Introduce VTTScanner - a parser helper for various VTT parsing needs

Source/core/html/track/vtt/VTTScanner.cpp

Index: Source/core/html/track/vtt/VTTScanner.cpp
diff --git a/Source/core/html/track/vtt/VTTScanner.cpp b/Source/core/html/track/vtt/VTTScanner.cpp
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+/*
+ * 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:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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.
+ * 3. Neither the name of Opera Software ASA 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 HOLDER 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.
+ */
+
+#include "config.h"
+#include "core/html/track/vtt/VTTScanner.h"
+
+namespace WebCore {
+
+VTTScanner::VTTScanner(const String& line) : m_is8Bit(line.is8Bit())
+{
+    if (m_is8Bit) {
+        m_data.characters8 = line.characters8();
+        m_end.characters8 = m_data.characters8 + line.length();
+    } else {
+        m_data.characters16 = line.characters16();
+        m_end.characters16 = m_data.characters16 + line.length();
+    }
+}
+
+bool VTTScanner::scan(char c)
+{
+    if (!match(c))
+        return false;
+    advance();
+    return true;
+}
+
+bool VTTScanner::scan(const LChar* characters, size_t charactersCount)
+{
+    unsigned matchLength = m_is8Bit ? m_end.characters8 - m_data.characters8 : m_end.characters16 - m_data.characters16;
+    if (matchLength < charactersCount)
+        return false;
+    bool matched;
+    if (m_is8Bit)
+        matched = WTF::equal(m_data.characters8, characters, charactersCount);
+    else
+        matched = WTF::equal(m_data.characters16, characters, charactersCount);
+    if (matched)
+        advance(charactersCount);
+    return matched;
+}
+
+String VTTScanner::restOfInputAsString()
+{
+    ASSERT(position() <= end());
+    String s;
+    if (m_is8Bit)
+        s = String(m_data.characters8, m_end.characters8 - m_data.characters8);
+    else
+        s = String(m_data.characters16, m_end.characters16 - m_data.characters16);
+    seekTo(end());
+    return s;
+}
+
+unsigned VTTScanner::scanDigits(int& number)
+{
+    Run runOfDigits = collectWhile<isASCIIDigit>();
+    if (runOfDigits.isEmpty()) {
+        number = 0;
+        return 0;
+    }
+    bool validNumber;
+    size_t numDigits = runOfDigits.length();
+    if (m_is8Bit)
+        number = charactersToInt(m_data.characters8, numDigits, &validNumber);
+    else
+        number = charactersToInt(m_data.characters16, numDigits, &validNumber);
+
+    // Since we know that scanDigits only scanned valid (ASCII) digits (and
+    // hence that's what got passed to charactersToInt()), the remaining
+    // failure mode for charactersToInt() is overflow, so if |validNumber| is
+    // not true, then set |number| to the maximum int value.
+    if (!validNumber)
+        number = std::numeric_limits<int>::max();
+    // Consume the digits.
+    seekTo(runOfDigits.end());
+    return numDigits;
+}
+
+}