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```{index} single: Compress::Raw::Bzip2
```

# Compress::Raw::Bzip2

```{pperl-module-badges} Compress::Raw::Bzip2
```

Low-level interface to the `bzip2` compression library.

`Compress::Raw::Bzip2` is the layer underneath `IO::Compress::Bzip2`
and `IO::Uncompress::Bunzip2`, and what Archive::Tar uses for `.tbz`
archives. It gives direct access to libbz2's streaming compressor
(`Compress::Raw::Bzip2`) and decompressor (`Compress::Raw::Bunzip2`)
and the `BZ_*` status constants. Most programs are better served by
`IO::Compress::Bzip2` and friends; this module is for code that needs
the streams themselves.

```perl
use Compress::Raw::Bzip2;

my $data = "hello, world\n" x 100;

# Compress: one bzdeflate call per chunk, bzclose at the end.
my ($bz, $status) = Compress::Raw::Bzip2->new(1, 9);   # append, 900k blocks
$status == BZ_OK or die "new: $status";
my $packed = '';
$bz->bzdeflate($data, $packed) == BZ_RUN_OK or die;
$bz->bzclose($packed) == BZ_STREAM_END or die;
printf "%d -> %d bytes\n", $bz->uncompressedBytes, $bz->compressedBytes;
# 1300 -> 66 bytes

# Uncompress: bzinflate eats its input and says BZ_STREAM_END at the end.
my $bunz = Compress::Raw::Bunzip2->new;
my $out = '';
$status = $bunz->bzinflate($packed, $out);
print "status: $status, round trip ", ($out eq $data ? "ok" : "BAD"), "\n";
# status: End of Stream, round trip ok
```

Every status is a dualvar: numeric `BZ_*` and the message text, so
`$status == BZ_STREAM_END` and `"$status"` both work. `bzdeflate`,
`bzflush` and `bzclose` append to the output buffer when the object
was made with `appendOut`; `bzinflate` consumes its input when made
with `consume` and, with `limitOutput`, decompresses at most one
buffer's worth per call.

This is a native implementation of the XS half of Compress::Raw::Bzip2
2.218; `Compress/Raw/Bzip2.pm` is upstream's own. libbz2 is the
system's `libbz2.so.1`, loaded when the module is first used.

## Differences from upstream

None.

## Functions

### Other Functions

#### `bzlibversion`

`Compress::Raw::Bzip2::bzlibversion()`: the version string of the libbz2 this process loaded, such as "1.0.8, 13-Jul-2019".

#### `new`

`Compress::Raw::Bzip2->new([$appendOut, $blockSize100k, $workfactor, $verbosity])`: a compressor. In list context also the status, `BZ_OK` on success.

#### `DispStream`

`$bz->DispStream([$message])`: prints the stream's state to stdout, for debugging.

#### `bzdeflate`

`$bz->bzdeflate($input, $output)`: compresses `$input`, appending to (or replacing, without `appendOut`) `$output`. Returns `BZ_RUN_OK` on success.

#### `bzclose`

`$bz->bzclose($output)`: ends the stream, writing what is pending and the end-of-stream marker into `$output`. Returns `BZ_STREAM_END`.

#### `bzflush`

`$bz->bzflush($output)`: writes what is pending into `$output` without ending the stream. Returns `BZ_RUN_OK`.

#### `total_in_lo32`

`$bz->total_in_lo32()`: bytes taken in so far (low 32 bits).

#### `total_out_lo32`

`$bz->total_out_lo32()`: bytes put out so far (low 32 bits).

#### `compressedBytes`

`$bz->compressedBytes()`: compressed bytes produced so far.

#### `uncompressedBytes`

`$bz->uncompressedBytes()`: uncompressed bytes taken in so far.