ypclnt.3yp

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3YP 代码 · 共 389 行

.\" SCCSID: @(#)ypclnt.3yp	8.1	9/11/90
.TH ypclnt 3yp
.SH Name
yp_get_default_domain, yp_bind, yp_unbind, yp_match, yp_first,
yp_next, yp_all, yp_order, yp_master, yperr_string, ypprot_err 
\- Yellow Pages client package
.SH Syntax
.nf
.B #include <rpcsvc/ypclnt.h>
.sp .5
.B yp_get_default_domain(\fIoutdomain\fP)
.B char \fI**outdomain\fP;
.sp .5
.B yp_bind(\fIindomain\fP)
.B char *\fIindomain\fP;
.sp .5
.B void yp_unbind(\fIindomain\fP)
.B char \fI*indomain\fP;
.sp .5
.B yp_match(\fIindomain, inmap, inkey, inkeylen, outval, outvallen\fP)
.B char \fI*indomain\fP;
.B char \fI*inmap\fP;
.B char \fI*inkey\fP;
.B int \fIinkeylen\fP;
.B char \fI**outval\fP;
.B int \fI*outvallen\fP;
.sp .5
.B yp_first(\fIindomain, inmap, outkey, outkeylen, outval, outvallen\fP)
.B char \fI*indomain\fP;
.B char \fI*inmap\fP;
.B char \fI**outkey\fP;
.B int \fI*outkeylen\fP;
.B char \fI**outval\fP;
.B int \fI*outvallen\fP;
.sp .5
.B yp_next(\fIindomain, inmap, inkey, inkeylen, outkey, outkeylen, outval, outvallen\fP)
.B char \fI*indomain\fP;
.B char \fI*inmap\fP;
.B char \fI*inkey\fP;
.B int \fIinkeylen\fP;
.B char \fI**outkey\fP;
.B int \fI*outkeylen\fP;
.B char \fI**outval\fP;
.B int \fI*outvallen\fP;
.sp .5
.B yp_all(\fIindomain, inmap, incallback\fP)
.B char \fI*indomain\fP;
.B char \fI*inmap\fP;
.B struct ypall_callback \fIincallback\fP;
.sp .5
.B yp_order(\fIindomain, inmap, outorder\fP)
.B char \fI*indomain\fP;
.B char \fI*inmap\fP;
.B int \fI*outorder\fP;
.sp .5
.B yp_master(\fIindomain, inmap, outname\fP)
.B char \fI*indomain\fP;
.B char \fI*inmap\fP;
.B char \fI**outname\fP;
.sp .5
.B char *yperr_string(\fIincode\fP)
.B int \fIincode\fP;
.sp .5
.B ypprot_err(\fIincode\fP)
.B unsigned int \fIincode\fP;
.fi
.SH Description
.NXR "ypclnt keyword"
.NXR "yp_get_default_domain subroutine"
.NXR "yp_bind subroutine"
.NXR "yp_unbind subroutine"
.NXR "yp_match subroutine"
.NXR "yp_first subroutine"
.NXR "yp_next subroutine"
.NXR "yp_all subroutine"
.NXR "yp_order subroutine"
.NXR "yp_master subroutine"
.NXR "yperr_string subroutine"
.NXR "ypprot_err subroutine"
.NXR "YP client interface"
This package of functions provides an interface to the 
Yellow Pages (YP) data base lookup service.  The package can be loaded 
from the standard library, 
.PN /lib/libc.a .
Refer to 
.MS ypfiles 5yp
and
.MS ypserv 8yp
for an overview of the Yellow Pages, including the definitions of 
.B map
and 
.B domain,
and for a description of the servers, data bases, 
and commands that constitute the YP application.
.PP
All input parameters names begin with 
.B in.
Output parameters begin with 
.B out.  
Output parameters of type
.B "char **"
should be addresses of uninitialized character pointers.
The YP client package allocates memory using
.MS malloc 3 .
This memory can be freed if
the user code has no continuing need for it.  
For each
.B outkey 
and
.B outval,
two extra bytes of memory are allocated at the end that contain
NEWLINE and NULL, respectively,
but these two bytes are not reflected in
.B outkeylen 
or
.B outvallen.
The
.B indomain
and 
.B inmap
strings must be non-null and null-terminated.  String
parameters that are accompanied by a count parameter cannot be null, but
can point to null strings, with the count parameter indicating this.
Counted strings need not be null-terminated.
.PP
All functions of type \fBint\fP
return 0 if they succeed, or a failure code (YPERR_ xxxx )
if they do not succeed.  Failure codes are described under 
.B Diagnostics.
.PP
The YP lookup calls require a map name and a domain name.
It is assumed that the client process knows the name of the map of 
interest.  Client processes 
fetch the node's default domain by calling 
.PN yp_get_default_domain ,
and use the returned
.B outdomain 
as the
.B indomain 
parameter to successive YP calls.
.PP
To use YP services, the client process must be bound to a YP 
server that serves the appropriate domain. The binding is accomplished
with
.PN yp_bind .
Binding need not be done explicitly by user code; it 
is done automatically whenever a YP lookup function is called.
The 
.PN yp_bind
function can be called directly for processes 
that make use of a backup strategy in cases when
YP services are not available.
.PP
Each binding allocates one client process socket descriptor;
each bound domain requires one socket descriptor.  Multiple 
requests to the same domain use that same descriptor.
The
.PN yp_unbind
function is available at the client interface for processes that 
explicitly manage their socket descriptors while accessing 
multiple domains.  The call to 
.PN yp_unbind
makes the domain unbound, 
and frees all per-process and per-node resources used to bind it.
.PP
If an RPC failure results upon use of a binding, that domain will be
unbound automatically.  At that point, the ypclnt layer will retry 
forever or until the operation succeeds. This action occurs provided that 
.PN ypbind
is running, and either
the client process cannot bind a server for the proper domain, or
RPC requests to the server fail.  
.PP
The 
.PN ypbind 
.B \-s 
option allows the system administrator
to lock 
.PN ypbind 
to a particular domain and set of servers.
Up to four servers can be specified.
An example of the 
.B \-s
option follows:
.EX
/etc/ypbind \-s domain,server1[,server2,server3,server4]
.EE
.PP
The ypclnt layer will return control to the user code, either with an
error code, or with a success code and any results under certain circumstances. 
For example, control will be returned to the user code when an error is not RPC-related
and also when the 
.PN ypbind
function is not running.
An additional situation that will cause the return of control is 
when a bound ypserv process returns any answer (success or failure).
.PP
The
.PN yp_match
function returns the value associated with a passed key.  This key 
must be exact; no pattern matching is available.
.PP
The
.PN yp_first
function returns the first key-value pair from the named map in the
named domain.
.PP
The
.PN yp_next
function returns the next key-value pair in a named map.  The 
.B inkey 
parameter should be the
.B outkey
returned from an initial call to 
.PN yp_first
(to get the second key-value pair)
or the one returned from the nth call to 
.PN yp_next
(to get the nth + second key-value pair).
.PP
The concept of first and of next is particular 
to the
structure of the YP map being processed; there is no relation in
retrieval order to either the lexical order within any original (non-YP)
data base, or to any obvious numerical sorting order on the keys, 
values, or key-value pairs.  The only ordering guarantee made is 
that if the 
.PN yp_first
function is called on a particular map, and then the
.PN yp_next
function is repeatedly called on the same map at the same server 
until the call fails with a reason of 
YPERR_NOMORE, 
every entry in the data base will be seen exactly once.  
Further, if the same sequence of operations is performed on the same 
map at the same server, the entries will be seen in the same order.  
.PP
Under conditions of heavy server load or server failure, it
is possible for the domain to become unbound, then bound
once again (perhaps to a different server) while a client is running.  
This can cause a break in one of the enumeration rules;
specific entries may be seen twice by the client, or not at all.
This approach protects the client from error messages that would
otherwise be returned in the midst of the enumeration.
Enumerating all 
entries in a map is accomplished with the
.PN yp_all
function.
.PP
The
.PN yp_all
function provides a way to transfer an entire map
from server to client in a single request using TCP 
(rather than UDP as with other functions in this package).
The entire transaction take place as a single RPC request and
response.
The 
.PN yp_all
function can be used like any other YP procedure, to 
identify the map in the normal manner, and to supply the name of a
function that will be called to process each key-value pair 
within the map.  Returns from the call to
.PN yp_all
occur only when the transaction is completed 
(successfully or unsuccessfully), or when the
.PN foreach
function decides that it does not want to see any more key-value pairs.
.PP
The third parameter to
.PN yp_all
is 
.EX
struct ypall_callback *incallback {
	int (*foreach)();
	char *data;
};
.EE
.PP
The function
.PN foreach
is called 
.EX
foreach(instatus, inkey, inkeylen, inval, invallen, indata);
int instatus;
char *inkey;
int inkeylen;
char *inval;
int invallen;
char *indata;
.EE
.PP
The
.B instatus
parameter will hold one of the return status values defined in 
<rpcsvc/yp_prot.h> \(em either YP_TRUE or an error code.  (See 
.B ypprot_err,
below, for a function that
converts a YP protocol error code to a ypclnt 
layer error code.)
.PP
The key and value parameters are somewhat different than defined in the 
syntax section above.  First, the memory pointed to by the 
.B inkey
and 
.B inval
parameters is private to the 
.PN yp_all
function and is overwritten with the
arrival of each new key-value pair.
It is the responsibility of the 
.PN foreach 
function to do something useful with the contents of that memory, but it
does not own the memory itself.  Key and value objects 
presented to the
.PN foreach 
function look exactly as they do in the server's map \(em if they
were not newline-terminated or null-terminated in the map, they will not be
here either.
.PP
The
.B indata
parameter is the contents of the 
.B incallback->data
element passed to
.PN yp_all .
The
.B data
element of the callback structure may be used to share state information
between the 
.PN foreach
function and the mainline code.  Its use is optional, 
and no part of the YP client package inspects its contents.
.PP
The 
.PN foreach
function returns a Boolean value.
It should return zero to indicate that it
wants to be called again for further received key-value pairs, or
nonzero to stop the flow of key-value pairs.  If
.PN foreach
returns a nonzero value, it is not called again; the functional
value of
.PN yp_all
is then 0.
.PP
The
.PN yp_order
function returns the order number for a map.
.PP
The
.PN yp_master
function returns the machine name of the master YP server for a map.
.PP
The
.PN yperr_string
function returns a pointer to an error message string that is
null-terminated but contains no period or new line.
.PP
The
.PN ypprot_err
function takes a YP protocol error code as input and returns a ypclnt
layer error code, which may be used in turn as an input to 
.PN yperr_string .
.SH Diagnostics
All integer functions return 0 if the requested operation is successful,
or one of the following errors if the operation fails.
.PP
.ta \w'#define\0'u +\w'YPERR_BADARGS\0\0'u +\w'1\0\0'u
.nf
#define YPERR_BADARGS	1	/* args to function are bad */
#define YPERR_RPC	2	/* RPC failure - domain has been unbound */
#define YPERR_DOMAIN	3	/* can't bind to server on this domain */
#define YPERR_MAP	4	/* no such map in server's domain */
#define YPERR_KEY	5	/* no such key in map */
#define YPERR_YPERR	6	/* internal yp server or client error */
#define YPERR_RESRC	7	/* resource allocation failure */
#define YPERR_NOMORE	8	/* no more records in map database */
#define YPERR_PMAP	9	/* can't communicate with portmapper */
#define YPERR_YPBIND	10	/* can't communicate with ypbind */
#define YPERR_YPSERV	11	/* can't communicate with ypserv */
#define YPERR_NODOM	12	/* local domain name not set */
.fi
.SH Files
/usr/include/rpcsvc/ypclnt.h
.br
/usr/include/rpcsvc/yp_prot.h
.SH See Also
ypfiles(5yp), ypserv(8yp)