Handle buffer boundaries in the WebVTT parser

Source/core/html/track/BufferedLineReader.h

+/*
+ * Copyright (C) 2013, Opera Software ASA. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef BufferedLineReader_h
+#define BufferedLineReader_h
+
+#include "platform/text/SegmentedString.h"
+#include "wtf/text/StringBuilder.h"
+
+namespace WebCore {
+
+// Line collection helper for the WebVTT Parser.
+//
+// Converts a stream of data (== a sequence of Strings) into a set of
+// lines. CR, LR or CRLF are considered linebreaks. Normalizes NULs (U+0000)
+// to 'REPLACEMENT CHARACTER' (U+FFFD) and does not return the linebreaks as
+// part of the result.
+class BufferedLineReader {
+    WTF_MAKE_NONCOPYABLE(BufferedLineReader);
+public:
+    BufferedLineReader()
+        : m_endOfStream(false)
+        , m_maybeSkipLF(false) { }
+
+    // Append data to the internal buffer.
+    void append(const String& data)
+    {
+        ASSERT(!m_endOfStream);
+        m_buffer.append(SegmentedString(data));
+    }
+
+    // Indicate that no more data will be appended. This will cause any
+    // potentially "unterminated" line to be returned from getLine.
+    void setEndOfStream() { m_endOfStream = true; }
+
+    // Attempt to read a line from the internal buffer (fed via append).
+    // If successful, true is returned and |line| is set to the line that was
+    // read. If no line could be read false is returned.
+    bool getLine(String& line);
+
+    // Returns true if EOS has been reached proper.
+    bool isAtEndOfStream() const { return m_endOfStream && m_buffer.isEmpty(); }
+
+private:
+    // Consume the next character the buffer if it is the character |c|.
+    void scanCharacter(UChar c)
+    {
+        ASSERT(!m_buffer.isEmpty());
+        if (m_buffer.currentChar() == c)
+            m_buffer.advance();
+    }
+
+    SegmentedString m_buffer;
+    StringBuilder m_lineBuffer;
+    bool m_endOfStream;
+    bool m_maybeSkipLF;
+};
+
+} // namespace WebCore
+
+#endif