Complete rework of package accessor logic

Hopefully we've finally arrived at package handling nirvana, or at least
this commit will get us a heck of a lot closer. The former method of getting
the depends list for a package was the following:

1. call alpm_pkg_get_depends()
2. this method would check if the package came from the cache
3. if so, ensure our cache level is correct, otherwise call db_load
4. finally return the depends list

Why did this suck? Because getting the depends list from the package
shouldn't care about whether the package was loaded from a file, from the
'package cache', or some other system which we can't even use because the
damn thing is so complicated. It should just return the depends list.

So what does this commit change? It adds a pointer to a struct of function
pointers to every package for all of these 'package operations'  as I've
decided to call them (I know, sounds completely straightforward, right?). So
now when we call an alpm_pkg_get-* function, we don't do any of the cache
logic or anything else there- we let the actual backend handle it by
delegating all work to the method at pkg->ops->get_depends.

Now that be_package has achieved equal status with be_files, we can treat
packages from these completely different load points differently. We know a
package loaded from a zip file will have all of its fields populated, so
we can set up all its accessor functions to be direct accessors. On the
other hand, the packages loaded from the local and sync DBs are not always
fully-loaded, so their accessor functions are routed through the same logic
as before.

Net result? More code. However, this code now make it roughly 52 times
easier to open the door to something like a read-only tar.gz database
backend.

Are you still reading? I'm impressed. Looking at the patch will probably be
clearer than this long-winded explanation.

Signed-off-by: Dan McGee <dan@archlinux.org>
[Allan: rebase and adjust]
Signed-off-by: Allan McRae <allan@archlinux.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/lib/libalpm/be_package.c b/lib/libalpm/be_package.c
index 3d8c4e38..f581813c 100644
--- a/lib/libalpm/be_package.c
+++ b/lib/libalpm/be_package.c
@@ -234,7 +234,9 @@ static pmpkg_t *pkg_load(const char *pkgfile, int full)
 
 	/* internal fields for package struct */
 	newpkg->origin = PKG_FROM_FILE;
+	/* TODO eventually kill/move this? */
 	newpkg->origin_data.file = strdup(pkgfile);
+	newpkg->ops = &default_pkg_ops;
 
 	if(full) {
 		/* "checking for conflicts" requires a sorted list, ensure that here */