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Date/Time: Thu, 19 Apr 2018 17:27:37 +0000



Post From: DTC Protocol

[2016-04-01 00:00:20]
vbmithr - Posts: 204
See my code here: https://github.com/vbmithr/ocaml-dtc/blob/master/lib/cstructs.ml

This is OCaml (well an OCaml extension to parse C structures), and you can see where fields are padded when I add a field like named like _padding (sometimes there are multiple padding fields).

The rules are that types (short, int, long, …) are aligned by a multiple of their size, i.e. for example a short cannot start on byte 5, a long (64 bits) cannot start on byte 6, and so on…, so that if you, say, have a structure like

struct MyStruct {
char a;
uint64 b;
}

the size will not be 9, but 16, and equivalent to

struct MyStruct {
char a[8];
uint64 b;
}

That's why I advise you to use the protobuf encoding (and you advised yourself to use JSON). It is tedious to deal with those padding oneself.
Date Time Of Last Edit: 2016-04-01 00:01:23