[mkgmap-dev] Binary OSM file support?

Mon Sep 13 23:21:54 BST 2010

On Mon, Sep 13, 2010 at 3:36 PM, Steve Ratcliffe <steve at parabola.me.uk> wrote:

> Its needed because mkgmap takes all kinds of input files and I don't
> want the user to have to say what the file format is, I just want
> mkgmap to work out the file format and use the correct reader.
>
> I do this by extension or by reading the beginning of the file and
> looking for something distinctive.  It doesn't have to be fool proof
> just good enough to tell genuine files apart.
>
> Hence why I was asking if OSMHeader and or OSMData would always
> be present near the beginning of the file, I could look for
> them.

Yes, I believe OSMHeader should occur in the first 16 bytes or so.
(Just looked at a hexdump. Yes, confirmed, byte offset [6,14].
Furthermore, I believe that byte offsets [4,15] will always be static
when the first block is an OSMHeader, however, I cannot guarantee it
because I cannot guarantee that a given protocol buffer will always
serialize to the same output in the future.

Scott