Convert string Find methods to return an Optional

The Find and ReverseFind methods for WideString, WideStringC,
ByteString, and ByteStringC have been converted from returning a raw
FX_STRSIZE, to returning Optional<FX_STRSIZE>, so that success/failure
can be indicated without using FX_STRNPOS.

This allows for removing FX_STRNPOS and by association makes the
conversion of FX_STRSIZE to size_t easier, since it forces checking
the return value of Find to be explictly done as well as taking the
error value out of the range of FX_STRSIZE.

New Contains methods have been added for cases where the success or
failure is all the call site to Find cared about, and the actual
position was ignored.

BUG=pdfium:828


Change-Id: Id827e508c8660affa68cc08a13d96121369364b7
Reviewed-on: https://pdfium-review.googlesource.com/11350
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>

2 files changed, 52 insertions, 49 deletions

diff --git a/core/fpdftext/cpdf_linkextract.cpp b/core/fpdftext/cpdf_linkextract.cpp
index fb228ec832..cfa9dbba7f 100644
--- a/core/fpdftext/cpdf_linkextract.cpp
+++ b/core/fpdftext/cpdf_linkextract.cpp
@@ -22,7 +22,7 @@ namespace {
 FX_STRSIZE FindWebLinkEnding(const CFX_WideString& str,
                              FX_STRSIZE start,
                              FX_STRSIZE end) {
-  if (str.Find(L'/', start) != FX_STRNPOS) {
+  if (str.Contains(L'/', start)) {
     // When there is a path and query after '/', most ASCII chars are allowed.
     // We don't sanitize in this case.
     return end;
@@ -33,16 +33,20 @@ FX_STRSIZE FindWebLinkEnding(const CFX_WideString& str,
   if (str[start] == L'[') {
     // IPv6 reference.
     // Find the end of the reference.
-    end = str.Find(L']', start + 1);
-    if (end != -1 && end > start + 1) {  // Has content inside brackets.
-      FX_STRSIZE len = str.GetLength();
-      FX_STRSIZE off = end + 1;
-      if (off < len && str[off] == L':') {
-        off++;
-        while (off < len && str[off] >= L'0' && str[off] <= L'9')
+    auto result = str.Find(L']', start + 1);
+    if (result.has_value()) {
+      end = result.value();
+      if (end > start + 1) {  // Has content inside brackets.
+        FX_STRSIZE len = str.GetLength();
+        FX_STRSIZE off = end + 1;
+        if (off < len && str[off] == L':') {
           off++;
-        if (off > end + 2 && off <= len)  // At least one digit in port number.
-          end = off - 1;  // |off| is offset of the first invalid char.
+          while (off < len && str[off] >= L'0' && str[off] <= L'9')
+            off++;
+          if (off > end + 2 &&
+              off <= len)   // At least one digit in port number.
+            end = off - 1;  // |off| is offset of the first invalid char.
+        }
       }
     }
     return end;
@@ -196,20 +200,20 @@ bool CPDF_LinkExtract::CheckWebLink(CFX_WideString* strBeCheck,
 
   FX_STRSIZE len = str.GetLength();
   // First, try to find the scheme.
-  FX_STRSIZE start = str.Find(kHttpScheme);
-  if (start != FX_STRNPOS) {
-    FX_STRSIZE off = start + kHttpSchemeLen;  // move after "http".
+  auto start = str.Find(kHttpScheme);
+  if (start.has_value()) {
+    FX_STRSIZE off = start.value() + kHttpSchemeLen;  // move after "http".
     if (len > off + 4) {                      // At least "://<char>" follows.
       if (str[off] == L's')                   // "https" scheme is accepted.
         off++;
       if (str[off] == L':' && str[off + 1] == L'/' && str[off + 2] == L'/') {
         off += 3;
-        FX_STRSIZE end =
-            TrimExternalBracketsFromWebLink(str, start, str.GetLength() - 1);
+        FX_STRSIZE end = TrimExternalBracketsFromWebLink(str, start.value(),
+                                                         str.GetLength() - 1);
         end = FindWebLinkEnding(str, off, end);
         if (end > off) {  // Non-empty host name.
-          *nStart = start;
-          *nCount = end - start + 1;
+          *nStart = start.value();
+          *nCount = end - start.value() + 1;
           *strBeCheck = strBeCheck->Mid(*nStart, *nCount);
           return true;
         }
@@ -219,13 +223,13 @@ bool CPDF_LinkExtract::CheckWebLink(CFX_WideString* strBeCheck,
 
   // When there is no scheme, try to find url starting with "www.".
   start = str.Find(kWWWAddrStart);
-  if (start != FX_STRNPOS && len > start + kWWWAddrStartLen) {
-    FX_STRSIZE end =
-        TrimExternalBracketsFromWebLink(str, start, str.GetLength() - 1);
-    end = FindWebLinkEnding(str, start, end);
-    if (end > start + kWWWAddrStartLen) {
-      *nStart = start;
-      *nCount = end - start + 1;
+  if (start.has_value() && len > start.value() + kWWWAddrStartLen) {
+    FX_STRSIZE end = TrimExternalBracketsFromWebLink(str, start.value(),
+                                                     str.GetLength() - 1);
+    end = FindWebLinkEnding(str, start.value(), end);
+    if (end > start.value() + kWWWAddrStartLen) {
+      *nStart = start.value();
+      *nCount = end - start.value() + 1;
       *strBeCheck = L"http://" + strBeCheck->Mid(*nStart, *nCount);
       return true;
     }
@@ -234,20 +238,20 @@ bool CPDF_LinkExtract::CheckWebLink(CFX_WideString* strBeCheck,
 }
 
 bool CPDF_LinkExtract::CheckMailLink(CFX_WideString* str) {
-  FX_STRSIZE aPos = str->Find(L'@');
+  auto aPos = str->Find(L'@');
   // Invalid when no '@' or when starts/ends with '@'.
-  if (aPos == FX_STRNPOS || aPos == 0 || aPos == str->GetLength() - 1)
+  if (!aPos.has_value() || aPos.value() == 0 || aPos == str->GetLength() - 1)
     return false;
 
   // Check the local part.
-  int pPos = aPos;  // Used to track the position of '@' or '.'.
-  for (int i = aPos - 1; i >= 0; i--) {
+  int pPos = aPos.value();  // Used to track the position of '@' or '.'.
+  for (int i = aPos.value() - 1; i >= 0; i--) {
     wchar_t ch = (*str)[i];
     if (ch == L'_' || ch == L'-' || FXSYS_iswalnum(ch))
       continue;
 
     if (ch != L'.' || i == pPos - 1 || i == 0) {
-      if (i == aPos - 1) {
+      if (i == aPos.value() - 1) {
         // There is '.' or invalid char before '@'.
         return false;
       }
@@ -263,21 +267,21 @@ bool CPDF_LinkExtract::CheckMailLink(CFX_WideString* str) {
 
   // Check the domain name part.
   aPos = str->Find(L'@');
-  if (aPos < 1 || aPos == FX_STRNPOS)
+  if (!aPos.has_value() || aPos.value() == 0)
     return false;
 
   str->TrimRight(L'.');
   // At least one '.' in domain name, but not at the beginning.
   // TODO(weili): RFC5322 allows domain names to be a local name without '.'.
   // Check whether we should remove this check.
-  FX_STRSIZE ePos = str->Find(L'.', aPos + 1);
-  if (ePos == FX_STRNPOS || ePos == aPos + 1)
+  auto ePos = str->Find(L'.', aPos.value() + 1);
+  if (!ePos.has_value() || ePos.value() == aPos.value() + 1)
     return false;
 
   // Validate all other chars in domain name.
   int nLen = str->GetLength();
   pPos = 0;  // Used to track the position of '.'.
-  for (int i = aPos + 1; i < nLen; i++) {
+  for (int i = aPos.value() + 1; i < nLen; i++) {
     wchar_t wch = (*str)[i];
     if (wch == L'-' || FXSYS_iswalnum(wch))
       continue;
@@ -285,7 +289,7 @@ bool CPDF_LinkExtract::CheckMailLink(CFX_WideString* str) {
     if (wch != L'.' || i == pPos + 1) {
       // Domain name should end before invalid char.
       int host_end = i == pPos + 1 ? i - 2 : i - 1;
-      if (pPos > 0 && host_end - aPos >= 3) {
+      if (pPos > 0 && host_end - aPos.value() >= 3) {
         // Trim the ending invalid chars if there is at least one '.' and name.
         *str = str->Left(host_end + 1);
         break;
@@ -295,7 +299,7 @@ bool CPDF_LinkExtract::CheckMailLink(CFX_WideString* str) {
     pPos = i;
   }
 
-  if (str->Find(L"mailto:") == FX_STRNPOS)
+  if (!str->Contains(L"mailto:"))
     *str = L"mailto:" + *str;
 
   return true;
diff --git a/core/fpdftext/cpdf_textpagefind.cpp b/core/fpdftext/cpdf_textpagefind.cpp
index 55f940cad7..fd6e3a0d00 100644
--- a/core/fpdftext/cpdf_textpagefind.cpp
+++ b/core/fpdftext/cpdf_textpagefind.cpp
@@ -142,9 +142,8 @@ bool CPDF_TextPageFind::FindNext() {
     return m_IsFind;
   }
   int nCount = pdfium::CollectionSize<int>(m_csFindWhatArray);
-  int nResultPos = 0;
-  int nStartPos = 0;
-  nStartPos = m_findNextStart;
+  pdfium::Optional<FX_STRSIZE> nResultPos = 0;
+  int nStartPos = m_findNextStart;
   bool bSpaceStart = false;
   for (int iWord = 0; iWord < nCount; iWord++) {
     CFX_WideString csWord = m_csFindWhatArray[iWord];
@@ -164,25 +163,25 @@ bool CPDF_TextPageFind::FindNext() {
     }
     int endIndex;
     nResultPos = m_strText.Find(csWord.c_str(), nStartPos);
-    if (nResultPos == FX_STRNPOS) {
+    if (!nResultPos.has_value()) {
       m_IsFind = false;
       return m_IsFind;
     }
-    endIndex = nResultPos + csWord.GetLength() - 1;
+    endIndex = nResultPos.value() + csWord.GetLength() - 1;
     if (iWord == 0)
-      m_resStart = nResultPos;
+      m_resStart = nResultPos.value();
     bool bMatch = true;
     if (iWord != 0 && !bSpaceStart) {
       int PreResEndPos = nStartPos;
       int curChar = csWord[0];
       CFX_WideString lastWord = m_csFindWhatArray[iWord - 1];
       int lastChar = lastWord[lastWord.GetLength() - 1];
-      if (nStartPos == nResultPos &&
+      if (nStartPos == nResultPos.value() &&
           !(IsIgnoreSpaceCharacter(lastChar) ||
             IsIgnoreSpaceCharacter(curChar))) {
         bMatch = false;
       }
-      for (int d = PreResEndPos; d < nResultPos; d++) {
+      for (int d = PreResEndPos; d < nResultPos.value(); d++) {
         wchar_t strInsert = m_strText[d];
         if (strInsert != TEXT_LINEFEED_CHAR && strInsert != TEXT_SPACE_CHAR &&
             strInsert != TEXT_RETURN_CHAR && strInsert != 160) {
@@ -191,19 +190,19 @@ bool CPDF_TextPageFind::FindNext() {
         }
       }
     } else if (bSpaceStart) {
-      if (nResultPos > 0) {
-        wchar_t strInsert = m_strText[nResultPos - 1];
+      if (nResultPos.value() > 0) {
+        wchar_t strInsert = m_strText[nResultPos.value() - 1];
         if (strInsert != TEXT_LINEFEED_CHAR && strInsert != TEXT_SPACE_CHAR &&
             strInsert != TEXT_RETURN_CHAR && strInsert != 160) {
           bMatch = false;
-          m_resStart = nResultPos;
+          m_resStart = nResultPos.value();
         } else {
-          m_resStart = nResultPos - 1;
+          m_resStart = nResultPos.value() - 1;
         }
       }
     }
     if (m_bMatchWholeWord && bMatch) {
-      bMatch = IsMatchWholeWord(m_strText, nResultPos, endIndex);
+      bMatch = IsMatchWholeWord(m_strText, nResultPos.value(), endIndex);
     }
     nStartPos = endIndex + 1;
     if (!bMatch) {
@@ -214,7 +213,7 @@ bool CPDF_TextPageFind::FindNext() {
         nStartPos = m_resStart + m_csFindWhatArray[0].GetLength();
     }
   }
-  m_resEnd = nResultPos + m_csFindWhatArray.back().GetLength() - 1;
+  m_resEnd = nResultPos.value() + m_csFindWhatArray.back().GetLength() - 1;
   m_IsFind = true;
   int resStart = GetCharIndex(m_resStart);
   int resEnd = GetCharIndex(m_resEnd);