1fifo2(n)                                                              fifo2(n)
2
3
4
5______________________________________________________________________________
6

NAME

8       fifo2 - Create and manipulate pipe fifo channels
9

SYNOPSIS

11       package require Tcl
12
13       package require memchan
14
15       fifo2
16
17______________________________________________________________________________
18

DESCRIPTION

20       The command described here is only available in a not-yet released ver‐
21       sion of the package. Use the CVS to get the sources.
22
23       fifo2  creates two stream-oriented in-memory channels and returns their
24              handles  as  a  two-element list. There is no restriction on the
25              ultimate size of the channels, they will always grow as much  as
26              is necessary to accommodate the data written into them.
27
28              In contrast to the channels generated by fifo a pair of channels
29              created here is connected internally in such  a  way  that  data
30              written  into  one  channel can be read from the other. All data
31              written into them is read in the same  order.  This  also  means
32              that the two channels of the pair are not seekable.
33
34              The  channels  created  here  can  be transferred between inter‐
35              preters in the same thread and between threads. As both channels
36              in the pair can be transferred independently they can be used to
37              create a bidirectional connection between two interpreters.
38
39       Memory channels created by fifo2 provide two  read-only  options  which
40       can be queried via the standard fconfigure command. These are
41
42       -rlength
43              The value of this option is the number of bytes currently avail‐
44              able for reading from the channel.
45
46       -wlength
47              The value of this option is the number of bytes currently  writ‐
48              ten into the channel.
49
50       Note  that  the two lengths are switched for the channels of a pair. In
51       other words, the number of bytes written for one of the channels is the
52       number of bytes readable from the other end.
53
54       As  the  channels  generated by fifo2 grow as necessary they are always
55       writable. This means that a writable fileevent-handler will  fire  con‐
56       tinuously.
57
58       The  channels  are  also readable if they contain more than zero bytes.
59       Under this conditions a readable fileevent-handler will  fire  continu‐
60       ously.
61

SEE ALSO

63       fifo, memchan, null
64

KEYWORDS

66       channel, fifo, i/o, in-memory channel, memchan, stream
67

69       Copyright (c) 1996-2003 Andreas Kupries <andreas_kupries@users.sourceforge.net>
70
71
72
73
74Memory channels                       2.2                             fifo2(n)
Impressum