TH NDB 2
SH NAME
ndbopen, ndbcat, ndbchanged, ndbclose, ndbreopen, ndbsearch, ndbsnext, ndbgetvalue, ndbfree, ipattr, ndbgetipaddr, ndbipinfo, csipinfo, ndbhash, ndbparse, csgetvalue, ndbfindattr, dnsquery, ndbdiscard, ndbconcatenate, ndbreorder, ndbsubstitute, ndbdedup \- network database
SH SYNOPSIS
B #include <u.h>
br
B #include <libc.h>
br
B #include <bio.h>
br
B #include <ndb.h>
ta \w'\fLNdbtuplexx 'u
PP
B
Ndb*    ndbopen(char *file)
PP
B
Ndb*    ndbcat(Ndb *db1, Ndb *db2)
PP
B
int     ndbchanged(Ndb *db)
PP
B
int     ndbreopen(Ndb *db)
PP
B
void    ndbclose(Ndb *db)
PP
B
Ndbtuple*       ndbsearch(Ndb *db, Ndbs *s, char *attr, char *val)
PP
B
Ndbtuple*       ndbsnext(Ndbs *s, char *attr, char *val)
PP
B
char*   ndbgetvalue(Ndb *db, Ndbs *s, char *attr, char *val,
br
B
               char *rattr, Ndbtuple **tp)
PP
B
char*   csgetvalue(char *netroot, char *attr, char *val,
B
               char *rattr, Ndbtuple **tp)
PP
B
char*   ipattr(char *name)
PP
B
Ndbtuple*       ndbgetipaddr(Ndb *db, char *sys);
PP
B
Ndbtuple*       ndbipinfo(Ndb *db, char *attr, char *val, char **attrs,
br
B               int nattr)
PP
B
Ndbtuple*       csipinfo(char *netroot, char *attr, char *val,
br
B               char **attrs, int nattr)
PP
B
ulong   ndbhash(char *val, int hlen)
PP
B
Ndbtuple*       ndbparse(Ndb *db)
PP
B
Ndbtuple*       dnsquery(char *netroot, char *domainname, char *type)
PP
B
Ndbtuple*       ndbfindattr(Ndbtuple *entry, Ndbtuple *line, char *attr)
PP
B
void    ndbfree(Ndbtuple *db)
PP
B
Ndbtuple*       ndbdiscard(Ndbtuple  *t, Ndbtuple *a)
PP
B
Ndbtuple*       ndbconcatenate(Ndbtuple *a, Ndbtuple *b)
PP
B
Ndbtuple*       ndbreorder(Ndbtuple *t, Ndbtuple *a)
PP
B
Ndbtuple*       ndbsubstitute(Ndbtuple *t, Ndbtuple *from, Ndbtuple *to)
PP
B
Ndbtuple*       ndbdedup(Ndbtuple *t)
PP
B
void    ndbsetmalloctag(Ndbtuple *t, uintptr tag)
SH DESCRIPTION
These routines are used by network administrative programs to search
the network database.
They operate on the database files described in
IR ndb (6).
PP
I Ndbopen
opens the database
I file
and calls
IR malloc (2)
to allocate a buffer for it.
If
I file
is zero, all network database files are opened.
PP
I Ndbcat
concatenates two open databases.  Either argument may be nil.
PP
I Ndbreopen
throws out any cached information
for the database files associated with
I db
and reopens the files.
PP
I Ndbclose
closes any database files associated with
I db
and frees all storage associated with them.
PP
I Ndbsearch
and
I ndbsnext
search a database for an entry containing the
attribute/value pair,
IR attr = val .
I Ndbsearch
is used to find the first match and
I ndbsnext
is used to find each successive match.
On a successful search both return a linked list of
I Ndbtuple
structures acquired by
IR malloc (2)
that represent the attribute/value pairs in the
entry.
On failure they return zero.
IP
EX
typedef struct Ndbtuple Ndbtuple;
struct Ndbtuple {
       char      attr[Ndbalen];
       char      *val;
       Ndbtuple  *entry;
       Ndbtuple  *line;
       ulong     ptr;    /* for the application; starts 0 */
       char      valbuf[Ndbvlen];  /* initial allocation for val */
};
EE
LP
The
I entry
pointers chain together all pairs in the entry in a null-terminated list.
The
I line
pointers chain together all pairs on the same line
in a circular list.
Thus, a program can implement 2 levels of binding for
pairs in an entry.
In general, pairs on the same line are bound tighter
than pairs on different lines.
PP
The argument
I s
of
I ndbsearch
has type
I Ndbs
and should be pointed to valid storage before calling
IR ndbsearch ,
which will fill it with information used by
I ndbsnext
to link successive searches.
The structure
I Ndbs
looks like:
IP
EX
typedef struct Ndbs Ndbs;
struct Ndbs {
       Ndb      *db;   /* data base file being searched */
       ...
       Ndbtuple *t;    /* last attribute value pair found */
};
EE
LP
The
I t
field points to the pair within the entry matched by the
I ndbsearch
or
IR ndbsnext .
PP
I Ndbgetvalue
searches the database for an entry containing not only an
attribute/value pair,
IR attr = val ,
but also a pair with the attribute
IR rattr .
If successful, it returns a malloced copy of the NUL-terminated value associated with
IR rattr .
If
I tp
is non nil,
I *tp
will point to the entry.  Otherwise the entry will be freed.
PP
I Csgetvalue
is like
I ndbgetvalue
but queries the connection server
instead of looking directly at the database.
Its first argument specifies the network root to use.
If the argument is 0, it defaults to
\f5"/net"\f1.
PP
I Ndbfree
frees a list of tuples returned by one of the other
routines.
PP
I Ipattr
takes the name of an IP system and returns the attribute
it corresponds to:
RS
TP
B dom
domain name
TP
B ip
Internet number
TP
B sys
system name
RE
PP
I Ndbgetipaddr
looks in
I db
for entries matching
I sys
as the value of a
B sys=
or
B dom=
attribute/value pair and returns all IP addresses.
If
I sys
is already an IP address, a tuple containing just
that address is returned.
PP
I Ndbipinfo
looks up Internet protocol information about a system.
This is an IP aware search.  It looks first for information
in the system's database entry and then in the database entries
for any IP subnets or networks containing the system.
The system is identified by the
attribute/value pair,
IR attr = val .
I Ndbipinfo
returns a list of tuples whose attributes match the
attributes in the
I n
element array
IR attrs .
If any
I attrs
begin with
LR @ ,
the
L @
is excluded from the attribute name,
but causes any corresponding value returned
to be a resolved IP address(es), not a name.
For example, consider the following database entries describing a network,
a subnetwork, and a system.
IP
EX
ipnet=big ip=10.0.0.0
       dns=dns.big.com
       smtp=smtp.big.com
ipnet=dept ip=10.1.1.0 ipmask=255.255.255.0
       smtp=smtp1.big.com
ip=10.1.1.4 dom=x.big.com
       bootf=/386/9pc
EE
PP
Calling
IP
EX
ndbipinfo(db, "dom", "x.big.com", ["bootf" "smtp" "dns"], 3)
EE
PP
will return the tuples
BR bootf=/386/9pc ,
BR smtp=smtp1.big.com ,
and
BR dns=dns.big.com .
PP
I Csipinfo
is to
I ndbipinfo
as
I csgetvalue
is to
IR ndbgetvalue .
PP
The next three routines are used by programs that create the
hash tables and database files.
I Ndbhash
computes a hash offset into a table of length
I hlen
for the string
IR val .
I Ndbparse
reads and parses the next entry from the database file.
Multiple calls to
IR ndbparse
parse sequential entries in the database file.
A zero is returned at end of file.
PP
I Dnsquery
submits a query about
I domainname
to the
I ndb/dns
mounted at
IB netroot /dns.
It returns a linked list of
I Ndbtuple's
representing a single database entry.
The tuples are logically arranged into lines using the
B line
field in the structure.
The possible
IR type 's
of query are and the attributes on each returned tuple line is:
TP
B ip
find the IP addresses.  Returns
domain name
RI ( dom )
and ip address
RI ( ip ).
TP
B ipv6
find the IPv6 addresses.  Returns
domain name
RI ( dom )
and ipv6 address
RI ( ip ).
TP
B mx
look up the mail exchangers.  Returns preference
RI ( pref )
and exchanger
RI ( mx ).
TP
B ptr
do a reverse query.  Here
I domainname
must be an
SM ASCII
IP address.  Returns reverse name
RI ( ptr )
and domain name
RI ( dom ).
TP
B cname
get the system that this name is a nickname for.  Returns the nickname
RI ( dom )
and the real name
RI ( cname ).
TP
B soa
return the start of area record for this field.  Returns
area name
RI ( dom ),
primary name server
RI ( ns ),
serial number
RI ( serial ),
refresh time in seconds
RI ( refresh ),
retry time in seconds
RI ( retry ),
expiration time in seconds
RI ( expire ),
and minimum time to lie
RI ( ttl ).
TP
B srv
get the service records.  Returns the priority of target host
RI ( pri ),
relative weight
RI ( weight )
for entries with the same priority,
port on this target host of this service
RI ( port ),
and the domain name of the target host
RI ( target ).
TP
B txt
get the descriptive text.  The semantics of the text depends
on the domain.
TP
B ns
name servers.  Returns domain name
RI ( dom )
and name server
RI ( ns ).
PP
I Ndbfindattr
searches
I entry
for the tuple
with attribute
I attr
and returns a pointer to the tuple.
If
I line
points to a particular line in the entry, the
search starts there and then wraps around to the beginning
of the entry.
PP
All of the routines provided to search the database
provide an always consistent view of the relevant
files.  However, it may be advantageous for an application
to read in the whole database using
I ndbopen
and
I ndbparse
and provide its own search routines.  The
I ndbchanged
routine can be used by the application to periodically
check for changes.  It returns zero
if none of the files comprising the database have
changes and non-zero if they have.
PP
Finally, a number of routines are provided for manipulating tuples.
PP
I Ndbdiscard
removes attr/val pair
I a
from tuple
I t
and frees it.
If
I a
isn't in
I t
it is just freed.
PP
I Ndbconcatenate
concatenates two tuples and returns the result.  Either
or both tuples may be nil.
PP
I Ndbreorder
reorders a tuple
IR t
to make the line containing attr/val pair
I a
first in the entry and making
I a
first in its line.
PP
I Ndbsubstitute
replaces a single attr/val pair
I from
in
I t
with the tuple
IR to .
All attr/val pairs in
I to
end up on the same line.
I from
is freed.
PP
I Ndbdedup
removes duplicate attr/val pairs from tuple list
IR t .
PP
I Ndbsetmalloctag
sets the malloc tag
(see
I setmalloctag
in
IR malloc (2))
of each tuple in the list
I t
to
IR tag .
SH FILES
BR /lib/ndb "    directory of network database files
SH SOURCE
B /sys/src/libndb
SH SEE ALSO
IR ndb (6),
IR ndb (8)

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