[protobuf] Re: How to retrieve parameters using tag numbers using CodedInputStream

2010-08-19 Thread Prakash Rao 
I tried YourProtocolMessage.getDefaultInstance() and as you said it is
of zero byte size. I've a required field called ID with default cluase
in pnroto file (with default value set to -1). When i send the default
instance, I see ID set to -1 (which is default value specified in
proto file) but on the client side while parsing it says required
field ID is not initialized. It looks like if we specify required
field in proto file then we can't return default instance. Then i
tried creating a proto message with -1 value in ID and as you said it
doesn't much cost. On the client side if ID is -1 then i assume it's a
null response.

Thanks for your response.

Regards,
Prakash

On Aug 16, 8:46 pm, Evan Jones ev...@mit.edu wrote:
 On Aug 16, 2010, at 10:56 , Prakash Rao wrote:

  I'm just looking for a easy way to write null response if data is not
  present in DB and write proto message object if data is present 
  parse these in client side appropriately. I didn't get a easy way to
  do this using CodedInputStream. Currently i'm creating a empty proto
  object on server side and checking for key attribute at client side as
  stated above.

 The empty protocol buffer message serializes to zero bytes, so if  
 your message has no content, you could just send a zero byte message.  
 This would avoid creating a protocol buffer message. However, I  
 suspect that isn't really a big overhead. You can also use  
 YourProtocolMessage.getDefaultInstance() to avoid creating a message.

 Hope this helps,

 Evan Jones

 --
 Evan Joneshttp://evanjones.ca/

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[protobuf] Re: How to retrieve parameters using tag numbers using CodedInputStream

2010-08-16 Thread Prakash Rao 
Thanks for your response. I had one more question. Is it possible to
write a null value to output stream? I'm writing a client/server
application and using PB as layer to transfer data. In certain cases
response would be null if required data is not there in my DB. For
null responses, i don't want to create a empty proto object (which is
an overhead as there would be many cases where response is going to be
null) and check on client side if key attribute is not populated then
treat as null.

I'm just looking for a easy way to write null response if data is not
present in DB and write proto message object if data is present 
parse these in client side appropriately. I didn't get a easy way to
do this using CodedInputStream. Currently i'm creating a empty proto
object on server side and checking for key attribute at client side as
stated above.

Regards,
Prakash

On Aug 12, 9:37 pm, Jason Hsueh jas...@google.com wrote:
 A tag indicates to the decoder what is coming next in the input stream, and
 allows the decoder to handle it appropriately. This is a key feature of the
 protobuf wire format - this enables forward and backward compatibility, as
 well omitting fields that aren't present from the serialization. The APIs
 that we have are built around this. A readString(int tag) method would never
 be used by the generated code.

 If you really want to take this approach, you can still call readTag(),
 check that the tag number is what you want, and then read the string.
 However, I would suggest just using a message. You may find that over time
 those two or three parameters will grow to the point that maintaining this
 is unwieldy.

 On Wed, Aug 11, 2010 at 10:55 PM, Prakash Rao prakashrao1...@gmail.comwrote:





  I don't have .proto message created for these. Most of my APIs
  takes .proto messages as parameters (as they represent my business
  data objects) and in 1-2 APIs I need to pass only 2-3 primitive
  parameters as arguments. In these cases I’m avoiding creation
  of .proto messages (as these don’t represent my business data object).
  As an alternative, I thought of using CodedOutputstream to pass
  parameters along with tag so that retrieval is easy on the receiving
  end using CodedInputStream but I don't see a way to retrieve parameter
  using tags with CodedInputStream. Currently I've the below code and
  thought the tag approach would make it simple but CodedInputStream
  doesn't support parameter retrieval based on tags.

  // Client Side code - which sends s1  s2 strings to server
  int s1Size = CodedOutputStream.computeStringSizeNoTag(s1);
  codedOutputStream.writeRawVarint32(s1Size);
  codedOutputStream.writeStringNoTag(s1);

  int s2Size = CodedOutputStream.computeStringSizeNoTag(s2);

 Note: computeStringSizeNoTag() gives the size of the string as well as the
 encoded length. If you write the result as the encoded length, you will end
 up reading more bytes than you should. You simply want to write the size of
 the string.



  codedOutputStream.writeRawVarint32(s2Size);
  codedOutputStream.writeStringNoTag(s2);

  // Server side code - which reads s1  s2 string
  CodedInputStream codedInputStream =
  CodedInputStream.newInstance(inputStream);
  int s1Size = codedInputStream.readRawVarint32();
  int s1SizeEntry = codedInputStream.pushLimit(s1Size);
  String s1 = codedInputStream.readString();
  codedInputStream.popLimit(s1SizeEntry);

  int s2Size = codedInputStream.readRawVarint32();
  int s2SizeEntry = codedInputStream.pushLimit(s2Size);
  String s2 = codedInputStream.readString();
  codedInputStream.popLimit(modifiedBySizeEntry);

  Regards,
  Prakash

  On Aug 11, 9:17 pm, Jason Hsueh jas...@google.com wrote:
   Suppose those strings are all defined as optional fields in the message.
   They may not be present in the serialization, so the decoder needs to
  read a
   tag to determine the field number and type before handling the value.

   On Wed, Aug 11, 2010 at 8:37 AM, Prakash Rao prakashrao1...@gmail.com
  wrote:

Hi,
I was just looking at CodedInputStream class and there are APIs to
write primitives with or without tag (for example, writeString 
writeStringNoTag). I thought if we set unique tags for multiple
parameters then we would be able to retrieve these parameters using
tag numbers specified using CodedInputStream class. I don't see any
APIs to read values based on tags in CodedInputStream. Am I missing
something? For the time being I’m using pushLimit  popLimit APIs to
get different parameter values (based on serializedSize).

For example,
int test(String s1, String s2, String s3) {
}

CodedOutputStream out = CodedOutputStream.newIInstance(Some Output
Stream);
out.writeString(1, s1);
out.writeString(2, s2);
out.writeString(3, s3);
out.flush();

Why these are not possible?
CodedInputStream in = CodedInputStream.newIInstance(Some Input
Stream);
String s1 = in.readString(1);
String

Re: [protobuf] Re: How to retrieve parameters using tag numbers using CodedInputStream

2010-08-16 Thread Evan Jones 

On Aug 16, 2010, at 10:56 , Prakash Rao wrote:

I'm just looking for a easy way to write null response if data is not
present in DB and write proto message object if data is present 
parse these in client side appropriately. I didn't get a easy way to
do this using CodedInputStream. Currently i'm creating a empty proto
object on server side and checking for key attribute at client side as
stated above.


The empty protocol buffer message serializes to zero bytes, so if  
your message has no content, you could just send a zero byte message.  
This would avoid creating a protocol buffer message. However, I  
suspect that isn't really a big overhead. You can also use  
YourProtocolMessage.getDefaultInstance() to avoid creating a message.


Hope this helps,

Evan Jones

--
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http://evanjones.ca/

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Re: [protobuf] Re: How to retrieve parameters using tag numbers using CodedInputStream

2010-08-12 Thread Jason Hsueh 
A tag indicates to the decoder what is coming next in the input stream, and
allows the decoder to handle it appropriately. This is a key feature of the
protobuf wire format - this enables forward and backward compatibility, as
well omitting fields that aren't present from the serialization. The APIs
that we have are built around this. A readString(int tag) method would never
be used by the generated code.

If you really want to take this approach, you can still call readTag(),
check that the tag number is what you want, and then read the string.
However, I would suggest just using a message. You may find that over time
those two or three parameters will grow to the point that maintaining this
is unwieldy.

On Wed, Aug 11, 2010 at 10:55 PM, Prakash Rao prakashrao1...@gmail.comwrote:

 I don't have .proto message created for these. Most of my APIs
 takes .proto messages as parameters (as they represent my business
 data objects) and in 1-2 APIs I need to pass only 2-3 primitive
 parameters as arguments. In these cases I’m avoiding creation
 of .proto messages (as these don’t represent my business data object).
 As an alternative, I thought of using CodedOutputstream to pass
 parameters along with tag so that retrieval is easy on the receiving
 end using CodedInputStream but I don't see a way to retrieve parameter
 using tags with CodedInputStream. Currently I've the below code and
 thought the tag approach would make it simple but CodedInputStream
 doesn't support parameter retrieval based on tags.

 // Client Side code - which sends s1  s2 strings to server
 int s1Size = CodedOutputStream.computeStringSizeNoTag(s1);
 codedOutputStream.writeRawVarint32(s1Size);
 codedOutputStream.writeStringNoTag(s1);

 int s2Size = CodedOutputStream.computeStringSizeNoTag(s2);


Note: computeStringSizeNoTag() gives the size of the string as well as the
encoded length. If you write the result as the encoded length, you will end
up reading more bytes than you should. You simply want to write the size of
the string.


 codedOutputStream.writeRawVarint32(s2Size);
 codedOutputStream.writeStringNoTag(s2);

 // Server side code - which reads s1  s2 string
 CodedInputStream codedInputStream =
 CodedInputStream.newInstance(inputStream);
 int s1Size = codedInputStream.readRawVarint32();
 int s1SizeEntry = codedInputStream.pushLimit(s1Size);
 String s1 = codedInputStream.readString();
 codedInputStream.popLimit(s1SizeEntry);

 int s2Size = codedInputStream.readRawVarint32();
 int s2SizeEntry = codedInputStream.pushLimit(s2Size);
 String s2 = codedInputStream.readString();
 codedInputStream.popLimit(modifiedBySizeEntry);

 Regards,
 Prakash

 On Aug 11, 9:17 pm, Jason Hsueh jas...@google.com wrote:
  Suppose those strings are all defined as optional fields in the message.
  They may not be present in the serialization, so the decoder needs to
 read a
  tag to determine the field number and type before handling the value.
 
  On Wed, Aug 11, 2010 at 8:37 AM, Prakash Rao prakashrao1...@gmail.com
 wrote:
 
 
 
   Hi,
   I was just looking at CodedInputStream class and there are APIs to
   write primitives with or without tag (for example, writeString 
   writeStringNoTag). I thought if we set unique tags for multiple
   parameters then we would be able to retrieve these parameters using
   tag numbers specified using CodedInputStream class. I don't see any
   APIs to read values based on tags in CodedInputStream. Am I missing
   something? For the time being I’m using pushLimit  popLimit APIs to
   get different parameter values (based on serializedSize).
 
   For example,
   int test(String s1, String s2, String s3) {
   }
 
   CodedOutputStream out = CodedOutputStream.newIInstance(Some Output
   Stream);
   out.writeString(1, s1);
   out.writeString(2, s2);
   out.writeString(3, s3);
   out.flush();
 
   Why these are not possible?
   CodedInputStream in = CodedInputStream.newIInstance(Some Input
   Stream);
   String s1 = in.readString(1);
   String s2 = in.readString(2);
   String s3 = in.readString(3);
 
   Regards,
   Prakash
 
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