Adjust loops in preperation for FX_STRSIZE int->size_t

Adjust loop conditions and behaviours in preperation for convering the
underlying type of FX_STRSIZE to size_t. These changes are not
dependent on the type switch occuring, so can be landed before hand.

BUG=pdfium:828

Change-Id: I5f950c99c10e5ef0836959e3b1dd2e09f8f5afc0
Reviewed-on: https://pdfium-review.googlesource.com/12750
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>

5 files changed, 44 insertions, 53 deletions

diff --git a/core/fpdfapi/font/cpdf_cmap.cpp b/core/fpdfapi/font/cpdf_cmap.cpp
index 7b88346d64..9e8c48bb27 100644
--- a/core/fpdfapi/font/cpdf_cmap.cpp
+++ b/core/fpdfapi/font/cpdf_cmap.cpp
@@ -184,48 +184,43 @@ const PredefinedCMap g_PredefinedCMaps[] = {
 int CheckFourByteCodeRange(uint8_t* codes,
                            FX_STRSIZE size,
                            const std::vector<CPDF_CMap::CodeRange>& ranges) {
-  int iSeg = pdfium::CollectionSize<int>(ranges) - 1;
-  while (iSeg >= 0) {
-    if (ranges[iSeg].m_CharSize < size) {
-      --iSeg;
+  for (size_t i = ranges.size(); i > 0; i--) {
+    size_t seg = i - 1;
+    if (ranges[seg].m_CharSize < size)
       continue;
-    }
-    int iChar = 0;
+    FX_STRSIZE iChar = 0;
     while (iChar < size) {
-      if (codes[iChar] < ranges[iSeg].m_Lower[iChar] ||
-          codes[iChar] > ranges[iSeg].m_Upper[iChar]) {
+      if (codes[iChar] < ranges[seg].m_Lower[iChar] ||
+          codes[iChar] > ranges[seg].m_Upper[iChar]) {
         break;
       }
       ++iChar;
     }
-    if (iChar == ranges[iSeg].m_CharSize)
+    if (iChar == ranges[seg].m_CharSize)
       return 2;
     if (iChar)
-      return (size == ranges[iSeg].m_CharSize) ? 2 : 1;
-    iSeg--;
+      return (size == ranges[seg].m_CharSize) ? 2 : 1;
   }
   return 0;
 }
 
-int GetFourByteCharSizeImpl(uint32_t charcode,
-                            const std::vector<CPDF_CMap::CodeRange>& ranges) {
+size_t GetFourByteCharSizeImpl(
+    uint32_t charcode,
+    const std::vector<CPDF_CMap::CodeRange>& ranges) {
   if (ranges.empty())
     return 1;
 
   uint8_t codes[4];
   codes[0] = codes[1] = 0x00;
-  codes[2] = (uint8_t)(charcode >> 8 & 0xFF);
-  codes[3] = (uint8_t)charcode;
-  FX_STRSIZE offset = 0;
-  int size = 4;
-  for (int i = 0; i < 4; ++i) {
-    int iSeg = pdfium::CollectionSize<int>(ranges) - 1;
-    while (iSeg >= 0) {
-      if (ranges[iSeg].m_CharSize < size) {
-        --iSeg;
+  codes[2] = static_cast<uint8_t>(charcode >> 8 & 0xFF);
+  codes[3] = static_cast<uint8_t>(charcode);
+  for (FX_STRSIZE offset = 0; offset < 4; offset++) {
+    FX_STRSIZE size = 4 - offset;
+    for (size_t j = 0; j < ranges.size(); j++) {
+      size_t iSeg = (ranges.size() - 1) - j;
+      if (ranges[iSeg].m_CharSize < size)
         continue;
-      }
-      int iChar = 0;
+      FX_STRSIZE iChar = 0;
       while (iChar < size) {
         if (codes[offset + iChar] < ranges[iSeg].m_Lower[iChar] ||
             codes[offset + iChar] > ranges[iSeg].m_Upper[iChar]) {
@@ -235,10 +230,7 @@ int GetFourByteCharSizeImpl(uint32_t charcode,
       }
       if (iChar == ranges[iSeg].m_CharSize)
         return size;
-      --iSeg;
     }
-    --size;
-    ++offset;
   }
   return 1;
 }
diff --git a/core/fpdftext/cpdf_linkextract.cpp b/core/fpdftext/cpdf_linkextract.cpp
index 880a4ceb92..a5eafe689a 100644
--- a/core/fpdftext/cpdf_linkextract.cpp
+++ b/core/fpdftext/cpdf_linkextract.cpp
@@ -245,24 +245,24 @@ bool CPDF_LinkExtract::CheckMailLink(CFX_WideString* str) {
 
   // Check the local part.
   FX_STRSIZE pPos = aPos.value();  // Used to track the position of '@' or '.'.
-  for (FX_STRSIZE i = aPos.value() - 1; i >= 0; i--) {
-    wchar_t ch = (*str)[i];
+  for (FX_STRSIZE i = aPos.value(); i > 0; i--) {
+    wchar_t ch = (*str)[i - 1];
     if (ch == L'_' || ch == L'-' || FXSYS_iswalnum(ch))
       continue;
 
-    if (ch != L'.' || i == pPos - 1 || i == 0) {
-      if (i == aPos.value() - 1) {
+    if (ch != L'.' || i == pPos || i == 1) {
+      if (i == aPos.value()) {
         // There is '.' or invalid char before '@'.
         return false;
       }
       // End extracting for other invalid chars, '.' at the beginning, or
       // consecutive '.'.
-      FX_STRSIZE removed_len = i == pPos - 1 ? i + 2 : i + 1;
+      FX_STRSIZE removed_len = i == pPos ? i + 1 : i;
       *str = str->Right(str->GetLength() - removed_len);
       break;
     }
     // Found a valid '.'.
-    pPos = i;
+    pPos = i - 1;
   }
 
   // Check the domain name part.
diff --git a/fpdfsdk/javascript/Document.cpp b/fpdfsdk/javascript/Document.cpp
index d5875aca69..77f67b5c8f 100644
--- a/fpdfsdk/javascript/Document.cpp
+++ b/fpdfsdk/javascript/Document.cpp
@@ -1016,16 +1016,17 @@ bool Document::documentFileName(CJS_Runtime* pRuntime,
     return false;
   }
   CFX_WideString wsFilePath = m_pFormFillEnv->JS_docGetFilePath();
-  FX_STRSIZE i = wsFilePath.GetLength() - 1;
-  for (; i >= 0; i--) {
-    if (wsFilePath[i] == L'\\' || wsFilePath[i] == L'/')
+  FX_STRSIZE i = wsFilePath.GetLength();
+  for (; i > 0; i--) {
+    if (wsFilePath[i - 1] == L'\\' || wsFilePath[i - 1] == L'/')
       break;
   }
-  if (i >= 0 && i < wsFilePath.GetLength() - 1) {
-    vp << (wsFilePath.GetBuffer(wsFilePath.GetLength()) + i + 1);
-  } else {
+
+  if (i > 0 && i < wsFilePath.GetLength())
+    vp << (wsFilePath.GetBuffer(wsFilePath.GetLength()) + i);
+  else
     vp << L"";
-  }
+
   return true;
 }
 
diff --git a/fxbarcode/oned/BC_OnedEAN8Writer.cpp b/fxbarcode/oned/BC_OnedEAN8Writer.cpp
index 5ca53e0568..6810e9e285 100644
--- a/fxbarcode/oned/BC_OnedEAN8Writer.cpp
+++ b/fxbarcode/oned/BC_OnedEAN8Writer.cpp
@@ -83,20 +83,18 @@ CFX_WideString CBC_OnedEAN8Writer::FilterContents(
 }
 
 int32_t CBC_OnedEAN8Writer::CalcChecksum(const CFX_ByteString& contents) {
-  FX_STRSIZE odd = 0;
-  FX_STRSIZE even = 0;
-  FX_STRSIZE j = 1;
-  for (FX_STRSIZE i = contents.GetLength() - 1; i >= 0; i--) {
-    if (j % 2) {
-      odd += FXSYS_atoi(contents.Mid(i, 1).c_str());
+  int32_t odd = 0;
+  int32_t even = 0;
+  for (FX_STRSIZE i = contents.GetLength(); i > 0; i--) {
+    if (i % 2) {
+      odd += FXSYS_atoi(contents.Mid(i - 1, 1).c_str());
     } else {
-      even += FXSYS_atoi(contents.Mid(i, 1).c_str());
+      even += FXSYS_atoi(contents.Mid(i - 1, 1).c_str());
     }
-    j++;
   }
   int32_t checksum = (odd * 3 + even) % 10;
   checksum = (10 - checksum) % 10;
-  return (checksum);
+  return checksum;
 }
 
 uint8_t* CBC_OnedEAN8Writer::EncodeWithHint(const CFX_ByteString& contents,
diff --git a/fxbarcode/oned/BC_OnedUPCAWriter.cpp b/fxbarcode/oned/BC_OnedUPCAWriter.cpp
index 87b68d364f..5782fe4e1a 100644
--- a/fxbarcode/oned/BC_OnedUPCAWriter.cpp
+++ b/fxbarcode/oned/BC_OnedUPCAWriter.cpp
@@ -70,17 +70,17 @@ int32_t CBC_OnedUPCAWriter::CalcChecksum(const CFX_ByteString& contents) {
   int32_t odd = 0;
   int32_t even = 0;
   FX_STRSIZE j = 1;
-  for (FX_STRSIZE i = contents.GetLength() - 1; i >= 0; i--) {
+  for (FX_STRSIZE i = contents.GetLength(); i > 0; i--) {
     if (j % 2) {
-      odd += FXSYS_atoi(contents.Mid(i, 1).c_str());
+      odd += FXSYS_atoi(contents.Mid(i - 1, 1).c_str());
     } else {
-      even += FXSYS_atoi(contents.Mid(i, 1).c_str());
+      even += FXSYS_atoi(contents.Mid(i - 1, 1).c_str());
     }
     j++;
   }
   int32_t checksum = (odd * 3 + even) % 10;
   checksum = (10 - checksum) % 10;
-  return (checksum);
+  return checksum;
 }
 
 uint8_t* CBC_OnedUPCAWriter::EncodeWithHint(const CFX_ByteString& contents,