cpp
index ec527d29a8..6034173ee4 100644
--- a/fxbarcode/datamatrix/BC_HighLevelEncoder.cpp
+++ b/fxbarcode/datamatrix/BC_HighLevelEncoder.cpp
@@ -76,13 +76,12 @@ CFX_WideString CBC_HighLevelEncoder::encodeHighLevel(CFX_WideString msg,
     return CFX_WideString();
 
   context.setAllowRectangular(allowRectangular);
-  if ((msg.Mid(0, 6) == MACRO_05_HEADER) &&
-      (msg.Mid(msg.GetLength() - 1, 1) == MACRO_TRAILER)) {
+  if ((msg.Left(6) == MACRO_05_HEADER) && (msg.Right(1) == MACRO_TRAILER)) {
     context.writeCodeword(MACRO_05);
     context.setSkipAtEnd(2);
     context.m_pos += 6;
-  } else if ((msg.Mid(0, 6) == MACRO_06_HEADER) &&
-             (msg.Mid(msg.GetLength() - 1, 1) == MACRO_TRAILER)) {
+  } else if ((msg.Left(6) == MACRO_06_HEADER) &&
+             (msg.Right(1) == MACRO_TRAILER)) {
     context.writeCodeword(MACRO_06);
     context.setSkipAtEnd(2);
     context.m_pos += 6;
diff --git a/fxbarcode/oned/BC_OnedEAN13Writer.cpp b/fxbarcode/oned/BC_OnedEAN13Writer.cpp
index 0e4bab9518..6f1d957a01 100644
--- a/fxbarcode/oned/BC_OnedEAN13Writer.cpp
+++ b/fxbarcode/oned/BC_OnedEAN13Writer.cpp
@@ -109,7 +109,7 @@ uint8_t* CBC_OnedEAN13Writer::EncodeImpl(const CFX_ByteString& contents,
     return nullptr;
 
   m_iDataLenth = 13;
-  int32_t firstDigit = FXSYS_atoi(contents.Mid(0, 1).c_str());
+  int32_t firstDigit = FXSYS_atoi(contents.Left(1).c_str());
   int32_t parities = FIRST_DIGIT_ENCODINGS[firstDigit];
   outLength = m_codeWidth;
   std::unique_ptr<uint8_t, FxFreeDeleter> result(
@@ -219,7 +219,7 @@ bool CBC_OnedEAN13Writer::ShowChars(const CFX_WideStringC& contents,
                            static_cast<float>(iFontSize), &affine_matrix1,
                            m_fontColor, FXTEXT_CLEARTYPE);
   }
-  tempStr = str.Mid(0, 1);
+  tempStr = str.Left(1);
   iLen = tempStr.GetLength();
   strWidth = multiple * 7;
   strWidth = (int32_t)(strWidth * m_outputHScale);
diff --git a/fxbarcode/oned/BC_OnedEAN8Writer.cpp b/fxbarcode/oned/BC_OnedEAN8Writer.cpp
index f891c08fc6..9a85f814a7 100644
--- a/fxbarcode/oned/BC_OnedEAN8Writer.cpp
+++ b/fxbarcode/oned/BC_OnedEAN8Writer.cpp
@@ -159,7 +159,7 @@ bool CBC_OnedEAN8Writer::ShowChars(const CFX_WideStringC& contents,
   CFX_ByteString str = FX_UTF8Encode(contents);
   int32_t iLength = str.GetLength();
   std::vector<FXTEXT_CHARPOS> charpos(iLength);
-  CFX_ByteString tempStr = str.Mid(0, 4);
+  CFX_ByteString tempStr = str.Left(4);
   int32_t iLen = tempStr.GetLength();
   int32_t strWidth = 7 * multiple * 4;
   float blank = 0.0;
diff --git a/fxbarcode/oned/BC_OnedUPCAWriter.cpp b/fxbarcode/oned/BC_OnedUPCAWriter.cpp
index 78ada1783a..13514eb53f 100644
--- a/fxbarcode/oned/BC_OnedUPCAWriter.cpp
+++ b/fxbarcode/oned/BC_OnedUPCAWriter.cpp
@@ -183,7 +183,7 @@ bool CBC_OnedUPCAWriter::ShowChars(const CFX_WideStringC& contents,
                            static_cast<float>(iFontSize), &affine_matrix1,
                            m_fontColor, FXTEXT_CLEARTYPE);
   }
-  tempStr = str.Mid(0, 1);
+  tempStr = str.Left(1);
   iLen = tempStr.GetLength();
   strWidth = (float)multiple * 7;
   strWidth = strWidth * m_outputHScale;
diff --git a/fxbarcode/qrcode/BC_QRCoderEncoder.cpp b/fxbarcode/qrcode/BC_QRCoderEncoder.cpp
index 955e2c7295..cad70b81c5 100644
--- a/fxbarcode/qrcode/BC_QRCoderEncoder.cpp
+++ b/fxbarcode/qrcode/BC_QRCoderEncoder.cpp
@@ -432,7 +432,7 @@ void SplitString(const CFX_ByteString& content,
     index += 2;
   }
   if (index)
-    result->push_back({CBC_QRCoderMode::sGBK, content.Mid(0, index)});
+    result->push_back({CBC_QRCoderMode::sGBK, content.Left(index)});
   if (index >= content.GetLength())
     return;
 
@@ -479,7 +479,7 @@ void SplitString(const CFX_ByteString& content,
   }
   flag = index;
   if (index < content.GetLength())
-    SplitString(content.Mid(index, content.GetLength() - index), result);
+    SplitString(content.Right(content.GetLength() - index), result);
 }
 
 CBC_QRCoderMode* ChooseMode(const CFX_ByteString& content,