Make FilePiece::ReadLine() skip carriage returns.

By default, ReadLine() will not include a trailing carriage return in
the line it returns.  This behaviour is optional, however.

util/file_piece.cc

@@ -65,12 +65,17 @@ FilePiece::FilePiece(std::istream &stream, const char *name, std::size_t min_buf
 
 FilePiece::~FilePiece() {}
 
-StringPiece FilePiece::ReadLine(char delim) {
+StringPiece FilePiece::ReadLine(char delim, bool strip_cr) {
   std::size_t skip = 0;
   while (true) {
     for (const char *i = position_ + skip; i < position_end_; ++i) {
       if (*i == delim) {
-        StringPiece ret(position_, i - position_);
+        // End of line.
+        // Take 1 byte off the end if it's an unwanted carriage return.
+        const std::size_t subtract_cr = (
+            (strip_cr && i > position_ && *(i - 1) == '\r') ?
+            1 : 0);
+        StringPiece ret(position_, i - position_ - subtract_cr);
         position_ = i + 1;
         return ret;
       }
@@ -86,9 +91,9 @@ StringPiece FilePiece::ReadLine(char delim) {
   }
 }
 
-bool FilePiece::ReadLineOrEOF(StringPiece &to, char delim) {
+bool FilePiece::ReadLineOrEOF(StringPiece &to, char delim, bool strip_cr) {
   try {
-    to = ReadLine(delim);
+    to = ReadLine(delim, strip_cr);
   } catch (const util::EndOfFileException &e) { return false; }
   return true;
 }

util/file_piece.hh

@@ -55,7 +55,7 @@ class FilePiece {
       return Consume(FindDelimiterOrEOF(delim));
     }
 
-    // Read word until the line or file ends.
+    /// Read word until the line or file ends.
     bool ReadWordSameLine(StringPiece &to, const bool *delim = kSpaces) {
       assert(delim[static_cast<unsigned char>('\n')]);
       // Skip non-enter spaces.
@@ -75,12 +75,30 @@ class FilePiece {
       return true;
     }
 
-    // Unlike ReadDelimited, this includes leading spaces and consumes the delimiter.
-    // It is similar to getline in that way.
-    StringPiece ReadLine(char delim = '\n');
-
-    // Doesn't throw EndOfFileException, just returns false.
-    bool ReadLineOrEOF(StringPiece &to, char delim = '\n');
+    /** Read a line of text from the file.
+     *
+     * Unlike ReadDelimited, this includes leading spaces and consumes the
+     * delimiter.   It is similar to getline in that way.
+     *
+     * If strip_cr is true, any trailing carriate return (as would be found on
+     * a file written on Windows) will be left out of the returned line.
+     *
+     * Throws EndOfFileException if the end of the file is encountered.  If the
+     * file does not end in a newline, this could mean that the last line is
+     * never read.
+     */
+    StringPiece ReadLine(char delim = '\n', bool strip_cr = true);
+
+    /** Read a line of text from the file, or return false on EOF.
+     *
+     * This is like ReadLine, except it returns false where ReadLine throws
+     * EndOfFileException.  Like ReadLine it may not read the last line in the
+     * file if the file does not end in a newline.
+     *
+     * If strip_cr is true, any trailing carriate return (as would be found on
+     * a file written on Windows) will be left out of the returned line.
+     */
+    bool ReadLineOrEOF(StringPiece &to, char delim = '\n', bool strip_cr = false);
 
     float ReadFloat();
     double ReadDouble();