gecko/js/src/xpconnect/loader/mozJSComponentLoader.cpp

/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Mozilla Communicator client code, released
 * March 31, 1998.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1999
 * the Initial Developer. All Rights Reserved.
 *
 * Contributors:
 *   Mike Shaver <shaver@zeroknowledge.com>
 *   John Bandhauer <jband@netscape.com>
 *   IBM Corp.
 *   Robert Ginda <rginda@netscape.com>
 *
 * Alternatively, the contents of this file may be used under the terms of
 * either of the GNU General Public License Version 2 or later (the "GPL"),
 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
 * in which case the provisions of the GPL or the LGPL are applicable instead
 * of those above. If you wish to allow use of your version of this file only
 * under the terms of either the GPL or the LGPL, and not to allow others to
 * use your version of this file under the terms of the MPL, indicate your
 * decision by deleting the provisions above and replace them with the notice
 * and other provisions required by the GPL or the LGPL. If you do not delete
 * the provisions above, a recipient may use your version of this file under
 * the terms of any one of the MPL, the GPL or the LGPL.
 *
 * ***** END LICENSE BLOCK ***** */

#ifdef MOZ_LOGGING
#define FORCE_PR_LOG
#endif

#include <stdarg.h>

#include "prlog.h"

#include "nsCOMPtr.h"
#include "nsAutoPtr.h"
#include "nsICategoryManager.h"
#include "nsIComponentManager.h"
#include "nsIComponentManagerObsolete.h"
#include "nsIGenericFactory.h"
#include "nsILocalFile.h"
#include "nsIModule.h"
#include "nsIServiceManager.h"
#include "nsISupports.h"
#include "mozJSComponentLoader.h"
#include "nsIJSRuntimeService.h"
#include "nsIJSContextStack.h"
#include "nsIXPConnect.h"
#include "nsCRT.h"
#include "nsMemory.h"
#include "nsIObserverService.h"
#include "nsIXPCScriptable.h"
#include "nsString.h"
#ifndef XPCONNECT_STANDALONE
#include "nsIScriptSecurityManager.h"
#include "nsIURI.h"
#include "nsIFileURL.h"
#include "nsNetUtil.h"
#endif
#include "jsxdrapi.h"
#include "jsprf.h"
#include "nsIFastLoadFileControl.h"
// For reporting errors with the console service
#include "nsIScriptError.h"
#include "nsIConsoleService.h"
#include "prmem.h"
#include "plbase64.h"

#if defined(MOZ_SHARK) || defined(MOZ_CALLGRIND) || defined(MOZ_VTUNE)
#include "jsdbgapi.h"
#endif

static const char kJSRuntimeServiceContractID[] = "@mozilla.org/js/xpc/RuntimeService;1";
static const char kXPConnectServiceContractID[] = "@mozilla.org/js/xpc/XPConnect;1";
static const char kObserverServiceContractID[] = "@mozilla.org/observer-service;1";

/* Some platforms don't have an implementation of PR_MemMap(). */
/* See bug 318077 for WinCE.                                   */
#if !defined(XP_BEOS) && !defined(XP_OS2) && !defined(WINCE)
#define HAVE_PR_MEMMAP
#endif

/**
 * Buffer sizes for serialization and deserialization of scripts.
 * FIXME: bug #411579 (tune this macro!) Last updated: Jan 2008
 */
#define XPC_SERIALIZATION_BUFFER_SIZE   (64 * 1024)
#define XPC_DESERIALIZATION_BUFFER_SIZE (12 * 8192)

// Inactivity delay before closing our fastload file stream.
static const int kFastLoadWriteDelay = 10000;   // 10 seconds

#ifdef PR_LOGGING
// NSPR_LOG_MODULES=JSComponentLoader:5
static PRLogModuleInfo *gJSCLLog;
#endif

#define LOG(args) PR_LOG(gJSCLLog, PR_LOG_DEBUG, args)

// Components.utils.import error messages
#define ERROR_SCOPE_OBJ "%s - Second argument must be an object."
#define ERROR_NOT_PRESENT "%s - EXPORTED_SYMBOLS is not present."
#define ERROR_NOT_AN_ARRAY "%s - EXPORTED_SYMBOLS is not an array."
#define ERROR_GETTING_ARRAY_LENGTH "%s - Error getting array length of EXPORTED_SYMBOLS."
#define ERROR_ARRAY_ELEMENT "%s - EXPORTED_SYMBOLS[%d] is not a string."
#define ERROR_GETTING_SYMBOL "%s - Could not get symbol '%s'."
#define ERROR_SETTING_SYMBOL "%s - Could not set symbol '%s' on target object."

void JS_DLL_CALLBACK
mozJSLoaderErrorReporter(JSContext *cx, const char *message, JSErrorReport *rep)
{
    nsresult rv;

    /* Use the console service to register the error. */
    nsCOMPtr<nsIConsoleService> consoleService =
        do_GetService(NS_CONSOLESERVICE_CONTRACTID);

    /*
     * Make an nsIScriptError, populate it with information from this
     * error, then log it with the console service.  The UI can then
     * poll the service to update the Error console.
     */
    nsCOMPtr<nsIScriptError> errorObject = 
        do_CreateInstance(NS_SCRIPTERROR_CONTRACTID);
    
    if (consoleService && errorObject) {
        /*
         * Got an error object; prepare appropriate-width versions of
         * various arguments to it.
         */
        nsAutoString fileUni;
        fileUni.AssignWithConversion(rep->filename);

        PRUint32 column = rep->uctokenptr - rep->uclinebuf;

        rv = errorObject->Init(reinterpret_cast<const PRUnichar*>
                                               (rep->ucmessage),
                               fileUni.get(),
                               reinterpret_cast<const PRUnichar*>
                                               (rep->uclinebuf),
                               rep->lineno, column, rep->flags,
                               "component javascript");
        if (NS_SUCCEEDED(rv)) {
            rv = consoleService->LogMessage(errorObject);
            if (NS_SUCCEEDED(rv)) {
                // We're done!  Skip return to fall thru to stderr
                // printout, for the benefit of those invoking the
                // browser with -console
                // return;
            }
        }
    }

    /*
     * If any of the above fails for some reason, fall back to
     * printing to stderr.
     */
#ifdef DEBUG
    fprintf(stderr, "JS Component Loader: %s %s:%d\n"
            "                     %s\n",
            JSREPORT_IS_WARNING(rep->flags) ? "WARNING" : "ERROR",
            rep->filename, rep->lineno,
            message ? message : "<no message>");
#endif
}

JS_STATIC_DLL_CALLBACK(JSBool)
Dump(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
{
    JSString *str;
    if (!argc)
        return JS_TRUE;
    
    str = JS_ValueToString(cx, argv[0]);
    if (!str)
        return JS_FALSE;

    char *bytes = JS_GetStringBytes(str);
    fputs(bytes, stderr);
    return JS_TRUE;
}

JS_STATIC_DLL_CALLBACK(JSBool)
Debug(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
{
#ifdef DEBUG
    return Dump(cx, obj, argc, argv, rval);
#else
    return JS_TRUE;
#endif
}

JS_STATIC_DLL_CALLBACK(JSBool)
Atob(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
{
    JSString *str;
    if (!argc)
        return JS_TRUE;

    str = JS_ValueToString(cx, argv[0]);
    if (!str)
        return JS_FALSE;

    size_t base64StrLength = JS_GetStringLength(str);
    char *base64Str = JS_GetStringBytes(str);

    PRUint32 bin_dataLength = (PRUint32)base64StrLength;
    if (base64Str[base64StrLength - 1] == '=') {
        if (base64Str[base64StrLength - 2] == '=')
            bin_dataLength -= 2;
        else  
            --bin_dataLength;
    }
    bin_dataLength = (PRUint32)((PRUint64)bin_dataLength * 3) / 4;

    char *bin_data = PL_Base64Decode(base64Str, base64StrLength, nsnull);
    if (!bin_data)
        return JS_FALSE;

    str = JS_NewStringCopyN(cx, bin_data, bin_dataLength);
    PR_Free(bin_data);
    if (!str)
        return JS_FALSE;

    *rval = STRING_TO_JSVAL(str);
    return JS_TRUE;
}

JS_STATIC_DLL_CALLBACK(JSBool)
Btoa(JSContext *cx, JSObject *obj, uintN argc, jsval *argv, jsval *rval)
{
    JSString *str;
    if (!argc)
        return JS_TRUE;

    str = JS_ValueToString(cx, argv[0]);
    if (!str)
        return JS_FALSE;

    char *bin_data = JS_GetStringBytes(str);
    size_t bin_dataLength = JS_GetStringLength(str);

    char *base64 = PL_Base64Encode(bin_data, bin_dataLength, nsnull);
    if (!base64)
        return JS_FALSE;

    PRUint32 base64Length = ((bin_dataLength + 2) / 3) * 4;
    str = JS_NewStringCopyN(cx, base64, base64Length);
    PR_Free(base64);
    if (!str)
        return JS_FALSE;

    *rval = STRING_TO_JSVAL(str);
    return JS_TRUE;
}

static JSFunctionSpec gGlobalFun[] = {
    {"dump",    Dump,   1,0,0},
    {"debug",   Debug,  1,0,0},
    {"atob",    Atob,   1,0,0},
    {"btoa",    Btoa,   1,0,0},
#ifdef MOZ_SHARK
    {"startShark",      js_StartShark,     0,0,0},
    {"stopShark",       js_StopShark,      0,0,0},
    {"connectShark",    js_ConnectShark,   0,0,0},
    {"disconnectShark", js_DisconnectShark,0,0,0},
#endif
#ifdef MOZ_CALLGRIND
    {"startCallgrind",  js_StartCallgrind, 0,0,0},
    {"stopCallgrind",   js_StopCallgrind,  0,0,0},
    {"dumpCallgrind",   js_DumpCallgrind,  1,0,0},
#endif
#ifdef MOZ_VTUNE
    {"startVtune",      js_StartVtune,     1,0,0},
    {"stopVtune",       js_StopVtune,      0,0,0},
    {"pauseVtune",      js_PauseVtune,     0,0,0},
    {"resumeVtune",     js_ResumeVtune,    0,0,0},
#endif
    {nsnull,nsnull,0,0,0}
};

class JSCLContextHelper
{
public:
    JSCLContextHelper(mozJSComponentLoader* loader);
    ~JSCLContextHelper();

    operator JSContext*() const {return mContext;}

    JSCLContextHelper(); // not implemnted
private:
    JSContext* mContext;
    intN       mContextThread;
    nsIThreadJSContextStack* mContextStack;
};


class JSCLAutoErrorReporterSetter
{
public:
    JSCLAutoErrorReporterSetter(JSContext* cx, JSErrorReporter reporter)
        {mContext = cx; mOldReporter = JS_SetErrorReporter(cx, reporter);}
    ~JSCLAutoErrorReporterSetter()
        {JS_SetErrorReporter(mContext, mOldReporter);} 
    JSCLAutoErrorReporterSetter(); // not implemented
private:
    JSContext* mContext;
    JSErrorReporter mOldReporter;
};

NS_IMPL_ISUPPORTS1(nsXPCFastLoadIO, nsIFastLoadFileIO)

NS_IMETHODIMP
nsXPCFastLoadIO::GetInputStream(nsIInputStream **_retval)
{
    if (! mInputStream) {
        nsCOMPtr<nsIInputStream> fileInput;
        nsresult rv = NS_NewLocalFileInputStream(getter_AddRefs(fileInput),
                                                 mFile);
        NS_ENSURE_SUCCESS(rv, rv);

        rv = NS_NewBufferedInputStream(getter_AddRefs(mInputStream),
                                       fileInput,
                                       XPC_DESERIALIZATION_BUFFER_SIZE);
        NS_ENSURE_SUCCESS(rv, rv);
    }

    NS_ADDREF(*_retval = mInputStream);
    return NS_OK;
}

NS_IMETHODIMP
nsXPCFastLoadIO::GetOutputStream(nsIOutputStream **_retval)
{
    if (! mOutputStream) {
        PRInt32 ioFlags = PR_WRONLY;
        if (! mInputStream) {
            ioFlags |= PR_CREATE_FILE | PR_TRUNCATE;
        }

        nsCOMPtr<nsIOutputStream> fileOutput;
        nsresult rv = NS_NewLocalFileOutputStream(getter_AddRefs(fileOutput),
                                                  mFile, ioFlags, 0644);
        NS_ENSURE_SUCCESS(rv, rv);

        rv = NS_NewBufferedOutputStream(getter_AddRefs(mOutputStream),
                                        fileOutput,
                                        XPC_SERIALIZATION_BUFFER_SIZE);
        NS_ENSURE_SUCCESS(rv, rv);
    }

    NS_ADDREF(*_retval = mOutputStream);
    return NS_OK;
}

static nsresult
ReadScriptFromStream(JSContext *cx, nsIObjectInputStream *stream,
                     JSScript **script)
{
    *script = nsnull;

    PRUint32 size;
    nsresult rv = stream->Read32(&size);
    NS_ENSURE_SUCCESS(rv, rv);

    char *data;
    rv = stream->ReadBytes(size, &data);
    NS_ENSURE_SUCCESS(rv, rv);

    JSXDRState *xdr = JS_XDRNewMem(cx, JSXDR_DECODE);
    NS_ENSURE_TRUE(xdr, NS_ERROR_OUT_OF_MEMORY);

    xdr->userdata = stream;
    JS_XDRMemSetData(xdr, data, size);

    if (!JS_XDRScript(xdr, script)) {
        rv = NS_ERROR_FAILURE;
    }

    // Update data in case ::JS_XDRScript called back into C++ code to
    // read an XPCOM object.
    //
    // In that case, the serialization process must have flushed a run
    // of counted bytes containing JS data at the point where the XPCOM
    // object starts, after which an encoding C++ callback from the JS
    // XDR code must have written the XPCOM object directly into the
    // nsIObjectOutputStream.
    //
    // The deserialization process will XDR-decode counted bytes up to
    // but not including the XPCOM object, then call back into C++ to
    // read the object, then read more counted bytes and hand them off
    // to the JSXDRState, so more JS data can be decoded.
    //
    // This interleaving of JS XDR data and XPCOM object data may occur
    // several times beneath the call to ::JS_XDRScript, above.  At the
    // end of the day, we need to free (via nsMemory) the data owned by
    // the JSXDRState.  So we steal it back, nulling xdr's buffer so it
    // doesn't get passed to ::JS_free by ::JS_XDRDestroy.

    uint32 length;
    data = static_cast<char*>(JS_XDRMemGetData(xdr, &length));
    if (data) {
        JS_XDRMemSetData(xdr, nsnull, 0);
    }
    JS_XDRDestroy(xdr);

    // If data is null now, it must have been freed while deserializing an
    // XPCOM object (e.g., a principal) beneath ::JS_XDRScript.
    if (data) {
        nsMemory::Free(data);
    }

    return rv;
}

static nsresult
WriteScriptToStream(JSContext *cx, JSScript *script,
                    nsIObjectOutputStream *stream)
{
    JSXDRState *xdr = JS_XDRNewMem(cx, JSXDR_ENCODE);
    NS_ENSURE_TRUE(xdr, NS_ERROR_OUT_OF_MEMORY);

    xdr->userdata = stream;
    nsresult rv = NS_OK;

    if (JS_XDRScript(xdr, &script)) {
        // Get the encoded JSXDRState data and write it.  The JSXDRState owns
        // this buffer memory and will free it beneath ::JS_XDRDestroy.
        //
        // If an XPCOM object needs to be written in the midst of the JS XDR
        // encoding process, the C++ code called back from the JS engine (e.g.,
        // nsEncodeJSPrincipals in caps/src/nsJSPrincipals.cpp) will flush data
        // from the JSXDRState to aStream, then write the object, then return
        // to JS XDR code with xdr reset so new JS data is encoded at the front
        // of the xdr's data buffer.
        //
        // However many XPCOM objects are interleaved with JS XDR data in the
        // stream, when control returns here from ::JS_XDRScript, we'll have
        // one last buffer of data to write to aStream.

        uint32 size;
        const char* data = reinterpret_cast<const char*>
                                           (JS_XDRMemGetData(xdr, &size));
        NS_ASSERTION(data, "no decoded JSXDRState data!");

        rv = stream->Write32(size);
        if (NS_SUCCEEDED(rv)) {
            rv = stream->WriteBytes(data, size);
        }
    } else {
        rv = NS_ERROR_FAILURE; // likely to be a principals serialization error
    }

    JS_XDRDestroy(xdr);
    return rv;
}

mozJSComponentLoader::mozJSComponentLoader()
    : mRuntime(nsnull),
      mContext(nsnull),
      mInitialized(PR_FALSE)
{
    NS_ASSERTION(!sSelf, "mozJSComponentLoader should be a singleton");

#ifdef PR_LOGGING
    if (!gJSCLLog) {
        gJSCLLog = PR_NewLogModule("JSComponentLoader");
    }
#endif

    sSelf = this;
}

mozJSComponentLoader::~mozJSComponentLoader()
{
    if (mInitialized) {
        NS_ERROR("'xpcom-shutdown-loaders' was not fired before cleaning up mozJSComponentLoader");
        UnloadModules();
    }

    NS_ASSERTION(!mFastLoadTimer,
                 "Fastload file should have been closed via xpcom-shutdown");

    sSelf = nsnull;
}

mozJSComponentLoader*
mozJSComponentLoader::sSelf;

NS_IMPL_ISUPPORTS3(mozJSComponentLoader,
                   nsIModuleLoader,
                   xpcIJSModuleLoader,
                   nsIObserver)
 
nsresult
mozJSComponentLoader::ReallyInit()
{
    nsresult rv;

    /*
     * Get the JSRuntime from the runtime svc, if possible.
     * We keep a reference around, because it's a Bad Thing if the runtime
     * service gets shut down before we're done.  Bad!
     */

    mRuntimeService = do_GetService(kJSRuntimeServiceContractID, &rv);
    if (NS_FAILED(rv) ||
        NS_FAILED(rv = mRuntimeService->GetRuntime(&mRuntime)))
        return rv;

    mContextStack = do_GetService("@mozilla.org/js/xpc/ContextStack;1", &rv);
    if (NS_FAILED(rv))
        return rv;

    // Create our compilation context.
    mContext = JS_NewContext(mRuntime, 256);
    if (!mContext)
        return NS_ERROR_OUT_OF_MEMORY;

    uint32 options = JS_GetOptions(mContext);
    JS_SetOptions(mContext, options | JSOPTION_XML);

    // Always use the latest js version
    JS_SetVersion(mContext, JSVERSION_LATEST);

    // Limit C stack consumption to a reasonable 512K
    int stackDummy;
    const jsuword kStackSize = 0x80000;
    jsuword stackLimit, currentStackAddr = (jsuword)&stackDummy;

#if JS_STACK_GROWTH_DIRECTION < 0
    stackLimit = (currentStackAddr > kStackSize)
                 ? currentStackAddr - kStackSize
                 : 0;
#else
    stackLimit = (currentStackAddr + kStackSize > currentStackAddr)
                 ? currentStackAddr + kStackSize
                 : (jsuword) -1;
#endif
    
    JS_SetThreadStackLimit(mContext, stackLimit);

#ifndef XPCONNECT_STANDALONE
    nsCOMPtr<nsIScriptSecurityManager> secman = 
        do_GetService(NS_SCRIPTSECURITYMANAGER_CONTRACTID);
    if (!secman)
        return NS_ERROR_FAILURE;

    rv = secman->GetSystemPrincipal(getter_AddRefs(mSystemPrincipal));
    if (NS_FAILED(rv) || !mSystemPrincipal)
        return NS_ERROR_FAILURE;
#endif

    if (!mModules.Init(32))
        return NS_ERROR_OUT_OF_MEMORY;
    if (!mImports.Init(32))
        return NS_ERROR_OUT_OF_MEMORY;
    if (!mInProgressImports.Init(32))
        return NS_ERROR_OUT_OF_MEMORY;

    // Set up our fastload file
    nsCOMPtr<nsIFastLoadService> flSvc = do_GetFastLoadService(&rv);
    if (NS_SUCCEEDED(rv))
        rv = flSvc->NewFastLoadFile("XPC", getter_AddRefs(mFastLoadFile));
    if (NS_FAILED(rv)) {
        LOG(("Could not get fastload file location\n"));
    }

    // Listen for xpcom-shutdown so that we can close out our fastload file
    // at that point (after that we can no longer create an input stream).
    nsCOMPtr<nsIObserverService> obsSvc =
        do_GetService(kObserverServiceContractID, &rv);
    NS_ENSURE_SUCCESS(rv, rv);

    rv = obsSvc->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, PR_FALSE);
    NS_ENSURE_SUCCESS(rv, rv);

    rv = obsSvc->AddObserver(this, "xpcom-shutdown-loaders", PR_FALSE);
    NS_ENSURE_SUCCESS(rv, rv);

#ifdef DEBUG_shaver_off
    fprintf(stderr, "mJCL: ReallyInit success!\n");
#endif
    mInitialized = PR_TRUE;

    return NS_OK;
}

NS_IMETHODIMP
mozJSComponentLoader::LoadModule(nsILocalFile* aComponentFile,
                                 nsIModule* *aResult)
{
    nsresult rv;

    nsCAutoString leafName;
    aComponentFile->GetNativeLeafName(leafName);
    if (!StringTail(leafName, 3).LowerCaseEqualsLiteral(".js"))
        return NS_ERROR_INVALID_ARG;

    if (!mInitialized) {
        rv = ReallyInit();
        if (NS_FAILED(rv))
            return rv;
    }

    nsCOMPtr<nsIHashable> lfhash(do_QueryInterface(aComponentFile));
    if (!lfhash) {
        NS_ERROR("nsLocalFile not implementing nsIHashable");
        return NS_NOINTERFACE;
    }

    ModuleEntry* mod;
    if (mModules.Get(lfhash, &mod)) {
        NS_ASSERTION(mod->module, "Bad hashtable data!");
        NS_ADDREF(*aResult = mod->module);
        return NS_OK;
    }

    nsAutoPtr<ModuleEntry> entry(new ModuleEntry);
    if (!entry)
        return NS_ERROR_OUT_OF_MEMORY;

    rv = GlobalForLocation(aComponentFile, &entry->global, &entry->location,
                           nsnull);
    if (NS_FAILED(rv)) {
#ifdef DEBUG_shaver
        fprintf(stderr, "GlobalForLocation failed!\n");
#endif
        return rv;
    }

    nsCOMPtr<nsIXPConnect> xpc = do_GetService(kXPConnectServiceContractID,
                                               &rv);
    if (NS_FAILED(rv))
        return rv;

    nsCOMPtr<nsIComponentManager> cm;
    rv = NS_GetComponentManager(getter_AddRefs(cm));
    if (NS_FAILED(rv))
        return rv;

    JSCLContextHelper cx(this);

    JSObject* cm_jsobj;
    nsCOMPtr<nsIXPConnectJSObjectHolder> cm_holder;
    rv = xpc->WrapNative(cx, entry->global, cm, 
                         NS_GET_IID(nsIComponentManager),
                         getter_AddRefs(cm_holder));

    if (NS_FAILED(rv)) {
#ifdef DEBUG_shaver
        fprintf(stderr, "WrapNative(%p,%p,nsIComponentManager) failed: %x\n",
                (void *)(JSContext*)cx, (void *)mCompMgr, rv);
#endif
        return rv;
    }

    rv = cm_holder->GetJSObject(&cm_jsobj);
    if (NS_FAILED(rv)) {
#ifdef DEBUG_shaver
        fprintf(stderr, "GetJSObject of ComponentManager failed\n");
#endif
        return rv;
    }

    JSObject* file_jsobj;
    nsCOMPtr<nsIXPConnectJSObjectHolder> file_holder;
    rv = xpc->WrapNative(cx, entry->global, aComponentFile, 
                         NS_GET_IID(nsIFile),
                         getter_AddRefs(file_holder));

    if (NS_FAILED(rv)) {
        return rv;
    }

    rv = file_holder->GetJSObject(&file_jsobj);
    if (NS_FAILED(rv)) {
        return rv;
    }

    JSCLAutoErrorReporterSetter aers(cx, mozJSLoaderErrorReporter);

    jsval argv[2], retval, NSGetModule_val;

    if (!JS_GetProperty(cx, entry->global, "NSGetModule", &NSGetModule_val) ||
        JSVAL_IS_VOID(NSGetModule_val)) {
        return NS_ERROR_FAILURE;
    }

    if (JS_TypeOfValue(cx, NSGetModule_val) != JSTYPE_FUNCTION) {
        nsCAutoString path;
        aComponentFile->GetNativePath(path);

        JS_ReportError(cx, "%s has NSGetModule property that is not a function",
                       path.get());
        return NS_ERROR_FAILURE;
    }
    
    argv[0] = OBJECT_TO_JSVAL(cm_jsobj);
    argv[1] = OBJECT_TO_JSVAL(file_jsobj);
    if (!JS_CallFunctionValue(cx, entry->global, NSGetModule_val,
                              2, argv, &retval)) {
        return NS_ERROR_FAILURE;
    }

#ifdef DEBUG_shaver_off
    JSString *s = JS_ValueToString(cx, retval);
    fprintf(stderr, "mJCL: %s::NSGetModule returned %s\n",
            registryLocation, JS_GetStringBytes(s));
#endif

    JSObject *jsModuleObj;
    if (!JS_ValueToObject(cx, retval, &jsModuleObj)) {
        /* XXX report error properly */
        return NS_ERROR_FAILURE;
    }

    rv = xpc->WrapJS(cx, jsModuleObj,
                     NS_GET_IID(nsIModule), getter_AddRefs(entry->module));
    if (NS_FAILED(rv)) {
        /* XXX report error properly */
#ifdef DEBUG
        fprintf(stderr, "mJCL: couldn't get nsIModule from jsval\n");
#endif
        return rv;
    }

    // Cache this module for later
    if (!mModules.Put(lfhash, entry))
        return NS_ERROR_OUT_OF_MEMORY;

    NS_ADDREF(*aResult = entry->module);

    // The hash owns the ModuleEntry now, forget about it
    entry.forget();

    return NS_OK;
}

// Some stack based classes for cleaning up on early return
#ifdef HAVE_PR_MEMMAP
class FileAutoCloser
{
 public:
    explicit FileAutoCloser(PRFileDesc *file) : mFile(file) {}
    ~FileAutoCloser() { PR_Close(mFile); }
 private:
    PRFileDesc *mFile;
};

class FileMapAutoCloser
{
 public:
    explicit FileMapAutoCloser(PRFileMap *map) : mMap(map) {}
    ~FileMapAutoCloser() { PR_CloseFileMap(mMap); }
 private:
    PRFileMap *mMap;
};
#endif

class JSPrincipalsHolder
{
 public:
    JSPrincipalsHolder(JSContext *cx, JSPrincipals *principals)
        : mCx(cx), mPrincipals(principals) {}
    ~JSPrincipalsHolder() { JSPRINCIPALS_DROP(mCx, mPrincipals); }
 private:
    JSContext *mCx;
    JSPrincipals *mPrincipals;
};

class JSScriptHolder
{
 public:
    JSScriptHolder(JSContext *cx, JSScript *script)
        : mCx(cx), mScript(script) {}
    ~JSScriptHolder() { ::JS_DestroyScript(mCx, mScript); }
 private:
    JSContext *mCx;
    JSScript *mScript;
};

class FastLoadStateHolder
{
 public:
    explicit FastLoadStateHolder(nsIFastLoadService *service);
    ~FastLoadStateHolder() { pop(); }

    void pop();

 private:
    nsCOMPtr<nsIFastLoadService> mService;
    nsCOMPtr<nsIFastLoadFileIO> mIO;
    nsCOMPtr<nsIObjectInputStream> mInputStream;
    nsCOMPtr<nsIObjectOutputStream> mOutputStream;
};

FastLoadStateHolder::FastLoadStateHolder(nsIFastLoadService *service)
{
    if (!service)
        return;

    mService = service;
    service->GetFileIO(getter_AddRefs(mIO));
    service->GetInputStream(getter_AddRefs(mInputStream));
    service->GetOutputStream(getter_AddRefs(mOutputStream));
}

void
FastLoadStateHolder::pop()
{
    if (!mService)
        return;

    mService->SetFileIO(mIO);
    mService->SetInputStream(mInputStream);
    mService->SetOutputStream(mOutputStream);

    mService = nsnull;
}

/* static */
void
mozJSComponentLoader::CloseFastLoad(nsITimer *timer, void *closure)
{
    static_cast<mozJSComponentLoader*>(closure)->CloseFastLoad();
}

void
mozJSComponentLoader::CloseFastLoad()
{
    // Close our fastload streams
    LOG(("Closing fastload file\n"));
    if (mFastLoadOutput) {
        nsresult rv = mFastLoadOutput->Close();
        if (NS_SUCCEEDED(rv)) {
            nsCOMPtr<nsIFastLoadService> flSvc = do_GetFastLoadService(&rv);
            if (NS_SUCCEEDED(rv)) {
                flSvc->CacheChecksum(mFastLoadFile, mFastLoadOutput);
            }
        }
        mFastLoadOutput = nsnull;
    }
    if (mFastLoadInput) {
        mFastLoadInput->Close();
        mFastLoadInput = nsnull;
    }

    mFastLoadIO = nsnull;
    mFastLoadTimer = nsnull;
}

nsresult
mozJSComponentLoader::StartFastLoad(nsIFastLoadService *flSvc)
{
    if (!mFastLoadFile || !flSvc) {
        return NS_ERROR_NOT_AVAILABLE;
    }

    // Now set our IO object as current, and create our streams.
    if (!mFastLoadIO) {
        mFastLoadIO = new nsXPCFastLoadIO(mFastLoadFile);
        NS_ENSURE_TRUE(mFastLoadIO, NS_ERROR_OUT_OF_MEMORY);
    }

    nsresult rv = flSvc->SetFileIO(mFastLoadIO);
    NS_ENSURE_SUCCESS(rv, rv);

    if (!mFastLoadInput && !mFastLoadOutput) {
        // First time accessing the fastload file
        PRBool exists;
        mFastLoadFile->Exists(&exists);
        if (exists) {
            LOG(("trying to use existing fastload file\n"));

            nsCOMPtr<nsIInputStream> input;
            rv = mFastLoadIO->GetInputStream(getter_AddRefs(input));
            NS_ENSURE_SUCCESS(rv, rv);

            rv = flSvc->NewInputStream(input, getter_AddRefs(mFastLoadInput));
            if (NS_SUCCEEDED(rv)) {
                LOG(("opened fastload file for reading\n"));

                nsCOMPtr<nsIFastLoadReadControl>
                    readControl(do_QueryInterface(mFastLoadInput));
                if (readControl) {
                    // Verify checksum, using the FastLoadService's
                    // checksum cache to avoid computing more than once
                    // per session.
                    PRUint32 checksum;
                    rv = readControl->GetChecksum(&checksum);
                    if (NS_SUCCEEDED(rv)) {
                        PRUint32 verified;
                        rv = flSvc->ComputeChecksum(mFastLoadFile,
                                                    readControl, &verified);
                        if (NS_SUCCEEDED(rv) && verified != checksum) {
                            LOG(("Incorrect checksum detected"));
                            rv = NS_ERROR_FAILURE;
                        }
                    }
                }

                if (NS_SUCCEEDED(rv)) {
                    /* Get the JS bytecode version number and validate it. */
                    PRUint32 version;
                    rv = mFastLoadInput->Read32(&version);
                    if (NS_SUCCEEDED(rv) && version != JSXDR_BYTECODE_VERSION) {
                        LOG(("Bad JS bytecode version\n"));
                        rv = NS_ERROR_UNEXPECTED;
                    }
                }
            }
            if (NS_FAILED(rv)) {
                LOG(("Invalid fastload file detected, removing it\n"));
                if (mFastLoadInput) {
                    mFastLoadInput->Close();
                    mFastLoadInput = nsnull;
                } else {
                    input->Close();
                }
                mFastLoadIO->SetInputStream(nsnull);
                mFastLoadFile->Remove(PR_FALSE);
                exists = PR_FALSE;
            }
        }

        if (!exists) {
            LOG(("Creating new fastload file\n"));

            nsCOMPtr<nsIOutputStream> output;
            rv = mFastLoadIO->GetOutputStream(getter_AddRefs(output));
            NS_ENSURE_SUCCESS(rv, rv);

            rv = flSvc->NewOutputStream(output,
                                        getter_AddRefs(mFastLoadOutput));

            if (NS_SUCCEEDED(rv))
                rv = mFastLoadOutput->Write32(JSXDR_BYTECODE_VERSION);

            if (NS_FAILED(rv)) {
                LOG(("Fatal error, could not create fastload file\n"));

                if (mFastLoadOutput) {
                    mFastLoadOutput->Close();
                    mFastLoadOutput = nsnull;
                } else {
                    output->Close();
                }
                mFastLoadIO->SetOutputStream(nsnull);
                mFastLoadFile->Remove(PR_FALSE);
                return rv;
            }
        }
    }

    flSvc->SetInputStream(mFastLoadInput);
    flSvc->SetOutputStream(mFastLoadOutput);

    // Start our update timer.  This allows us to keep the stream open
    // when many components are loaded in succession, but close it once
    // there has been a period of inactivity.

    if (!mFastLoadTimer) {
        mFastLoadTimer = do_CreateInstance(NS_TIMER_CONTRACTID, &rv);
        NS_ENSURE_SUCCESS(rv, rv);

        rv = mFastLoadTimer->InitWithFuncCallback(&mozJSComponentLoader::CloseFastLoad,
                                                  this,
                                                  kFastLoadWriteDelay,
                                                  nsITimer::TYPE_ONE_SHOT);
    } else {
        rv = mFastLoadTimer->SetDelay(kFastLoadWriteDelay);
    }

    return rv;
}

nsresult
mozJSComponentLoader::ReadScript(nsIFastLoadService *flSvc,
                                 const char *nativePath, nsIURI *uri,
                                 JSContext *cx, JSScript **script)
{
    NS_ASSERTION(flSvc, "fastload not initialized");

    nsresult rv = flSvc->StartMuxedDocument(uri, nativePath,
                                            nsIFastLoadService::NS_FASTLOAD_READ);
    if (NS_FAILED(rv)) {
        return rv; // don't warn since NOT_AVAILABLE is an ok error
    }

    LOG(("Found %s in fastload file\n", nativePath));

    nsCOMPtr<nsIURI> oldURI;
    rv = flSvc->SelectMuxedDocument(uri, getter_AddRefs(oldURI));
    NS_ENSURE_SUCCESS(rv, rv);

    NS_ASSERTION(mFastLoadInput,
                 "FASTLOAD_READ should only succeed with an input stream");

    rv = ReadScriptFromStream(cx, mFastLoadInput, script);
    if (NS_SUCCEEDED(rv)) {
        rv = flSvc->EndMuxedDocument(uri);
    }

    return rv;
}

nsresult
mozJSComponentLoader::WriteScript(nsIFastLoadService *flSvc, JSScript *script,
                                  nsIFile *component, const char *nativePath,
                                  nsIURI *uri, JSContext *cx)
{
    NS_ASSERTION(flSvc, "fastload not initialized");
    nsresult rv;

    if (!mFastLoadOutput) {
        // Trying to read a URI that was not in the fastload file will have
        // created an output stream for us.  But, if we haven't tried to
        // load anything that was missing, it will still be null.
        rv = flSvc->GetOutputStream(getter_AddRefs(mFastLoadOutput));
        NS_ENSURE_SUCCESS(rv, rv);
    }

    NS_ASSERTION(mFastLoadOutput, "must have an output stream here");

    LOG(("Writing %s to fastload\n", nativePath));
    rv = flSvc->AddDependency(component);
    NS_ENSURE_SUCCESS(rv, rv);

    rv = flSvc->StartMuxedDocument(uri, nativePath,
                                   nsIFastLoadService::NS_FASTLOAD_WRITE);
    NS_ENSURE_SUCCESS(rv, rv);

    nsCOMPtr<nsIURI> oldURI;
    rv = flSvc->SelectMuxedDocument(uri, getter_AddRefs(oldURI));
    NS_ENSURE_SUCCESS(rv, rv);

    rv = WriteScriptToStream(cx, script, mFastLoadOutput);
    NS_ENSURE_SUCCESS(rv, rv);

    return flSvc->EndMuxedDocument(uri);
}

nsresult
mozJSComponentLoader::GlobalForLocation(nsILocalFile *aComponent,
                                        JSObject **aGlobal,
                                        char **aLocation,
                                        jsval *exception)
{
    nsresult rv;

    JSPrincipals* jsPrincipals = nsnull;
    JSCLContextHelper cx(this);

#ifndef XPCONNECT_STANDALONE
    rv = mSystemPrincipal->GetJSPrincipals(cx, &jsPrincipals);
    NS_ENSURE_SUCCESS(rv, rv);

    JSPrincipalsHolder princHolder(mContext, jsPrincipals);
#endif

    nsCOMPtr<nsIXPCScriptable> backstagePass;
    rv = mRuntimeService->GetBackstagePass(getter_AddRefs(backstagePass));
    NS_ENSURE_SUCCESS(rv, rv);

    JSCLAutoErrorReporterSetter aers(cx, mozJSLoaderErrorReporter);

    nsCOMPtr<nsIXPConnect> xpc =
        do_GetService(kXPConnectServiceContractID, &rv);
    NS_ENSURE_SUCCESS(rv, rv);

    // Make sure InitClassesWithNewWrappedGlobal() installs the
    // backstage pass as the global in our compilation context.
    JS_SetGlobalObject(cx, nsnull);

    nsCOMPtr<nsIXPConnectJSObjectHolder> holder;
    rv = xpc->InitClassesWithNewWrappedGlobal(cx, backstagePass,
                                              NS_GET_IID(nsISupports),
                                              nsIXPConnect::
                                                  FLAG_SYSTEM_GLOBAL_OBJECT,
                                              getter_AddRefs(holder));
    NS_ENSURE_SUCCESS(rv, rv);

    JSObject *global;
    rv = holder->GetJSObject(&global);
    NS_ENSURE_SUCCESS(rv, rv);

    if (!JS_DefineFunctions(cx, global, gGlobalFun)) {
        return NS_ERROR_FAILURE;
    }

    nsCOMPtr<nsIXPConnectJSObjectHolder> locationHolder;
    rv = xpc->WrapNative(cx, global, aComponent,
                         NS_GET_IID(nsILocalFile),
                         getter_AddRefs(locationHolder));
    NS_ENSURE_SUCCESS(rv, rv);

    JSObject *locationObj;
    rv = locationHolder->GetJSObject(&locationObj);
    NS_ENSURE_SUCCESS(rv, rv);

    if (!JS_DefineProperty(cx, global, "__LOCATION__",
                           OBJECT_TO_JSVAL(locationObj), nsnull, nsnull, 0)) {
        return NS_ERROR_FAILURE;
    }

    nsCAutoString nativePath;
    // Quick hack to unbust XPCONNECT_STANDALONE.
    // This leaves the jsdebugger with a non-URL pathname in the 
    // XPCONNECT_STANDALONE case - but at least it builds and runs otherwise.
    // See: http://bugzilla.mozilla.org/show_bug.cgi?id=121438
#ifdef XPCONNECT_STANDALONE
    localFile->GetNativePath(nativePath);
#else
    NS_GetURLSpecFromFile(aComponent, nativePath);
#endif

    // Before compiling the script, first check to see if we have it in
    // the fastload file.  Note: as a rule, fastload errors are not fatal
    // to loading the script, since we can always slow-load.
    nsCOMPtr<nsIFastLoadService> flSvc = do_GetFastLoadService(&rv);

    // Save the old state and restore it upon return
    FastLoadStateHolder flState(flSvc);
    PRBool fastLoading = PR_FALSE;

    if (NS_SUCCEEDED(rv)) {
        rv = StartFastLoad(flSvc);
        if (NS_SUCCEEDED(rv)) {
            fastLoading = PR_TRUE;
        }
    }

    nsCOMPtr<nsIURI> uri;
    rv = NS_NewURI(getter_AddRefs(uri), nativePath);
    NS_ENSURE_SUCCESS(rv, rv);

    JSScript *script = nsnull;

    if (fastLoading) {
        rv = ReadScript(flSvc, nativePath.get(), uri, cx, &script);
        if (NS_SUCCEEDED(rv)) {
            LOG(("Successfully loaded %s from fastload\n", nativePath.get()));
            fastLoading = PR_FALSE; // no need to write out the script
        } else if (rv == NS_ERROR_NOT_AVAILABLE) {
            // This is ok, it just means the script is not yet in the
            // fastload file.
            rv = NS_OK;
        } else {
            LOG(("Failed to deserialize %s\n", nativePath.get()));

            // Remove the fastload file, it may be corrupted.
            LOG(("Invalid fastload file detected, removing it\n"));
            nsCOMPtr<nsIObjectOutputStream> objectOutput;
            flSvc->GetOutputStream(getter_AddRefs(objectOutput));
            if (objectOutput) {
                flSvc->SetOutputStream(nsnull);
                objectOutput->Close();
            }
            nsCOMPtr<nsIObjectInputStream> objectInput;
            flSvc->GetInputStream(getter_AddRefs(objectInput));
            if (objectInput) {
                flSvc->SetInputStream(nsnull);
                objectInput->Close();
            }
            if (mFastLoadFile) {
                mFastLoadFile->Remove(PR_FALSE);
            }
            fastLoading = PR_FALSE;
        }
    }


    if (!script || NS_FAILED(rv)) {
        // The script wasn't in the fastload cache, so compile it now.
        LOG(("Slow loading %s\n", nativePath.get()));

        // If |exception| is non-null, then our caller wants to propagate any
        // exceptions out to our caller. Ensure that the engine doesn't
        // eagerly report the exception.
        uint32 oldopts = 0;
        if (exception) {
            oldopts = JS_GetOptions(cx);
            JS_SetOptions(cx, oldopts | JSOPTION_DONT_REPORT_UNCAUGHT);
        }

#ifdef HAVE_PR_MEMMAP
        PRInt64 fileSize;
        rv = aComponent->GetFileSize(&fileSize);
        if (NS_FAILED(rv)) {
            JS_SetOptions(cx, oldopts);
            return rv;
        }

        PRInt64 maxSize;
        LL_UI2L(maxSize, PR_UINT32_MAX);
        if (LL_CMP(fileSize, >, maxSize)) {
            NS_ERROR("file too large");
            JS_SetOptions(cx, oldopts);
            return NS_ERROR_FAILURE;
        }

        PRFileDesc *fileHandle;
        rv = aComponent->OpenNSPRFileDesc(PR_RDONLY, 0, &fileHandle);
        if (NS_FAILED(rv)) {
            JS_SetOptions(cx, oldopts);
            return NS_ERROR_FILE_NOT_FOUND;
        }

        // Make sure the file is closed, no matter how we return.
        FileAutoCloser fileCloser(fileHandle);

        PRFileMap *map = PR_CreateFileMap(fileHandle, fileSize,
                                          PR_PROT_READONLY);
        if (!map) {
            NS_ERROR("Failed to create file map");
            JS_SetOptions(cx, oldopts);
            return NS_ERROR_FAILURE;
        }

        // Make sure the file map is closed, no matter how we return.
        FileMapAutoCloser mapCloser(map);

        PRUint32 fileSize32;
        LL_L2UI(fileSize32, fileSize);

        char *buf = static_cast<char*>(PR_MemMap(map, 0, fileSize32));
        if (!buf) {
            NS_WARNING("Failed to map file");
            JS_SetOptions(cx, oldopts);
            return NS_ERROR_FAILURE;
        }

        script = JS_CompileScriptForPrincipals(cx, global,
                                               jsPrincipals,
                                               buf, fileSize32,
                                               nativePath.get(), 1);
        PR_MemUnmap(buf, fileSize32);

#else  /* HAVE_PR_MEMMAP */

        /**
         * No memmap implementation, so fall back to using
         * JS_CompileFileHandleForPrincipals().
         */

        FILE *fileHandle;
        rv = aComponent->OpenANSIFileDesc("r", &fileHandle);
        if (NS_FAILED(rv)) {
            JS_SetOptions(cx, oldopts);
            return NS_ERROR_FILE_NOT_FOUND;
        }

        script = JS_CompileFileHandleForPrincipals(cx, global,
                                                   nativePath.get(),
                                                   fileHandle, jsPrincipals);

        /* JS will close the filehandle after compilation is complete. */
#endif /* HAVE_PR_MEMMAP */

        // Propagate the exception, if one exists. Also, don't leave the stale
        // exception on this context.
        // NB: The caller must stick exception into a rooted slot (probably on
        // its context) as soon as possible to avoid GC hazards.
        if (exception) {
            JS_SetOptions(cx, oldopts);
            if (!script) {
                JS_GetPendingException(cx, exception);
                JS_ClearPendingException(cx);
            }
        }
    }

    if (!script) {
#ifdef DEBUG_shaver_off
        fprintf(stderr, "mJCL: script compilation of %s FAILED\n",
                nativePath.get());
#endif
        return NS_ERROR_FAILURE;
    }

    // Ensure that we clean up the script on return.
    JSScriptHolder scriptHolder(cx, script);

    // Flag this script as a system script
    // FIXME: BUG 346139: We actually want to flag this exact filename, not
    // anything that starts with this filename... Maybe we need a way to do
    // that?  On the other hand, the fact that this is in our components dir
    // means that if someone snuck a malicious file into this dir we're screwed
    // anyway...  So maybe flagging as a prefix is fine.
    xpc->FlagSystemFilenamePrefix(nativePath.get(), PR_TRUE);

#ifdef DEBUG_shaver_off
    fprintf(stderr, "mJCL: compiled JS component %s\n",
            nativePath.get());
#endif

    if (fastLoading) {
        // We successfully compiled the script, so cache it in fastload.
        rv = WriteScript(flSvc, script, aComponent, nativePath.get(), uri, cx);

        // Don't treat failure to write as fatal, since we might be working
        // with a read-only fastload file.
        if (NS_SUCCEEDED(rv)) {
            LOG(("Successfully wrote to fastload\n"));
        } else {
            LOG(("Failed to write to fastload\n"));
        }
    }

    // Restore the old state of the fastload service.
    flState.pop();

    // Assign aGlobal here so that it's available to recursive imports.
    // See bug 384168.
    *aGlobal = global;

    jsval retval;
    if (!JS_ExecuteScript(cx, global, script, &retval)) {
#ifdef DEBUG_shaver_off
        fprintf(stderr, "mJCL: failed to execute %s\n", nativePath.get());
#endif
        *aGlobal = nsnull;
        return NS_ERROR_FAILURE;
    }

    /* Freed when we remove from the table. */
    nsCAutoString path;
    aComponent->GetNativePath(path);
    *aLocation = ToNewCString(path);
    if (!*aLocation) {
        *aGlobal = nsnull;
        return NS_ERROR_OUT_OF_MEMORY;
    }

    JS_AddNamedRoot(cx, aGlobal, *aLocation);
    return NS_OK;
}

void
mozJSComponentLoader::UnloadModules()
{
    mInitialized = PR_FALSE;

    mInProgressImports.Clear();
    mImports.Clear();
    mModules.Clear();

    // Destroying our context will force a GC.
    JS_DestroyContext(mContext);
    mContext = nsnull;

    mRuntimeService = nsnull;
    mContextStack = nsnull;
#ifdef DEBUG_shaver_off
    fprintf(stderr, "mJCL: UnloadAll(%d)\n", aWhen);
#endif
}

/* [JSObject] import (in AUTF8String registryLocation,
                      [optional] in JSObject targetObj ); */
NS_IMETHODIMP
mozJSComponentLoader::Import(const nsACString & registryLocation)
{
    // This function should only be called from JS.
    nsresult rv;

    nsCOMPtr<nsIXPConnect> xpc =
        do_GetService(kXPConnectServiceContractID, &rv);
    NS_ENSURE_SUCCESS(rv, rv);
    
    nsAXPCNativeCallContext *cc = nsnull;
    rv = xpc->GetCurrentNativeCallContext(&cc);
    NS_ENSURE_SUCCESS(rv, rv);

#ifdef DEBUG
    {
    // ensure that we are being call from JS, from this method
    nsCOMPtr<nsIInterfaceInfo> info;
    rv = cc->GetCalleeInterface(getter_AddRefs(info));
    NS_ENSURE_SUCCESS(rv, rv);
    nsXPIDLCString name;
    info->GetName(getter_Copies(name));
    NS_ASSERTION(nsCRT::strcmp("nsIXPCComponents_Utils", name.get()) == 0,
                 "Components.utils.import must only be called from JS.");
    PRUint16 methodIndex;
    const nsXPTMethodInfo *methodInfo;
    rv = info->GetMethodInfoForName("import", &methodIndex, &methodInfo);
    NS_ENSURE_SUCCESS(rv, rv);
    PRUint16 calleeIndex;
    rv = cc->GetCalleeMethodIndex(&calleeIndex);
    NS_ASSERTION(calleeIndex == methodIndex,
                 "Components.utils.import called from another utils method.");
    }
#endif

    JSContext *cx = nsnull;
    rv = cc->GetJSContext(&cx);
    NS_ENSURE_SUCCESS(rv, rv);

    JSAutoRequest ar(cx);

    JSObject *targetObject = nsnull;

    PRUint32 argc = 0;
    rv = cc->GetArgc(&argc);
    NS_ENSURE_SUCCESS(rv, rv);

    if (argc > 1) {
        // The caller passed in the optional second argument. Get it.
        jsval *argv = nsnull;
        rv = cc->GetArgvPtr(&argv);
        NS_ENSURE_SUCCESS(rv, rv);
        if (!JSVAL_IS_OBJECT(argv[1])) {
            return ReportOnCaller(cc, ERROR_SCOPE_OBJ,
                                  PromiseFlatCString(registryLocation).get());
        }
        targetObject = JSVAL_TO_OBJECT(argv[1]);
    } else {
        // Our targetObject is the caller's global object. Find it by
        // walking the calling object's parent chain.

        nsCOMPtr<nsIXPConnectWrappedNative> wn;
        rv = cc->GetCalleeWrapper(getter_AddRefs(wn));
        NS_ENSURE_SUCCESS(rv, rv);
        
        wn->GetJSObject(&targetObject);
        if (!targetObject) {
            NS_ERROR("null calling object");
            return NS_ERROR_FAILURE;
        }

        targetObject = JS_GetGlobalForObject(cx, targetObject);
    }
 
    JSObject *globalObj = nsnull;
    rv = ImportInto(registryLocation, targetObject, cc, &globalObj);

    jsval *retval = nsnull;
    cc->GetRetValPtr(&retval);
    if (*retval)
        *retval = OBJECT_TO_JSVAL(globalObj);

    return rv;
}

/* [noscript] JSObjectPtr importInto(in AUTF8String registryLocation,
                                     in JSObjectPtr targetObj); */
NS_IMETHODIMP
mozJSComponentLoader::ImportInto(const nsACString & aLocation,
                                 JSObject * targetObj,
                                 nsAXPCNativeCallContext * cc,
                                 JSObject * *_retval)
{
    nsresult rv;
    *_retval = nsnull;

    if (!mInitialized) {
        rv = ReallyInit();
        NS_ENSURE_SUCCESS(rv, rv);
    }
    
    nsCOMPtr<nsIIOService> ioService = do_GetIOService(&rv);
    NS_ENSURE_SUCCESS(rv, rv);

    // Get the URI.
    nsCOMPtr<nsIURI> resURI;
    rv = ioService->NewURI(aLocation, nsnull, nsnull, getter_AddRefs(resURI));
    nsCOMPtr<nsIFileURL> fileURL = do_QueryInterface(resURI, &rv);
    // If we don't have a file URL, then the location passed in is invalid.
    NS_ENSURE_SUCCESS(rv, NS_ERROR_INVALID_ARG);

    // Get the file belonging to it.
    nsCOMPtr<nsIFile> file;
    rv = fileURL->GetFile(getter_AddRefs(file));
    NS_ENSURE_SUCCESS(rv, rv);
    nsCOMPtr<nsILocalFile> componentFile = do_QueryInterface(file, &rv);
    NS_ENSURE_SUCCESS(rv, rv);

    nsCOMPtr<nsIHashable> lfhash(do_QueryInterface(componentFile));
    if (!lfhash) {
        NS_ERROR("nsLocalFile not implementing nsIHashable");
        return NS_NOINTERFACE;
    }

    ModuleEntry* mod;
    nsAutoPtr<ModuleEntry> newEntry;
    if (!mImports.Get(lfhash, &mod) && !mInProgressImports.Get(lfhash, &mod)) {
        newEntry = new ModuleEntry;
        if (!newEntry || !mInProgressImports.Put(lfhash, newEntry))
            return NS_ERROR_OUT_OF_MEMORY;

        jsval exception = JSVAL_VOID;
        rv = GlobalForLocation(componentFile, &newEntry->global,
                               &newEntry->location, &exception);

        mInProgressImports.Remove(lfhash);

        if (NS_FAILED(rv)) {
            *_retval = nsnull;

            if (!JSVAL_IS_VOID(exception)) {
                // An exception was thrown during compilation. Propagate it
                // out to our caller so they can report it.
                JSContext *callercx;
                cc->GetJSContext(&callercx);
                JS_SetPendingException(callercx, exception);
                cc->SetExceptionWasThrown(PR_TRUE);
                return NS_OK;
            }

            // Something failed, but we don't know what it is, guess.
            return rv;
        }

        mod = newEntry;
    }

    NS_ASSERTION(mod->global, "Import table contains entry with no global");
    *_retval = mod->global;

    jsval symbols;
    if (targetObj) {
        JSAutoRequest ar(mContext);

        if (!JS_GetProperty(mContext, mod->global,
                            "EXPORTED_SYMBOLS", &symbols)) {
            return ReportOnCaller(cc, ERROR_NOT_PRESENT,
                                  PromiseFlatCString(aLocation).get());
        }

        JSObject *symbolsObj = nsnull;
        if (!JSVAL_IS_OBJECT(symbols) ||
            !(symbolsObj = JSVAL_TO_OBJECT(symbols)) ||
            !JS_IsArrayObject(mContext, symbolsObj)) {
            return ReportOnCaller(cc, ERROR_NOT_AN_ARRAY,
                                  PromiseFlatCString(aLocation).get());
        }

        // Iterate over symbols array, installing symbols on targetObj:

        jsuint symbolCount = 0;
        if (!JS_GetArrayLength(mContext, symbolsObj, &symbolCount)) {
            return ReportOnCaller(cc, ERROR_GETTING_ARRAY_LENGTH,
                                  PromiseFlatCString(aLocation).get());
        }

#ifdef DEBUG
        nsCAutoString logBuffer;
#endif

        for (jsuint i = 0; i < symbolCount; ++i) {
            jsval val;
            JSString *symbolName;

            if (!JS_GetElement(mContext, symbolsObj, i, &val) ||
                !JSVAL_IS_STRING(val)) {
                return ReportOnCaller(cc, ERROR_ARRAY_ELEMENT,
                                      PromiseFlatCString(aLocation).get(), i);
            }

            symbolName = JSVAL_TO_STRING(val);
            if (!JS_GetProperty(mContext, mod->global,
                                JS_GetStringBytes(symbolName), &val)) {
                return ReportOnCaller(cc, ERROR_GETTING_SYMBOL,
                                      PromiseFlatCString(aLocation).get(),
                                      JS_GetStringBytes(symbolName));
            }

            if (!JS_SetProperty(mContext, targetObj,
                                JS_GetStringBytes(symbolName), &val)) {
                return ReportOnCaller(cc, ERROR_SETTING_SYMBOL,
                                      PromiseFlatCString(aLocation).get(),
                                      JS_GetStringBytes(symbolName));
            }
#ifdef DEBUG
            if (i == 0) {
                logBuffer.AssignLiteral("Installing symbols [ ");
            }
            logBuffer.Append(JS_GetStringBytes(symbolName));
            logBuffer.AppendLiteral(" ");
            if (i == symbolCount - 1) {
                LOG(("%s] from %s\n", PromiseFlatCString(logBuffer).get(),
                                      PromiseFlatCString(aLocation).get()));
            }
#endif
        }
    }

    // Cache this module for later
    if (newEntry) {
        if (!mImports.Put(lfhash, newEntry))
            return NS_ERROR_OUT_OF_MEMORY;
        newEntry.forget();
    }
    
    return NS_OK;
}

nsresult
mozJSComponentLoader::ReportOnCaller(nsAXPCNativeCallContext *cc,
                                     const char *format, ...) {
    if (!cc) {
        return NS_ERROR_FAILURE;
    }
    
    va_list ap;
    va_start(ap, format);

    nsresult rv;
    JSContext *callerContext;
    rv = cc->GetJSContext(&callerContext);
    NS_ENSURE_SUCCESS(rv, rv);
    char* buf = JS_vsmprintf(format, ap);
    JS_ReportError(callerContext, buf);
    JS_smprintf_free(buf);
    return cc->SetExceptionWasThrown(PR_TRUE);
}

NS_IMETHODIMP
mozJSComponentLoader::Observe(nsISupports *subject, const char *topic,
                              const PRUnichar *data)
{
    if (!strcmp(topic, NS_XPCOM_SHUTDOWN_OBSERVER_ID)) {
        if (mFastLoadTimer) {
            mFastLoadTimer->Cancel();
        }

        JS_GC(mContext);

        CloseFastLoad();
    }
    else if (!strcmp(topic, "xpcom-shutdown-loaders")) {
        UnloadModules();
    }
    else {
        NS_ERROR("Unexpected observer topic.");
    }

    return NS_OK;
}

//----------------------------------------------------------------------

JSCLContextHelper::JSCLContextHelper(mozJSComponentLoader *loader)
    : mContext(loader->mContext), mContextThread(0),
      mContextStack(loader->mContextStack)
{
    mContextStack->Push(mContext);
    mContextThread = JS_GetContextThread(mContext);
    if (mContextThread) {
        JS_BeginRequest(mContext);
    } 
}

JSCLContextHelper::~JSCLContextHelper()
{
    JS_ClearNewbornRoots(mContext);
    if (mContextThread)
        JS_EndRequest(mContext);

    mContextStack->Pop(nsnull);
}