I've finally got tired of all the code throughout PuTTY that repeats
the same logic about how to format the SSH binary primitives like
uint32, string, mpint. We've got reasonably organised code in ssh.c
that appends things like that to 'struct Packet'; something similar in
sftp.c which repeats a lot of the work; utility functions in various
places to format an mpint to feed to one or another hash function; and
no end of totally ad-hoc stuff in functions like public key blob
formatters which actually have to _count up_ the size of data
painstakingly, then malloc exactly that much and mess about with
PUT_32BIT.
It's time to bring all of that into one place, and stop repeating
myself in error-prone ways everywhere. The new marshal.h defines a
system in which I centralise all the actual marshalling functions, and
then layer a touch of C macro trickery on top to allow me to (look as
if I) pass a wide range of different types to those functions, as long
as the target type has been set up in the right way to have a write()
function.
This commit adds the new header and source file, and sets up some
general centralised types (strbuf and the various hash-function
contexts like SHA_State), but doesn't use the new calls for anything
yet.
(I've also renamed some internal functions in import.c which were
using the same names that I've just defined macros over. That won't
last long - those functions are going to go away soon, so the changed
names are strictly temporary.)
Now, instead of being a black box that you shovel strings into and
eventually extract a final answer, it exposes enough structure fields
to the world that you can append things to it _and_ look inside its
current contents. For convenience, it exports its internal pointer as
both a char * and an unsigned char *.
This centralises a few things that multiple header files were
previously defining, and were protecting against each other's
redefinition with ifdefs - small things like structs and typedefs. Now
all those things are in a defs.h which is by definition safe to
include _first_ (out of all the codebase-local headers) and only need
to be defined once.
