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package resize_fat::io;
use diagnostics;
use strict;
use resize_fat::fat;
1;
sub read($$$) {
my ($fs, $pos, $size) = @_;
my $buf = "\0" x $size;
sysseek $fs->{fd}, $pos, 0 or die "seeking to byte #$pos failed on device $fs->{fs_name}";
sysread $fs->{fd}, $buf, $size or die "reading at byte #$pos failed on device $fs->{fs_name}";
$buf;
}
sub write($$$$) {
my ($fs, $pos, $size, $buf) = @_;
sysseek $fs->{fd}, $pos, 0 or die "seeking to byte #$pos failed on device $fs->{fs_name}";
syswrite $fs->{fd}, $buf or die "writing at byte #$pos failed on device $fs->{fs_name}";
}
sub read_cluster($$) {
my ($fs, $cluster) = @_;
my $buf;
eval {
$buf = &read($fs,
$fs->{cluster_offset} + $cluster * $fs->{cluster_size},
$fs->{cluster_size});
}; @$ and die "reading cluster #$cluster failed on device $fs->{fs_name}";
$buf;
}
sub write_cluster($$$) {
my ($fs, $cluster, $buf) = @_;
eval {
&write($fs,
$fs->{cluster_offset} + $cluster * $fs->{cluster_size},
$fs->{cluster_size},
$buf);
}; @$ and die "writing cluster #$cluster failed on device $fs->{fs_name}";
}
sub read_file($$) {
my ($fs, $cluster) = @_;
my $buf = '';
for (; !resize_fat::fat::is_eof($cluster); $cluster = resize_fat::fat::next ($fs, $cluster)) {
$cluster == 0 and die "Bad FAT: unterminated chain\n";
$buf .= read_cluster($fs, $cluster);
}
$buf;
}
sub check_mounted($) {
my ($f) = @_;
local *F;
open F, "/proc/mounts" or die "error opening /proc/mounts\n";
foreach (<F>) {
/^$f\s/ and die "device is mounted";
}
}
sub open($) {
my ($fs) = @_;
check_mounted($fs->{device});
sysopen F, $fs->{fs_name}, 2 or sysopen F, $fs->{fs_name}, 0 or die "error opening device $fs->{fs_name} for writing\n";
$fs->{fd} = *F;
}
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