hi Kenton：
getSegmentsForOutput() performance better than messageToFlatArray
right? These two interfaces What scenarios are applied to?
best wish
whutbd
在 2019年10月7日星期一 UTC+8上午3:41:23，Kenton Varda写道：
>
> Your code only handles the case of a single segment. I recommend using the
> methods in capnp/serialize.h and org.capnproto.Serialize. I do not
> recommend using getSegmentsForOutput() nor constructing a MessageReader
> directly from a segment array, as these are advanced functions that can
> more easily go wrong.
>
> That said, in your example case, only a single segment should be needed,
> so something else is wrong too.
>
> I don't see any other obvious problems with the code you provided. I
> suspect a bug exists in the code you didn't show. I recommend you try to
> verify that the bytes on the receiving end are actually exactly the bytes
> from the sending end. Try logging the byte values and the size of the
> segment at each end to make sure everything matches.
>
> I think the most likely problem is that somewhere your `char*` is being
> interpreted as a NUL-terminated string, and is therefore being truncated at
> the first zero-valued byte. Most likely, the very first byte in the segment
> is a zero, so probably your ByteBuffer on the Java end ends up being
> zero-length. This probably leads to the struct appearing to contain only
> default values, hence goodsId is 0.
>
> -Kenton
>
> On Sat, Oct 5, 2019 at 11:28 PM 张小 <[email protected] <javascript:>> wrote:
>
>> hi Kenton：
>> I need your help,This problem has been bothering me for many days.
>>
>> In c++ server ,code like this
>> capnp::MallocMessageBuilder message;
>> FullInfo::Builder fullInfo = message.initRoot<FullInfo>();
>> fullInfo.setGoodsId(919731)
>>
>> kj::ArrayPtr<const kj::ArrayPtr<const capnp::word>> segments
>> = message.getSegmentsForOutput();
>> kj::ArrayPtr<const capnp::word> segment = segments[0];
>> kj::ArrayPtr<const char> chars = segment.asChars();
>> const char* mem_buf = chars.begin();
>> int32_t mem_buf_len = chars.size();
>>
>> and c++ server send the mem_buf to java_client by rpc call(bytes field)
>>
>> *Client and server communicate through protobuf rpc*
>>
>> In java_client code like this:()
>>
>> com.google.protobuf.ByteString capn_object_bytes =
>> response.getCapnObject();
>> ByteBuffer[] bytes_buffer = new ByteBuffer[1];
>> bytes_buffer[0] = capn_object_bytes.asReadOnlyByteBuffer();
>> MessageReader message = new MessageReader(bytes_buffer,
>> ReaderOptions.DEFAULT_READER_OPTIONS);
>> Display.FullInfo.Reader fullInfo =
>> message.getRoot(Display.FullInfo.factory);
>> System.out.println("goodsId:" + fullInfo.getGoodsId());
>>
>> but in java_client ，print goodsId is 0, however in c++ server, I
>> setGoodsId(919731) ,What's wrong with my method of use? @Kenton
>>
>> the fullinfo.capnp code is:
>> @0xcb70f505c89d1634;
>>
>> using Java = import "./compiler/src/main/schema/capnp/java.capnp";
>> $Java.package("org.capnproto.examples");
>> $Java.outerClassname("Display");
>>
>> struct FullInfo{
>> goodsId @1 :Int64;
>> }
>>
>>
>>
>>
>>
>> 在 2019年10月1日星期二 UTC+8上午3:23:37，Kenton Varda写道：
>>>
>>> Are you transmitting one big buffer containing all the segments, or are
>>> you transmitting each segment separately?
>>>
>>> It looks like you're trying to do the latter, but in that case you
>>> cannot use Serialize.read() to read it. You need to use `new
>>> MessageReader(segments)`.
>>>
>>> -Kenton
>>>
>>> On Mon, Sep 30, 2019 at 5:52 AM 张小 <[email protected]> wrote:
>>>
>>>> First Time:
>>>> In C++ server,I Use capnp::DynamicStruct, code like this:
>>>> capnp::MallocMessageBuilder msg;
>>>> capnp::DynamicStruct::Builder fullinfo_builder
>>>> = msg.initRoot<capnp::DynamicStruct>(g_schema);
>>>> capnp::DynamicStruct::Builder fullInfo =
>>>> msg.initRoot<capnp::DynamicStruct>(g_schema);
>>>>
>>>> capnp::messageToFlatArray(msg); ---->convert it to char* send to
>>>> java_cliet
>>>>
>>>> Java Client ,code like this:
>>>> MessageReader message
>>>> = org.capnproto.Serialize.read(capn_object_bytes.asReadOnlyByteBuffer());,
>>>> Info.Reader adInfo = message.getRoot(Info.factory);
>>>>
>>>> Above ， My First Time do work , but The Second Time, I do like this ,it
>>>> do not work:
>>>> In C++ server, code like this:
>>>>
>>>> capnp::MallocMessageBuilder message;
>>>> Info::Builder info = message.initRoot<Info>();
>>>> info.setId(123);
>>>> kj::ArrayPtr<const kj::ArrayPtr<const capnp::word>> segments =
>>>> message.getSegmentsForOutput();
>>>>
>>>> then I convert the segments object to char* send to java_client by
>>>> proto rpc_call (bytes field)
>>>>
>>>>
>>>> Java Client ,code like this:
>>>> MessageReader message
>>>> = org.capnproto.Serialize.read(capn_object_bytes.asReadOnlyByteBuffer());,
>>>> Info.Reader adInfo = message.getRoot(Info.factory);
>>>>
>>>>
>>>> In Second Time, happen Error like this:
>>>>
>>>> Exception in thread "main" java.lang.IllegalArgumentException
>>>> at java.nio.Buffer.limit(Buffer.java:275)
>>>> at org.capnproto.Serialize.read(Serialize.java:140)
>>>> at org.capnproto.Serialize.read(Serialize.java:111)
>>>>
>>>> How Can I do , In Second Time ,thanks
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> 在 2019年9月30日星期一 UTC+8下午8:29:41，David Renshaw写道：
>>>>>
>>>>> On the Java side, you need to first read the bytes into a
>>>>> `MessageReader`. That's typically done via one of the `Serialize.read()`
>>>>> methods.
>>>>>
>>>>> The `AnyPointer.Reader()` is not intended for external use. Probably
>>>>> we should make it private.
>>>>>
>>>>>
>>>>> On Mon, Sep 30, 2019 at 6:25 AM 张小 <[email protected]> wrote:
>>>>>
>>>>>> C++ server send Capn Object to JavaClient like this
>>>>>>
>>>>>> capnp::MallocMessageBuilder message;
>>>>>> Info::Builder info = message.initRoot<Info>();
>>>>>> info.setId(123);
>>>>>> kj::ArrayPtr<const kj::ArrayPtr<const capnp::word>> segments =
>>>>>> message.getSegmentsForOutput();
>>>>>>
>>>>>> then I convert the segments object to char* send to java_client by
>>>>>> proto rpc_call (bytes field)
>>>>>>
>>>>>>
>>>>>> Then In java_client, I do like this to read the capn object
>>>>>> com.google.protobuf.ByteString capn_object_bytes =
>>>>>> response.getCapnObject()
>>>>>> SegmentReader segment = new
>>>>>> SegmentReader(capn_object_bytes.asReadOnlyByteBuffer(), null);
>>>>>> AnyPointer.Reader any = new AnyPointer.Reader(segment, 0,
>>>>>> 64*1024*1024);
>>>>>> Info.Reader info = any.getAs(Info.factory);
>>>>>> System.out.println("Id:" + info.getId());
>>>>>>
>>>>>>
>>>>>> run java_cliet ,happend error like this :
>>>>>> Exception in thread "main" java.lang.NullPointerException
>>>>>> at org.capnproto.WireHelpers.readStructPointer(WireHelpers.java:918)
>>>>>> at
>>>>>> org.capnproto.StructFactory.fromPointerReaderRefDefault(StructFactory.java:34)
>>>>>> at
>>>>>> org.capnproto.StructFactory.fromPointerReader(StructFactory.java:41)
>>>>>> at
>>>>>> org.capnproto.StructFactory.fromPointerReader(StructFactory.java:24)
>>>>>> at org.capnproto.AnyPointer$Reader.getAs(AnyPointer.java:56)
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> --
>>>>>> You received this message because you are subscribed to the Google
>>>>>> Groups "Cap'n Proto" group.
>>>>>> To unsubscribe from this group and stop receiving emails from it,
>>>>>> send an email to [email protected].
>>>>>> To view this discussion on the web visit
>>>>>> https://groups.google.com/d/msgid/capnproto/081ab20b-5eae-43d5-a4fc-8230ef39d4a5%40googlegroups.com
>>>>>>
>>>>>> <https://groups.google.com/d/msgid/capnproto/081ab20b-5eae-43d5-a4fc-8230ef39d4a5%40googlegroups.com?utm_medium=email&utm_source=footer>
>>>>>> .
>>>>>>
>>>>> --
>>>> You received this message because you are subscribed to the Google
>>>> Groups "Cap'n Proto" group.
>>>> To unsubscribe from this group and stop receiving emails from it, send
>>>> an email to [email protected].
>>>> To view this discussion on the web visit
>>>> https://groups.google.com/d/msgid/capnproto/816c3227-c2b2-4b72-8ead-e707759a257c%40googlegroups.com
>>>>
>>>> <https://groups.google.com/d/msgid/capnproto/816c3227-c2b2-4b72-8ead-e707759a257c%40googlegroups.com?utm_medium=email&utm_source=footer>
>>>> .
>>>>
>>> --
>> You received this message because you are subscribed to the Google Groups
>> "Cap'n Proto" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to [email protected] <javascript:>.
>> To view this discussion on the web visit
>> https://groups.google.com/d/msgid/capnproto/1e177ff5-e49f-4d4a-b5f3-1c096604bb29%40googlegroups.com
>>
>> <https://groups.google.com/d/msgid/capnproto/1e177ff5-e49f-4d4a-b5f3-1c096604bb29%40googlegroups.com?utm_medium=email&utm_source=footer>
>> .
>>
>
--
You received this message because you are subscribed to the Google Groups
"Cap'n Proto" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To view this discussion on the web visit
https://groups.google.com/d/msgid/capnproto/222eed4a-8f6a-48e7-828e-09235b228253%40googlegroups.com.
