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1 | .\" -*-nroff-*- |
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2 | .TH selbuf 3 "23 May 1999" mLib |
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3 | .SH NAME |
4 | selbuf \- line-buffering input selector |
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5 | .\" @selbuf_enable |
6 | .\" @selbuf_disable |
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7 | .\" @selbuf_setsize |
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8 | .\" @selbuf_init |
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9 | .\" @selbuf_destroy |
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10 | .SH SYNOPSIS |
11 | .nf |
12 | .B "#include <mLib/selbuf.h>" |
13 | |
14 | .BI "void selbuf_enable(selbuf *" b ); |
15 | .BI "void selbuf_disable(selbuf *" b ); |
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16 | .BI "void selbuf_setsize(selbuf *" b ", size_t " sz ); |
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17 | .BI "void selbuf_init(selbuf *" b , |
18 | .BI " sel_state *" s , |
19 | .BI " int " fd , |
20 | .BI " void (*" func ")(char *" s ", void *" p ), |
21 | .BI " void *" p ); |
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22 | .BI "void selbuf_destroy(selbuf *" b ); |
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23 | .fi |
24 | .SH DESCRIPTION |
25 | The |
26 | .B selbuf |
27 | subsystem is a selector which integrates with the |
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28 | .BR sel (3) |
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29 | system for I/O multiplexing. It reads entire text lines from a file |
30 | descriptor and passes them to a caller-defined function. It uses the |
31 | line buffer described in |
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32 | .BR lbuf (3) |
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33 | to do its work: you should read about it in order to understand exactly |
34 | what gets considered to be a line of text and what doesn't, and the |
35 | exact rules about what your line handling function should and shouldn't |
36 | do. |
37 | .PP |
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38 | The data for a line selector is stored in an object of type |
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39 | .BR selbuf . |
40 | This object must be allocated by the caller, and initialized using the |
41 | .B selbuf_init |
42 | function. This requires a fair few arguments: |
43 | .TP |
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44 | .BI "selbuf *" b |
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45 | Pointer to the |
46 | .B selbuf |
47 | object to initialize. |
48 | .TP |
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49 | .BI "sel_state *" s |
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50 | Pointer to a multiplexor object (type |
51 | .BR sel_state ) |
52 | to which this selector should be attached. See |
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53 | .BR sel (3) |
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54 | for more details about multiplexors, and how this whole system works. |
55 | .TP |
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56 | .BI "int " fd |
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57 | The file descriptor of the stream the selector should read from. |
58 | .TP |
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59 | .BI "void (*" func ")(char *" s ", void *" p ) |
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60 | The |
61 | .I "line handler" |
62 | function. It is passed a pointer to each line read from the file (or |
63 | null to indicate end-of-file) and an arbitrary pointer (the |
64 | .I p |
65 | argument to |
66 | .B selbuf_init |
67 | described below). |
68 | .TP |
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69 | .BI "void *" p |
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70 | A pointer argument passed to |
71 | .I func |
72 | for each line read from the file. Apart from this, the pointer is not |
73 | used at all. |
74 | .PP |
75 | The |
76 | .B selbuf |
77 | selector is immediately active. Subsequent calls to |
78 | .B sel_select |
79 | on the same multiplexor will cause any complete lines read from the file |
80 | to be passed to your handling function. This function can at any time |
81 | call |
82 | .B selbuf_disable |
83 | to stop itself from being called any more. The selector is then |
84 | disengaged from the I/O multiplexor and won't do anything until |
85 | .B selbuf_enable |
86 | is called. Note that |
87 | .B selbuf_enable |
88 | may well immediately start emitting complete lines of text which were |
89 | queued up from the last I/O operation: it doesn't necessarily wait for |
90 | the next |
91 | .B sel_select |
92 | call. |
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93 | .PP |
94 | The line buffer has a finite amount of memory for reading strings. The |
95 | size of this buffer is set by calling |
96 | .B selbuf_setsize |
97 | with the requested size. The default buffer size is 256 bytes. |
98 | .PP |
99 | When it's finished with, a line buffer selector must be destroyed by |
100 | calling |
101 | .BR selbuf_destroy . |
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102 | .SH "SEE ALSO" |
103 | .BR lbuf (3), |
104 | .BR sel (3), |
105 | .BR mLib (3). |
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106 | .SH AUTHOR |
107 | Mark Wooding, <mdw@nsict.org> |