Add a parser for Link headers

Source/core/loader/LinkHeader.cpp

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "config.h"
+#include "core/loader/LinkHeader.h"
+
+#include "platform/ParsingUtilities.h"
+
+namespace blink {
+
+// LWSP definition in https://www.ietf.org/rfc/rfc0822.txt
+template <typename CharType>
+static bool isWhitespace(CharType chr)
+{
+    return (chr == ' ') || (chr == '\t');
+}
+
+template <typename CharType>
+static bool isValidURLChar(CharType chr)
+{
+    return !isWhitespace(chr) && chr != '>';
+}
+
+template <typename CharType>
+static bool isValidParameterNameChar(CharType chr)
+{
+    return !isWhitespace(chr) && chr != '=';
+}
+
+template <typename CharType>
+static bool isValidParameterValueChar(CharType chr)
+{
+    return !isWhitespace(chr) && chr != ';';
+}
+
+// Before:
+//
+// <cat.jpg>; rel=preload
+// ^                     ^
+// position              end
+//
+// After (if successful: otherwise the method returns false)
+//
+// <cat.jpg>; rel=preload
+//          ^            ^
+//          position     end
+template <typename CharType>
+static bool parseURL(CharType*& position, CharType* end, String& url)
+{
+    skipWhile<CharType, isWhitespace>(position, end);
+    if (!skipExactly<CharType>(position, end, '<'))
+        return false;
+    skipWhile<CharType, isWhitespace>(position, end);
+
+    CharType* urlStart = position;
+    skipWhile<CharType, isValidURLChar>(position, end);
+    CharType* urlEnd = position;
+    skipUntil<CharType>(position, end, '>');
+    if (!skipExactly<CharType>(position, end, '>'))
+        return false;
+
+    url = String(urlStart, urlEnd - urlStart);
+    return true;
+}
+
+// Before:
+//
+// <cat.jpg>; rel=preload
+//          ^            ^
+//          position     end
+//
+// After (if successful: otherwise the method returns false, and modifies the isValid boolean accordingly)
+//
+// <cat.jpg>; rel=preload
+//            ^          ^
+//            position  end
+template <typename CharType>
+static bool parseParameterDelimiter(CharType*& position, CharType* end, bool& isValidDelimiter)
+{
+    isValidDelimiter = true;
+    skipWhile<CharType, isWhitespace>(position, end);
+    if (!skipExactly<CharType>(position, end, ';') && (position < end)) {
+        isValidDelimiter = false;
+        return false;
+    }
+    skipWhile<CharType, isWhitespace>(position, end);
+    if (position == end)
+        return false;
+    return true;
+}
+
+static LinkHeader::LinkParameterName paramterNameFromString(String name)
+{
+    // FIXME: Add support for more header parameters as neccessary.
+    if (name == "rel")
+        return LinkHeader::LinkParameterRel;
+    return LinkHeader::LinkParameterUnknown;
+}
+
+// Before:
+//
+// <cat.jpg>; rel=preload
+//            ^          ^
+//            position   end
+//
+// After (if successful: otherwise the method returns false)
+//
+// <cat.jpg>; rel=preload
+//                ^      ^
+//            position  end
+template <typename CharType>
+static bool parseParameterName(CharType*& position, CharType* end, LinkHeader::LinkParameterName& name)
+{
+    CharType* nameStart = position;
+    skipWhile<CharType, isValidParameterNameChar>(position, end);
+    CharType* nameEnd = position;
+    skipWhile<CharType, isWhitespace>(position, end);
+    if (!skipExactly<CharType>(position, end, '='))
+        return false;
+    skipWhile<CharType, isWhitespace>(position, end);
+    name = paramterNameFromString(String(nameStart, nameEnd - nameStart));
+    return true;
+}
+
+// Before:
+//
+// <cat.jpg>; rel=preload; foo=bar
+//                ^               ^
+//            position            end
+//
+// After (if successful: otherwise the method returns false)
+//
+// <cat.jpg>; rel=preload; foo=bar
+//                       ^        ^
+//                   position     end
+template <typename CharType>
+static bool parseParameterValue(CharType*& position, CharType* end, String& value)
+{
+    CharType* valueStart = position;
+    skipWhile<CharType, isValidParameterValueChar>(position, end);
+    CharType* valueEnd = position;
+    skipWhile<CharType, isWhitespace>(position, end);
+    if ((valueEnd == valueStart) || (*position != ';' && position != end))
+        return false;
+    value = String(valueStart, valueEnd - valueStart);
+    return true;
+}
+
+void LinkHeader::setValue(LinkParameterName name, String value)
+{
+    // FIXME: Add support for more header parameters as neccessary.
+    if (name == LinkParameterRel)
+        m_rel = value;
+}
+
+template <typename CharType>
+bool LinkHeader::init(CharType* headerValue, unsigned len)
+{
+    CharType* position = headerValue;
+    CharType* end = headerValue + len;
+
+    if (!parseURL(position, end, m_url))
+        return false;
+
+    while (position < end) {
+        bool isValidDelimiter;
+        if (!parseParameterDelimiter(position, end, isValidDelimiter))
+            return isValidDelimiter;
+
+        LinkParameterName parameterName;
+        if (!parseParameterName(position, end, parameterName))
+            return false;
+
+        String parameterValue;
+        if (!parseParameterValue(position, end, parameterValue))
+            return false;
+
+        setValue(parameterName, parameterValue);
+    }
+
+    return true;
+}
+
+LinkHeader::LinkHeader(const String& header)
+{
+    if (header.isNull()) {
+        m_isValid = false;
+        return;
+    }
+
+    if (header.is8Bit())
+        m_isValid = init(header.characters8(), header.length());
+    else
+        m_isValid = init(header.characters16(), header.length());
+}
+
+}