diff options
Diffstat (limited to 'perl-install/resize_fat/fat.pm')
| -rw-r--r-- | perl-install/resize_fat/fat.pm | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/perl-install/resize_fat/fat.pm b/perl-install/resize_fat/fat.pm new file mode 100644 index 000000000..2b64bd6f7 --- /dev/null +++ b/perl-install/resize_fat/fat.pm @@ -0,0 +1,167 @@ +package resize_fat::fat; + +use diagnostics; +use strict; + +use resize_fat::any; +use resize_fat::io; + +1; + +sub read($) { + my ($fs) = @_; + + @{$fs->{fats}} = map { + my $fat = eval { resize_fat::io::read($fs, $fs->{fat_offset} + $_ * $fs->{fat_size}, $fs->{fat_size}) }; + $@ and die "reading fat #$_ failed"; + vec($fat, 0, 8) == $fs->{media} or die "FAT $_ has invalid signature"; + $fat; + } (0 .. $fs->{nb_fats} - 1); + + $fs->{fat} = $fs->{fats}->[0]; + + my ($free, $bad, $used) = (0, 0, 0); + + for (my $i = 2; $i < $fs->{nb_clusters} + 2; $i++) { + my $cluster = &next($fs, $i); + if ($cluster == 0) { $free++; } + elsif ($cluster == $resize_fat::bad_cluster_value) { $bad++; } + else { $used++; } + } + @{$fs->{clusters}->{count}}{qw(free bad used)} = ($free, $bad, $used); +} + +sub write($) { + my ($fs) = @_; + + sysseek $fs->{fd}, $fs->{fat_offset}, 0 or die "write_fat: seek failed"; + foreach (1..$fs->{nb_fats}) { + syswrite $fs->{fd}, $fs->{fat}, $fs->{fat_size} or die "write_fat: write failed"; + } +} + + + +# allocates where all the clusters will be moved to. Clusters before cut_point +# remain in the same position, however cluster that are part of a directory are +# moved regardless (this is a mechanism to prevent data loss) (cut_point is the +# first cluster that won't occur in the new fs) +sub allocate_remap { + my ($fs, $cut_point) = @_; + my ($cluster, $new_cluster); + my $remap = sub { $fs->{fat_remap}->[$cluster] = $new_cluster; }; + my $get_new = sub { + $new_cluster = get_free($fs); + 0 < $new_cluster && $new_cluster < $cut_point or die "no free clusters"; + set_eof($fs, $new_cluster); # mark as used + #log::ld("resize_fat: [$cluster,", &next($fs, $cluster), "...]->$new_cluster..."); + }; + + $fs->{fat_remap}->[0] = 0; + $fs->{last_free_cluster} = 2; + for ($cluster = 2; $cluster < $fs->{nb_clusters} + 2; $cluster++) { + if ($cluster < $cut_point) { + if ($fs->{fat_flag_map}->[$cluster] == $resize_fat::any::DIRECTORY) { + &$get_new(); + } else { + $new_cluster = $cluster; + } + &$remap(); + } elsif (!is_empty(&next($fs, $cluster))) { + &$get_new(); + &$remap(); + } + } +} + + +# updates the fat for the resized filesystem +sub update { + my ($fs) = @_; + + for (my $cluster = 2; $cluster < $fs->{nb_clusters} + 2; $cluster++) { + if ($fs->{fat_flag_map}->[$cluster]) { + my $old_next = &next($fs, $cluster); + my $new = $fs->{fat_remap}->[$cluster]; + my $new_next = $fs->{fat_remap}->[$old_next]; + + set_available($fs, $cluster); + + is_eof($old_next) ? + set_eof($fs, $new) : + set_next($fs, $new, $new_next); + } + } +} + + +# - compares the two FATs (one's a backup that should match) - skips first entry +# - its just a signature (already checked above) NOTE: checks for cross-linking +# are done in count.c +sub check($) { + my ($fs) = @_; + foreach (@{$fs->{fats}}) { + $_ eq $fs->{fats}->[0] or die "FAT tables do not match"; + } +} + +sub endianness16($) { (($_[0] & 0xff) << 8) + ($_[0] >> 8); } +sub endianness($$) { + my ($val, $nb_bits) = @_; + my $r = 0; + for (; $nb_bits > 0; $nb_bits -= 8) { + $r <<= 8; + $r += $val & 0xff; + $val >>= 8; + } + $nb_bits < 0 and die "error: endianness only handle numbers divisible by 8"; + $r; +} + +sub next($$) { + my ($fs, $cluster) = @_; + $cluster > $fs->{nb_clusters} + 2 and die "fat::next: cluster $cluster outside filesystem"; + endianness(vec($fs->{fat}, $cluster, $fs->{fs_type_size}), $fs->{fs_type_size}); + +} +sub set_next($$$) { + my ($fs, $cluster, $new_v) = @_; + $cluster > $fs->{nb_clusters} + 2 and die "fat::set_next: cluster $cluster outside filesystem"; + vec($fs->{fat}, $cluster, $fs->{fs_type_size}) = endianness($new_v, $fs->{fs_type_size}); +} + + +sub get_free($) { + my ($fs) = @_; + foreach (my $i = 0; $i < $fs->{nb_clusters}; $i++) { + my $cluster = ($i + $fs->{last_free_cluster} - 2) % $fs->{nb_clusters} + 2; + is_available(&next($fs, $cluster)) and return $fs->{last_free_cluster} = $cluster; + } + die "no free clusters"; +} + +# returns true if <cluster> represents an EOF marker +sub is_eof($) { + my ($cluster) = @_; + $cluster >= $resize_fat::bad_cluster_value; +} +sub set_eof($$) { + my ($fs, $cluster) = @_; + set_next($fs, $cluster, $resize_fat::bad_cluster_value + 1); +} + +# returns true if <cluster> is empty. Note that this includes bad clusters. +sub is_empty($) { + my ($cluster) = @_; + $cluster == 0 || $cluster == $resize_fat::bad_cluster_value; +} + +# returns true if <cluster> is available. +sub is_available($) { + my ($cluster) = @_; + $cluster == 0; +} +sub set_available($$) { + my ($fs, $cluster) = @_; + set_next($fs, $cluster, 0); +} |