SSDI(3C)SSDI(3C)NAMEssdi_get_config_and_load - consult configuration file and load DSO
corresponding to the source for a given system database
SYNOPSIS
#include <ssdi.h>
int ssdi_get_config_and_load(char *dbname, struct ssdiconfiginfo *cfinfo,
struct ssdisrcinfo *srcinfo);
DESCRIPTION
The ssdi_get_config_and_load function provides the means for an
application to load the dynamic shared object (DSO) corresponding to a
source for a given system database. A database is a collection of
information related to users, groups, networks, etc. that the operating
system expects to be maintained by user-level libraries. For example,
information relating to users is encapsulated by the passwd database.
Each such has a definite interface. For example, the getpwent(3C)
routines define the interface for the passwd database. The information
contained in a given database may be stored in multiple sources. Almost
all standard databases come with sources that are compiled-in with the
interface. The files source for the passwd database which maintains
relevant information in files is one such. A Dynamic source for a
database is one whose implementation is not fixed at the time of
compilation of interface for the database. Thus, a dynamic source allows
for custom implementations of database repositories.
The file /etc/ssdi.conf (see ssdi(4)) is used to add a dynamic source for
a database. Each application can cache configuration information for a
given database using a variable of type struct ssdiconfiginfo, which
includes the following members:
int ssdi_ci_got_config If non-zero, the rest of the fields
contain configuration information.
char *ssdi_ci_dsrcs[_SSDI_MAXSRCS]
Names of dynamic sources for the given
database.
char **ssdi_ci_currdsrc Next dynamic source to load. Pointer to
the name in the above array.
Initially, the variable used to cache configuration information should be
set to _SSDI_InitConfigInfo.
Each dynamic source should be implemented as a DSO, and should reside in
a standard directory as defined by _SSDI_STD_SRC_DIR. The DSO should
export a variable which represents a vector of functions. This vector
contains addresses of functions which implement corresponding
functionality of the database interface. The correspondence between the
vector and the routines of the database interface is defined in a
database specific header file, <di_{database-name}.h>. For example, the
file <di_group.h> defines the correspondence for the group database. If a
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source does not implement a particular routine then the corresponding
element in the vector should be set to NULL.
On its very first invocation, ssdi_get_config_and_load function gathers
information for the database dbname from the configuration file, and
caches it in the variable pointed to by cfinfo. Then, it loads (using
dlopen(3)) the DSO corresponding to the first source listed in the
configuration. Information concerning the loaded source is returned in
srcinfo, which is of type struct ssdisrcinfo, and has the following
fields:
char ssdi_si_name[_SSDI_MAXSRCNAME]
The name of the source that was loaded.
_SSDI_VOIDFUNC *ssdi_si_funcs A pointer to the vector of routines
implemented by the source; resolved
using dlsym(3) from the DSO
corresponding to the source.
On subsequent invocations (with the same arguments),
ssdi_get_config_and_load loads the next source in the cached
configuration information; srcinfo is overwritten with data from this new
source. Since ssdi_get_config_and_load maintains state between
invocations in cfinfo, it should not be manipulated by the caller, except
for proper initialization before the first invocation.
SEE ALSOssdi(4), dlopen(3), dlsym(3), getpwent(3C), getgrent(3C)DIAGNOSTICS
If a source was successfully loaded, ssdi_get_config_and_load returns
zero. Otherwise, a non-zero value is returned.
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