In this case you would want to construct `org.capnproto.MessageReader` directly from the array of `ByteBuffer`s; you would not use `Serialize`.
-Kenton On Fri, Nov 15, 2019 at 5:04 PM 张钊 <[email protected]> wrote: > Hi Kenton: > If use repeated bytes In java client ,read capn object 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()); > > > *or use org.capnproto.Serialize.read(byteBuffer)?* > > thanks > whutbd > > > ------------------ 原始邮件 ------------------ > *发件人:* "Kenton Varda"<[email protected]>; > *发送时间:* 2019年11月16日(星期六) 凌晨5:53 > *收件人:* "张钊"<[email protected]>; > *抄送:* "Cap'n Proto"<[email protected]>; > *主题:* Re: [capnproto] C++ Server Send capnp segments to java_client by > rpc_call, In java_client how can I get the message in Correct > > Your message may have more than one segment if you put enough data into > it. You shouldn't assume that messages will always have one segment, unless > you know that your message will always be less than a certain overall size, > and you tell the MessageBuilder to allocate the first segment to be larger > than that. > > If you are embedding the message into a protobuf, you could use a > `repeated bytes` field to allow for more than one segment. In that case it > could make sense to use `getSegmentsForOutput()`. > > -Kenton > > On Fri, Nov 15, 2019 at 2:58 PM whutbd <[email protected]> wrote: > >> >> hi Kenton Varda >> * when I do this:* >> kj::ArrayPtr<const kj::ArrayPtr<const capnp::word>> segments >> = message.getSegmentsForOutput(); >> >> the segments size Always 1，so in protobuf I use bytes field to send >> the segments[0].asChars(); >> >> *Is there any problem in using it like this* >> >> >> >> 在 2019年10月8日星期二 UTC+8上午12:31:10，Kenton Varda写道： >>> >>> messageToFlatArray() involves an extra copy compared to >>> getSegmentsForOutput(). >>> >>> However, you are putting the bytes into a protobuf anyway. Protobuf will >>> make many copies. So I don't think you should worry too much about this one >>> extra copy. >>> >>> If you really want to use getSegmentsForOutput(), then you need to use a >>> `repeated bytes` field in protobuf and you need to add each segment to the >>> repeated bytes. >>> >>> -Kenton >>> >>> On Sun, Oct 6, 2019 at 8:00 PM 张小 <[email protected]> wrote: >>> >>>> 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]> 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]. >>>>>> 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 >>>> <https://groups.google.com/d/msgid/capnproto/222eed4a-8f6a-48e7-828e-09235b228253%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/fa2451ad-4441-4c3a-8af0-39a9b45cb7c9%40googlegroups.com >> <https://groups.google.com/d/msgid/capnproto/fa2451ad-4441-4c3a-8af0-39a9b45cb7c9%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- You received this message because you are subscribed to the Google Groups "Cap'n Proto" group. 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