[nanomsg] nn_recv with padding
- From: Drew Crawford <drew@xxxxxxxxxxxxxxxxxx>
- To: nanomsg@xxxxxxxxxxxxx
- Date: Mon, 12 May 2014 05:08:47 -0500
A common case for me is to receive a message to which my application will add
some additional information of known size. For a message of fixed size I can do
const int fixedSize;
uint8_t buf[fixedSize+padding];
rc = nn_recv(socket,buf,fixedSize,0);
And similar to get appended rather than prepended padding. But for messages of
variable size I have to use the form
void *buf = NULL;
nn_recv(socket,&buf,NN_MSG,0)
which would require memcpy to copy into a buffer with space for padding.
Ideally I would like something like
struct nn_padding_description {
int paddingSize = 20;
int paddingType = NN_PREPEND;
}
nn_recv(socket,&buf,padding_description,NN_LENGTH_IS_PADDING_DESCRIPTION_NOT_ACTUAL_LENGTH);
An alternate idea would be some way to find out the size in advance
int size = nn_peeksize(socket,options);
uint8_t buf[size + padding];
rc = nn_recv(socket,buf,size,0);
This approach has the advantage of supporting size-dependent padding schemes
(for example, padding that is exactly double message length) but there may be
some implementation detail why message size cannot be known in advance.
Drew
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