How to add an int array in a protobuf message

Question

I have to compose a protobuf message which should have 1 integer variables and a integer array.

package protobuf;

message myProto {

optional uint32 message_id =1;
optional int update = 2;
//here I have to add a array of integers
//can I write like     optional int[] array =3;
//or should I use      optional repeated array;
//where array is another message with int variable

}

Is my approach correct?

Marc Gravell · Accepted Answer · 2011-09-13 20:51:48Z

103

Array is mapped via "repeated":

 repeated int32 data = 4;

Note you might want sint32/uint32. Also note that in all three cases "packed arrays" can be used, which are more efficient;

repeated int32 data = 4 [packed=true];

answered Sep 13, 2011 at 20:51

Marc Gravell

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8 Comments

javaMan Over a year ago

is the packed array concept applicable for double arrays also?

Raj Over a year ago

in above 4 is tag or array size ?

Marc Gravell Over a year ago

@Raj tag; the size of the data is determined solely at runtime by how much data is there; there are no fixed sized arrays in protobuf. In the case of "packed", the size (in bytes) is prefixed to the data.

Jason Doucette Over a year ago

Update: developers.google.com/protocol-buffers/docs/proto3 states "In proto3, repeated fields of scalar numeric types use packed encoding by default."

Marc Gravell Over a year ago

@Jason very true (I wrote a different reply, then realised the question was purely about .proto schema, not the thing I was talking about)

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