Yearly Archives: 2017

The following post is for the https://lionet.info/asn1c/ (repository: https://github.com/vlm/asn1c/)

When trying to link an ASN.1 structure that uses a SET OF, with support for Unaligned Packed Encoding Rules (UPER), we get the following error: undefined reference to 'SET_OF_encode_uper'.

Unfortunately, there is currently no solution for this problem, so we replaced the SET OF with a SEQUENCE OF.

The SEQUENCE OF type is the list (array) of simple or constructed types. The SET OF type models the bag of structures. It resembles the SEQUENCE OF type, but the order is not important: i.e. the elements may arrive in the order which is not necessarily the same as the in-memory order on the remote machines.

— From http://lionet.info/asn1c/asn1c-usage.html

Original (problematic) code

Elements ::= SEQUENCE
{
    property INTEGER,
    objects SET OF object
}

Updated (working) code

Elements ::= SEQUENCE
{
    property INTEGER,
    objects SEQUENCE OF object
}

The following post is for the https://lionet.info/asn1c/ (repository: https://github.com/vlm/asn1c/)

There is no need to compute the space needed.

If you pass the address to a pointer that is NULL pointer as the last parameter of uper_encode_to_new_buffer(asn_TYPE_descriptor_t *td, asn_per_constraints_t *constraints, void *sptr, void **buffer_r) , then it will allocate by itself the required space.

void *buffer = NULL;
asn_per_constraints_s *constraints = NULL;
ssize_t ec = uper_encode_to_new_buffer(&asn_DEF_Image, constraints, image, &buffer);

The following post is for the https://lionet.info/asn1c/ (repository: https://github.com/vlm/asn1c/)

The asn1c usage manual (PDF), mentions an element called write_stream but it does not define what it is.

What write_stream is can be found in converter-sample.c  and in the manual under the name write_out:

/* Dump the buffer out to the specified FILE */
static int write_out(const void *buffer, size_t size, void *key) {
  FILE *fp = (FILE *)key;
  return (fwrite(buffer, 1, size, fp) == size) ? 0 : -1;
}

write_out is function that has the following signature write_out(const void *buffer, size_t size, void *app_key) and is used as a callback by der_encode() and other functions.

This callback receives as input the pointer to an element (const void *buffer), the size of that element (size_t size) and some context (void *app_key).
In this example, we can see that the user is using der_encode() which accepts a FILE * as the last parameter, which later is passed to write_out() as the context.