Remove extracting characters from input

Throughout the lexer there is use of a pattern where a character is
extracted from the location currently being pointed at in the input
and tests are done on this value. This is uneeded, since normally the
pointer isn't being modified while the character is stored, so the
pointer can be dereferenced directly.

This CL also cleans ups the implementation of string extraction from
the input to be easier to read, since it did depend on the character
being extracted to work. The IsFooCharacter methods are also
changed to take in a character instead of a pointer, since they are
only testing the character value not the pointer.

BUG=pdfium:814

Change-Id: I8eda01e0af59ff1f6c6e97d6fb504856c7a08a24
Reviewed-on: https://pdfium-review.googlesource.com/8690
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>

2 files changed, 127 insertions, 191 deletions

diff --git a/xfa/fxfa/fm2js/cxfa_fmlexer.cpp b/xfa/fxfa/fm2js/cxfa_fmlexer.cpp
index 6b8508a503..0b94cde944 100644
--- a/xfa/fxfa/fm2js/cxfa_fmlexer.cpp
+++ b/xfa/fxfa/fm2js/cxfa_fmlexer.cpp
@@ -14,20 +14,20 @@
 
 namespace {
 
-bool IsValidFormCalcCharacter(const wchar_t* p) {
-  return *p == 0 || (*p >= 0x09 && *p <= 0x0D) ||
-         (*p >= 0x20 && *p <= 0xd7FF) || (*p >= 0xE000 && *p <= 0xFFFD);
+bool IsValidFormCalcCharacter(wchar_t c) {
+  return c == 0 || (c >= 0x09 && c <= 0x0D) || (c >= 0x20 && c <= 0xd7FF) ||
+         (c >= 0xE000 && c <= 0xFFFD);
 }
 
-bool IsValidIdentifierCharacter(const wchar_t* p) {
-  return u_isalnum(*p) || *p == 0x005F ||  // '_'
-         *p == 0x0024;                     // '$'
+bool IsValidIdentifierCharacter(wchar_t c) {
+  return u_isalnum(c) || c == 0x005F ||  // '_'
+         c == 0x0024;                    // '$'
 }
 
-bool IsValidInitialIdentifierCharacter(const wchar_t* p) {
-  return u_isalpha(*p) || *p == 0x005F ||  // '_'
-         *p == 0x0024 ||                   // '$'
-         *p == 0x0021;                     // '!'
+bool IsValidInitialIdentifierCharacter(wchar_t c) {
+  return u_isalpha(c) || c == 0x005F ||  // '_'
+         c == 0x0024 ||                  // '$'
+         c == 0x0021;                    // '!'
 }
 
 const XFA_FMKeyword keyWords[] = {
@@ -119,47 +119,17 @@ CXFA_FMLexer::CXFA_FMLexer(const CFX_WideStringC& wsFormCalc)
 CXFA_FMLexer::~CXFA_FMLexer() {}
 
 CXFA_FMToken* CXFA_FMLexer::NextToken() {
-  // Make sure we don't walk off the end of the string.
-  if (m_ptr > m_end) {
-    m_pToken = pdfium::MakeUnique<CXFA_FMToken>(m_uCurrentLine);
-    m_pToken->m_type = TOKeof;
-  } else {
-    m_pToken = Scan();
-  }
-  return m_pToken.get();
-}
-
-std::unique_ptr<CXFA_FMToken> CXFA_FMLexer::Scan() {
-  wchar_t ch = 0;
-  auto p = pdfium::MakeUnique<CXFA_FMToken>(m_uCurrentLine);
-  if (!IsValidFormCalcCharacter(m_ptr)) {
-    ch = *m_ptr;
-    m_LexerError = true;
-    return p;
-  }
-
-  while (1) {
-    // Make sure we don't walk off the end of the string. If we don't currently
-    // have a token type then mark it EOF.
-    if (m_ptr > m_end) {
-      if (p->m_type == TOKreserver)
-        p->m_type = TOKeof;
-      return p;
-    }
-
-    ch = *m_ptr;
-    if (!IsValidFormCalcCharacter(m_ptr)) {
+  m_pToken = pdfium::MakeUnique<CXFA_FMToken>(m_uCurrentLine);
+  while (m_ptr <= m_end && *m_ptr) {
+    if (!IsValidFormCalcCharacter(*m_ptr)) {
       m_LexerError = true;
-      return p;
+      return m_pToken.get();
     }
 
-    switch (ch) {
-      case 0:
-        p->m_type = TOKeof;
-        return p;
+    switch (*m_ptr) {
       case 0x0A:
         ++m_uCurrentLine;
-        p->m_uLinenum = m_uCurrentLine;
+        m_pToken->m_uLinenum = m_uCurrentLine;
         ++m_ptr;
         break;
       case 0x0D:
@@ -170,9 +140,9 @@ std::unique_ptr<CXFA_FMToken> CXFA_FMLexer::Scan() {
         break;
       }
       case '"': {
-        p->m_type = TOKstring;
-        m_ptr = String(p.get(), m_ptr);
-        return p;
+        m_pToken->m_type = TOKstring;
+        m_ptr = String(m_pToken.get(), m_ptr);
+        return m_pToken.get();
       }
       case '0':
       case '1':
@@ -184,129 +154,121 @@ std::unique_ptr<CXFA_FMToken> CXFA_FMLexer::Scan() {
       case '7':
       case '8':
       case '9': {
-        p->m_type = TOKnumber;
-        m_ptr = Number(p.get(), m_ptr);
-        return p;
+        m_pToken->m_type = TOKnumber;
+        m_ptr = Number(m_pToken.get(), m_ptr);
+        return m_pToken.get();
       }
       case '=':
         ++m_ptr;
         if (m_ptr > m_end) {
-          p->m_type = TOKassign;
-          return p;
+          m_pToken->m_type = TOKassign;
+          return m_pToken.get();
         }
 
-        if (IsValidFormCalcCharacter(m_ptr)) {
-          ch = *m_ptr;
-          if (ch == '=') {
-            p->m_type = TOKeq;
+        if (IsValidFormCalcCharacter(*m_ptr)) {
+          if (*m_ptr == '=') {
+            m_pToken->m_type = TOKeq;
             ++m_ptr;
           } else {
-            p->m_type = TOKassign;
+            m_pToken->m_type = TOKassign;
           }
         } else {
-          ch = *m_ptr;
           m_LexerError = true;
         }
-        return p;
+        return m_pToken.get();
       case '<':
         ++m_ptr;
         if (m_ptr > m_end) {
-          p->m_type = TOKlt;
-          return p;
+          m_pToken->m_type = TOKlt;
+          return m_pToken.get();
         }
 
-        if (IsValidFormCalcCharacter(m_ptr)) {
-          ch = *m_ptr;
-          if (ch == '=') {
-            p->m_type = TOKle;
+        if (IsValidFormCalcCharacter(*m_ptr)) {
+          if (*m_ptr == '=') {
+            m_pToken->m_type = TOKle;
             ++m_ptr;
-          } else if (ch == '>') {
-            p->m_type = TOKne;
+          } else if (*m_ptr == '>') {
+            m_pToken->m_type = TOKne;
             ++m_ptr;
           } else {
-            p->m_type = TOKlt;
+            m_pToken->m_type = TOKlt;
           }
         } else {
-          ch = *m_ptr;
           m_LexerError = true;
         }
-        return p;
+        return m_pToken.get();
       case '>':
         ++m_ptr;
         if (m_ptr > m_end) {
-          p->m_type = TOKgt;
-          return p;
+          m_pToken->m_type = TOKgt;
+          return m_pToken.get();
         }
 
-        if (IsValidFormCalcCharacter(m_ptr)) {
-          ch = *m_ptr;
-          if (ch == '=') {
-            p->m_type = TOKge;
+        if (IsValidFormCalcCharacter(*m_ptr)) {
+          if (*m_ptr == '=') {
+            m_pToken->m_type = TOKge;
             ++m_ptr;
           } else {
-            p->m_type = TOKgt;
+            m_pToken->m_type = TOKgt;
           }
         } else {
-          ch = *m_ptr;
           m_LexerError = true;
         }
-        return p;
+        return m_pToken.get();
       case ',':
-        p->m_type = TOKcomma;
+        m_pToken->m_type = TOKcomma;
         ++m_ptr;
-        return p;
+        return m_pToken.get();
       case '(':
-        p->m_type = TOKlparen;
+        m_pToken->m_type = TOKlparen;
         ++m_ptr;
-        return p;
+        return m_pToken.get();
       case ')':
-        p->m_type = TOKrparen;
+        m_pToken->m_type = TOKrparen;
         ++m_ptr;
-        return p;
+        return m_pToken.get();
       case '[':
-        p->m_type = TOKlbracket;
+        m_pToken->m_type = TOKlbracket;
         ++m_ptr;
-        return p;
+        return m_pToken.get();
       case ']':
-        p->m_type = TOKrbracket;
+        m_pToken->m_type = TOKrbracket;
         ++m_ptr;
-        return p;
+        return m_pToken.get();
       case '&':
         ++m_ptr;
-        p->m_type = TOKand;
-        return p;
+        m_pToken->m_type = TOKand;
+        return m_pToken.get();
       case '|':
         ++m_ptr;
-        p->m_type = TOKor;
-        return p;
+        m_pToken->m_type = TOKor;
+        return m_pToken.get();
       case '+':
         ++m_ptr;
-        p->m_type = TOKplus;
-        return p;
+        m_pToken->m_type = TOKplus;
+        return m_pToken.get();
       case '-':
         ++m_ptr;
-        p->m_type = TOKminus;
-        return p;
+        m_pToken->m_type = TOKminus;
+        return m_pToken.get();
       case '*':
         ++m_ptr;
-        p->m_type = TOKmul;
-        return p;
+        m_pToken->m_type = TOKmul;
+        return m_pToken.get();
       case '/': {
         ++m_ptr;
         if (m_ptr > m_end) {
-          p->m_type = TOKdiv;
-          return p;
+          m_pToken->m_type = TOKdiv;
+          return m_pToken.get();
         }
 
-        if (!IsValidFormCalcCharacter(m_ptr)) {
-          ch = *m_ptr;
+        if (!IsValidFormCalcCharacter(*m_ptr)) {
           m_LexerError = true;
-          return p;
+          return m_pToken.get();
         }
-        ch = *m_ptr;
-        if (ch != '/') {
-          p->m_type = TOKdiv;
-          return p;
+        if (*m_ptr != '/') {
+          m_pToken->m_type = TOKdiv;
+          return m_pToken.get();
         }
         m_ptr = Comment(m_ptr);
         break;
@@ -314,33 +276,31 @@ std::unique_ptr<CXFA_FMToken> CXFA_FMLexer::Scan() {
       case '.':
         ++m_ptr;
         if (m_ptr > m_end) {
-          p->m_type = TOKdot;
-          return p;
+          m_pToken->m_type = TOKdot;
+          return m_pToken.get();
         }
 
-        if (IsValidFormCalcCharacter(m_ptr)) {
-          ch = *m_ptr;
-          if (ch == '.') {
-            p->m_type = TOKdotdot;
+        if (IsValidFormCalcCharacter(*m_ptr)) {
+          if (*m_ptr == '.') {
+            m_pToken->m_type = TOKdotdot;
             ++m_ptr;
-          } else if (ch == '*') {
-            p->m_type = TOKdotstar;
+          } else if (*m_ptr == '*') {
+            m_pToken->m_type = TOKdotstar;
             ++m_ptr;
-          } else if (ch == '#') {
-            p->m_type = TOKdotscream;
+          } else if (*m_ptr == '#') {
+            m_pToken->m_type = TOKdotscream;
             ++m_ptr;
-          } else if (ch <= '9' && ch >= '0') {
-            p->m_type = TOKnumber;
+          } else if (*m_ptr <= '9' && *m_ptr >= '0') {
+            m_pToken->m_type = TOKnumber;
             --m_ptr;
-            m_ptr = Number(p.get(), m_ptr);
+            m_ptr = Number(m_pToken.get(), m_ptr);
           } else {
-            p->m_type = TOKdot;
+            m_pToken->m_type = TOKdot;
           }
         } else {
-          ch = *m_ptr;
           m_LexerError = true;
         }
-        return p;
+        return m_pToken.get();
       case 0x09:
       case 0x0B:
       case 0x0C:
@@ -348,15 +308,20 @@ std::unique_ptr<CXFA_FMToken> CXFA_FMLexer::Scan() {
         ++m_ptr;
         break;
       default: {
-        if (!IsValidInitialIdentifierCharacter(m_ptr)) {
+        if (!IsValidInitialIdentifierCharacter(*m_ptr)) {
           m_LexerError = true;
-          return p;
+          return m_pToken.get();
         }
-        m_ptr = Identifiers(p.get(), m_ptr);
-        return p;
+        m_ptr = Identifiers(m_pToken.get(), m_ptr);
+        return m_pToken.get();
       }
     }
   }
+
+  // If there isn't currently a token type then mark it EOF.
+  if (m_pToken->m_type == TOKreserver)
+    m_pToken->m_type = TOKeof;
+  return m_pToken.get();
 }
 
 const wchar_t* CXFA_FMLexer::Number(CXFA_FMToken* t, const wchar_t* p) {
@@ -374,55 +339,36 @@ const wchar_t* CXFA_FMLexer::Number(CXFA_FMToken* t, const wchar_t* p) {
 }
 
 const wchar_t* CXFA_FMLexer::String(CXFA_FMToken* t, const wchar_t* p) {
-  const wchar_t* pStart = p;
-
+  const wchar_t* start = p;
   ++p;
-  if (p > m_end) {
-    m_LexerError = true;
-    return p;
-  }
-
-  uint16_t ch = *p;
-  while (ch) {
-    if (!IsValidFormCalcCharacter(p)) {
-      ch = *p;
-      t->m_wstring = CFX_WideStringC(pStart, (p - pStart));
-      m_LexerError = true;
-      return p;
-    }
+  while (p <= m_end && *p) {
+    if (!IsValidFormCalcCharacter(*p))
+      break;
 
-    ++p;
-    if (ch != '"') {
-      // We've hit the end of the input, return the string.
+    if (*p == '"') {
+      // Check for escaped "s, i.e. "".
+      ++p;
+      // If the end of the input has been reached it was not escaped.
       if (p > m_end) {
-        m_LexerError = true;
+        t->m_wstring = CFX_WideStringC(start, (p - start));
+        return p;
+      }
+      // If the next character is not a " then the end of the string has been
+      // found.
+      if (*p != '"') {
+        if (!IsValidFormCalcCharacter(*p)) {
+          break;
+        }
+        t->m_wstring = CFX_WideStringC(start, (p - start));
         return p;
       }
-      ch = *p;
-      continue;
-    }
-    // We've hit the end of the input, return the string.
-    if (p > m_end)
-      break;
-
-    if (!IsValidFormCalcCharacter(p)) {
-      ch = *p;
-      t->m_wstring = CFX_WideStringC(pStart, (p - pStart));
-      m_LexerError = true;
-      return p;
     }
-    ch = *p;
-    if (ch != '"')
-      break;
-
     ++p;
-    if (p > m_end) {
-      m_LexerError = true;
-      return p;
-    }
-    ch = *p;
   }
-  t->m_wstring = CFX_WideStringC(pStart, (p - pStart));
+
+  // Didn't find the end of the string.
+  t->m_wstring = CFX_WideStringC(start, (p - start));
+  m_LexerError = true;
   return p;
 }
 
@@ -430,18 +376,16 @@ const wchar_t* CXFA_FMLexer::Identifiers(CXFA_FMToken* t, const wchar_t* p) {
   const wchar_t* pStart = p;
   ++p;
   while (p <= m_end && *p) {
-    if (!IsValidFormCalcCharacter(p)) {
+    if (!IsValidFormCalcCharacter(*p)) {
       t->m_wstring = CFX_WideStringC(pStart, (p - pStart));
       m_LexerError = true;
       return p;
     }
 
-    if (!IsValidIdentifierCharacter(p)) {
+    if (!IsValidIdentifierCharacter(*p)) {
       break;
     }
     ++p;
-    if (p > m_end)
-      break;
   }
   t->m_wstring = CFX_WideStringC(pStart, (p - pStart));
   t->m_type = IsKeyword(t->m_wstring);
@@ -449,23 +393,15 @@ const wchar_t* CXFA_FMLexer::Identifiers(CXFA_FMToken* t, const wchar_t* p) {
 }
 
 const wchar_t* CXFA_FMLexer::Comment(const wchar_t* p) {
-  ++p;
-
-  if (p > m_end)
-    return p;
-
-  unsigned ch = *p;
-  while (ch) {
-    ++p;
-    if (ch == L'\r')
-      return p;
-    if (ch == L'\n') {
+  p++;
+  while (p <= m_end && *p) {
+    if (*p == L'\r')
+      return ++p;
+    if (*p == L'\n') {
       ++m_uCurrentLine;
-      return p;
+      return ++p;
     }
-    if (p > m_end)
-      return p;
-    ch = *p;
+    ++p;
   }
   return p;
 }
diff --git a/xfa/fxfa/fm2js/cxfa_fmlexer.h b/xfa/fxfa/fm2js/cxfa_fmlexer.h
index 3b5b3727e7..11076f8d72 100644
--- a/xfa/fxfa/fm2js/cxfa_fmlexer.h
+++ b/xfa/fxfa/fm2js/cxfa_fmlexer.h
@@ -123,8 +123,8 @@ class CXFA_FMLexer {
   const wchar_t* String(CXFA_FMToken* t, const wchar_t* p);
   const wchar_t* Identifiers(CXFA_FMToken* t, const wchar_t* p);
   const wchar_t* Comment(const wchar_t* p);
+
   XFA_FM_TOKEN IsKeyword(const CFX_WideStringC& p);
-  std::unique_ptr<CXFA_FMToken> Scan();
 
   const wchar_t* m_ptr;
   const wchar_t* const m_end;