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2fifo(n)                                                                fifo(n)
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NAME

7       fifo - Create and manipulate u-turn fifo channels
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SYNOPSIS

10       package require Tcl
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12       package require memchan
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14       fifo
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DESCRIPTION

18       fifo   creates a stream-oriented in-memory channel and returns its han‐
19              dle. There is no restriction on the ultimate size of  the  chan‐
20              nel,  it  will always grow as much as is necessary to accomodate
21              the data written into it.
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23              In contrast to the channels generated by memchan a channel  cre‐
24              ated  here  effectively  represents  an U-turn. All data written
25              into it can be read out, but only in the same order.  This  also
26              means that a fifo channel is not seekable.
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28              The channels created here can be transfered between interpreters
29              in the same thread and between threads, but only as a whole.  It
30              is  not  possible  to use them to create a bi- or unidirectional
31              connection between two interpreters.
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33       Memory channels created by fifo provide two read-only options which can
34       be queried via the standard fconfigure command. These are
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36       -length
37              The value of this option is the number of bytes currently stored
38              in the queried memory channel.
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40       -allocated
41              The value of this option is the number of bytes currently  allo‐
42              cated  by the queried memory channel. This number is at least as
43              big as the value of -length.
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45       As the channels generated by fifo grow as  necessary  they  are  always
46       writable.  This  means that a writable fileevent-handler will fire con‐
47       tinuously.
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49       The channels are also readable if they contain more  than  zero  bytes.
50       Under  this  conditions a readable fileevent-handler will fire continu‐
51       ously.
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NOTES

54       One possible application of memory channels created by memchan or  fifo
55       is  as temporay storage device to collect data coming in over a pipe or
56       a socket. If part of the processing of the incoming data is to read and
57       process  header  bytes or similar fifo are easier to use as they do not
58       require seeking back and forth to switch between  the  assimilation  of
59       headers at the beginning and writing new data at the end.
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SEE ALSO

62       memchan, fifo2, null
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KEYWORDS

65       fifo, stream, memchan, in-memory channel, channel, i/o
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68       Copyright (c) 1996-2003 Andreas Kupries <andreas_kupries@users.sourceforge.net>
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72Memory channels                       2.1                              fifo(n)
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