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, 245 insertions, 2 deletions

diff --git a/lib/libalpm/be_files.c b/lib/libalpm/be_files.c
index c0298049..e8573947 100644
--- a/lib/libalpm/be_files.c
+++ b/lib/libalpm/be_files.c
@@ -1,8 +1,8 @@
 /*
  *  be_files.c
  *
- *  Copyright (c) 2006 by Christian Hamar <krics@linuxforum.hu>
- *  Copyright (c) 2006 by Miklos Vajna <vmiklos@frugalware.org>
+ *  Copyright (c) 2006-2010 Pacman Development Team <pacman-dev@archlinux.org>
+ *  Copyright (c) 2002-2006 by Judd Vinet <jvinet@zeroflux.org>
  *
  *  This program is free software; you can redistribute it and/or modify
  *  it under the terms of the GNU General Public License as published by
@@ -51,6 +51,247 @@
 #include "dload.h"
 
 
+#define LAZY_LOAD(info, errret) \
+	do { \
+		ALPM_LOG_FUNC; \
+		ASSERT(handle != NULL, return(errret)); \
+		ASSERT(pkg != NULL, return(errret)); \
+		if(pkg->origin != PKG_FROM_FILE && !(pkg->infolevel & info)) { \
+			_alpm_db_read(pkg->origin_data.db, pkg, info); \
+		} \
+	} while(0)
+
+
+/* Cache-specific accessor functions. These implementations allow for lazy
+ * loading by the files backend when a data member is actually needed
+ * rather than loading all pieces of information when the package is first
+ * initialized.
+ */
+
+const char *_cache_get_filename(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, NULL);
+	return pkg->filename;
+}
+
+const char *_cache_get_name(pmpkg_t *pkg)
+{
+	ASSERT(pkg != NULL, return(NULL));
+	return pkg->name;
+}
+
+static const char *_cache_get_version(pmpkg_t *pkg)
+{
+	ASSERT(pkg != NULL, return(NULL));
+	return pkg->version;
+}
+
+static const char *_cache_get_desc(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, NULL);
+	return pkg->desc;
+}
+
+const char *_cache_get_url(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, NULL);
+	return pkg->url;
+}
+
+time_t _cache_get_builddate(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, 0);
+	return pkg->builddate;
+}
+
+time_t _cache_get_installdate(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, 0);
+	return pkg->installdate;
+}
+
+const char *_cache_get_packager(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, NULL);
+	return pkg->packager;
+}
+
+const char *_cache_get_md5sum(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, NULL);
+	return pkg->md5sum;
+}
+
+const char *_cache_get_arch(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, NULL);
+	return pkg->arch;
+}
+
+off_t _cache_get_size(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, -1);
+	return pkg->size;
+}
+
+off_t _cache_get_isize(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, -1);
+	return pkg->isize;
+}
+
+pmpkgreason_t _cache_get_reason(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, -1);
+	return pkg->reason;
+}
+
+alpm_list_t *_cache_get_licenses(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, NULL);
+	return pkg->licenses;
+}
+
+alpm_list_t *_cache_get_groups(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, NULL);
+	return pkg->groups;
+}
+
+int _cache_has_force(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, -1);
+	return pkg->force;
+}
+
+alpm_list_t *_cache_get_depends(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DEPENDS, NULL);
+	return pkg->depends;
+}
+
+alpm_list_t *_cache_get_optdepends(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DEPENDS, NULL);
+	return pkg->optdepends;
+}
+
+alpm_list_t *_cache_get_conflicts(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DEPENDS, NULL);
+	return pkg->conflicts;
+}
+
+alpm_list_t *_cache_get_provides(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DEPENDS, NULL);
+	return pkg->provides;
+}
+
+alpm_list_t *_cache_get_replaces(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DESC, NULL);
+	return pkg->replaces;
+}
+
+alpm_list_t *_cache_get_deltas(pmpkg_t *pkg)
+{
+	LAZY_LOAD(INFRQ_DELTAS, NULL);
+	return pkg->deltas;
+}
+
+alpm_list_t *_cache_get_files(pmpkg_t *pkg)
+{
+	ALPM_LOG_FUNC;
+
+	/* Sanity checks */
+	ASSERT(handle != NULL, return(NULL));
+	ASSERT(pkg != NULL, return(NULL));
+
+	if(pkg->origin == PKG_FROM_LOCALDB
+		 && !(pkg->infolevel & INFRQ_FILES)) {
+		_alpm_db_read(pkg->origin_data.db, pkg, INFRQ_FILES);
+	}
+	return pkg->files;
+}
+
+alpm_list_t *_cache_get_backup(pmpkg_t *pkg)
+{
+	ALPM_LOG_FUNC;
+
+	/* Sanity checks */
+	ASSERT(handle != NULL, return(NULL));
+	ASSERT(pkg != NULL, return(NULL));
+
+	if(pkg->origin == PKG_FROM_LOCALDB
+		 && !(pkg->infolevel & INFRQ_FILES)) {
+		_alpm_db_read(pkg->origin_data.db, pkg, INFRQ_FILES);
+	}
+	return pkg->backup;
+}
+
+/** The sync database operations struct. Get package fields through
+ * lazy accessor methods that handle any backend loading and caching
+ * logic.
+ */
+static struct pkg_operations sync_pkg_ops = {
+	.get_filename    = _cache_get_filename,
+	.get_name        = _cache_get_name,
+	.get_version     = _cache_get_version,
+	.get_desc        = _cache_get_desc,
+	.get_url         = _cache_get_url,
+	.get_builddate   = _cache_get_builddate,
+	.get_installdate = _cache_get_installdate,
+	.get_packager    = _cache_get_packager,
+	.get_md5sum      = _cache_get_md5sum,
+	.get_arch        = _cache_get_arch,
+	.get_size        = _cache_get_size,
+	.get_isize       = _cache_get_isize,
+	.get_reason      = _cache_get_reason,
+	.has_force       = _cache_has_force,
+	.get_licenses    = _cache_get_licenses,
+	.get_groups      = _cache_get_groups,
+	.get_depends     = _cache_get_depends,
+	.get_optdepends  = _cache_get_optdepends,
+	.get_conflicts   = _cache_get_conflicts,
+	.get_provides    = _cache_get_provides,
+	.get_replaces    = _cache_get_replaces,
+	.get_deltas      = _cache_get_deltas,
+	.get_files       = _cache_get_files,
+	.get_backup      = _cache_get_backup,
+};
+
+/** The local database operations struct. Get package fields through
+ * lazy accessor methods that handle any backend loading and caching
+ * logic.
+ */
+static struct pkg_operations local_pkg_ops = {
+	.get_filename    = _cache_get_filename,
+	.get_name        = _cache_get_name,
+	.get_version     = _cache_get_version,
+	.get_desc        = _cache_get_desc,
+	.get_url         = _cache_get_url,
+	.get_builddate   = _cache_get_builddate,
+	.get_installdate = _cache_get_installdate,
+	.get_packager    = _cache_get_packager,
+	.get_md5sum      = _cache_get_md5sum,
+	.get_arch        = _cache_get_arch,
+	.get_size        = _cache_get_size,
+	.get_isize       = _cache_get_isize,
+	.get_reason      = _cache_get_reason,
+	.has_force       = _cache_has_force,
+	.get_licenses    = _cache_get_licenses,
+	.get_groups      = _cache_get_groups,
+	.get_depends     = _cache_get_depends,
+	.get_optdepends  = _cache_get_optdepends,
+	.get_conflicts   = _cache_get_conflicts,
+	.get_provides    = _cache_get_provides,
+	.get_replaces    = _cache_get_replaces,
+	.get_deltas      = _cache_get_deltas,
+	.get_files       = _cache_get_files,
+	.get_backup      = _cache_get_backup,
+};
+
 static int checkdbdir(pmdb_t *db)
 {
 	struct stat buf;
@@ -417,8 +658,10 @@ int _alpm_db_populate(pmdb_t *db)
 		}
 		if(db == handle->db_local) {
 			pkg->origin = PKG_FROM_LOCALDB;
+			pkg->ops = &local_pkg_ops;
 		}  else {
 			pkg->origin = PKG_FROM_SYNCDB;
+			pkg->ops = &sync_pkg_ops;
 		}
 		pkg->origin_data.db = db;
 		/* add to the collection */