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1 | package PerlIO::Via; |
2 | our $VERSION = '0.01'; |
3 | use XSLoader (); |
4 | XSLoader::load 'PerlIO::Via'; |
5 | 1; |
6 | __END__ |
7 | |
8 | =head1 NAME |
9 | |
10 | PerlIO::Via - Helper class for PerlIO layers implemented in perl |
11 | |
12 | =head1 SYNOPSIS |
13 | |
14 | use Some::Package; |
15 | |
16 | open($fh,"<:Via(Some::Package)",...); |
17 | |
18 | =head1 DESCRIPTION |
19 | |
20 | The package to be used as a layer should implement at least some of the |
21 | following methods. In the method descriptions below I<$fh> will be |
22 | a reference to a glob which can be treated as a perl file handle. |
23 | It refers to the layer below. I<$fh> is not passed if the layer |
24 | is at the bottom of the stack, for this reason and to maintain |
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25 | some level of "compatibility" with TIEHANDLE classes it is passed last. |
26 | |
27 | As an example, in Perl release 5.8.0 the MIME::QuotedPrint module |
28 | defines the required TIEHANDLE methods so that you can say |
29 | |
30 | use MIME::QuotedPrint; |
31 | open(my $fh, ">Via(MIME::QuotedPrint)", "qp"); |
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32 | |
33 | =over 4 |
34 | |
35 | =item $class->PUSHED([$mode][,$fh]) |
36 | |
37 | Should return an object or the class. (Compare TIEHANDLE.) |
38 | Mandatory. |
39 | |
40 | =item $obj->POPPED([$fh]) |
41 | |
42 | Optional - layer is about to be removed. |
43 | |
44 | =item $class->OPEN($path,$mode[,$fh]) |
45 | |
46 | Not yet in use. |
47 | |
48 | =item $class->FDOPEN($fd) |
49 | |
50 | Not yet in use. |
51 | |
52 | =item $class->SYSOPEN($path,$imode,$perm,$fh) |
53 | |
54 | Not yet in use. |
55 | |
56 | =item $obj->FILENO($fh) |
57 | |
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58 | Returns a numeric value for Unix-like file descriptor. Return -1 if |
59 | there isn't one. Optional. Default is fileno($fh). |
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60 | |
61 | =item $obj->READ($buffer,$len,$fh) |
62 | |
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63 | Returns the number of octets placed in $buffer (must be less than or |
64 | equal to $len). Optional. Default is to use FILL instead. |
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65 | |
66 | =item $obj->WRITE($buffer,$fh) |
67 | |
68 | Returns the number of octets from buffer that have been sucessfully written. |
69 | |
70 | =item $obj->FILL($fh) |
71 | |
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72 | Should return a string to be placed in the buffer. Optional. If not |
73 | provided must provide READ or reject handles open for reading in |
74 | PUSHED. |
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75 | |
76 | =item $obj->CLOSE($fh) |
77 | |
78 | Should return 0 on success, -1 on error. |
79 | Optional. |
80 | |
81 | =item $obj->SEEK($posn,$whence,$fh) |
82 | |
83 | Should return 0 on success, -1 on error. |
84 | Optional. Default is to fail, but that is likely to be changed. |
85 | |
86 | =item $obj->TELL($fh) |
87 | |
88 | Returns file postion. |
89 | Optional. Default to be determined. |
90 | |
91 | =item $obj->UNREAD($buffer,$fh) |
92 | |
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93 | Returns the number of octets from buffer that have been sucessfully |
94 | saved to be returned on future FILL/READ calls. Optional. Default is |
95 | to push data into a temporary layer above this one. |
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96 | |
97 | =item $obj->FLUSH($fh) |
98 | |
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99 | Flush any buffered write data. May possibly be called on readable |
100 | handles too. Should return 0 on success, -1 on error. |
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101 | |
102 | =item $obj->SETLINEBUF($fh) |
103 | |
104 | Optional. No return. |
105 | |
106 | =item $obj->CLEARERR($fh) |
107 | |
108 | Optional. No return. |
109 | |
110 | =item $obj->ERROR($fh) |
111 | |
112 | Optional. Returns error state. Default is no error until a mechanism |
113 | to signal error (die?) is worked out. |
114 | |
115 | =item $obj->EOF($fh) |
116 | |
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117 | Optional. Returns end-of-file state. Default is function of return |
118 | value of FILL or READ. |
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119 | |
120 | =back |
121 | |
122 | =cut |
123 | |
124 | |