1e7e4330 |
1 | .\" -*-nroff-*- |
fbf20b5b |
2 | .TH selpk 3 "23 May 1999" "Straylight/Edgeware" "mLib utilities library" |
1e7e4330 |
3 | .SH NAME |
4 | selpk \- packet-buffering input selector |
5 | .\" @selpk_enable |
6 | .\" @selpk_disable |
7 | .\" @selpk_want |
8 | .\" @selpk_init |
9 | .\" @selpk_destroy |
10 | .SH SYNOPSIS |
11 | .nf |
12 | .B "#include <mLib/selpk.h>" |
13 | |
14 | .BI "void selpk_enable(selpk *" pk ); |
15 | .BI "void selpk_disable(selpk *" pk ); |
16 | .BI "void selpk_want(selpk *" pk ", size_t " sz ); |
17 | .BI "void selpk_init(selpk *" pk , |
18 | .BI " sel_state *" s , |
19 | .BI " int " fd , |
20 | .BI " void (*" func ")(octet *" b ", size_t " sz ", pkbuf *" pk , |
21 | .BI " size_t *" keep ", void *" p ), |
22 | .BI " void *" p ); |
23 | .BI "void selpk_destroy(selpk *" b ); |
24 | .fi |
25 | .SH DESCRIPTION |
26 | The |
27 | .B selpk |
28 | subsystem is a selector which integrates with the |
29 | .BR sel (3) |
30 | system for I/O multiplexing. It reads packets from a file descriptor |
31 | and passes them to a caller-defined function. It uses the packet buffer |
32 | described in |
33 | .BR pkbuf (3) |
34 | to do its work: you should read about it in order to understand exactly |
35 | how the packet buffer decides how much data is in each packet and the |
36 | exact rules about what your packet handling function should and |
37 | shouldn't do. |
38 | .PP |
39 | The data for a packet selector is stored in an object of type |
40 | .BR selpk . |
41 | This object must be allocated by the caller, and initialized using the |
42 | .B selpk_init |
43 | function. This requires a fair few arguments: |
44 | .TP |
45 | .BI "selpk *" pk |
46 | Pointer to the |
47 | .B selpk |
48 | object to initialize. |
49 | .TP |
50 | .BI "sel_state *" s |
51 | Pointer to a multiplexor object (type |
52 | .BR sel_state ) |
53 | to which this selector should be attached. See |
54 | .BR sel (3) |
55 | for more details about multiplexors, and how this whole system works. |
56 | .TP |
57 | .BI "int " fd |
58 | The file descriptor of the stream the selector should read from. |
59 | .TP |
60 | .nf |
61 | .BI "void (*" func ")(octet *" b ", size_t " sz ", pkbuf *" p , |
62 | .BI " size_t *" keep ", void *" p ) |
63 | .fi |
64 | The |
65 | .I "packet handler" |
66 | function. It is passed a pointer to each packet read from the file (or |
67 | null to indicate end-of-file) and an arbitrary pointer (the |
68 | .I p |
69 | argument to |
70 | .B selpk_init |
71 | described below). |
72 | .TP |
73 | .BI "void *" p |
74 | A pointer argument passed to |
75 | .I func |
76 | for each packet read from the file. Apart from this, the pointer is not |
77 | used at all. |
78 | .PP |
79 | The |
80 | .B selpk |
81 | selector is immediately active. Subsequent calls to |
82 | .B sel_select |
83 | on the same multiplexor will cause any packets read from the file to be |
84 | passed to your handling function. This function can at any time call |
85 | .B selpk_disable |
86 | to stop itself from being called any more. The selector is then |
87 | disengaged from the I/O multiplexor and won't do anything until |
88 | .B selpk_enable |
89 | is called. Note that |
90 | .B selpk_enable |
91 | may well immediately start emitting complete packets of text which were |
92 | queued up from the last I/O operation: it doesn't necessarily wait for |
93 | the next |
94 | .B sel_select |
95 | call. |
96 | .PP |
97 | The size of packets read by the buffer is set by calling |
98 | .BR selpk_want . |
99 | See |
100 | .BR pkbuf (3) |
101 | for more details about how packet buffering works. |
102 | .PP |
103 | When it's finished with, a packet selector must be destroyed by calling |
104 | .BR selpk_destroy . |
105 | .SH "SEE ALSO" |
106 | .BR pkbuf (3), |
107 | .BR sel (3), |
108 | .BR selbuf (3), |
109 | .BR mLib (3). |
110 | .SH AUTHOR |
111 | Mark Wooding, <mdw@nsict.org> |