# SPDX-License-Identifier: GPL-2.0-or-later

package Amavis::IO::Zlib;

# A simple IO::File -compatible wrapper around Compress::Zlib,
# much like IO::Zlib but simpler: does only what we need and does it carefully

use strict;
use re 'taint';

BEGIN {
  require Exporter;
  use vars qw(@ISA @EXPORT @EXPORT_OK %EXPORT_TAGS $VERSION);
  $VERSION = '2.412';
  @ISA = qw(Exporter);
}
use Errno qw(EIO);
use Compress::Zlib;

sub new {
  my $class = shift;  my $self = bless {}, $class;
  if (@_) { $self->open(@_) or return }
  $self;
}

sub close {
  my $self = $_[0];
  my $status; my $eval_stat; local($1,$2);
  eval { $status = $self->{fh}->gzclose; 1 }
    or do { $eval_stat = $@ ne '' ? $@ : "errno=$!" };
  delete $self->{fh};
  if (defined $eval_stat) {
    chomp $eval_stat;
    die $eval_stat  if $eval_stat =~ /^timed out\b/;   # resignal timeout
    # can't stash arbitrary text into $!
    die "gzclose error: $eval_stat, $gzerrno";
    $! = EIO; return;  # not reached
  } elsif ($status != Z_OK) {
    die "gzclose error: $gzerrno";  # can't stash arbitrary text into $!
    $! = EIO; return;  # not reached
  }
  1;
}

sub DESTROY {
  my $self = $_[0]; local($@,$!,$_);
  # ignore failure, make perlcritic happy
  if ($self && $self->{fh}) { eval { $self->close } or 1 }
}

sub open {
  my($self,$fname,$mode) = @_;
  # ignore failure, make perlcritic happy
  if (exists($self->{fh})) { eval { $self->close } or 1; delete $self->{fh} }
  $self->{fname} = $fname; $self->{mode} = $mode; $self->{pos} = 0;
  my $gz = gzopen($fname,$mode);
  if ($gz) {
    $self->{fh} = $gz;
  } else {
    die "gzopen error: $gzerrno";  # can't stash arbitrary text into $!
    $! = EIO; undef $gz;  # not reached
  }
  $gz;
}

sub seek {
  my($self,$pos,$whence) = @_;
  $whence == 0  or die "Only absolute seek is supported on gzipped file";
  $pos >= 0     or die "Can't seek to a negative absolute position";
  $self->{mode} eq 'rb'
    or die "Seek to $whence,$pos on gzipped file only supported for 'rb' mode";
  if ($pos < $self->{pos}) {
    $self->close or die "seek: can't close gzipped file: $!";
    $self->open($self->{fname},$self->{mode})
      or die "seek: can't reopen gzipped file: $!";
  }
  my $skip = $pos - $self->{pos};
  while ($skip > 0) {
    my $s;  my $nbytes = $self->read($s,$skip);  # acceptable for small skips
    defined $nbytes && $nbytes > 0
      or die "seek: error skipping $skip bytes on gzipped file: $!";
    $skip -= $nbytes;
  }
  1;  # seek is supposed to return 1 upon success, 0 otherwise
}

sub read {  # SCALAR,LENGTH,OFFSET
  my $self = shift; my $len = $_[1]; my $offset = $_[2];
  defined $len  or die "Amavis::IO::Zlib::read: length argument undefined";
  my $nbytes;
  if (!defined($offset) || $offset == 0) {
    $nbytes = $self->{fh}->gzread($_[0], $len);
  } else {
    my $buff;
    $nbytes = $self->{fh}->gzread($buff, $len);
    substr($_[0],$offset) = $buff;
  }
  if ($nbytes < 0) {
    die "gzread error: $gzerrno";  # can't stash arbitrary text into $!
    $! = EIO; undef $nbytes;  # not reached
  } else {
    $self->{pos} += $nbytes;
  }
  $nbytes;   # eof: 0;  error: undef
}

sub getline {
  my $self = $_[0];  my($nbytes,$line);
  $nbytes = $self->{fh}->gzreadline($line);
  if ($nbytes <= 0) {  # eof (0) or error (-1)
    $! = 0; $line = undef;
    if ($nbytes < 0 && $gzerrno != Z_STREAM_END) {
      die "gzreadline error: $gzerrno";  # can't stash arbitrary text into $!
      $! = EIO;  # not reached
    }
  } else {
    $self->{pos} += $nbytes;
  }
  $line;  # eof: undef, $! zero;  error: undef, $! nonzero
}

sub print {
  my $self = shift;
  my $buff_ref = @_ == 1 ? \$_[0] : \join('',@_);
  my $nbytes; my $len = length($$buff_ref);
  if ($len <= 0) {
    $nbytes = "0 but true";
  } else {
    $nbytes = $self->{fh}->gzwrite($$buff_ref);  $self->{pos} += $len;
    if ($nbytes <= 0) {
      die "gzwrite error: $gzerrno";  # can't stash arbitrary text into $!
      $! = EIO; undef $nbytes;  # not reached
    }
  }
  $nbytes;
}

sub printf { shift->print(sprintf(shift,@_)) }

1;