/*
 * Copyright (C) 2004, 2007, 2008, 2011, 2012 Apple Inc. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 APPLE COMPUTER, INC. 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 "KURL.h"

#include "DecodeEscapeSequences.h"
#include "TextEncoding.h"
#include <stdio.h>
#include <wtf/HashMap.h>
#include <wtf/HexNumber.h>
#include <wtf/StdLibExtras.h>
#include <wtf/text/CString.h>
#include <wtf/text/StringBuilder.h>
#include <wtf/text/StringHash.h>

#if USE(ICU_UNICODE)
#include <unicode/uidna.h>
#elif USE(QT4_UNICODE)
#include <QUrl>
#elif USE(GLIB_UNICODE)
#include <glib.h>
#include "GOwnPtr.h"
#endif

// FIXME: This file makes too much use of the + operator on String.
// We either have to optimize that operator so it doesn't involve
// so many allocations, or change this to use StringBuffer instead.

using namespace std;
using namespace WTF;

namespace WebCore {

typedef Vector<char, 512> CharBuffer;
typedef Vector<UChar, 512> UCharBuffer;

static const unsigned maximumValidPortNumber = 0xFFFE;
static const unsigned invalidPortNumber = 0xFFFF;

static inline bool isLetterMatchIgnoringCase(UChar character, char lowercaseLetter)
{
    ASSERT(isASCIILower(lowercaseLetter));
    return (character | 0x20) == lowercaseLetter;
}

#if !USE(GOOGLEURL)

static const char wsScheme[] = {'w', 's'};
static const char ftpScheme[] = {'f', 't', 'p'};
static const char ftpPort[] = {'2', '1'};
static const char wssScheme[] = {'w', 's', 's'};
static const char fileScheme[] = {'f', 'i', 'l', 'e'};
static const char httpScheme[] = {'h', 't', 't', 'p'};
static const char httpPort[] = {'8', '0'};
static const char httpsScheme[] = {'h', 't', 't', 'p', 's'};
static const char httpsPort[] = {'4', '4', '3'};
static const char gopherScheme[] = {'g', 'o', 'p', 'h', 'e', 'r'};
static const char gopherPort[] = {'7', '0'};

static inline bool isLetterMatchIgnoringCase(char character, char lowercaseLetter)
{
    ASSERT(isASCIILower(lowercaseLetter));
    return (character | 0x20) == lowercaseLetter;
}

enum URLCharacterClasses {
    // alpha 
    SchemeFirstChar = 1 << 0,

    // ( alpha | digit | "+" | "-" | "." )
    SchemeChar = 1 << 1,

    // mark        = "-" | "_" | "." | "!" | "~" | "*" | "'" | "(" | ")"
    // unreserved  = alphanum | mark
    // ( unreserved | escaped | ";" | ":" | "&" | "=" | "+" | "$" | "," )
    UserInfoChar = 1 << 2,

    // alnum | "." | "-" | "%"
    // The above is what the specification says, but we are lenient to
    // match existing practice and also allow:
    // "_"
    HostnameChar = 1 << 3,

    // hexdigit | ":" | "%"
    IPv6Char = 1 << 4,

    // "#" | "?" | "/" | nul
    PathSegmentEndChar = 1 << 5,

    // not allowed in path
    BadChar = 1 << 6
};

static const unsigned char characterClassTable[256] = {
    /* 0 nul */ PathSegmentEndChar,    /* 1 soh */ BadChar,
    /* 2 stx */ BadChar,    /* 3 etx */ BadChar,
    /* 4 eot */ BadChar,    /* 5 enq */ BadChar,    /* 6 ack */ BadChar,    /* 7 bel */ BadChar,
    /* 8 bs */ BadChar,     /* 9 ht */ BadChar,     /* 10 nl */ BadChar,    /* 11 vt */ BadChar,
    /* 12 np */ BadChar,    /* 13 cr */ BadChar,    /* 14 so */ BadChar,    /* 15 si */ BadChar,
    /* 16 dle */ BadChar,   /* 17 dc1 */ BadChar,   /* 18 dc2 */ BadChar,   /* 19 dc3 */ BadChar,
    /* 20 dc4 */ BadChar,   /* 21 nak */ BadChar,   /* 22 syn */ BadChar,   /* 23 etb */ BadChar,
    /* 24 can */ BadChar,   /* 25 em */ BadChar,    /* 26 sub */ BadChar,   /* 27 esc */ BadChar,
    /* 28 fs */ BadChar,    /* 29 gs */ BadChar,    /* 30 rs */ BadChar,    /* 31 us */ BadChar,
    /* 32 sp */ BadChar,    /* 33  ! */ UserInfoChar,
    /* 34  " */ BadChar,    /* 35  # */ PathSegmentEndChar | BadChar,
    /* 36  $ */ UserInfoChar,    /* 37  % */ UserInfoChar | HostnameChar | IPv6Char | BadChar,
    /* 38  & */ UserInfoChar,    /* 39  ' */ UserInfoChar,
    /* 40  ( */ UserInfoChar,    /* 41  ) */ UserInfoChar,
    /* 42  * */ UserInfoChar,    /* 43  + */ SchemeChar | UserInfoChar,
    /* 44  , */ UserInfoChar,
    /* 45  - */ SchemeChar | UserInfoChar | HostnameChar,
    /* 46  . */ SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 47  / */ PathSegmentEndChar,
    /* 48  0 */ SchemeChar | UserInfoChar | HostnameChar | IPv6Char, 
    /* 49  1 */ SchemeChar | UserInfoChar | HostnameChar | IPv6Char,    
    /* 50  2 */ SchemeChar | UserInfoChar | HostnameChar | IPv6Char, 
    /* 51  3 */ SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 52  4 */ SchemeChar | UserInfoChar | HostnameChar | IPv6Char, 
    /* 53  5 */ SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 54  6 */ SchemeChar | UserInfoChar | HostnameChar | IPv6Char, 
    /* 55  7 */ SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 56  8 */ SchemeChar | UserInfoChar | HostnameChar | IPv6Char, 
    /* 57  9 */ SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 58  : */ UserInfoChar | IPv6Char,    /* 59  ; */ UserInfoChar,
    /* 60  < */ BadChar,    /* 61  = */ UserInfoChar,
    /* 62  > */ BadChar,    /* 63  ? */ PathSegmentEndChar | BadChar,
    /* 64  @ */ 0,
    /* 65  A */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar | IPv6Char,    
    /* 66  B */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 67  C */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 68  D */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 69  E */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 70  F */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 71  G */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 72  H */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 73  I */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 74  J */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 75  K */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 76  L */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 77  M */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 78  N */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 79  O */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 80  P */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 81  Q */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 82  R */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 83  S */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 84  T */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 85  U */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 86  V */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 87  W */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 88  X */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar, 
    /* 89  Y */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 90  Z */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 91  [ */ 0,
    /* 92  \ */ 0,    /* 93  ] */ 0,
    /* 94  ^ */ 0,
    /* 95  _ */ UserInfoChar | HostnameChar,
    /* 96  ` */ 0,
    /* 97  a */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 98  b */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar | IPv6Char, 
    /* 99  c */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 100  d */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar | IPv6Char, 
    /* 101  e */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar | IPv6Char,
    /* 102  f */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar | IPv6Char, 
    /* 103  g */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 104  h */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar, 
    /* 105  i */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 106  j */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar, 
    /* 107  k */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 108  l */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar, 
    /* 109  m */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 110  n */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar, 
    /* 111  o */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 112  p */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar, 
    /* 113  q */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 114  r */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar, 
    /* 115  s */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 116  t */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar, 
    /* 117  u */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 118  v */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar, 
    /* 119  w */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 120  x */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar, 
    /* 121  y */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar,
    /* 122  z */ SchemeFirstChar | SchemeChar | UserInfoChar | HostnameChar, 
    /* 123  { */ 0,
    /* 124  | */ 0,   /* 125  } */ 0,   /* 126  ~ */ UserInfoChar,   /* 127 del */ BadChar,
    /* 128 */ BadChar, /* 129 */ BadChar, /* 130 */ BadChar, /* 131 */ BadChar,
    /* 132 */ BadChar, /* 133 */ BadChar, /* 134 */ BadChar, /* 135 */ BadChar,
    /* 136 */ BadChar, /* 137 */ BadChar, /* 138 */ BadChar, /* 139 */ BadChar,
    /* 140 */ BadChar, /* 141 */ BadChar, /* 142 */ BadChar, /* 143 */ BadChar,
    /* 144 */ BadChar, /* 145 */ BadChar, /* 146 */ BadChar, /* 147 */ BadChar,
    /* 148 */ BadChar, /* 149 */ BadChar, /* 150 */ BadChar, /* 151 */ BadChar,
    /* 152 */ BadChar, /* 153 */ BadChar, /* 154 */ BadChar, /* 155 */ BadChar,
    /* 156 */ BadChar, /* 157 */ BadChar, /* 158 */ BadChar, /* 159 */ BadChar,
    /* 160 */ BadChar, /* 161 */ BadChar, /* 162 */ BadChar, /* 163 */ BadChar,
    /* 164 */ BadChar, /* 165 */ BadChar, /* 166 */ BadChar, /* 167 */ BadChar,
    /* 168 */ BadChar, /* 169 */ BadChar, /* 170 */ BadChar, /* 171 */ BadChar,
    /* 172 */ BadChar, /* 173 */ BadChar, /* 174 */ BadChar, /* 175 */ BadChar,
    /* 176 */ BadChar, /* 177 */ BadChar, /* 178 */ BadChar, /* 179 */ BadChar,
    /* 180 */ BadChar, /* 181 */ BadChar, /* 182 */ BadChar, /* 183 */ BadChar,
    /* 184 */ BadChar, /* 185 */ BadChar, /* 186 */ BadChar, /* 187 */ BadChar,
    /* 188 */ BadChar, /* 189 */ BadChar, /* 190 */ BadChar, /* 191 */ BadChar,
    /* 192 */ BadChar, /* 193 */ BadChar, /* 194 */ BadChar, /* 195 */ BadChar,
    /* 196 */ BadChar, /* 197 */ BadChar, /* 198 */ BadChar, /* 199 */ BadChar,
    /* 200 */ BadChar, /* 201 */ BadChar, /* 202 */ BadChar, /* 203 */ BadChar,
    /* 204 */ BadChar, /* 205 */ BadChar, /* 206 */ BadChar, /* 207 */ BadChar,
    /* 208 */ BadChar, /* 209 */ BadChar, /* 210 */ BadChar, /* 211 */ BadChar,
    /* 212 */ BadChar, /* 213 */ BadChar, /* 214 */ BadChar, /* 215 */ BadChar,
    /* 216 */ BadChar, /* 217 */ BadChar, /* 218 */ BadChar, /* 219 */ BadChar,
    /* 220 */ BadChar, /* 221 */ BadChar, /* 222 */ BadChar, /* 223 */ BadChar,
    /* 224 */ BadChar, /* 225 */ BadChar, /* 226 */ BadChar, /* 227 */ BadChar,
    /* 228 */ BadChar, /* 229 */ BadChar, /* 230 */ BadChar, /* 231 */ BadChar,
    /* 232 */ BadChar, /* 233 */ BadChar, /* 234 */ BadChar, /* 235 */ BadChar,
    /* 236 */ BadChar, /* 237 */ BadChar, /* 238 */ BadChar, /* 239 */ BadChar,
    /* 240 */ BadChar, /* 241 */ BadChar, /* 242 */ BadChar, /* 243 */ BadChar,
    /* 244 */ BadChar, /* 245 */ BadChar, /* 246 */ BadChar, /* 247 */ BadChar,
    /* 248 */ BadChar, /* 249 */ BadChar, /* 250 */ BadChar, /* 251 */ BadChar,
    /* 252 */ BadChar, /* 253 */ BadChar, /* 254 */ BadChar, /* 255 */ BadChar
};

static int copyPathRemovingDots(char* dst, const char* src, int srcStart, int srcEnd);
static void encodeRelativeString(const String& rel, const TextEncoding&, CharBuffer& ouput);
static String substituteBackslashes(const String&);

static inline bool isSchemeFirstChar(char c) { return characterClassTable[static_cast<unsigned char>(c)] & SchemeFirstChar; }
static inline bool isSchemeFirstChar(UChar c) { return c <= 0xff && (characterClassTable[c] & SchemeFirstChar); }
static inline bool isSchemeChar(char c) { return characterClassTable[static_cast<unsigned char>(c)] & SchemeChar; }
static inline bool isSchemeChar(UChar c) { return c <= 0xff && (characterClassTable[c] & SchemeChar); }
static inline bool isUserInfoChar(unsigned char c) { return characterClassTable[c] & UserInfoChar; }
static inline bool isHostnameChar(unsigned char c) { return characterClassTable[c] & HostnameChar; }
static inline bool isIPv6Char(unsigned char c) { return characterClassTable[c] & IPv6Char; }
static inline bool isPathSegmentEndChar(char c) { return characterClassTable[static_cast<unsigned char>(c)] & PathSegmentEndChar; }
static inline bool isPathSegmentEndChar(UChar c) { return c <= 0xff && (characterClassTable[c] & PathSegmentEndChar); }
static inline bool isBadChar(unsigned char c) { return characterClassTable[c] & BadChar; }
    
static inline bool isSchemeCharacterMatchIgnoringCase(char character, char schemeCharacter)
{
    ASSERT(isSchemeChar(character));
    ASSERT(schemeCharacter & 0x20);
    ASSERT(isASCIILower(schemeCharacter) || (!isASCIIUpper(schemeCharacter) && isSchemeChar(schemeCharacter)));
    return (character | 0x20) == schemeCharacter;
}

// Copies the source to the destination, assuming all the source characters are
// ASCII. The destination buffer must be large enough. Null characters are allowed
// in the source string, and no attempt is made to null-terminate the result.
static void copyASCII(const String& string, char* dest)
{
    if (string.isEmpty())
        return;

    if (string.is8Bit())
        memcpy(dest, string.characters8(), string.length());
    else {
        const UChar* src = string.characters16();
        size_t length = string.length();
        for (size_t i = 0; i < length; i++)
            dest[i] = static_cast<char>(src[i]);
    }
}

static void appendASCII(const String& base, const char* rel, size_t len, CharBuffer& buffer)
{
    buffer.resize(base.length() + len + 1);
    copyASCII(base, buffer.data());
    memcpy(buffer.data() + base.length(), rel, len);
    buffer[buffer.size() - 1] = '\0';
}

// FIXME: Move to PlatformString.h eventually.
// Returns the index of the first index in string |s| of any of the characters
// in |toFind|. |toFind| should be a null-terminated string, all characters up
// to the null will be searched. Returns int if not found.
static int findFirstOf(const UChar* s, int sLen, int startPos, const char* toFind)
{
    for (int i = startPos; i < sLen; i++) {
        const char* cur = toFind;
        while (*cur) {
            if (s[i] == *(cur++))
                return i;
        }
    }
    return -1;
}

static inline void checkEncodedString(const String& url)
{
    ASSERT_UNUSED(url, url.containsOnlyASCII());
    ASSERT_UNUSED(url, url.isEmpty() || isSchemeFirstChar(url[0]));
}

inline bool KURL::protocolIs(const String& string, const char* protocol)
{
    return WebCore::protocolIs(string, protocol);
}

void KURL::invalidate()
{
    m_isValid = false;
    m_protocolIsInHTTPFamily = false;
    m_schemeEnd = 0;
    m_userStart = 0;
    m_userEnd = 0;
    m_passwordEnd = 0;
    m_hostEnd = 0;
    m_portEnd = 0;
    m_pathEnd = 0;
    m_pathAfterLastSlash = 0;
    m_queryEnd = 0;
    m_fragmentEnd = 0;
}

KURL::KURL(ParsedURLStringTag, const String& url)
{
    parse(url);
    ASSERT(url == m_string);
}

KURL::KURL(const KURL& base, const String& relative)
{
    init(base, relative, UTF8Encoding());
}

KURL::KURL(const KURL& base, const String& relative, const TextEncoding& encoding)
{
    // For UTF-{7,16,32}, we want to use UTF-8 for the query part as 
    // we do when submitting a form. A form with GET method
    // has its contents added to a URL as query params and it makes sense
    // to be consistent.
    init(base, relative, encoding.encodingForFormSubmission());
}

static bool shouldTrimFromURL(unsigned char c)
{
    // Browsers ignore leading/trailing whitespace and control
    // characters from URLs.  Note that c is an *unsigned* char here
    // so this comparison should only catch control characters.
    return c <= ' ';
}

void KURL::init(const KURL& base, const String& relative, const TextEncoding& encoding)
{
    // Allow resolutions with a null or empty base URL, but not with any other invalid one.
    // FIXME: Is this a good rule?
    if (!base.m_isValid && !base.isEmpty()) {
        m_string = relative;
        invalidate();
        return;
    }

    // For compatibility with Win IE, treat backslashes as if they were slashes,
    // as long as we're not dealing with javascript: or data: URLs.
    String rel = relative;
    if (rel.contains('\\') && !(protocolIsJavaScript(rel) || protocolIs(rel, "data")))
        rel = substituteBackslashes(rel);

    bool allASCII = rel.containsOnlyASCII();
    CharBuffer strBuffer;
    char* str;
    size_t len;
    if (allASCII) {
        len = rel.length();
        strBuffer.resize(len + 1);
        copyASCII(rel, strBuffer.data());
        strBuffer[len] = 0;
        str = strBuffer.data();
    } else {
        encodeRelativeString(rel, encoding, strBuffer);
        str = strBuffer.data();
        len = strlen(str);
    }

    // Get rid of leading whitespace and control characters.
    while (len && shouldTrimFromURL(*str)) {
        str++;
        --len;
    }

    // Get rid of trailing whitespace and control characters.
    while (len && shouldTrimFromURL(str[len - 1]))
        str[--len] = '\0';

    // According to the RFC, the reference should be interpreted as an
    // absolute URI if possible, using the "leftmost, longest"
    // algorithm. If the URI reference is absolute it will have a
    // scheme, meaning that it will have a colon before the first
    // non-scheme element.
    bool absolute = false;
    char* p = str;
    if (isSchemeFirstChar(*p)) {
        ++p;
        while (isSchemeChar(*p)) {
            ++p;
        }
        if (*p == ':') {
            if (p[1] != '/' && equalIgnoringCase(base.protocol(), String(str, p - str)) && base.isHierarchical())
                str = p + 1;
            else
                absolute = true;
        }
    }

    CharBuffer parseBuffer;

    if (absolute) {
        parse(str, &relative);
    } else {
        // If the base is empty or opaque (e.g. data: or javascript:), then the URL is invalid
        // unless the relative URL is a single fragment.
        if (!base.isHierarchical()) {
            if (str[0] == '#') {
                appendASCII(base.m_string.left(base.m_queryEnd), str, len, parseBuffer);
                parse(parseBuffer.data(), &relative);
            } else {
                m_string = relative;
                invalidate();
            }
            return;
        }

        switch (str[0]) {
        case '\0':
            // The reference is empty, so this is a reference to the same document with any fragment identifier removed.
            *this = base;
            removeFragmentIdentifier();
            break;
        case '#': {
            // must be fragment-only reference
            appendASCII(base.m_string.left(base.m_queryEnd), str, len, parseBuffer);
            parse(parseBuffer.data(), &relative);
            break;
        }
        case '?': {
            // query-only reference, special case needed for non-URL results
            appendASCII(base.m_string.left(base.m_pathEnd), str, len, parseBuffer);
            parse(parseBuffer.data(), &relative);
            break;
        }
        case '/':
            // must be net-path or absolute-path reference
            if (str[1] == '/') {
                // net-path
                appendASCII(base.m_string.left(base.m_schemeEnd + 1), str, len, parseBuffer);
                parse(parseBuffer.data(), &relative);
            } else {
                // abs-path
                appendASCII(base.m_string.left(base.m_portEnd), str, len, parseBuffer);
                parse(parseBuffer.data(), &relative);
            }
            break;
        default:
            {
                // must be relative-path reference

                // Base part plus relative part plus one possible slash added in between plus terminating \0 byte.
                const size_t bufferSize = base.m_pathEnd + 1 + len + 1;
                parseBuffer.resize(bufferSize);

                char* bufferPos = parseBuffer.data();
                char* bufferStart = bufferPos;

                // first copy everything before the path from the base
                CharBuffer baseStringBuffer(base.m_string.length());
                copyASCII(base.m_string, baseStringBuffer.data());
                const char* baseString = baseStringBuffer.data();
                const char* baseStringStart = baseString;
                const char* pathStart = baseStringStart + base.m_portEnd;
                while (baseStringStart < pathStart)
                    *bufferPos++ = *baseStringStart++;
                char* bufferPathStart = bufferPos;

                // now copy the base path
                const char* baseStringEnd = baseString + base.m_pathEnd;

                // go back to the last slash
                while (baseStringEnd > baseStringStart && baseStringEnd[-1] != '/')
                    baseStringEnd--;

                if (baseStringEnd == baseStringStart) {
                    // no path in base, add a path separator if necessary
                    if (base.m_schemeEnd + 1 != base.m_pathEnd && *str && *str != '?' && *str != '#')
                        *bufferPos++ = '/';
                } else {
                    bufferPos += copyPathRemovingDots(bufferPos, baseStringStart, 0, baseStringEnd - baseStringStart);
                }

                const char* relStringStart = str;
                const char* relStringPos = relStringStart;

                while (*relStringPos && *relStringPos != '?' && *relStringPos != '#') {
                    if (relStringPos[0] == '.' && bufferPos[-1] == '/') {
                        if (isPathSegmentEndChar(relStringPos[1])) {
                            // skip over "." segment
                            relStringPos += 1;
                            if (relStringPos[0] == '/')
                                relStringPos++;
                            continue;
                        } else if (relStringPos[1] == '.' && isPathSegmentEndChar(relStringPos[2])) {
                            // skip over ".." segment and rewind the last segment
                            // the RFC leaves it up to the app to decide what to do with excess
                            // ".." segments - we choose to drop them since some web content
                            // relies on this.
                            relStringPos += 2;
                            if (relStringPos[0] == '/')
                                relStringPos++;
                            if (bufferPos > bufferPathStart + 1)
                                bufferPos--;
                            while (bufferPos > bufferPathStart + 1  && bufferPos[-1] != '/')
                                bufferPos--;
                            continue;
                        }
                    }

                    *bufferPos = *relStringPos;
                    relStringPos++;
                    bufferPos++;
                }

                // all done with the path work, now copy any remainder
                // of the relative reference; this will also add a null terminator
                strncpy(bufferPos, relStringPos, bufferSize - (bufferPos - bufferStart));

                parse(parseBuffer.data(), &relative);

                ASSERT(strlen(parseBuffer.data()) + 1 <= parseBuffer.size());
                break;
            }
        }
    }
}

KURL KURL::copy() const
{
    KURL result = *this;
    result.m_string = result.m_string.isolatedCopy();
    return result;
}

bool KURL::hasPath() const
{
    return m_pathEnd != m_portEnd;
}

String KURL::lastPathComponent() const
{
    if (!hasPath())
        return String();

    unsigned end = m_pathEnd - 1;
    if (m_string[end] == '/')
        --end;

    size_t start = m_string.reverseFind('/', end);
    if (start < static_cast<unsigned>(m_portEnd))
        return String();
    ++start;

    return m_string.substring(start, end - start + 1);
}

String KURL::protocol() const
{
    return m_string.left(m_schemeEnd);
}

String KURL::host() const
{
    int start = hostStart();
    return decodeURLEscapeSequences(m_string.substring(start, m_hostEnd - start));
}

unsigned short KURL::port() const
{
    // We return a port of 0 if there is no port specified. This can happen in two situations:
    // 1) The URL contains no colon after the host name and before the path component of the URL.
    // 2) The URL contains a colon but there's no port number before the path component of the URL begins.
    if (m_hostEnd == m_portEnd || m_hostEnd == m_portEnd - 1)
        return 0;

    const UChar* stringData = m_string.characters();
    bool ok = false;
    unsigned number = charactersToUIntStrict(stringData + m_hostEnd + 1, m_portEnd - m_hostEnd - 1, &ok);
    if (!ok || number > maximumValidPortNumber)
        return invalidPortNumber;
    return number;
}

String KURL::pass() const
{
    if (m_passwordEnd == m_userEnd)
        return String();

    return decodeURLEscapeSequences(m_string.substring(m_userEnd + 1, m_passwordEnd - m_userEnd - 1)); 
}

String KURL::user() const
{
    return decodeURLEscapeSequences(m_string.substring(m_userStart, m_userEnd - m_userStart));
}

String KURL::fragmentIdentifier() const
{
    if (m_fragmentEnd == m_queryEnd)
        return String();

    return m_string.substring(m_queryEnd + 1, m_fragmentEnd - (m_queryEnd + 1));
}

bool KURL::hasFragmentIdentifier() const
{
    return m_fragmentEnd != m_queryEnd;
}

void KURL::copyParsedQueryTo(ParsedURLParameters& parameters) const
{
    const UChar* pos = m_string.characters() + m_pathEnd + 1;
    const UChar* end = m_string.characters() + m_queryEnd;
    while (pos < end) {
        const UChar* parameterStart = pos;
        while (pos < end && *pos != '&')
            ++pos;
        const UChar* parameterEnd = pos;
        if (pos < end) {
            ASSERT(*pos == '&');
            ++pos;
        }
        if (parameterStart == parameterEnd)
            continue;
        const UChar* nameStart = parameterStart;
        const UChar* equalSign = parameterStart;
        while (equalSign < parameterEnd && *equalSign != '=')
            ++equalSign;
        if (equalSign == nameStart)
            continue;
        String name(nameStart, equalSign - nameStart);
        String value = equalSign == parameterEnd ? String() : String(equalSign + 1, parameterEnd - equalSign - 1);
        parameters.set(name, value);
    }
}

String KURL::baseAsString() const
{
    return m_string.left(m_pathAfterLastSlash);
}

#ifdef NDEBUG

static inline void assertProtocolIsGood(const char*)
{
}

#else

static void assertProtocolIsGood(const char* protocol)
{
    const char* p = protocol;
    while (*p) {
        ASSERT(*p > ' ' && *p < 0x7F && !(*p >= 'A' && *p <= 'Z'));
        ++p;
    }
}

#endif

bool KURL::protocolIs(const char* protocol) const
{
    assertProtocolIsGood(protocol);

    // JavaScript URLs are "valid" and should be executed even if KURL decides they are invalid.
    // The free function protocolIsJavaScript() should be used instead. 
    ASSERT(!equalIgnoringCase(protocol, String("javascript")));

    if (!m_isValid)
        return false;

    // Do the comparison without making a new string object.
    for (int i = 0; i < m_schemeEnd; ++i) {
        if (!protocol[i] || !isSchemeCharacterMatchIgnoringCase(m_string[i], protocol[i]))
            return false;
    }
    return !protocol[m_schemeEnd]; // We should have consumed all characters in the argument.
}

String KURL::query() const
{
    if (m_queryEnd == m_pathEnd)
        return String();

    return m_string.substring(m_pathEnd + 1, m_queryEnd - (m_pathEnd + 1)); 
}

String KURL::path() const
{
    return m_string.substring(m_portEnd, m_pathEnd - m_portEnd);
}

bool KURL::setProtocol(const String& s)
{
    // Firefox and IE remove everything after the first ':'.
    size_t separatorPosition = s.find(':');
    String newProtocol = s.substring(0, separatorPosition);

    if (!isValidProtocol(newProtocol))
        return false;

    if (!m_isValid) {
        parse(newProtocol + ":" + m_string);
        return true;
    }

    parse(newProtocol + m_string.substring(m_schemeEnd));
    return true;
}

void KURL::setHost(const String& s)
{
    if (!m_isValid)
        return;

    // FIXME: Non-ASCII characters must be encoded and escaped to match parse() expectations,
    // and to avoid changing more than just the host.

    bool slashSlashNeeded = m_userStart == m_schemeEnd + 1;

    parse(m_string.left(hostStart()) + (slashSlashNeeded ? "//" : "") + s + m_string.substring(m_hostEnd));
}

void KURL::removePort()
{
    if (m_hostEnd == m_portEnd)
        return;
    parse(m_string.left(m_hostEnd) + m_string.substring(m_portEnd));
}

void KURL::setPort(unsigned short i)
{
    if (!m_isValid)
        return;

    bool colonNeeded = m_portEnd == m_hostEnd;
    int portStart = (colonNeeded ? m_hostEnd : m_hostEnd + 1);

    parse(m_string.left(portStart) + (colonNeeded ? ":" : "") + String::number(i) + m_string.substring(m_portEnd));
}

void KURL::setHostAndPort(const String& hostAndPort)
{
    if (!m_isValid)
        return;

    // FIXME: Non-ASCII characters must be encoded and escaped to match parse() expectations,
    // and to avoid changing more than just host and port.

    bool slashSlashNeeded = m_userStart == m_schemeEnd + 1;

    parse(m_string.left(hostStart()) + (slashSlashNeeded ? "//" : "") + hostAndPort + m_string.substring(m_portEnd));
}

void KURL::setUser(const String& user)
{
    if (!m_isValid)
        return;

    // FIXME: Non-ASCII characters must be encoded and escaped to match parse() expectations,
    // and to avoid changing more than just the user login.
    String u;
    int end = m_userEnd;
    if (!user.isEmpty()) {
        u = user;
        if (m_userStart == m_schemeEnd + 1)
            u = "//" + u;
        // Add '@' if we didn't have one before.
        if (end == m_hostEnd || (end == m_passwordEnd && m_string[end] != '@'))
            u.append('@');
    } else {
        // Remove '@' if we now have neither user nor password.
        if (m_userEnd == m_passwordEnd && end != m_hostEnd && m_string[end] == '@')
            end += 1;
    }
    parse(m_string.left(m_userStart) + u + m_string.substring(end));
}

void KURL::setPass(const String& password)
{
    if (!m_isValid)
        return;

    // FIXME: Non-ASCII characters must be encoded and escaped to match parse() expectations,
    // and to avoid changing more than just the user password.
    String p;
    int end = m_passwordEnd;
    if (!password.isEmpty()) {
        p = ":" + password + "@";
        if (m_userEnd == m_schemeEnd + 1)
            p = "//" + p;
        // Eat the existing '@' since we are going to add our own.
        if (end != m_hostEnd && m_string[end] == '@')
            end += 1;
    } else {
        // Remove '@' if we now have neither user nor password.
        if (m_userStart == m_userEnd && end != m_hostEnd && m_string[end] == '@')
            end += 1;
    }
    parse(m_string.left(m_userEnd) + p + m_string.substring(end));
}

void KURL::setFragmentIdentifier(const String& s)
{
    if (!m_isValid)
        return;

    // FIXME: Non-ASCII characters must be encoded and escaped to match parse() expectations.
    parse(m_string.left(m_queryEnd) + "#" + s);
}

void KURL::removeFragmentIdentifier()
{
    if (!m_isValid)
        return;
    parse(m_string.left(m_queryEnd));
}
    
void KURL::setQuery(const String& query)
{
    if (!m_isValid)
        return;

    // FIXME: '#' and non-ASCII characters must be encoded and escaped.
    // Usually, the query is encoded using document encoding, not UTF-8, but we don't have
    // access to the document in this function.
    if ((query.isEmpty() || query[0] != '?') && !query.isNull())
        parse(m_string.left(m_pathEnd) + "?" + query + m_string.substring(m_queryEnd));
    else
        parse(m_string.left(m_pathEnd) + query + m_string.substring(m_queryEnd));

}

void KURL::setPath(const String& s)
{
    if (!m_isValid)
        return;

    // FIXME: encodeWithURLEscapeSequences does not correctly escape '#' and '?', so fragment and query parts
    // may be inadvertently affected.
    String path = s;
    if (path.isEmpty() || path[0] != '/')
        path = "/" + path;

    parse(m_string.left(m_portEnd) + encodeWithURLEscapeSequences(path) + m_string.substring(m_pathEnd));
}

String KURL::deprecatedString() const
{
    if (!m_isValid)
        return m_string;

    StringBuilder result;

    result.append(protocol());
    result.append(':');

    StringBuilder authority;

    if (m_hostEnd != m_passwordEnd) {
        if (m_userEnd != m_userStart) {
            authority.append(user());
            authority.append('@');
        }
        authority.append(host());
        if (hasPort()) {
            authority.append(':');
            authority.append(String::number(port()));
        }
    }

    if (!authority.isEmpty()) {
        result.append('/');
        result.append('/');
        result.append(authority.characters(), authority.length());
    } else if (protocolIs("file")) {
        result.append('/');
        result.append('/');
    }

    result.append(path());

    if (m_pathEnd != m_queryEnd) {
        result.append('?');
        result.append(query());
    }

    if (m_fragmentEnd != m_queryEnd) {
        result.append('#');
        result.append(fragmentIdentifier());
    }

    return result.toString();
}

String decodeURLEscapeSequences(const String& string)
{
    return decodeEscapeSequences<URLEscapeSequence>(string, UTF8Encoding());
}

String decodeURLEscapeSequences(const String& string, const TextEncoding& encoding)
{
    return decodeEscapeSequences<URLEscapeSequence>(string, encoding);
}

// Caution: This function does not bounds check.
static void appendEscapedChar(char*& buffer, unsigned char c)
{
    *buffer++ = '%';
    placeByteAsHex(c, buffer);
}

static void appendEscapingBadChars(char*& buffer, const char* strStart, size_t length)
{
    char* p = buffer;

    const char* str = strStart;
    const char* strEnd = strStart + length;
    while (str < strEnd) {
        unsigned char c = *str++;
        if (isBadChar(c)) {
            if (c == '%' || c == '?')
                *p++ = c;
            else if (c != 0x09 && c != 0x0a && c != 0x0d)
                appendEscapedChar(p, c);
        } else
            *p++ = c;
    }

    buffer = p;
}

static void escapeAndAppendNonHierarchicalPart(char*& buffer, const char* strStart, size_t length)
{
    char* p = buffer;

    const char* str = strStart;
    const char* strEnd = strStart + length;
    while (str < strEnd) {
        unsigned char c = *str++;
        // Strip CR, LF and Tab from fragments, per:
        // https://bugs.webkit.org/show_bug.cgi?id=8770
        if (c == 0x09 || c == 0x0a || c == 0x0d)
            continue;

        // Chrome and IE allow non-ascii characters in fragments, however doing
        // so would hit an ASSERT in checkEncodedString, so for now we don't.
        if (c < 0x20 || c >= 127) {
            appendEscapedChar(p, c);
            continue;
        }
        *p++ = c;
    }

    buffer = p;
}

// copy a path, accounting for "." and ".." segments
static int copyPathRemovingDots(char* dst, const char* src, int srcStart, int srcEnd)
{
    char* bufferPathStart = dst;

    // empty path is a special case, and need not have a leading slash
    if (srcStart != srcEnd) {
        const char* baseStringStart = src + srcStart;
        const char* baseStringEnd = src + srcEnd;
        const char* baseStringPos = baseStringStart;

        // this code is unprepared for paths that do not begin with a
        // slash and we should always have one in the source string
        ASSERT(baseStringPos[0] == '/');

        // copy the leading slash into the destination
        *dst = *baseStringPos;
        baseStringPos++;
        dst++;

        while (baseStringPos < baseStringEnd) {
            if (baseStringPos[0] == '.' && dst[-1] == '/') {
                if (baseStringPos[1] == '/' || baseStringPos + 1 == baseStringEnd) {
                    // skip over "." segment
                    baseStringPos += 2;
                    continue;
                } else if (baseStringPos[1] == '.' && (baseStringPos[2] == '/' ||
                                       baseStringPos + 2 == baseStringEnd)) {
                    // skip over ".." segment and rewind the last segment
                    // the RFC leaves it up to the app to decide what to do with excess
                    // ".." segments - we choose to drop them since some web content
                    // relies on this.
                    baseStringPos += 3;
                    if (dst > bufferPathStart + 1)
                        dst--;
                    while (dst > bufferPathStart && dst[-1] != '/')
                        dst--;
                    continue;
                }
            }

            *dst = *baseStringPos;
            baseStringPos++;
            dst++;
        }
    }
    *dst = '\0';
    return dst - bufferPathStart;
}

static inline bool hasSlashDotOrDotDot(const char* str)
{
    const unsigned char* p = reinterpret_cast<const unsigned char*>(str);
    if (!*p)
        return false;
    unsigned char pc = *p;
    while (unsigned char c = *++p) {
        if (c == '.' && (pc == '/' || pc == '.'))
            return true;
        pc = c;
    }
    return false;
}

void KURL::parse(const String& string)
{
    checkEncodedString(string);

    CharBuffer buffer(string.length() + 1);
    copyASCII(string, buffer.data());
    buffer[string.length()] = '\0';
    parse(buffer.data(), &string);
}

template<size_t length>
static inline bool equal(const char* a, const char (&b)[length])
{
    for (size_t i = 0; i < length; ++i) {
        if (a[i] != b[i])
            return false;
    }
    return true;
}

template<size_t lengthB>
static inline bool equal(const char* stringA, size_t lengthA, const char (&stringB)[lengthB])
{
    return lengthA == lengthB && equal(stringA, stringB);
}

// List of default schemes is taken from google-url:
// http://code.google.com/p/google-url/source/browse/trunk/src/url_canon_stdurl.cc#120
static inline bool isDefaultPortForScheme(const char* port, size_t portLength, const char* scheme, size_t schemeLength)
{
    // This switch is theoretically a performance optimization.  It came over when
    // the code was moved from google-url, but may be removed later.
    switch (schemeLength) {
    case 2:
        return equal(scheme, wsScheme) && equal(port, portLength, httpPort);
    case 3:
        if (equal(scheme, ftpScheme))
            return equal(port, portLength, ftpPort);
        if (equal(scheme, wssScheme))
            return equal(port, portLength, httpsPort);
        break;
    case 4:
        return equal(scheme, httpScheme) && equal(port, portLength, httpPort);
    case 5:
        return equal(scheme, httpsScheme) && equal(port, portLength, httpsPort);
    case 6:
        return equal(scheme, gopherScheme) && equal(port, portLength, gopherPort);
    }
    return false;
}

static inline bool hostPortIsEmptyButCredentialsArePresent(int hostStart, int portEnd, char userEndChar)
{
    return userEndChar == '@' && hostStart == portEnd;
}

static bool isNonFileHierarchicalScheme(const char* scheme, size_t schemeLength)
{
    switch (schemeLength) {
    case 2:
        return equal(scheme, wsScheme);
    case 3:
        return equal(scheme, ftpScheme) || equal(scheme, wssScheme);
    case 4:
        return equal(scheme, httpScheme);
    case 5:
        return equal(scheme, httpsScheme);
    case 6:
        return equal(scheme, gopherScheme);
    }
    return false;
}

static bool isCanonicalHostnameLowercaseForScheme(const char* scheme, size_t schemeLength)
{
    switch (schemeLength) {
    case 2:
        return equal(scheme, wsScheme);
    case 3:
        return equal(scheme, ftpScheme) || equal(scheme, wssScheme);
    case 4:
        return equal(scheme, httpScheme) || equal(scheme, fileScheme);
    case 5:
        return equal(scheme, httpsScheme);
    case 6:
        return equal(scheme, gopherScheme);
    }
    return false;
}

void KURL::parse(const char* url, const String* originalString)
{
    if (!url || url[0] == '\0') {
        // valid URL must be non-empty
        m_string = originalString ? *originalString : url;
        invalidate();
        return;
    }

    if (!isSchemeFirstChar(url[0])) {
        // scheme must start with an alphabetic character
        m_string = originalString ? *originalString : url;
        invalidate();
        return;
    }

    int schemeEnd = 0;
    while (isSchemeChar(url[schemeEnd]))
        schemeEnd++;

    if (url[schemeEnd] != ':') {
        m_string = originalString ? *originalString : url;
        invalidate();
        return;
    }

    int userStart = schemeEnd + 1;
    int userEnd;
    int passwordStart;
    int passwordEnd;
    int hostStart;
    int hostEnd;
    int portStart;
    int portEnd;

    bool hierarchical = url[schemeEnd + 1] == '/';
    bool hasSecondSlash = hierarchical && url[schemeEnd + 2] == '/';

    bool isFile = schemeEnd == 4
        && isLetterMatchIgnoringCase(url[0], 'f')
        && isLetterMatchIgnoringCase(url[1], 'i')
        && isLetterMatchIgnoringCase(url[2], 'l')
        && isLetterMatchIgnoringCase(url[3], 'e');

    m_protocolIsInHTTPFamily = isLetterMatchIgnoringCase(url[0], 'h')
        && isLetterMatchIgnoringCase(url[1], 't')
        && isLetterMatchIgnoringCase(url[2], 't')
        && isLetterMatchIgnoringCase(url[3], 'p')
        && (url[4] == ':' || (isLetterMatchIgnoringCase(url[4], 's') && url[5] == ':'));

    if ((hierarchical && hasSecondSlash) || isNonFileHierarchicalScheme(url, schemeEnd)) {
        // The part after the scheme is either a net_path or an abs_path whose first path segment is empty.
        // Attempt to find an authority.
        // FIXME: Authority characters may be scanned twice, and it would be nice to be faster.

        if (hierarchical)
            userStart++;
        if (hasSecondSlash)
            userStart++;
        userEnd = userStart;

        int colonPos = 0;
        while (isUserInfoChar(url[userEnd])) {
            if (url[userEnd] == ':' && colonPos == 0)
                colonPos = userEnd;
            userEnd++;
        }

        if (url[userEnd] == '@') {
            // actual end of the userinfo, start on the host
            if (colonPos != 0) {
                passwordEnd = userEnd;
                userEnd = colonPos;
                passwordStart = colonPos + 1;
            } else
                passwordStart = passwordEnd = userEnd;

            hostStart = passwordEnd + 1;
        } else if (url[userEnd] == '[' || isPathSegmentEndChar(url[userEnd])) {
            // hit the end of the authority, must have been no user
            // or looks like an IPv6 hostname
            // either way, try to parse it as a hostname
            userEnd = userStart;
            passwordStart = passwordEnd = userEnd;
            hostStart = userStart;
        } else {
            // invalid character
            m_string = originalString ? *originalString : url;
            invalidate();
            return;
        }

        hostEnd = hostStart;

        // IPV6 IP address
        if (url[hostEnd] == '[') {
            hostEnd++;
            while (isIPv6Char(url[hostEnd]))
                hostEnd++;
            if (url[hostEnd] == ']')
                hostEnd++;
            else {
                // invalid character
                m_string = originalString ? *originalString : url;
                invalidate();
                return;
            }
        } else {
            while (isHostnameChar(url[hostEnd]))
                hostEnd++;
        }
        
        if (url[hostEnd] == ':') {
            portStart = portEnd = hostEnd + 1;
 
            // possible start of port
            portEnd = portStart;
            while (isASCIIDigit(url[portEnd]))
                portEnd++;
        } else
            portStart = portEnd = hostEnd;

        if (!isPathSegmentEndChar(url[portEnd])) {
            // invalid character
            m_string = originalString ? *originalString : url;
            invalidate();
            return;
        }

        if (hostPortIsEmptyButCredentialsArePresent(hostStart, portEnd, url[userEnd])) {
            // in this circumstance, act as if there is an erroneous hostname containing an '@'
            userEnd = userStart;
            hostStart = userEnd;
        }

        if (userStart == portEnd && !m_protocolIsInHTTPFamily && !isFile) {
            // No authority found, which means that this is not a net_path, but rather an abs_path whose first two
            // path segments are empty. For file, http and https only, an empty authority is allowed.
            userStart -= 2;
            userEnd = userStart;
            passwordStart = userEnd;
            passwordEnd = passwordStart;
            hostStart = passwordEnd;
            hostEnd = hostStart;
            portStart = hostEnd;
            portEnd = hostEnd;
        }
    } else {
        // the part after the scheme must be an opaque_part or an abs_path
        userEnd = userStart;
        passwordStart = passwordEnd = userEnd;
        hostStart = hostEnd = passwordEnd;
        portStart = portEnd = hostEnd;
    }

    int pathStart = portEnd;
    int pathEnd = pathStart;
    while (url[pathEnd] && url[pathEnd] != '?' && url[pathEnd] != '#')
        pathEnd++;

    int queryStart = pathEnd;
    int queryEnd = queryStart;
    if (url[queryStart] == '?') {
        while (url[queryEnd] && url[queryEnd] != '#')
            queryEnd++;
    }

    int fragmentStart = queryEnd;
    int fragmentEnd = fragmentStart;
    if (url[fragmentStart] == '#') {
        fragmentStart++;
        fragmentEnd = fragmentStart;
        while (url[fragmentEnd])
            fragmentEnd++;
    }

    // assemble it all, remembering the real ranges

    Vector<char, 4096> buffer(fragmentEnd * 3 + 1);

    char *p = buffer.data();
    const char *strPtr = url;

    // copy in the scheme
    const char *schemeEndPtr = url + schemeEnd;
    while (strPtr < schemeEndPtr)
        *p++ = toASCIILower(*strPtr++);
    m_schemeEnd = p - buffer.data();

    bool hostIsLocalHost = portEnd - userStart == 9
        && isLetterMatchIgnoringCase(url[userStart], 'l')
        && isLetterMatchIgnoringCase(url[userStart+1], 'o')
        && isLetterMatchIgnoringCase(url[userStart+2], 'c')
        && isLetterMatchIgnoringCase(url[userStart+3], 'a')
        && isLetterMatchIgnoringCase(url[userStart+4], 'l')
        && isLetterMatchIgnoringCase(url[userStart+5], 'h')
        && isLetterMatchIgnoringCase(url[userStart+6], 'o')
        && isLetterMatchIgnoringCase(url[userStart+7], 's')
        && isLetterMatchIgnoringCase(url[userStart+8], 't');

    // File URLs need a host part unless it is just file:// or file://localhost
    bool degenerateFilePath = pathStart == pathEnd && (hostStart == hostEnd || hostIsLocalHost);

    bool haveNonHostAuthorityPart = userStart != userEnd || passwordStart != passwordEnd || portStart != portEnd;

    // add ":" after scheme
    *p++ = ':';

    // if we have at least one authority part or a file URL - add "//" and authority
    if (isFile ? !degenerateFilePath : (haveNonHostAuthorityPart || hostStart != hostEnd)) {
        *p++ = '/';
        *p++ = '/';

        m_userStart = p - buffer.data();

        // copy in the user
        strPtr = url + userStart;
        const char* userEndPtr = url + userEnd;
        while (strPtr < userEndPtr)
            *p++ = *strPtr++;
        m_userEnd = p - buffer.data();

        // copy in the password
        if (passwordEnd != passwordStart) {
            *p++ = ':';
            strPtr = url + passwordStart;
            const char* passwordEndPtr = url + passwordEnd;
            while (strPtr < passwordEndPtr)
                *p++ = *strPtr++;
        }
        m_passwordEnd = p - buffer.data();

        // If we had any user info, add "@"
        if (p - buffer.data() != m_userStart)
            *p++ = '@';

        // copy in the host, except in the case of a file URL with authority="localhost"
        if (!(isFile && hostIsLocalHost && !haveNonHostAuthorityPart)) {
            strPtr = url + hostStart;
            const char* hostEndPtr = url + hostEnd;
            if (isCanonicalHostnameLowercaseForScheme(buffer.data(), m_schemeEnd)) {
                while (strPtr < hostEndPtr)
                    *p++ = toASCIILower(*strPtr++);
            } else {
                while (strPtr < hostEndPtr)
                    *p++ = *strPtr++;
            }
        }
        m_hostEnd = p - buffer.data();

        // Copy in the port if the URL has one (and it's not default).
        if (hostEnd != portStart) {
            const char* portStr = url + portStart;
            size_t portLength = portEnd - portStart;
            if (portLength && !isDefaultPortForScheme(portStr, portLength, buffer.data(), m_schemeEnd)) {
                *p++ = ':';
                const char* portEndPtr = url + portEnd;
                while (portStr < portEndPtr)
                    *p++ = *portStr++;
            }
        }
        m_portEnd = p - buffer.data();
    } else {
        if (isFile) {
            ASSERT(degenerateFilePath);
            *p++ = '/';
            *p++ = '/';
        }
        m_userStart = m_userEnd = m_passwordEnd = m_hostEnd = m_portEnd = p - buffer.data();
    }

    // For canonicalization, ensure we have a '/' for no path.
    // Do this only for URL with protocol file, http or https.
    if ((m_protocolIsInHTTPFamily || isFile) && pathEnd == pathStart)
        *p++ = '/';

    // add path, escaping bad characters
    if (!hierarchical)
        escapeAndAppendNonHierarchicalPart(p, url + pathStart, pathEnd - pathStart);
    else if (!hasSlashDotOrDotDot(url))
        appendEscapingBadChars(p, url + pathStart, pathEnd - pathStart);
    else {
        CharBuffer pathBuffer(pathEnd - pathStart + 1);
        size_t length = copyPathRemovingDots(pathBuffer.data(), url, pathStart, pathEnd);
        appendEscapingBadChars(p, pathBuffer.data(), length);
    }

    m_pathEnd = p - buffer.data();

    // Find the position after the last slash in the path, or
    // the position before the path if there are no slashes in it.
    int i;
    for (i = m_pathEnd; i > m_portEnd; --i) {
        if (buffer[i - 1] == '/')
            break;
    }
    m_pathAfterLastSlash = i;

    // add query, escaping bad characters
    appendEscapingBadChars(p, url + queryStart, queryEnd - queryStart);
    m_queryEnd = p - buffer.data();

    // add fragment, escaping bad characters
    if (fragmentEnd != queryEnd) {
        *p++ = '#';
        escapeAndAppendNonHierarchicalPart(p, url + fragmentStart, fragmentEnd - fragmentStart);
    }
    m_fragmentEnd = p - buffer.data();

    ASSERT(p - buffer.data() <= static_cast<int>(buffer.size()));
    ASSERT(buffer.size() > 0);

    // If we didn't end up actually changing the original string and
    // it was already in a String, reuse it to avoid extra allocation.
    if (originalString && *originalString == buffer)
        m_string = *originalString;
    else
        m_string = String(buffer.data(), m_fragmentEnd);

    m_isValid = true;
}

bool equalIgnoringFragmentIdentifier(const KURL& a, const KURL& b)
{
    if (a.m_queryEnd != b.m_queryEnd)
        return false;
    unsigned queryLength = a.m_queryEnd;
    for (unsigned i = 0; i < queryLength; ++i)
        if (a.string()[i] != b.string()[i])
            return false;
    return true;
}

bool protocolHostAndPortAreEqual(const KURL& a, const KURL& b)
{
    if (a.m_schemeEnd != b.m_schemeEnd)
        return false;

    int hostStartA = a.hostStart();
    int hostLengthA = a.hostEnd() - hostStartA;
    int hostStartB = b.hostStart();
    int hostLengthB = b.hostEnd() - b.hostStart();
    if (hostLengthA != hostLengthB)
        return false;

    // Check the scheme
    for (int i = 0; i < a.m_schemeEnd; ++i)
        if (a.string()[i] != b.string()[i])
            return false;

    // And the host
    for (int i = 0; i < hostLengthA; ++i)
        if (a.string()[hostStartA + i] != b.string()[hostStartB + i])
            return false;

    if (a.port() != b.port())
        return false;

    return true;
}

String encodeWithURLEscapeSequences(const String& notEncodedString)
{
    CString asUTF8 = notEncodedString.utf8();

    CharBuffer buffer(asUTF8.length() * 3 + 1);
    char* p = buffer.data();

    const char* str = asUTF8.data();
    const char* strEnd = str + asUTF8.length();
    while (str < strEnd) {
        unsigned char c = *str++;
        if (isBadChar(c))
            appendEscapedChar(p, c);
        else
            *p++ = c;
    }

    ASSERT(p - buffer.data() <= static_cast<int>(buffer.size()));

    return String(buffer.data(), p - buffer.data());
}

// Appends the punycoded hostname identified by the given string and length to
// the output buffer. The result will not be null terminated.
static void appendEncodedHostname(UCharBuffer& buffer, const UChar* str, unsigned strLen)
{
    // Needs to be big enough to hold an IDN-encoded name.
    // For host names bigger than this, we won't do IDN encoding, which is almost certainly OK.
    const unsigned hostnameBufferLength = 2048;

    if (strLen > hostnameBufferLength || charactersAreAllASCII(str, strLen)) {
        buffer.append(str, strLen);
        return;
    }

#if USE(ICU_UNICODE)
    UChar hostnameBuffer[hostnameBufferLength];
    UErrorCode error = U_ZERO_ERROR;
    int32_t numCharactersConverted = uidna_IDNToASCII(str, strLen, hostnameBuffer,
        hostnameBufferLength, UIDNA_ALLOW_UNASSIGNED, 0, &error);
    if (error == U_ZERO_ERROR)
        buffer.append(hostnameBuffer, numCharactersConverted);
#elif USE(QT4_UNICODE)
    QByteArray result = QUrl::toAce(String(str, strLen));
    buffer.append(result.constData(), result.length());
#elif USE(GLIB_UNICODE)
    GOwnPtr<gchar> utf8Hostname;
    GOwnPtr<GError> utf8Err;
    utf8Hostname.set(g_utf16_to_utf8(str, strLen, 0, 0, &utf8Err.outPtr()));
    if (utf8Err)
        return;

    GOwnPtr<gchar> encodedHostname;
    encodedHostname.set(g_hostname_to_ascii(utf8Hostname.get()));
    if (!encodedHostname) 
        return;

    buffer.append(encodedHostname.get(), strlen(encodedHostname.get()));
#endif
}

static void findHostnamesInMailToURL(const UChar* str, int strLen, Vector<pair<int, int> >& nameRanges)
{
    // In a mailto: URL, host names come after a '@' character and end with a '>' or ',' or '?' or end of string character.
    // Skip quoted strings so that characters in them don't confuse us.
    // When we find a '?' character, we are past the part of the URL that contains host names.

    nameRanges.clear();

    int p = 0;
    while (1) {
        // Find start of host name or of quoted string.
        int hostnameOrStringStart = findFirstOf(str, strLen, p, "\"@?");
        if (hostnameOrStringStart == -1)
            return;
        UChar c = str[hostnameOrStringStart];
        p = hostnameOrStringStart + 1;

        if (c == '?')
            return;

        if (c == '@') {
            // Find end of host name.
            int hostnameStart = p;
            int hostnameEnd = findFirstOf(str, strLen, p, ">,?");
            bool done;
            if (hostnameEnd == -1) {
                hostnameEnd = strLen;
                done = true;
            } else {
                p = hostnameEnd;
                done = false;
            }

            nameRanges.append(make_pair(hostnameStart, hostnameEnd));

            if (done)
                return;
        } else {
            // Skip quoted string.
            ASSERT(c == '"');
            while (1) {
                int escapedCharacterOrStringEnd = findFirstOf(str, strLen, p, "\"\\");
                if (escapedCharacterOrStringEnd == -1)
                    return;

                c = str[escapedCharacterOrStringEnd];
                p = escapedCharacterOrStringEnd + 1;

                // If we are the end of the string, then break from the string loop back to the host name loop.
                if (c == '"')
                    break;

                // Skip escaped character.
                ASSERT(c == '\\');
                if (p == strLen)
                    return;

                ++p;
            }
        }
    }
}

static bool findHostnameInHierarchicalURL(const UChar* str, int strLen, int& startOffset, int& endOffset)
{
    // Find the host name in a hierarchical URL.
    // It comes after a "://" sequence, with scheme characters preceding, and
    // this should be the first colon in the string.
    // It ends with the end of the string or a ":" or a path segment ending character.
    // If there is a "@" character, the host part is just the part after the "@".
    int separator = findFirstOf(str, strLen, 0, ":");
    if (separator == -1 || separator + 2 >= strLen ||
        str[separator + 1] != '/' || str[separator + 2] != '/')
        return false;

    // Check that all characters before the :// are valid scheme characters.
    if (!isSchemeFirstChar(str[0]))
        return false;
    for (int i = 1; i < separator; ++i) {
        if (!isSchemeChar(str[i]))
            return false;
    }

    // Start after the separator.
    int authorityStart = separator + 3;

    // Find terminating character.
    int hostnameEnd = strLen;
    for (int i = authorityStart; i < strLen; ++i) {
        UChar c = str[i];
        if (c == ':' || (isPathSegmentEndChar(c) && c != 0)) {
            hostnameEnd = i;
            break;
        }
    }

    // Find "@" for the start of the host name.
    int userInfoTerminator = findFirstOf(str, strLen, authorityStart, "@");
    int hostnameStart;
    if (userInfoTerminator == -1 || userInfoTerminator > hostnameEnd)
        hostnameStart = authorityStart;
    else
        hostnameStart = userInfoTerminator + 1;

    startOffset = hostnameStart;
    endOffset = hostnameEnd;
    return true;
}

// Converts all hostnames found in the given input to punycode, preserving the
// rest of the URL unchanged. The output will NOT be null-terminated.
static void encodeHostnames(const String& str, UCharBuffer& output)
{
    output.clear();

    if (protocolIs(str, "mailto")) {
        Vector<pair<int, int> > hostnameRanges;
        findHostnamesInMailToURL(str.characters(), str.length(), hostnameRanges);
        int n = hostnameRanges.size();
        int p = 0;
        for (int i = 0; i < n; ++i) {
            const pair<int, int>& r = hostnameRanges[i];
            output.append(&str.characters()[p], r.first - p);
            appendEncodedHostname(output, &str.characters()[r.first], r.second - r.first);
            p = r.second;
        }
        // This will copy either everything after the last hostname, or the
        // whole thing if there is no hostname.
        output.append(&str.characters()[p], str.length() - p);
    } else {
        int hostStart, hostEnd;
        if (findHostnameInHierarchicalURL(str.characters(), str.length(), hostStart, hostEnd)) {
            output.append(str.characters(), hostStart); // Before hostname.
            appendEncodedHostname(output, &str.characters()[hostStart], hostEnd - hostStart);
            output.append(&str.characters()[hostEnd], str.length() - hostEnd); // After hostname.
        } else {
            // No hostname to encode, return the input.
            output.append(str.characters(), str.length());
        }
    }
}

static void encodeRelativeString(const String& rel, const TextEncoding& encoding, CharBuffer& output)
{
    UCharBuffer s;
    encodeHostnames(rel, s);

    TextEncoding pathEncoding(UTF8Encoding()); // Path is always encoded as UTF-8; other parts may depend on the scheme.

    int pathEnd = -1;
    if (encoding != pathEncoding && encoding.isValid() && !protocolIs(rel, "mailto") && !protocolIs(rel, "data") && !protocolIsJavaScript(rel)) {
        // Find the first instance of either # or ?, keep pathEnd at -1 otherwise.
        pathEnd = findFirstOf(s.data(), s.size(), 0, "#?");
    }

    if (pathEnd == -1) {
        CString decoded = pathEncoding.encode(s.data(), s.size(), URLEncodedEntitiesForUnencodables);
        output.resize(decoded.length());
        memcpy(output.data(), decoded.data(), decoded.length());
    } else {
        CString pathDecoded = pathEncoding.encode(s.data(), pathEnd, URLEncodedEntitiesForUnencodables);
        // Unencodable characters in URLs are represented by converting
        // them to XML entities and escaping non-alphanumeric characters.
        CString otherDecoded = encoding.encode(s.data() + pathEnd, s.size() - pathEnd, URLEncodedEntitiesForUnencodables);

        output.resize(pathDecoded.length() + otherDecoded.length());
        memcpy(output.data(), pathDecoded.data(), pathDecoded.length());
        memcpy(output.data() + pathDecoded.length(), otherDecoded.data(), otherDecoded.length());
    }
    output.append('\0'); // null-terminate the output.
}

static String substituteBackslashes(const String& string)
{
    size_t questionPos = string.find('?');
    size_t hashPos = string.find('#');
    unsigned pathEnd;

    if (hashPos != notFound && (questionPos == notFound || questionPos > hashPos))
        pathEnd = hashPos;
    else if (questionPos != notFound)
        pathEnd = questionPos;
    else
        pathEnd = string.length();

    return string.left(pathEnd).replace('\\','/') + string.substring(pathEnd);
}

bool KURL::isHierarchical() const
{
    if (!m_isValid)
        return false;
    ASSERT(m_string[m_schemeEnd] == ':');
    return m_string[m_schemeEnd + 1] == '/';
}

void KURL::copyToBuffer(CharBuffer& buffer) const
{
    // FIXME: This throws away the high bytes of all the characters in the string!
    // That's fine for a valid URL, which is all ASCII, but not for invalid URLs.
    buffer.resize(m_string.length());
    copyASCII(m_string, buffer.data());
}

bool protocolIs(const String& url, const char* protocol)
{
    // Do the comparison without making a new string object.
    assertProtocolIsGood(protocol);
    for (int i = 0; ; ++i) {
        if (!protocol[i])
            return url[i] == ':';
        if (!isLetterMatchIgnoringCase(url[i], protocol[i]))
            return false;
    }
}

bool isValidProtocol(const String& protocol)
{
    // RFC3986: ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )
    if (protocol.isEmpty())
        return false;
    if (!isSchemeFirstChar(protocol[0]))
        return false;
    unsigned protocolLength = protocol.length();
    for (unsigned i = 1; i < protocolLength; i++) {
        if (!isSchemeChar(protocol[i]))
            return false;
    }
    return true;
}

#ifndef NDEBUG
void KURL::print() const
{
    printf("%s\n", m_string.utf8().data());
}
#endif

#endif // !USE(GOOGLEURL)

String KURL::strippedForUseAsReferrer() const
{
    KURL referrer(*this);
    referrer.setUser(String());
    referrer.setPass(String());
    referrer.removeFragmentIdentifier();
    return referrer.string();
}

bool KURL::isLocalFile() const
{
    // Including feed here might be a bad idea since drag and drop uses this check
    // and including feed would allow feeds to potentially let someone's blog
    // read the contents of the clipboard on a drag, even without a drop.
    // Likewise with using the FrameLoader::shouldTreatURLAsLocal() function.
    return protocolIs("file");
}

bool protocolIsJavaScript(const String& url)
{
    return protocolIs(url, "javascript");
}

const KURL& blankURL()
{
    DEFINE_STATIC_LOCAL(KURL, staticBlankURL, (ParsedURLString, "about:blank"));
    return staticBlankURL;
}

bool isDefaultPortForProtocol(unsigned short port, const String& protocol)
{
    if (protocol.isEmpty())
        return false;

    typedef HashMap<String, unsigned, CaseFoldingHash> DefaultPortsMap;
    DEFINE_STATIC_LOCAL(DefaultPortsMap, defaultPorts, ());
    if (defaultPorts.isEmpty()) {
        defaultPorts.set("http", 80);
        defaultPorts.set("https", 443);
        defaultPorts.set("ftp", 21);
        defaultPorts.set("ftps", 990);
    }
    return defaultPorts.get(protocol) == port;
}

bool portAllowed(const KURL& url)
{
    unsigned short port = url.port();

    // Since most URLs don't have a port, return early for the "no port" case.
    if (!port)
        return true;

    // This blocked port list matches the port blocking that Mozilla implements.
    // See http://www.mozilla.org/projects/netlib/PortBanning.html for more information.
    static const unsigned short blockedPortList[] = {
        1,    // tcpmux
        7,    // echo
        9,    // discard
        11,   // systat
        13,   // daytime
        15,   // netstat
        17,   // qotd
        19,   // chargen
        20,   // FTP-data
        21,   // FTP-control
        22,   // SSH
        23,   // telnet
        25,   // SMTP
        37,   // time
        42,   // name
        43,   // nicname
        53,   // domain
        77,   // priv-rjs
        79,   // finger
        87,   // ttylink
        95,   // supdup
        101,  // hostriame
        102,  // iso-tsap
        103,  // gppitnp
        104,  // acr-nema
        109,  // POP2
        110,  // POP3
        111,  // sunrpc
        113,  // auth
        115,  // SFTP
        117,  // uucp-path
        119,  // nntp
        123,  // NTP
        135,  // loc-srv / epmap
        139,  // netbios
        143,  // IMAP2
        179,  // BGP
        389,  // LDAP
        465,  // SMTP+SSL
        512,  // print / exec
        513,  // login
        514,  // shell
        515,  // printer
        526,  // tempo
        530,  // courier
        531,  // Chat
        532,  // netnews
        540,  // UUCP
        556,  // remotefs
        563,  // NNTP+SSL
        587,  // ESMTP
        601,  // syslog-conn
        636,  // LDAP+SSL
        993,  // IMAP+SSL
        995,  // POP3+SSL
        2049, // NFS
        3659, // apple-sasl / PasswordServer [Apple addition]
        4045, // lockd
        6000, // X11
        6665, // Alternate IRC [Apple addition]
        6666, // Alternate IRC [Apple addition]
        6667, // Standard IRC [Apple addition]
        6668, // Alternate IRC [Apple addition]
        6669, // Alternate IRC [Apple addition]
        invalidPortNumber, // Used to block all invalid port numbers
    };
    const unsigned short* const blockedPortListEnd = blockedPortList + WTF_ARRAY_LENGTH(blockedPortList);

#ifndef NDEBUG
    // The port list must be sorted for binary_search to work.
    static bool checkedPortList = false;
    if (!checkedPortList) {
        for (const unsigned short* p = blockedPortList; p != blockedPortListEnd - 1; ++p)
            ASSERT(*p < *(p + 1));
        checkedPortList = true;
    }
#endif

    // If the port is not in the blocked port list, allow it.
    if (!binary_search(blockedPortList, blockedPortListEnd, port))
        return true;

    // Allow ports 21 and 22 for FTP URLs, as Mozilla does.
    if ((port == 21 || port == 22) && url.protocolIs("ftp"))
        return true;

    // Allow any port number in a file URL, since the port number is ignored.
    if (url.protocolIs("file"))
        return true;

    return false;
}

String mimeTypeFromDataURL(const String& url)
{
    ASSERT(protocolIs(url, "data"));
    size_t index = url.find(';');
    if (index == notFound)
        index = url.find(',');
    if (index != notFound) {
        if (index > 5)
            return url.substring(5, index - 5);
        return "text/plain"; // Data URLs with no MIME type are considered text/plain.
    }
    return "";
}

bool protocolIsInHTTPFamily(const String& url)
{
    unsigned length = url.length();
    const UChar* characters = url.characters();
    return length > 4
        && isLetterMatchIgnoringCase(characters[0], 'h')
        && isLetterMatchIgnoringCase(characters[1], 't')
        && isLetterMatchIgnoringCase(characters[2], 't')
        && isLetterMatchIgnoringCase(characters[3], 'p')
        && (characters[4] == ':'
            || (isLetterMatchIgnoringCase(characters[4], 's') && length > 5 && characters[5] == ':'));
}

}
