Function anjay_download_set_next_block_offset

Function Documentation

avs_error_t anjay_download_set_next_block_offset(anjay_t *anjay, anjay_download_handle_t dl_handle, size_t next_block_offset)

Changes the offset of the remote resource that the user wants to receive the next response data block from.

This function is only intended to be called from within an implementation of anjay_download_next_block_handler_t.

The offset can only be moved forward relative to the last known starting offset. Attempting to set it to an offset of byte that was already received in a previously finished call to anjay_download_next_block_handler_t, or is smaller than an offset already passed to this function, will result in an error.

When called from within anjay_download_next_block_handler_t, next_block_offset may be set to a position that lies after or within the data buffer passed to it (but further than the current offset). If a position within the buffer is passed, the block handler will be called again with a portion of the same buffer, starting at the desired offset.

If this function is never called during a call to anjay_download_next_block_handler_t, the file pointer is implicitly moved by the whole size of the buffer passed to it.

It is guaranteed that if there will be a next call to anjay_download_next_block_handler_t for the given download, it will be passed data from the specified offset.

NOTE: Actual efficient skipping of already downloaded data is currently only supported for CoAP. Using this function with HTTP downloads will only suppress passing the skipped data; full file will still be transmitted over the network.

Parameters:

  • anjay – Anjay object managing the download process.

  • dl_handle – Download handle previously returned by anjay_download.

  • next_block_offset – Block offset to set.

Returns:

  • AVS_OK for success

  • avs_errno(AVS_ENOENT) if dl_handle does not refer to an existing download process

  • avs_errno(AVS_EINVAL) if next_block_offset is smaller than the currently recognized value

  • avs_errno(AVS_ENOTSUP) if Anjay has been compiled without support for downloads