[pacman-dev] About pacman and libalpm workflow

[Allan McRae]

On 21/05/11 19:15, Rémy Oudompheng wrote:
> On 2011/5/21 ari edelkind<edelkind+arch-pacman at gmail.com>  wrote:
>>   - What's the general idea -- the program flow -- of the way it's
>>     currently being implemented?  Pseudo-code would be perfect for
>>     answering this, but really, anything with system-level details
>>     will do (the "package signing proposal" is not current and does
>>     not contain system-level details).
>
> Hello Ari,
>
> It's a bit difficult to answer that question, I don't exactly what
> documentation sources there are out there. I'll try a rough draft, and
> then you can ask more questions if you want. Also try to have a look
> at pyalpm: it contains example scripts in Python that try to replicate
> pacman 3.5 behaviour.
>
> Here is how to use libalpm :
> - initialize it (alpm_initialize)
> - set options (alpm_option_set_*)
> - register databases (alpm_db_register_sync)
> - do something (many functions there)
> - unregister databases
> - release the library (alpm_release)
>
> In the "do something" part, you may perform a transaction, that is,
> installation or uninstallation of packages. Transactions are done as
> follows :
> - alpm_trans_init with proper options
> - alpm_trans_add / alpm_trans_remove (says which packages you want to
> add or remove)
> - alpm_trans_prepare : this will resolve dependencies and conflicts
> - alpm_trans_commit : this will download packages, check them (md5 or
> signature), and install/remove them
> - alpm_trans_release()
>
> The functions that are called to check signature are
> alpm_db_check_pgp_signature, alpm_pkg_check_pgp_signature. Options
> make this check optional if needed.

To be honest, I have very little idea about pacman "program flow".   I 
follow something like this every time I go to dig deeper into the pacman 
code and fix something:

http://allanmcrae.com/2010/11/basic-overview-of-pacman-code/

Allan