firefox - NPP_NewStream : seekable set to 0 (false) for local file

Question

我正在尝试实现一个具有流媒体功能的 NPAPI 插件(NP_SEEK+ NPN_RequestRead)。无论我尝试什么， bool NPBool seekable 始终设置为 0(假)。

我正在从本地文件的命令行启动 firefox(Debian 上的 iceweasel):

$ iceweasel test1.html

如果我将 gdb 附加到 npapi 插件，我会看到:

(gdb) 
#2  0x00007f7e9da54e14 in mozilla::plugins::BrowserStreamChild::StreamConstructed (this=0x7f7e925cf310, mimeType=..., seekable=<optimized out>, stype=<optimized out>)
    at /tmp/buildd/iceweasel-24.6.0esr/dom/plugins/ipc/BrowserStreamChild.cpp:62
62      &mStream, seekable, stype);
(gdb) 
#3  0x00007f7e9da5688e in mozilla::plugins::PluginInstanceChild::AnswerPBrowserStreamConstructor (this=<optimized out>, aActor=<optimized out>, url=..., 
    length=<optimized out>, lastmodified=<optimized out>, notifyData=<optimized out>, headers=..., mimeType=..., seekable=@0x7fff25ed51df: false, rv=0x7fff25ed51e0, 
    stype=0x7fff25ed51e2) at /tmp/buildd/iceweasel-24.6.0esr/dom/plugins/ipc/PluginInstanceChild.cpp:2285
2285              ->StreamConstructed(mimeType, seekable, stype);
(gdb) p seekable
$1 = (const bool &) @0x7fff25ed51df: false
(gdb) up
#4  0x00007f7e9da8f77f in mozilla::plugins::PPluginInstanceChild::OnCallReceived (this=0x7f7e925f2c00, __msg=..., __reply=@0x7fff25ed5470: 0x0)
    at /tmp/buildd/iceweasel-24.6.0esr/build-xulrunner/ipc/ipdl/PPluginInstanceChild.cpp:2479
warning: Source file is more recent than executable.
2479                if ((!(AnswerPBrowserStreamConstructor(actor, url, length, lastmodified, notifyData, headers, mimeType, seekable, (&(rv)), (&(stype)))))) {
(gdb) list -
2469                if ((!(actor))) {
2470                    return MsgValueError;
2471                }
2472                (actor)->mId = RegisterID(actor, (__handle).mId);
2473                (actor)->mManager = this;
2474                (actor)->mChannel = mChannel;
2475                (mManagedPBrowserStreamChild).InsertElementSorted(actor);
2476                (actor)->mState = mozilla::plugins::PBrowserStream::__Start;
2477    
2478                int32_t __id = mId;
(gdb) list -
2459                    FatalError("Error deserializing 'bool'");
2460                    return MsgValueError;
2461                }
2462                (__msg).EndRead(__iter);
2463                if ((!(PPluginInstance::Transition(mState, Trigger(Trigger::Send, PPluginInstance::Msg_PBrowserStreamConstructor__ID), (&(mState)))))) {
2464                    NS_WARNING("bad state transition!");
2465                }
2466                NPError rv;
2467                uint16_t stype;
2468                actor = AllocPBrowserStream(url, length, lastmodified, notifyData, headers, mimeType, seekable, (&(rv)), (&(stype)));
(gdb) list -
2449                }
2450                if ((!(Read((&(headers)), (&(__msg)), (&(__iter)))))) {
2451                    FatalError("Error deserializing 'nsCString'");
2452                    return MsgValueError;
2453                }
2454                if ((!(Read((&(mimeType)), (&(__msg)), (&(__iter)))))) {
2455                    FatalError("Error deserializing 'nsCString'");
2456                    return MsgValueError;
2457                }
2458                if ((!(Read((&(seekable)), (&(__msg)), (&(__iter)))))) {
(gdb) up
#5  0x00007f7e9da868f0 in mozilla::plugins::PPluginModuleChild::OnCallReceived (this=<optimized out>, __msg=..., __reply=@0x7fff25ed5470: 0x0)
    at /tmp/buildd/iceweasel-24.6.0esr/build-xulrunner/ipc/ipdl/PPluginModuleChild.cpp:1023
warning: Source file is more recent than executable.
1023            return (__routed)->OnCallReceived(__msg, __reply);
(gdb) list -
1013    PPluginModuleChild::OnCallReceived(
1014            const Message& __msg,
1015            Message*& __reply)
1016    {
1017        int32_t __route = (__msg).routing_id();
1018        if ((MSG_ROUTING_CONTROL) != (__route)) {
1019            ChannelListener* __routed = Lookup(__route);
1020            if ((!(__routed))) {
1021                return MsgRouteError;
1022            }
(gdb) bt

如果我将 test1.html 复制到 /var/www ，然后指向 http://localhost/test1.html 一切都按预期工作。

然而 documentation 提到

seekable
Boolean indicating whether the stream is seekable:
true: Seekable. Stream supports random access through calls to NPN_RequestRead (for example, local files or HTTP servers that support byte-range requests).

Answer 1

文档完全是谎言。

seekable对 NPP_NewStream 的调用中的标志

源自 OnStartBinding

调用 nsPluginStreamListenerPeer::IsSeekable

只返回 nsPluginStreamListenerPeer::mSeekable .

唯一一次mSeekable曾经设置过true是什么时候(source)

流是 http (https, spdy)

http 响应没有 Content-Encoding

http 响应提供 Content-Length .

http 响应有 Accept-Ranges: bytes (不支持省略标题)

对于所有其他流类型(包括 file:// )和不符合要求的 http 流，seekable因此标志总是false .

此外， NPN_RequestRead是 only implemented for http streams , 但实际上并不关心 seekable而且实际上并不检查服务器是否返回 206 .

结论

您只能使用 NP_SEEK使用 http (https, spdy) 流式传输。这就是为什么东西从 http://localhost 开始工作的原因，但不是来自本地文件( file:// )。