Source/WebCore/xml/XMLHttpRequest.cpp

/*
 *  Copyright (C) 2004, 2006, 2008 Apple Inc. All rights reserved.
 *  Copyright (C) 2005-2007 Alexey Proskuryakov <ap@webkit.org>
 *  Copyright (C) 2007, 2008 Julien Chaffraix <jchaffraix@webkit.org>
 *  Copyright (C) 2008, 2011 Google Inc. All rights reserved.
 *
 *  This library is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU Lesser General Public
 *  License as published by the Free Software Foundation; either
 *  version 2 of the License, or (at your option) any later version.
 *
 *  This library is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 *  Lesser General Public License for more details.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with this library; if not, write to the Free Software
 *  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include "config.h"
#include "XMLHttpRequest.h"

#include "Blob.h"
#include "BlobData.h"
#include "ContentSecurityPolicy.h"
#include "ContextFeatures.h"
#include "CrossOriginAccessControl.h"
#include "DOMFormData.h"
#include "DOMImplementation.h"
#include "Event.h"
#include "EventException.h"
#include "EventListener.h"
#include "EventNames.h"
#include "ExceptionCode.h"
#include "File.h"
#include "HTMLDocument.h"
#include "HTTPParsers.h"
#include "HTTPValidation.h"
#include "InspectorInstrumentation.h"
#include "MemoryCache.h"
#include "ResourceError.h"
#include "ResourceRequest.h"
#include "ScriptCallStack.h"
#include "ScriptProfile.h"
#include "SecurityOrigin.h"
#include "Settings.h"
#include "SharedBuffer.h"
#include "TextResourceDecoder.h"
#include "ThreadableLoader.h"
#include "XMLHttpRequestException.h"
#include "XMLHttpRequestProgressEvent.h"
#include "XMLHttpRequestUpload.h"
#include "markup.h"
#include <wtf/ArrayBuffer.h>
#include <wtf/RefCountedLeakCounter.h>
#include <wtf/StdLibExtras.h>
#include <wtf/UnusedParam.h>
#include <wtf/text/CString.h>

#if USE(JSC)
#include "JSDOMBinding.h"
#include "JSDOMWindow.h"
#include <heap/Strong.h>
#include <runtime/JSLock.h>
#endif

namespace WebCore {

DEFINE_DEBUG_ONLY_GLOBAL(WTF::RefCountedLeakCounter, xmlHttpRequestCounter, ("XMLHttpRequest"));

struct XMLHttpRequestStaticData {
    WTF_MAKE_NONCOPYABLE(XMLHttpRequestStaticData); WTF_MAKE_FAST_ALLOCATED;
public:
    XMLHttpRequestStaticData();
    String m_proxyHeaderPrefix;
    String m_secHeaderPrefix;
    HashSet<String, CaseFoldingHash> m_forbiddenRequestHeaders;
};

XMLHttpRequestStaticData::XMLHttpRequestStaticData()
    : m_proxyHeaderPrefix("proxy-")
    , m_secHeaderPrefix("sec-")
{
    m_forbiddenRequestHeaders.add("accept-charset");
    m_forbiddenRequestHeaders.add("accept-encoding");
    m_forbiddenRequestHeaders.add("access-control-request-headers");
    m_forbiddenRequestHeaders.add("access-control-request-method");
    m_forbiddenRequestHeaders.add("connection");
    m_forbiddenRequestHeaders.add("content-length");
    m_forbiddenRequestHeaders.add("content-transfer-encoding");
    m_forbiddenRequestHeaders.add("cookie");
    m_forbiddenRequestHeaders.add("cookie2");
    m_forbiddenRequestHeaders.add("date");
    m_forbiddenRequestHeaders.add("expect");
    m_forbiddenRequestHeaders.add("host");
    m_forbiddenRequestHeaders.add("keep-alive");
    m_forbiddenRequestHeaders.add("origin");
    m_forbiddenRequestHeaders.add("referer");
    m_forbiddenRequestHeaders.add("te");
    m_forbiddenRequestHeaders.add("trailer");
    m_forbiddenRequestHeaders.add("transfer-encoding");
    m_forbiddenRequestHeaders.add("upgrade");
    m_forbiddenRequestHeaders.add("user-agent");
    m_forbiddenRequestHeaders.add("via");
}

static bool isSetCookieHeader(const AtomicString& name)
{
    return equalIgnoringCase(name, "set-cookie") || equalIgnoringCase(name, "set-cookie2");
}

static void replaceCharsetInMediaType(String& mediaType, const String& charsetValue)
{
    unsigned int pos = 0, len = 0;

    findCharsetInMediaType(mediaType, pos, len);

    if (!len) {
        // When no charset found, do nothing.
        return;
    }

    // Found at least one existing charset, replace all occurrences with new charset.
    while (len) {
        mediaType.replace(pos, len, charsetValue);
        unsigned int start = pos + charsetValue.length();
        findCharsetInMediaType(mediaType, pos, len, start);
    }
}

static const XMLHttpRequestStaticData* staticData = 0;

static const XMLHttpRequestStaticData* createXMLHttpRequestStaticData()
{
    staticData = new XMLHttpRequestStaticData;
    return staticData;
}

static const XMLHttpRequestStaticData* initializeXMLHttpRequestStaticData()
{
    // Uses dummy to avoid warnings about an unused variable.
    AtomicallyInitializedStatic(const XMLHttpRequestStaticData*, dummy = createXMLHttpRequestStaticData());
    return dummy;
}

static void logConsoleError(ScriptExecutionContext* context, const String& message)
{
    if (!context)
        return;
    // FIXME: It's not good to report the bad usage without indicating what source line it came from.
    // We should pass additional parameters so we can tell the console where the mistake occurred.
    context->addConsoleMessage(JSMessageSource, LogMessageType, ErrorMessageLevel, message);
}

PassRefPtr<XMLHttpRequest> XMLHttpRequest::create(ScriptExecutionContext* context, PassRefPtr<SecurityOrigin> securityOrigin)
{
    RefPtr<XMLHttpRequest> xmlHttpRequest(adoptRef(new XMLHttpRequest(context, securityOrigin)));
    xmlHttpRequest->suspendIfNeeded();

    return xmlHttpRequest.release();
}

XMLHttpRequest::XMLHttpRequest(ScriptExecutionContext* context, PassRefPtr<SecurityOrigin> securityOrigin)
    : ActiveDOMObject(context, this)
    , m_async(true)
    , m_includeCredentials(false)
    , m_state(UNSENT)
    , m_createdDocument(false)
    , m_error(false)
    , m_uploadEventsAllowed(true)
    , m_uploadComplete(false)
    , m_sameOriginRequest(true)
    , m_receivedLength(0)
    , m_lastSendLineNumber(0)
    , m_exceptionCode(0)
    , m_progressEventThrottle(this)
    , m_responseTypeCode(ResponseTypeDefault)
    , m_securityOrigin(securityOrigin)
{
    initializeXMLHttpRequestStaticData();
#ifndef NDEBUG
    xmlHttpRequestCounter.increment();
#endif
}

XMLHttpRequest::~XMLHttpRequest()
{
#ifndef NDEBUG
    xmlHttpRequestCounter.decrement();
#endif
}

Document* XMLHttpRequest::document() const
{
    ASSERT(scriptExecutionContext()->isDocument());
    return static_cast<Document*>(scriptExecutionContext());
}

SecurityOrigin* XMLHttpRequest::securityOrigin() const
{
    return m_securityOrigin ? m_securityOrigin.get() : scriptExecutionContext()->securityOrigin();
}

#if ENABLE(DASHBOARD_SUPPORT)
bool XMLHttpRequest::usesDashboardBackwardCompatibilityMode() const
{
    if (scriptExecutionContext()->isWorkerContext())
        return false;
    Settings* settings = document()->settings();
    return settings && settings->usesDashboardBackwardCompatibilityMode();
}
#endif

XMLHttpRequest::State XMLHttpRequest::readyState() const
{
    return m_state;
}

String XMLHttpRequest::responseText(ExceptionCode& ec)
{
    if (m_responseTypeCode != ResponseTypeDefault && m_responseTypeCode != ResponseTypeText) {
        ec = INVALID_STATE_ERR;
        return "";
    }
    return m_responseBuilder.toStringPreserveCapacity();
}

Document* XMLHttpRequest::responseXML(ExceptionCode& ec)
{
    if (m_responseTypeCode != ResponseTypeDefault && m_responseTypeCode != ResponseTypeDocument) {
        ec = INVALID_STATE_ERR;
        return 0;
    }

    if (m_error || m_state != DONE)
        return 0;

    if (!m_createdDocument) {
        bool isHTML = equalIgnoringCase(responseMIMEType(), "text/html");

        // The W3C spec requires the final MIME type to be some valid XML type, or text/html.
        // If it is text/html, then the responseType of "document" must have been supplied explicitly.
        if ((m_response.isHTTP() && !responseIsXML() && !isHTML)
            || (isHTML && m_responseTypeCode == ResponseTypeDefault)
            || scriptExecutionContext()->isWorkerContext()) {
            m_responseDocument = 0;
        } else {
            if (isHTML)
                m_responseDocument = HTMLDocument::create(0, m_url);
            else
                m_responseDocument = Document::create(0, m_url);
            // FIXME: Set Last-Modified.
            m_responseDocument->setContent(m_responseBuilder.toStringPreserveCapacity());
            m_responseDocument->setSecurityOrigin(securityOrigin());
            m_responseDocument->setContextFeatures(document()->contextFeatures());
            if (!m_responseDocument->wellFormed())
                m_responseDocument = 0;
        }
        m_createdDocument = true;
    }

    return m_responseDocument.get();
}

#if ENABLE(XHR_RESPONSE_BLOB)
Blob* XMLHttpRequest::responseBlob(ExceptionCode& ec)
{
    if (m_responseTypeCode != ResponseTypeBlob) {
        ec = INVALID_STATE_ERR;
        return 0;
    }
    // We always return null before DONE.
    if (m_state != DONE)
        return 0;

    if (!m_responseBlob) {
        // FIXME: This causes two (or more) unnecessary copies of the data.
        // Chromium stores blob data in the browser process, so we're pulling the data
        // from the network only to copy it into the renderer to copy it back to the browser.
        // Ideally we'd get the blob/file-handle from the ResourceResponse directly
        // instead of copying the bytes. Embedders who store blob data in the
        // same process as WebCore would at least to teach BlobData to take
        // a SharedBuffer, even if they don't get the Blob from the network layer directly.
        OwnPtr<BlobData> blobData = BlobData::create();
        // If we errored out or got no data, we still return a blob, just an empty one.
        size_t size = 0;
        if (m_binaryResponseBuilder) {
            RefPtr<RawData> rawData = RawData::create();
            size = m_binaryResponseBuilder->size();
            rawData->mutableData()->append(m_binaryResponseBuilder->data(), size);
            blobData->appendData(rawData, 0, BlobDataItem::toEndOfFile);
            blobData->setContentType(responseMIMEType()); // responseMIMEType defaults to text/xml which may be incorrect.
            m_binaryResponseBuilder.clear();
        }
        m_responseBlob = Blob::create(blobData.release(), size);
    }

    return m_responseBlob.get();
}
#endif

ArrayBuffer* XMLHttpRequest::responseArrayBuffer(ExceptionCode& ec)
{
    if (m_responseTypeCode != ResponseTypeArrayBuffer) {
        ec = INVALID_STATE_ERR;
        return 0;
    }

    if (m_state != DONE)
        return 0;

    if (!m_responseArrayBuffer.get() && m_binaryResponseBuilder.get() && m_binaryResponseBuilder->size() > 0) {
        m_responseArrayBuffer = ArrayBuffer::create(const_cast<char*>(m_binaryResponseBuilder->data()), static_cast<unsigned>(m_binaryResponseBuilder->size()));
        m_binaryResponseBuilder.clear();
    }

    return m_responseArrayBuffer.get();
}

void XMLHttpRequest::setResponseType(const String& responseType, ExceptionCode& ec)
{
    if (m_state >= LOADING) {
        ec = INVALID_STATE_ERR;
        return;
    }

    // Newer functionality is not available to synchronous requests in window contexts, as a spec-mandated 
    // attempt to discourage synchronous XHR use. responseType is one such piece of functionality.
    // We'll only disable this functionality for HTTP(S) requests since sync requests for local protocols
    // such as file: and data: still make sense to allow.
    if (!m_async && scriptExecutionContext()->isDocument() && m_url.protocolIsInHTTPFamily()) {
        logConsoleError(scriptExecutionContext(), "XMLHttpRequest.responseType cannot be changed for synchronous HTTP(S) requests made from the window context.");
        ec = INVALID_ACCESS_ERR;
        return;
    }

    if (responseType == "")
        m_responseTypeCode = ResponseTypeDefault;
    else if (responseType == "text")
        m_responseTypeCode = ResponseTypeText;
    else if (responseType == "document")
        m_responseTypeCode = ResponseTypeDocument;
    else if (responseType == "blob") {
#if ENABLE(XHR_RESPONSE_BLOB)
        m_responseTypeCode = ResponseTypeBlob;
#endif
    } else if (responseType == "arraybuffer") {
        m_responseTypeCode = ResponseTypeArrayBuffer;
    } else
        ec = SYNTAX_ERR;
}

String XMLHttpRequest::responseType()
{
    switch (m_responseTypeCode) {
    case ResponseTypeDefault:
        return "";
    case ResponseTypeText:
        return "text";
    case ResponseTypeDocument:
        return "document";
    case ResponseTypeBlob:
        return "blob";
    case ResponseTypeArrayBuffer:
        return "arraybuffer";
    }
    return "";
}

XMLHttpRequestUpload* XMLHttpRequest::upload()
{
    if (!m_upload)
        m_upload = XMLHttpRequestUpload::create(this);
    return m_upload.get();
}

void XMLHttpRequest::changeState(State newState)
{
    if (m_state != newState) {
        m_state = newState;
        callReadyStateChangeListener();
    }
}

void XMLHttpRequest::callReadyStateChangeListener()
{
    if (!scriptExecutionContext())
        return;

    InspectorInstrumentationCookie cookie = InspectorInstrumentation::willChangeXHRReadyState(scriptExecutionContext(), this);

    if (m_async || (m_state <= OPENED || m_state == DONE))
        m_progressEventThrottle.dispatchReadyStateChangeEvent(XMLHttpRequestProgressEvent::create(eventNames().readystatechangeEvent), m_state == DONE ? FlushProgressEvent : DoNotFlushProgressEvent);

    InspectorInstrumentation::didChangeXHRReadyState(cookie);

    if (m_state == DONE && !m_error) {
        InspectorInstrumentationCookie cookie = InspectorInstrumentation::willLoadXHR(scriptExecutionContext(), this);
        m_progressEventThrottle.dispatchEvent(XMLHttpRequestProgressEvent::create(eventNames().loadEvent));
        InspectorInstrumentation::didLoadXHR(cookie);
        m_progressEventThrottle.dispatchEvent(XMLHttpRequestProgressEvent::create(eventNames().loadendEvent));
    }
}

void XMLHttpRequest::setWithCredentials(bool value, ExceptionCode& ec)
{
    if (m_state > OPENED || m_loader) {
        ec = INVALID_STATE_ERR;
        return;
    }

    m_includeCredentials = value;
}

#if ENABLE(XHR_RESPONSE_BLOB)
void XMLHttpRequest::setAsBlob(bool value, ExceptionCode& ec)
{
    if (m_state != OPENED || m_loader) {
        ec = INVALID_STATE_ERR;
        return;
    }
    
    m_responseTypeCode = value ? ResponseTypeBlob : ResponseTypeDefault;
}
#endif

bool XMLHttpRequest::isAllowedHTTPMethod(const String& method)
{
    return !equalIgnoringCase(method, "TRACE")
        && !equalIgnoringCase(method, "TRACK")
        && !equalIgnoringCase(method, "CONNECT");
}

String XMLHttpRequest::uppercaseKnownHTTPMethod(const String& method)
{
    if (equalIgnoringCase(method, "COPY") || equalIgnoringCase(method, "DELETE") || equalIgnoringCase(method, "GET")
        || equalIgnoringCase(method, "HEAD") || equalIgnoringCase(method, "INDEX") || equalIgnoringCase(method, "LOCK")
        || equalIgnoringCase(method, "M-POST") || equalIgnoringCase(method, "MKCOL") || equalIgnoringCase(method, "MOVE")
        || equalIgnoringCase(method, "OPTIONS") || equalIgnoringCase(method, "POST") || equalIgnoringCase(method, "PROPFIND")
        || equalIgnoringCase(method, "PROPPATCH") || equalIgnoringCase(method, "PUT") || equalIgnoringCase(method, "UNLOCK")) {
        return method.upper();
    }
    return method;
}

bool XMLHttpRequest::isAllowedHTTPHeader(const String& name)
{
    initializeXMLHttpRequestStaticData();
    return !staticData->m_forbiddenRequestHeaders.contains(name) && !name.startsWith(staticData->m_proxyHeaderPrefix, false)
        && !name.startsWith(staticData->m_secHeaderPrefix, false);
}

void XMLHttpRequest::open(const String& method, const KURL& url, ExceptionCode& ec)
{
    open(method, url, true, ec);
}

void XMLHttpRequest::open(const String& method, const KURL& url, bool async, ExceptionCode& ec)
{
    internalAbort();
    State previousState = m_state;
    m_state = UNSENT;
    m_error = false;
    m_uploadComplete = false;

    // clear stuff from possible previous load
    clearResponse();
    clearRequest();

    ASSERT(m_state == UNSENT);

    if (!isValidHTTPToken(method)) {
        ec = SYNTAX_ERR;
        return;
    }

    if (!isAllowedHTTPMethod(method)) {
        ec = SECURITY_ERR;
        return;
    }

    if (!scriptExecutionContext()->contentSecurityPolicy()->allowConnectToSource(url)) {
        // FIXME: Should this be throwing an exception?
        ec = SECURITY_ERR;
        return;
    }

    if (!async && scriptExecutionContext()->isDocument()) {
        if (!document()->settings()->syncXHRInDocumentsEnabled()) {
            logConsoleError(scriptExecutionContext(), "Synchronous XMLHttpRequests are disabled for this page.");
            ec = INVALID_ACCESS_ERR;
            return;
        }

        // Newer functionality is not available to synchronous requests in window contexts, as a spec-mandated
        // attempt to discourage synchronous XHR use. responseType is one such piece of functionality.
        // We'll only disable this functionality for HTTP(S) requests since sync requests for local protocols
        // such as file: and data: still make sense to allow.
        if (url.protocolIsInHTTPFamily() && m_responseTypeCode != ResponseTypeDefault) {
            logConsoleError(scriptExecutionContext(), "Synchronous HTTP(S) requests made from the window context cannot have XMLHttpRequest.responseType set.");
            ec = INVALID_ACCESS_ERR;
            return;
        }
    }

    m_method = uppercaseKnownHTTPMethod(method);

    m_url = url;

    m_async = async;

    ASSERT(!m_loader);

    // Check previous state to avoid dispatching readyState event
    // when calling open several times in a row.
    if (previousState != OPENED)
        changeState(OPENED);
    else
        m_state = OPENED;
}

void XMLHttpRequest::open(const String& method, const KURL& url, bool async, const String& user, ExceptionCode& ec)
{
    KURL urlWithCredentials(url);
    urlWithCredentials.setUser(user);

    open(method, urlWithCredentials, async, ec);
}

void XMLHttpRequest::open(const String& method, const KURL& url, bool async, const String& user, const String& password, ExceptionCode& ec)
{
    KURL urlWithCredentials(url);
    urlWithCredentials.setUser(user);
    urlWithCredentials.setPass(password);

    open(method, urlWithCredentials, async, ec);
}

bool XMLHttpRequest::initSend(ExceptionCode& ec)
{
    if (!scriptExecutionContext())
        return false;

    if (m_state != OPENED || m_loader) {
        ec = INVALID_STATE_ERR;
        return false;
    }

    m_error = false;
    return true;
}

void XMLHttpRequest::send(ExceptionCode& ec)
{
    send(String(), ec);
}

void XMLHttpRequest::send(Document* document, ExceptionCode& ec)
{
    ASSERT(document);

    if (!initSend(ec))
        return;

    if (m_method != "GET" && m_method != "HEAD" && m_url.protocolIsInHTTPFamily()) {
        String contentType = getRequestHeader("Content-Type");
        if (contentType.isEmpty()) {
#if ENABLE(DASHBOARD_SUPPORT)
            if (usesDashboardBackwardCompatibilityMode())
                setRequestHeaderInternal("Content-Type", "application/x-www-form-urlencoded");
            else
#endif
                // FIXME: this should include the charset used for encoding.
                setRequestHeaderInternal("Content-Type", "application/xml");
        }

        // FIXME: According to XMLHttpRequest Level 2, this should use the Document.innerHTML algorithm
        // from the HTML5 specification to serialize the document.
        String body = createMarkup(document);

        // FIXME: this should use value of document.inputEncoding to determine the encoding to use.
        TextEncoding encoding = UTF8Encoding();
        m_requestEntityBody = FormData::create(encoding.encode(body.characters(), body.length(), EntitiesForUnencodables));
        if (m_upload)
            m_requestEntityBody->setAlwaysStream(true);
    }

    createRequest(ec);
}

void XMLHttpRequest::send(const String& body, ExceptionCode& ec)
{
    if (!initSend(ec))
        return;

    if (!body.isNull() && m_method != "GET" && m_method != "HEAD" && m_url.protocolIsInHTTPFamily()) {
        String contentType = getRequestHeader("Content-Type");
        if (contentType.isEmpty()) {
#if ENABLE(DASHBOARD_SUPPORT)
            if (usesDashboardBackwardCompatibilityMode())
                setRequestHeaderInternal("Content-Type", "application/x-www-form-urlencoded");
            else
#endif
                setRequestHeaderInternal("Content-Type", "application/xml");
        } else {
            replaceCharsetInMediaType(contentType, "UTF-8");
            m_requestHeaders.set("Content-Type", contentType);
        }

        m_requestEntityBody = FormData::create(UTF8Encoding().encode(body.characters(), body.length(), EntitiesForUnencodables));
        if (m_upload)
            m_requestEntityBody->setAlwaysStream(true);
    }

    createRequest(ec);
}

void XMLHttpRequest::send(Blob* body, ExceptionCode& ec)
{
    if (!initSend(ec))
        return;

    if (m_method != "GET" && m_method != "HEAD" && m_url.protocolIsInHTTPFamily()) {
        // FIXME: Should we set a Content-Type if one is not set.
        // FIXME: add support for uploading bundles.
        m_requestEntityBody = FormData::create();
        if (body->isFile())
            m_requestEntityBody->appendFile(toFile(body)->path());
#if ENABLE(BLOB)
        else
            m_requestEntityBody->appendBlob(body->url());
#endif
    }

    createRequest(ec);
}

void XMLHttpRequest::send(DOMFormData* body, ExceptionCode& ec)
{
    if (!initSend(ec))
        return;

    if (m_method != "GET" && m_method != "HEAD" && m_url.protocolIsInHTTPFamily()) {
        m_requestEntityBody = FormData::createMultiPart(*(static_cast<FormDataList*>(body)), body->encoding(), document());

        // We need to ask the client to provide the generated file names if needed. When FormData fills the element
        // for the file, it could set a flag to use the generated file name, i.e. a package file on Mac.
        m_requestEntityBody->generateFiles(document());

        String contentType = getRequestHeader("Content-Type");
        if (contentType.isEmpty()) {
            contentType = "multipart/form-data; boundary=";
            contentType += m_requestEntityBody->boundary().data();
            setRequestHeaderInternal("Content-Type", contentType);
        }
    }

    createRequest(ec);
}

void XMLHttpRequest::send(ArrayBuffer* body, ExceptionCode& ec)
{
    if (!initSend(ec))
        return;

    if (m_method != "GET" && m_method != "HEAD" && m_url.protocolIsInHTTPFamily()) {
        m_requestEntityBody = FormData::create(body->data(), body->byteLength());
        if (m_upload)
            m_requestEntityBody->setAlwaysStream(true);
    }

    createRequest(ec);
}

void XMLHttpRequest::createRequest(ExceptionCode& ec)
{
#if ENABLE(BLOB)
    // Only GET request is supported for blob URL.
    if (m_url.protocolIs("blob") && m_method != "GET") {
        ec = XMLHttpRequestException::NETWORK_ERR;
        return;
    }
#endif

    // The presence of upload event listeners forces us to use preflighting because POSTing to an URL that does not
    // permit cross origin requests should look exactly like POSTing to an URL that does not respond at all.
    // Also, only async requests support upload progress events.
    bool uploadEvents = false;
    if (m_async) {
        m_progressEventThrottle.dispatchEvent(XMLHttpRequestProgressEvent::create(eventNames().loadstartEvent));
        if (m_requestEntityBody && m_upload) {
            uploadEvents = m_upload->hasEventListeners();
            m_upload->dispatchEvent(XMLHttpRequestProgressEvent::create(eventNames().loadstartEvent));
        }
    }

    m_sameOriginRequest = securityOrigin()->canRequest(m_url);

    // We also remember whether upload events should be allowed for this request in case the upload listeners are
    // added after the request is started.
    m_uploadEventsAllowed = m_sameOriginRequest || uploadEvents || !isSimpleCrossOriginAccessRequest(m_method, m_requestHeaders);

    ResourceRequest request(m_url);
    request.setHTTPMethod(m_method);
#if PLATFORM(CHROMIUM) || PLATFORM(BLACKBERRY)
    request.setTargetType(ResourceRequest::TargetIsXHR);
#endif

    if (m_requestEntityBody) {
        ASSERT(m_method != "GET");
        ASSERT(m_method != "HEAD");
        request.setHTTPBody(m_requestEntityBody.release());
    }

    if (m_requestHeaders.size() > 0)
        request.addHTTPHeaderFields(m_requestHeaders);

    ThreadableLoaderOptions options;
    options.sendLoadCallbacks = SendCallbacks;
    options.sniffContent = DoNotSniffContent;
    options.preflightPolicy = uploadEvents ? ForcePreflight : ConsiderPreflight;
    options.allowCredentials = (m_sameOriginRequest || m_includeCredentials) ? AllowStoredCredentials : DoNotAllowStoredCredentials;
    options.crossOriginRequestPolicy = UseAccessControl;
    options.securityOrigin = securityOrigin();

    m_exceptionCode = 0;
    m_error = false;

    if (m_async) {
        if (m_upload)
            request.setReportUploadProgress(true);

        // ThreadableLoader::create can return null here, for example if we're no longer attached to a page.
        // This is true while running onunload handlers.
        // FIXME: Maybe we need to be able to send XMLHttpRequests from onunload, <http://bugs.webkit.org/show_bug.cgi?id=10904>.
        // FIXME: Maybe create() can return null for other reasons too?
        m_loader = ThreadableLoader::create(scriptExecutionContext(), this, request, options);
        if (m_loader) {
            // Neither this object nor the JavaScript wrapper should be deleted while
            // a request is in progress because we need to keep the listeners alive,
            // and they are referenced by the JavaScript wrapper.
            setPendingActivity(this);
        }
    } else {
        InspectorInstrumentation::willLoadXHRSynchronously(scriptExecutionContext());
        ThreadableLoader::loadResourceSynchronously(scriptExecutionContext(), request, *this, options);
        InspectorInstrumentation::didLoadXHRSynchronously(scriptExecutionContext());
    }

    if (!m_exceptionCode && m_error)
        m_exceptionCode = XMLHttpRequestException::NETWORK_ERR;
    ec = m_exceptionCode;
}

void XMLHttpRequest::abort()
{
    // internalAbort() calls dropProtection(), which may release the last reference.
    RefPtr<XMLHttpRequest> protect(this);

    bool sendFlag = m_loader;

    internalAbort();

    clearResponseBuffers();

    // Clear headers as required by the spec
    m_requestHeaders.clear();

    if ((m_state <= OPENED && !sendFlag) || m_state == DONE)
        m_state = UNSENT;
    else {
        ASSERT(!m_loader);
        changeState(DONE);
        m_state = UNSENT;
    }

    m_progressEventThrottle.dispatchEventAndLoadEnd(XMLHttpRequestProgressEvent::create(eventNames().abortEvent));
    if (!m_uploadComplete) {
        m_uploadComplete = true;
        if (m_upload && m_uploadEventsAllowed)
            m_upload->dispatchEventAndLoadEnd(XMLHttpRequestProgressEvent::create(eventNames().abortEvent));
    }
}

void XMLHttpRequest::internalAbort()
{
    bool hadLoader = m_loader;

    m_error = true;

    // FIXME: when we add the support for multi-part XHR, we will have to think be careful with this initialization.
    m_receivedLength = 0;

    if (hadLoader) {
        m_loader->cancel();
        m_loader = 0;
    }

    m_decoder = 0;

    if (hadLoader)
        dropProtection();
}

void XMLHttpRequest::clearResponse()
{
    m_response = ResourceResponse();
    clearResponseBuffers();
}

void XMLHttpRequest::clearResponseBuffers()
{
    m_responseBuilder.clear();
    m_createdDocument = false;
    m_responseDocument = 0;
#if ENABLE(XHR_RESPONSE_BLOB)
    m_responseBlob = 0;
#endif
    m_binaryResponseBuilder.clear();
    m_responseArrayBuffer.clear();
}

void XMLHttpRequest::clearRequest()
{
    m_requestHeaders.clear();
    m_requestEntityBody = 0;
}

void XMLHttpRequest::genericError()
{
    clearResponse();
    clearRequest();
    m_error = true;

    changeState(DONE);
}

void XMLHttpRequest::networkError()
{
    genericError();
    m_progressEventThrottle.dispatchEventAndLoadEnd(XMLHttpRequestProgressEvent::create(eventNames().errorEvent));
    if (!m_uploadComplete) {
        m_uploadComplete = true;
        if (m_upload && m_uploadEventsAllowed)
            m_upload->dispatchEventAndLoadEnd(XMLHttpRequestProgressEvent::create(eventNames().errorEvent));
    }
    internalAbort();
}

void XMLHttpRequest::abortError()
{
    genericError();
    m_progressEventThrottle.dispatchEventAndLoadEnd(XMLHttpRequestProgressEvent::create(eventNames().abortEvent));
    if (!m_uploadComplete) {
        m_uploadComplete = true;
        if (m_upload && m_uploadEventsAllowed)
            m_upload->dispatchEventAndLoadEnd(XMLHttpRequestProgressEvent::create(eventNames().abortEvent));
    }
}

void XMLHttpRequest::dropProtection()
{
#if USE(JSC)
    // The XHR object itself holds on to the responseText, and
    // thus has extra cost even independent of any
    // responseText or responseXML objects it has handed
    // out. But it is protected from GC while loading, so this
    // can't be recouped until the load is done, so only
    // report the extra cost at that point.
    JSC::JSLock lock(JSC::SilenceAssertionsOnly);
    JSC::JSGlobalData* globalData = scriptExecutionContext()->globalData();
    globalData->heap.reportExtraMemoryCost(m_responseBuilder.length() * 2);
#endif

    unsetPendingActivity(this);
}

void XMLHttpRequest::overrideMimeType(const String& override)
{
    m_mimeTypeOverride = override;
}

void XMLHttpRequest::setRequestHeader(const AtomicString& name, const String& value, ExceptionCode& ec)
{
    if (m_state != OPENED || m_loader) {
#if ENABLE(DASHBOARD_SUPPORT)
        if (usesDashboardBackwardCompatibilityMode())
            return;
#endif

        ec = INVALID_STATE_ERR;
        return;
    }

    if (!isValidHTTPToken(name) || !isValidHTTPHeaderValue(value)) {
        ec = SYNTAX_ERR;
        return;
    }

    // A privileged script (e.g. a Dashboard widget) can set any headers.
    if (!securityOrigin()->canLoadLocalResources() && !isAllowedHTTPHeader(name)) {
        logConsoleError(scriptExecutionContext(), "Refused to set unsafe header \"" + name + "\"");
        return;
    }

    setRequestHeaderInternal(name, value);
}

void XMLHttpRequest::setRequestHeaderInternal(const AtomicString& name, const String& value)
{
    HTTPHeaderMap::AddResult result = m_requestHeaders.add(name, value);
    if (!result.isNewEntry)
        result.iterator->second += ", " + value;
}

String XMLHttpRequest::getRequestHeader(const AtomicString& name) const
{
    return m_requestHeaders.get(name);
}

String XMLHttpRequest::getAllResponseHeaders(ExceptionCode& ec) const
{
    if (m_state < HEADERS_RECEIVED) {
        ec = INVALID_STATE_ERR;
        return "";
    }

    StringBuilder stringBuilder;

    HTTPHeaderSet accessControlExposeHeaderSet;
    parseAccessControlExposeHeadersAllowList(m_response.httpHeaderField("Access-Control-Expose-Headers"), accessControlExposeHeaderSet);
    HTTPHeaderMap::const_iterator end = m_response.httpHeaderFields().end();
    for (HTTPHeaderMap::const_iterator it = m_response.httpHeaderFields().begin(); it!= end; ++it) {
        // Hide Set-Cookie header fields from the XMLHttpRequest client for these reasons:
        //     1) If the client did have access to the fields, then it could read HTTP-only
        //        cookies; those cookies are supposed to be hidden from scripts.
        //     2) There's no known harm in hiding Set-Cookie header fields entirely; we don't
        //        know any widely used technique that requires access to them.
        //     3) Firefox has implemented this policy.
        if (isSetCookieHeader(it->first) && !securityOrigin()->canLoadLocalResources())
            continue;

        if (!m_sameOriginRequest && !isOnAccessControlResponseHeaderWhitelist(it->first) && !accessControlExposeHeaderSet.contains(it->first))
            continue;

        stringBuilder.append(it->first);
        stringBuilder.append(':');
        stringBuilder.append(' ');
        stringBuilder.append(it->second);
        stringBuilder.append('\r');
        stringBuilder.append('\n');
    }

    return stringBuilder.toString();
}

String XMLHttpRequest::getResponseHeader(const AtomicString& name, ExceptionCode& ec) const
{
    if (m_state < HEADERS_RECEIVED) {
        ec = INVALID_STATE_ERR;
        return String();
    }

    // See comment in getAllResponseHeaders above.
    if (isSetCookieHeader(name) && !securityOrigin()->canLoadLocalResources()) {
        logConsoleError(scriptExecutionContext(), "Refused to get unsafe header \"" + name + "\"");
        return String();
    }
    
    HTTPHeaderSet accessControlExposeHeaderSet;
    parseAccessControlExposeHeadersAllowList(m_response.httpHeaderField("Access-Control-Expose-Headers"), accessControlExposeHeaderSet);

    if (!m_sameOriginRequest && !isOnAccessControlResponseHeaderWhitelist(name) && !accessControlExposeHeaderSet.contains(name)) {
        logConsoleError(scriptExecutionContext(), "Refused to get unsafe header \"" + name + "\"");
        return String();
    }
    return m_response.httpHeaderField(name);
}

String XMLHttpRequest::responseMIMEType() const
{
    String mimeType = extractMIMETypeFromMediaType(m_mimeTypeOverride);
    if (mimeType.isEmpty()) {
        if (m_response.isHTTP())
            mimeType = extractMIMETypeFromMediaType(m_response.httpHeaderField("Content-Type"));
        else
            mimeType = m_response.mimeType();
    }
    if (mimeType.isEmpty())
        mimeType = "text/xml";

    return mimeType;
}

bool XMLHttpRequest::responseIsXML() const
{
    // FIXME: Remove the lower() call when DOMImplementation.isXMLMIMEType() is modified
    //        to do case insensitive MIME type matching.
    return DOMImplementation::isXMLMIMEType(responseMIMEType().lower());
}

int XMLHttpRequest::status(ExceptionCode& ec) const
{
    if (m_response.httpStatusCode())
        return m_response.httpStatusCode();

    if (m_state == OPENED) {
        // Firefox only raises an exception in this state; we match it.
        // Note the case of local file requests, where we have no HTTP response code! Firefox never raises an exception for those, but we match HTTP case for consistency.
        ec = INVALID_STATE_ERR;
    }

    return 0;
}

String XMLHttpRequest::statusText(ExceptionCode& ec) const
{
    if (!m_response.httpStatusText().isNull())
        return m_response.httpStatusText();

    if (m_state == OPENED) {
        // See comments in status() above.
        ec = INVALID_STATE_ERR;
    }

    return String();
}

void XMLHttpRequest::didFail(const ResourceError& error)
{

    // If we are already in an error state, for instance we called abort(), bail out early.
    if (m_error)
        return;

    if (error.isCancellation()) {
        m_exceptionCode = XMLHttpRequestException::ABORT_ERR;
        abortError();
        return;
    }

    // Network failures are already reported to Web Inspector by ResourceLoader.
    if (error.domain() == errorDomainWebKitInternal)
        logConsoleError(scriptExecutionContext(), "XMLHttpRequest cannot load " + error.failingURL() + ". " + error.localizedDescription());

    m_exceptionCode = XMLHttpRequestException::NETWORK_ERR;
    networkError();
}

void XMLHttpRequest::didFailRedirectCheck()
{
    networkError();
}

void XMLHttpRequest::didFinishLoading(unsigned long identifier, double)
{
    if (m_error)
        return;

    if (m_state < HEADERS_RECEIVED)
        changeState(HEADERS_RECEIVED);

    if (m_decoder)
        m_responseBuilder.append(m_decoder->flush());

    m_responseBuilder.shrinkToFit();

    InspectorInstrumentation::resourceRetrievedByXMLHttpRequest(scriptExecutionContext(), identifier, m_responseBuilder.toStringPreserveCapacity(), m_url, m_lastSendURL, m_lastSendLineNumber);

    bool hadLoader = m_loader;
    m_loader = 0;

    changeState(DONE);
    m_decoder = 0;

    if (hadLoader)
        dropProtection();
}

void XMLHttpRequest::didSendData(unsigned long long bytesSent, unsigned long long totalBytesToBeSent)
{
    if (!m_upload)
        return;

    if (m_uploadEventsAllowed)
        m_upload->dispatchEvent(XMLHttpRequestProgressEvent::create(eventNames().progressEvent, true, bytesSent, totalBytesToBeSent));

    if (bytesSent == totalBytesToBeSent && !m_uploadComplete) {
        m_uploadComplete = true;
        if (m_uploadEventsAllowed)
            m_upload->dispatchEventAndLoadEnd(XMLHttpRequestProgressEvent::create(eventNames().loadEvent));
    }
}

void XMLHttpRequest::didReceiveResponse(unsigned long identifier, const ResourceResponse& response)
{
    InspectorInstrumentation::didReceiveXHRResponse(scriptExecutionContext(), identifier);

    m_response = response;
    m_responseEncoding = extractCharsetFromMediaType(m_mimeTypeOverride);
    if (m_responseEncoding.isEmpty())
        m_responseEncoding = response.textEncodingName();
}

void XMLHttpRequest::didReceiveData(const char* data, int len)
{
    if (m_error)
        return;

    if (m_state < HEADERS_RECEIVED)
        changeState(HEADERS_RECEIVED);

    bool useDecoder = m_responseTypeCode == ResponseTypeDefault || m_responseTypeCode == ResponseTypeText || m_responseTypeCode == ResponseTypeDocument;

    if (useDecoder && !m_decoder) {
        if (!m_responseEncoding.isEmpty())
            m_decoder = TextResourceDecoder::create("text/plain", m_responseEncoding);
        // allow TextResourceDecoder to look inside the m_response if it's XML or HTML
        else if (responseIsXML()) {
            m_decoder = TextResourceDecoder::create("application/xml");
            // Don't stop on encoding errors, unlike it is done for other kinds of XML resources. This matches the behavior of previous WebKit versions, Firefox and Opera.
            m_decoder->useLenientXMLDecoding();
        } else if (equalIgnoringCase(responseMIMEType(), "text/html"))
            m_decoder = TextResourceDecoder::create("text/html", "UTF-8");
        else
            m_decoder = TextResourceDecoder::create("text/plain", "UTF-8");
    }

    if (!len)
        return;

    if (len == -1)
        len = strlen(data);

    if (useDecoder)
        m_responseBuilder.append(m_decoder->decode(data, len));
    else if (m_responseTypeCode == ResponseTypeArrayBuffer
#if ENABLE(XHR_RESPONSE_BLOB)
             || m_responseTypeCode == ResponseTypeBlob
#endif
             ) {
        // Buffer binary data.
        if (!m_binaryResponseBuilder)
            m_binaryResponseBuilder = SharedBuffer::create();
        m_binaryResponseBuilder->append(data, len);
    }

    if (!m_error) {
        long long expectedLength = m_response.expectedContentLength();
        m_receivedLength += len;

        if (m_async) {
            bool lengthComputable = expectedLength > 0 && m_receivedLength <= expectedLength;
            unsigned long long total = lengthComputable ? expectedLength : 0;
            m_progressEventThrottle.dispatchProgressEvent(lengthComputable, m_receivedLength, total);
        }

        if (m_state != LOADING)
            changeState(LOADING);
        else
            // Firefox calls readyStateChanged every time it receives data, 4449442
            callReadyStateChangeListener();
    }
}

bool XMLHttpRequest::canSuspend() const
{
    return !m_loader;
}

void XMLHttpRequest::suspend(ReasonForSuspension)
{
    m_progressEventThrottle.suspend();
}

void XMLHttpRequest::resume()
{
    m_progressEventThrottle.resume();
}

void XMLHttpRequest::stop()
{
    internalAbort();
}

void XMLHttpRequest::contextDestroyed()
{
    ASSERT(!m_loader);
    ActiveDOMObject::contextDestroyed();
}

const AtomicString& XMLHttpRequest::interfaceName() const
{
    return eventNames().interfaceForXMLHttpRequest;
}

ScriptExecutionContext* XMLHttpRequest::scriptExecutionContext() const
{
    return ActiveDOMObject::scriptExecutionContext();
}

EventTargetData* XMLHttpRequest::eventTargetData()
{
    return &m_eventTargetData;
}

EventTargetData* XMLHttpRequest::ensureEventTargetData()
{
    return &m_eventTargetData;
}

} // namespace WebCore