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=head1 NAME |
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Data::Entropy::RawSource::CryptCounter - counter mode of block cipher |
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as I/O handle |
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=head1 SYNOPSIS |
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use Data::Entropy::RawSource::CryptCounter; |
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my $rawsrc = Data::Entropy::RawSource::CryptCounter |
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->new(Crypt::Rijndael->new($key)); |
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$c = $rawsrc->getc; |
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# and the rest of the I/O handle interface |
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=head1 DESCRIPTION |
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This class provides an I/O handle connected to a virtual file which |
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contains the output of a block cipher in counter mode. This makes a |
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good source of pseudorandom bits. The handle implements a substantial |
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subset of the interfaces described in L and L. |
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For use as a general entropy source, it is recommended to wrap an object |
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of this class using C, which provides methods to |
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extract entropy in more convenient forms than mere octets. |
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The amount of entropy the virtual file actually contains is only the |
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amount that is in the key, which is at most the length of the key. |
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It superficially appears to be much more than this, if (and to the |
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extent that) the block cipher is secure. This technique is not |
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suitable for all problems, and requires a careful choice of block |
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cipher and keying method. Applications requiring true entropy |
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should generate it (see L) or |
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download it (see L and |
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L). |
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=cut |
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package Data::Entropy::RawSource::CryptCounter; |
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37395
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{ use 5.006; } |
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140
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use warnings; |
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90
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use strict; |
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932
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use Params::Classify 0.000 qw(is_number is_ref is_string); |
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2767
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3
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10665
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our $VERSION = "0.007"; |
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49
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=head1 CONSTRUCTOR |
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51
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=over |
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53
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=item Data::Entropy::RawSource::CryptCounter->new(KEYED_CIPHER) |
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55
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KEYED_CIPHER must be a cipher object supporting the standard C |
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and C methods. For example, an instance of C |
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(with the default C) would be appropriate. A handle object |
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is created and returned which refers to a virtual file containing the |
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output of the cipher's counter mode. |
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61
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=cut |
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63
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sub new { |
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3
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3
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1
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my($class, $cipher) = @_; |
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3
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61
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return bless({ |
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cipher => $cipher, |
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blksize => $cipher->blocksize, |
68
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counter => "\0" x $cipher->blocksize, |
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subpos => 0, |
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}, $class); |
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} |
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73
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=back |
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75
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=head1 METHODS |
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77
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A subset of the interfaces described in L and L |
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are provided: |
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80
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=over |
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82
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=item $rawsrc->read(BUFFER, LENGTH[, OFFSET]) |
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84
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=item $rawsrc->getc |
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86
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=item $rawsrc->ungetc(ORD) |
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88
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=item $rawsrc->eof |
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90
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Buffered reading from the source, as in L. |
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92
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=item $rawsrc->sysread(BUFFER, LENGTH[, OFFSET]) |
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94
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Unbuffered reading from the source, as in L. |
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96
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=item $rawsrc->close |
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98
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Does nothing. |
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100
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=item $rawsrc->opened |
101
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102
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Retruns true to indicate that the source is available for I/O. |
103
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104
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=item $rawsrc->clearerr |
105
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106
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=item $rawsrc->error |
107
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108
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Error handling, as in L. |
109
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110
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=item $rawsrc->getpos |
111
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112
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=item $rawsrc->setpos(POS) |
113
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114
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=item $rawsrc->tell |
115
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116
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=item $rawsrc->seek(POS, WHENCE) |
117
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118
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Move around within the buffered source, as in L. |
119
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120
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=item $rawsrc->sysseek(POS, WHENCE) |
121
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122
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Move around within the unbuffered source, as in L. |
123
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124
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=back |
125
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126
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The buffered (C et al) and unbuffered (C et al) sets |
127
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of methods are interchangeable, because no such distinction is made by |
128
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this class. |
129
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130
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C, C, and C only work within the first 4 GiB of the |
131
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virtual file. The file is actually much larger than that: for Rijndael |
132
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(AES), or any other cipher with a 128-bit block, the file is 2^52 YiB |
133
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(2^132 B). C and C work throughout the file. |
134
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135
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Methods to write to the file are unimplemented because the virtual file |
136
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is fundamentally read-only. |
137
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138
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=cut |
139
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140
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sub _ensure_buffer { |
141
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60018
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60018
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78152
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my($self) = @_; |
142
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60018
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100
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191095
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$self->{buffer} = $self->{cipher}->encrypt($self->{counter}) |
143
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unless exists $self->{buffer}; |
144
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} |
145
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146
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sub _clear_buffer { |
147
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3762
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3762
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5070
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my($self) = @_; |
148
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3762
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11912
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delete $self->{buffer}; |
149
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} |
150
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151
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sub _increment_counter { |
152
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3753
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3753
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6110
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my($self) = @_; |
153
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3753
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9951
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for(my $i = 0; $i != $self->{blksize}; $i++) { |
154
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3767
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8735
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my $c = ord(substr($self->{counter}, $i, 1)); |
155
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3767
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100
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8310
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unless($c == 255) { |
156
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3753
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9963
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substr $self->{counter}, $i, 1, chr($c + 1); |
157
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3753
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7057
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return; |
158
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} |
159
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14
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55
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substr $self->{counter}, $i, 1, "\0"; |
160
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} |
161
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0
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0
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$self->{counter} = undef; |
162
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} |
163
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164
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sub _decrement_counter { |
165
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0
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0
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0
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my($self) = @_; |
166
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0
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0
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for(my $i = 0; ; $i++) { |
167
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0
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0
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my $c = ord(substr($self->{counter}, $i, 1)); |
168
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0
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0
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0
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unless($c == 0) { |
169
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0
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0
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substr $self->{counter}, $i, 1, chr($c - 1); |
170
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0
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0
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return; |
171
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} |
172
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0
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0
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substr $self->{counter}, $i, 1, "\xff"; |
173
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} |
174
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} |
175
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176
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1
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1
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1
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6
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sub close { 1 } |
177
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178
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1
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1
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1
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5
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sub opened { 1 } |
179
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180
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1
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1
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1
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5
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sub error { 0 } |
181
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182
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1
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1
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1
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5
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sub clearerr { 0 } |
183
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184
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sub getc { |
185
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60010
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60010
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1
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82133
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my($self) = @_; |
186
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60010
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50
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151329
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return undef unless defined $self->{counter}; |
187
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60010
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121444
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$self->_ensure_buffer; |
188
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60010
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135660
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my $ret = substr($self->{buffer}, $self->{subpos}, 1); |
189
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60010
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100
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168358
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if(++$self->{subpos} == $self->{blksize}) { |
190
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3750
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11412
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$self->_increment_counter; |
191
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3750
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4857
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$self->{subpos} = 0; |
192
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3750
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7805
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$self->_clear_buffer; |
193
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} |
194
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60010
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219198
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return $ret; |
195
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} |
196
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197
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sub ungetc { |
198
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1
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1
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1
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3
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my($self, undef) = @_; |
199
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1
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50
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23
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unless($self->{subpos} == 0) { |
200
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1
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2
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$self->{subpos}--; |
201
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1
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3
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return; |
202
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} |
203
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0
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0
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0
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return if $self->{counter} =~ /\A\0*\z/; |
204
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0
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0
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$self->_decrement_counter; |
205
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0
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0
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$self->{subpos} = $self->{blksize} - 1; |
206
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0
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0
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$self->_clear_buffer; |
207
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} |
208
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209
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sub read { |
210
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7
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7
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1
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18
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my($self, undef, $length, $offset) = @_; |
211
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7
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50
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21
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return undef if $length < 0; |
212
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7
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100
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21
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$_[1] = "" unless defined $_[1]; |
213
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7
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100
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94
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if(!defined($offset)) { |
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100
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100
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214
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4
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6
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$offset = 0; |
215
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4
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8
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$_[1] = ""; |
216
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} elsif($offset < 0) { |
217
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1
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50
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6
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return undef if $offset < -length($_[1]); |
218
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1
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3
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substr $_[1], $offset, -$offset, ""; |
219
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1
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2
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$offset = length($_[1]); |
220
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} elsif($offset > length($_[1])) { |
221
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1
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5
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$_[1] .= "\0" x ($offset - length($_[1])); |
222
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} else { |
223
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1
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4
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substr $_[1], $offset, length($_[1]) - $offset, ""; |
224
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} |
225
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7
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10
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my $original_offset = $offset; |
226
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7
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66
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46
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while($length != 0 && defined($self->{counter})) { |
227
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8
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19
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$self->_ensure_buffer; |
228
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8
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18
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my $avail = $self->{blksize} - $self->{subpos}; |
229
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8
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100
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25
|
if($length < $avail) { |
230
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5
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13
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$_[1] .= substr($self->{buffer}, $self->{subpos}, |
231
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$length); |
232
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5
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7
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$offset += $length; |
233
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5
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10
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$self->{subpos} += $length; |
234
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5
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7
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last; |
235
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} |
236
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3
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12
|
$_[1] .= substr($self->{buffer}, $self->{subpos}, $avail); |
237
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3
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6
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$offset += $avail; |
238
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3
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3
|
$length -= $avail; |
239
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3
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11
|
$self->_increment_counter; |
240
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3
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5
|
$self->{subpos} = 0; |
241
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3
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11
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$self->_clear_buffer; |
242
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} |
243
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7
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42
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return $offset - $original_offset; |
244
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} |
245
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246
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*sysread = \&read; |
247
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248
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sub tell { |
249
|
20
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20
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1
|
780
|
my($self) = @_; |
250
|
3
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|
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3
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|
1948
|
use integer; |
|
3
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|
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23
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3
|
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20
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|
251
|
20
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40
|
my $ctr = $self->{counter}; |
252
|
20
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|
24
|
my $nblocks; |
253
|
20
|
50
|
|
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|
492
|
if(defined $ctr) { |
254
|
20
|
50
|
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|
98
|
return -1 if $ctr =~ /\A.{4,}[^\0]/s; |
255
|
20
|
50
|
|
|
|
54
|
$ctr .= "\0\0\0\0" if $self->{blksize} < 4; |
256
|
20
|
|
|
|
|
67
|
$nblocks = unpack("V", $ctr); |
257
|
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|
|
} else { |
258
|
0
|
0
|
|
|
|
0
|
return -1 if $self->{blksize} >= 4; |
259
|
0
|
|
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|
|
0
|
$nblocks = 1 << ($self->{blksize} << 3); |
260
|
|
|
|
|
|
|
} |
261
|
20
|
|
|
|
|
46
|
my $pos = $nblocks * $self->{blksize} + $self->{subpos}; |
262
|
20
|
50
|
|
|
|
70
|
return -1 unless ($pos-$self->{subpos}) / $self->{blksize} == $nblocks; |
263
|
20
|
|
|
|
|
78
|
return $pos; |
264
|
|
|
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|
|
|
} |
265
|
|
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|
|
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|
266
|
3
|
|
|
3
|
|
6387
|
use constant SEEK_SET => 0; |
|
3
|
|
|
|
|
11
|
|
|
3
|
|
|
|
|
293
|
|
267
|
3
|
|
|
3
|
|
30
|
use constant SEEK_CUR => 1; |
|
3
|
|
|
|
|
6
|
|
|
3
|
|
|
|
|
161
|
|
268
|
3
|
|
|
3
|
|
48
|
use constant SEEK_END => 2; |
|
3
|
|
|
|
|
12
|
|
|
3
|
|
|
|
|
420
|
|
269
|
|
|
|
|
|
|
|
270
|
|
|
|
|
|
|
sub sysseek { |
271
|
19
|
|
|
19
|
1
|
34
|
my($self, $offset, $whence) = @_; |
272
|
19
|
100
|
|
|
|
60
|
if($whence == SEEK_SET) { |
|
|
100
|
|
|
|
|
|
|
|
50
|
|
|
|
|
|
273
|
3
|
|
|
3
|
|
18
|
use integer; |
|
3
|
|
|
|
|
5
|
|
|
3
|
|
|
|
|
15
|
|
274
|
11
|
100
|
|
|
|
44
|
return undef if $offset < 0; |
275
|
8
|
|
|
|
|
17
|
my $ctr = $offset / $self->{blksize}; |
276
|
8
|
|
|
|
|
13
|
my $subpos = $offset % $self->{blksize}; |
277
|
8
|
|
|
|
|
27
|
$ctr = pack("V", $ctr); |
278
|
8
|
50
|
|
|
|
19
|
if($self->{blksize} < 4) { |
279
|
|
|
|
|
|
|
return undef unless |
280
|
0
|
0
|
|
|
|
0
|
my $chopped = substr($ctr, $self->{blksize}, |
281
|
|
|
|
|
|
|
4-$self->{blksize}, ""); |
282
|
0
|
0
|
0
|
|
|
0
|
if($chopped =~ /\A\x{01}\0*\z/ && $subpos == 0) { |
|
|
0
|
|
|
|
|
|
283
|
0
|
|
|
|
|
0
|
$self->{counter} = undef; |
284
|
0
|
|
|
|
|
0
|
$self->{subpos} = 0; |
285
|
0
|
|
|
|
|
0
|
$self->_clear_buffer; |
286
|
0
|
|
|
|
|
0
|
return $offset; |
287
|
|
|
|
|
|
|
} elsif($chopped !~ /\A\0+\z/) { |
288
|
0
|
|
|
|
|
0
|
return undef; |
289
|
|
|
|
|
|
|
} |
290
|
|
|
|
|
|
|
} else { |
291
|
8
|
|
|
|
|
26
|
$ctr .= "\0" x ($self->{blksize} - 4); |
292
|
|
|
|
|
|
|
} |
293
|
8
|
|
|
|
|
15
|
$self->{counter} = $ctr; |
294
|
8
|
|
|
|
|
14
|
$self->{subpos} = $subpos; |
295
|
8
|
|
|
|
|
22
|
$self->_clear_buffer; |
296
|
8
|
|
100
|
|
|
63
|
return $offset || "0 but true"; |
297
|
|
|
|
|
|
|
} elsif($whence == SEEK_CUR) { |
298
|
7
|
|
|
|
|
19
|
my $pos = $self->tell; |
299
|
7
|
50
|
|
|
|
20
|
return undef if $pos == -1; |
300
|
7
|
|
|
|
|
25
|
return $self->sysseek($pos + $offset, SEEK_SET); |
301
|
|
|
|
|
|
|
} elsif($whence == SEEK_END) { |
302
|
3
|
|
|
3
|
|
1700
|
use integer; |
|
3
|
|
|
|
|
7
|
|
|
3
|
|
|
|
|
18
|
|
303
|
1
|
50
|
|
|
|
5
|
return undef if $offset > 0; |
304
|
1
|
50
|
|
|
|
10
|
return undef if $self->{blksize} >= 4; |
305
|
0
|
|
|
|
|
0
|
my $nblocks = 1 << ($self->{blksize} << 3); |
306
|
0
|
|
|
|
|
0
|
my $pos = $nblocks * $self->{blksize}; |
307
|
0
|
0
|
|
|
|
0
|
return undef unless $pos/$self->{blksize} == $nblocks; |
308
|
0
|
|
|
|
|
0
|
return $self->sysseek($pos + $offset, SEEK_SET); |
309
|
|
|
|
|
|
|
} else { |
310
|
0
|
|
|
|
|
0
|
return undef; |
311
|
|
|
|
|
|
|
} |
312
|
|
|
|
|
|
|
} |
313
|
|
|
|
|
|
|
|
314
|
7
|
100
|
|
7
|
1
|
30
|
sub seek { shift->sysseek(@_) ? 1 : 0 } |
315
|
|
|
|
|
|
|
|
316
|
|
|
|
|
|
|
sub getpos { |
317
|
1
|
|
|
1
|
1
|
4
|
my($self) = @_; |
318
|
1
|
|
|
|
|
6
|
return [ $self->{counter}, $self->{subpos} ]; |
319
|
|
|
|
|
|
|
} |
320
|
|
|
|
|
|
|
|
321
|
|
|
|
|
|
|
sub setpos { |
322
|
1
|
|
|
1
|
1
|
3
|
my($self, $pos) = @_; |
323
|
1
|
50
|
33
|
|
|
14
|
return undef unless is_ref($pos, "ARRAY") && @$pos == 2; |
324
|
1
|
|
|
|
|
3
|
my($ctr, $subpos) = @$pos; |
325
|
1
|
50
|
33
|
|
|
5
|
unless(!defined($ctr) && $subpos == 0) { |
326
|
1
|
50
|
33
|
|
|
16
|
return undef unless is_string($ctr) && |
|
|
|
33
|
|
|
|
|
|
|
|
33
|
|
|
|
|
|
|
|
33
|
|
|
|
|
327
|
|
|
|
|
|
|
length($ctr) == $self->{blksize} && |
328
|
|
|
|
|
|
|
is_number($subpos) && |
329
|
|
|
|
|
|
|
$subpos >= 0 && $subpos < $self->{blksize}; |
330
|
|
|
|
|
|
|
} |
331
|
1
|
|
|
|
|
33
|
$self->{counter} = $ctr; |
332
|
1
|
|
|
|
|
2
|
$self->{subpos} = $subpos; |
333
|
1
|
|
|
|
|
3
|
$self->_clear_buffer; |
334
|
1
|
|
|
|
|
4
|
return "0 but true"; |
335
|
|
|
|
|
|
|
} |
336
|
|
|
|
|
|
|
|
337
|
|
|
|
|
|
|
sub eof { |
338
|
1
|
|
|
1
|
1
|
3
|
my($self) = @_; |
339
|
1
|
|
|
|
|
5
|
return !defined($self->{counter}); |
340
|
|
|
|
|
|
|
} |
341
|
|
|
|
|
|
|
|
342
|
|
|
|
|
|
|
=head1 SEE ALSO |
343
|
|
|
|
|
|
|
|
344
|
|
|
|
|
|
|
L, |
345
|
|
|
|
|
|
|
L, |
346
|
|
|
|
|
|
|
L, |
347
|
|
|
|
|
|
|
L, |
348
|
|
|
|
|
|
|
L |
349
|
|
|
|
|
|
|
|
350
|
|
|
|
|
|
|
=head1 AUTHOR |
351
|
|
|
|
|
|
|
|
352
|
|
|
|
|
|
|
Andrew Main (Zefram) |
353
|
|
|
|
|
|
|
|
354
|
|
|
|
|
|
|
=head1 COPYRIGHT |
355
|
|
|
|
|
|
|
|
356
|
|
|
|
|
|
|
Copyright (C) 2006, 2007, 2009, 2011 |
357
|
|
|
|
|
|
|
Andrew Main (Zefram) |
358
|
|
|
|
|
|
|
|
359
|
|
|
|
|
|
|
=head1 LICENSE |
360
|
|
|
|
|
|
|
|
361
|
|
|
|
|
|
|
This module is free software; you can redistribute it and/or modify it |
362
|
|
|
|
|
|
|
under the same terms as Perl itself. |
363
|
|
|
|
|
|
|
|
364
|
|
|
|
|
|
|
=cut |
365
|
|
|
|
|
|
|
|
366
|
|
|
|
|
|
|
1; |