NDB(2)

NAME

ndbopen, ndbclose, ndbreopen, ndbsearch, ndbsnext, ndbgetval, ndbfree, ipattr, ipinfo, ndbhash, ndbparse, csgetval − network database

SYNOPSIS

#include <u.h>
#include <libc.h>
#include <bio.h>
#include <ndb.h>

Ndb∗ndbopen(char ∗file);

intndbreopen(Ndb ∗db);

voidndbclose(Ndb ∗db);

Ndbtuple∗ndbsearch(Ndb ∗db, Ndbs ∗s, char ∗attr, char ∗val);

Ndbtuple∗ndbsnext(Ndbs ∗s, char ∗attr, char ∗val);

Ndbtuple∗ndbgetval(Ndb ∗db, Ndbs ∗s, char ∗attr, char ∗val,
char ∗rattr, char ∗buf);

Ndbtuple∗csgetval(char ∗attr, char ∗val, char ∗rattr, char ∗buf);

voidndbfree(Ndbtuple ∗db);

char∗ipattr(char ∗name);

intipinfo(Ndb ∗db, char ∗ether, char ∗ip, char ∗name,
Ipinfo ∗iip);

ulongndbhash(char ∗val, int hlen);

Ndbtuple∗ndbparse(Ndb ∗db);

DESCRIPTION

These routines are used by network administrative programs to search the network database. They operate on the database files described in ndb(6).

Ndbopen opens the database file and calls malloc(2) to allocate a buffer for it. If file is zero, all network database files are opened.

Ndbreopen checks if the database files associated with db have changed and if so throws out any cached information and reopens the files.

Ndbclose closes any database files associated with db and frees all storage associated with them.

Ndbsearch and ndbsnext search a database for an entry containing the attribute/value pair, attr=val. Ndbsearch is used to find the first match and ndbsnext is used to find each successive match. On a successful search both return a linked list of Ndbtuple structures acquired by malloc(2) that represent the attribute/value pairs in the entry. On failure they return zero.

typedef struct Ndbtuple Ndbtuple;
struct Ndbtuple {
        char      attr[Ndbalen];
        char      val[Ndbvlen];
        Ndbtuple ∗entry;
        Ndbtuple ∗line;
        ulong     ptr;    /∗ for the application; starts 0 ∗/
};

The entry pointers chain together all pairs in the entry in a null-terminated list. The 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.

The argument s of ndbsearch has type Ndbs and should be pointed to valid storage before calling ndbsearch, which will fill it with information used by ndbsnext to link successive searches. The structure Ndbs looks like:

typedef struct Ndbs Ndbs;
struct Ndbs {
        Ndb      ∗db;   /∗ data base file being searched ∗/
        ...
        Ndbtuple ∗t;    /∗ last attribute value pair found ∗/
};

The t field points to the pair within the entry matched by the ndbsearch or ndbsnext.

Ndbgetval searches the database for an entry containing not only an attribute/value pair, attr=val, but also a pair with the attribute rattr. If successful, it copies the value associated with rattr into buf. Buf must point to an area at least Ndbvlen long. Csgetval is like ndbgetval but queries the connection server instead of looking directly at the database.

Ndbfree frees a list of tuples returned by one of the other routines.

Ipattr takes the name of an IP system and returns the attribute it corresponds to:

dom domain name

ip Internet number

sys system name

Ipinfo searches the database for Internet Protocol information about a system and returns it in the structure addressed by iip. The arguments ether (textual Ethernet address), ip (textual IP address), and name identify the system. At least one must be non-zero. Ipinfo returns 0 if successful, −1 otherwise. Both bootp(8) and ipconfig(8) use ipinfo to search the database.

The last three calls are used by programs that create the hash tables and database files. Ndbhash computes a hash offset into a table of length hlen for the string val. Ndbparse reads and parses the next entry from the database file. Multiple calls to ndbparse parse sequential entries in the database file. A zero is returned at end of file.

SOURCE

/sys/src/libndb

DIAGNOSTICS

These routines set errstr.

Plan 9 — April 04, 1995

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