| PLUMB(3) | PLUMB(3)

NAME

| eplumb, plumbfree, plumbopen, plumbunmount, plumbopenfid, plumbsend, plumbsendtofid, plumbsendtext, plumblookup, plumbpack, plumbpackattr, plumbaddattr, plumbdelattr, plumbrecv, plumbrecvfid, plumbunpack, plumbunpackpartial, plumbunpackattr, Plumbmsg – plumb messages

SYNOPSIS

`#include <u.h>
#include <libc.h>
#include <plumb.h>

`

`int plumbopen(char *port, int omode)

` `int plumbunmount(void)

` `int plumbsend(int fd, Plumbmsg *m)

` `int plumbsendtext(int fd, char *src, char *dst, char *wdir, char *data)

` `void plumbfree(Plumbmsg *m)

` `Plumbmsg* plumbrecv(int fd)

` `char* plumbpack(Plumbmsg *m, int *np)

` `Plumbmsg* plumbunpack(char *buf, int n)

` `Plumbmsg* plumbunpackpartial(char *buf, int n, int *morep)

` `char* plumbpackattr(Plumbattr *a)

` `Plumbattr* plumbunpackattr(char *a)

` `char* plumblookup(Plumbattr *a, char *name)

` `Plumbattr* plumbaddattr(Plumbattr *a, Plumbattr *new)

` `Plumbattr* plumbdelattr(Plumbattra *a, char *name)

` `int eplumb(int key, char *port)

` `#include <9pclient.h>

` `CFid *plumbopenfid(char *port, int omode)

` `Plumbmsg* plumbrecvfid(CFid *fid)

` `int plumbsendtofid(CFid *fid, Plumbmsg *m)
`

DESCRIPTION

These routines manipulate plumb(7) messages, transmitting them, receiving them, and converting them between text and these data structures:

`typedef
struct Plumbmsg
{

| char *src; char *dst; char *wdir; char *type; Plumbattr *attr; int ndata; char *data;

} Plumbmsg;
typedef
struct Plumbattr
{

| char *name; char *value; Plumbattr *next;

} Plumbattr;

`

Plumbopen opens the named plumb port, using open(3) mode omode. If port begins with a slash, it is taken as a literal file name; otherwise plumbopen searches for the location of the plumber(4) service and opens the port there.

For programs using the event(3) interface, eplumb registers, using the given key, receipt of messages from the named port.

The library mounts the plumber(4) service on demand (using the 9pclient(3)) library and reuses the mount instance for future calls to plumbopen. Plumbunmount causes the library to discard its cached mount. This can be useful if the plumber service itself has been restarted and a client wishes to reconnect.

Plumbsend formats and writes message m to the file descriptor fd, which will usually be the result of `plumbopen("send", OWRITE)`. Plumbsendtext is a simplified version for text-only messages; it assumes `type` is `text`, sets `attr` to nil, and sets `ndata` to `strlen(`data`)`.

Plumbfree frees all the data associated with the message m, all the components of which must therefore have been allocated with malloc(3).

Plumbrecv returns the next message available on the file descriptor fd, or nil for error.

Plumbpack encodes message m as a character string in the format of plumb(7), setting `*`np to the length in bytes of the string. Plumbunpack does the inverse, translating the n bytes of buf into a `Plumbmsg`.

Plumbunpackpartial enables unpacking of messages that arrive in pieces. The first call to plumbunpackpartial for a given message must be sufficient to unpack the header; subsequent calls permit unpacking messages with long data sections. For each call, buf points to the beginning of the complete message received so far, and n reports the total number of bytes received for that message. If the message is complete, the return value will be as in plumbunpack. If not, and morep is not null, the return value will be `nil` and `*`morep will be set to the number of bytes remaining to be read for this message to be complete (recall that the byte count is in the header). Those bytes should be read by the caller, placed at location buf`+`n, and the message unpacked again. If an error is encountered, the return value will be `nil` and `*`morep will be zero.

Plumbpackattr converts the list a of `Plumbattr` structures into a null-terminated string. If an attribute value contains white space, quote characters, or equal signs, the value will be quoted appropriately. A newline character will terminate processing. Plumbunpackattr converts the null-terminated string a back into a list of Plumbattr structures.

Plumblookup searches the `Plumbattr` list a for an attribute with the given name and returns the associated value. The returned string is the original value, not a copy. If the attribute has no value, the returned value will be the empty string; if the attribute does not occur in the list at all, the value will be nil.

Plumbaddattr appends the new `Plumbattr` (which may be a list) to the attribute list a and returns the new list. Plumbattr searches the list a for the first attribute with name name and deletes it from the list, returning the resulting list. Plumbdelattr is a no-op if no such attribute exists.

The file descriptor returned by plumbopen is created with fsopenfd (see 9pclient(3)), which masks information about read and write errors. This is acceptable for use in plumbrecv but not for plumbsend, which depends on seeing details of write errors. Plumbopenfid, plumbrecvfid, and plumbsendtofid provide an explicit interface to lib9pclient that preserves the exact error details.

SOURCE

| `/usr/local/plan9/src/libplumb`

SEE ALSO

| plumb(1), event(3), plumber(4), plumb(7)

DIAGNOSTICS

| When appropriate, including when a plumbsend fails, these routine set errstr.

BUGS

| To avoid rewriting clients that use plumbsend, the call `plumbopen("send", OWRITE)` returns a useless file descriptor (it is opened to `/dev/null`). Plumbsend looks for this particular file descriptor and uses a static copy of the `CFid` instead.