Class: Zstdlib::Deflate

Inherits:
ZStream show all
Defined in:
ext/zstdlib/ruby/zlib-2.7/zstdlib.c,
ext/zstdlib/ruby/zlib-2.7/zstdlib.c,
ext/zstdlib/ruby/zlib-2.6/zstdlib.c,
ext/zstdlib/ruby/zlib-2.6/zstdlib.c,
ext/zstdlib/ruby/zlib-2.5/zstdlib.c,
ext/zstdlib/ruby/zlib-2.5/zstdlib.c,
ext/zstdlib/ruby/zlib-2.4/zstdlib.c,
ext/zstdlib/ruby/zlib-2.4/zstdlib.c,
ext/zstdlib/ruby/zlib-2.3/zstdlib.c,
ext/zstdlib/ruby/zlib-2.3/zstdlib.c,
ext/zstdlib/ruby/zlib-2.2/zstdlib.c,
ext/zstdlib/ruby/zlib-2.2/zstdlib.c

Overview

Zstdlib::Deflate is the class for compressing data. See Zstdlib::ZStream for more information.

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from ZStream

#adler, #avail_in, #avail_out, #avail_out=, #close, #closed?, #data_type, #end, #ended?, #finish, #finished?, #flush_next_in, #flush_next_out, #reset, #stream_end?, #total_in, #total_out

Constructor Details

#initialize(*args) ⇒ Object

call-seq: Zstdlib::Deflate.new(level=DEFAULT_COMPRESSION, window_bits=MAX_WBITS, mem_level=DEF_MEM_LEVEL, strategy=DEFAULT_STRATEGY)

Creates a new deflate stream for compression. If a given argument is nil, the default value of that argument is used.

The +level+ sets the compression level for the deflate stream between 0 (no compression) and 9 (best compression). The following constants have been defined to make code more readable:

  • Zstdlib::DEFAULT_COMPRESSION
  • Zstdlib::NO_COMPRESSION
  • Zstdlib::BEST_SPEED
  • Zstdlib::BEST_COMPRESSION

See http://www.zlib.net/manual.html#Constants for further information.

The +window_bits+ sets the size of the history buffer and should be between 8 and 15. Larger values of this parameter result in better compression at the expense of memory usage.

The +mem_level+ specifies how much memory should be allocated for the internal compression state. 1 uses minimum memory but is slow and reduces compression ratio while 9 uses maximum memory for optimal speed. The default value is 8. Two constants are defined:

  • Zstdlib::DEF_MEM_LEVEL
  • Zstdlib::MAX_MEM_LEVEL

The +strategy+ sets the deflate compression strategy. The following strategies are available:

Zstdlib::DEFAULT_STRATEGY:: For normal data Zstdlib::FILTERED:: For data produced by a filter or predictor Zstdlib::FIXED:: Prevents dynamic Huffman codes Zstdlib::HUFFMAN_ONLY:: Prevents string matching Zstdlib::RLE:: Designed for better compression of PNG image data

See the constants for further description.

== Examples

=== Basic

open "compressed.file", "w+" do |io| io << Zstdlib::Deflate.new.deflate(File.read("big.file")) end

=== Custom compression

open "compressed.file", "w+" do |compressed_io| deflate = Zstdlib::Deflate.new(Zstdlib::BEST_COMPRESSION, Zstdlib::MAX_WBITS, Zstdlib::MAX_MEM_LEVEL, Zstdlib::HUFFMAN_ONLY)

begin
  open "big.file" do |big_io|
    until big_io.eof? do
      compressed_io << zd.deflate(big_io.read(16384))
    end
  end
ensure
  deflate.close
end

end

While this example will work, for best optimization review the flags for your specific time, memory usage and output space requirements.



1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
 
# File 'ext/zstdlib/ruby/zlib-2.7/zstdlib.c', line 1564

static VALUE
rb_deflate_initialize(int argc, VALUE *argv, VALUE obj)
{
    struct zstream *z;
    VALUE level, wbits, memlevel, strategy;
    int err;

    rb_scan_args(argc, argv, "04", &level, &wbits, &memlevel, &strategy);
    TypedData_Get_Struct(obj, struct zstream, &zstream_data_type, z);

    err = deflateInit2(&z->stream, ARG_LEVEL(level), Z_DEFLATED,
           ARG_WBITS(wbits), ARG_MEMLEVEL(memlevel),
           ARG_STRATEGY(strategy));
    if (err != Z_OK) {
  raise_zlib_error(err, z->stream.msg);
    }
    ZSTREAM_READY(z);

    return obj;
}

Class Method Details

.deflate(*args) ⇒ Object

call-seq: Zstdlib.deflate(string[, level]) Zstdlib::Deflate.deflate(string[, level])

Compresses the given +string+. Valid values of level are Zstdlib::NO_COMPRESSION, Zstdlib::BEST_SPEED, Zstdlib::BEST_COMPRESSION, Zstdlib::DEFAULT_COMPRESSION, or an integer from 0 to 9.

This method is almost equivalent to the following code:

def deflate(string, level) z = Zstdlib::Deflate.new(level) dst = z.deflate(string, Zstdlib::FINISH) z.close dst end

See also Zstdlib.inflate



1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
 
# File 'ext/zstdlib/ruby/zlib-2.7/zstdlib.c', line 1644

static VALUE
rb_deflate_s_deflate(int argc, VALUE *argv, VALUE klass)
{
    struct zstream z;
    VALUE src, level, dst, args[2];
    int err, lev;

    rb_scan_args(argc, argv, "11", &src, &level);

    lev = ARG_LEVEL(level);
    StringValue(src);
    zstream_init_deflate(&z);
    err = deflateInit(&z.stream, lev);
    if (err != Z_OK) {
  raise_zlib_error(err, z.stream.msg);
    }
    ZSTREAM_READY(&z);

    args[0] = (VALUE)&z;
    args[1] = src;
    dst = rb_ensure(deflate_run, (VALUE)args, zstream_ensure_end, (VALUE)&z);

    return dst;
}

Instance Method Details

#<<(src) ⇒ Object

call-seq: << string

Inputs +string+ into the deflate stream just like Zstdlib::Deflate#deflate, but returns the Zstdlib::Deflate object itself. The output from the stream is preserved in output buffer.



1729
1730
1731
1732
1733
1734
 
# File 'ext/zstdlib/ruby/zlib-2.7/zstdlib.c', line 1729

static VALUE
rb_deflate_addstr(VALUE obj, VALUE src)
{
    do_deflate(get_zstream(obj), src, Z_NO_FLUSH);
    return obj;
}

#deflate(*args) ⇒ Object

call-seq: z.deflate(string, flush = Zstdlib::NO_FLUSH) -> String z.deflate(string, flush = Zstdlib::NO_FLUSH) { |chunk| ... } -> nil

Inputs +string+ into the deflate stream and returns the output from the stream. On calling this method, both the input and the output buffers of the stream are flushed. If +string+ is nil, this method finishes the stream, just like Zstdlib::ZStream#finish.

If a block is given consecutive deflated chunks from the +string+ are yielded to the block and +nil+ is returned.

The +flush+ parameter specifies the flush mode. The following constants may be used:

Zstdlib::NO_FLUSH:: The default Zstdlib::SYNC_FLUSH:: Flushes the output to a byte boundary Zstdlib::FULL_FLUSH:: SYNC_FLUSH + resets the compression state Zstdlib::FINISH:: Pending input is processed, pending output is flushed.

See the constants for further description.



1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
 
# File 'ext/zstdlib/ruby/zlib-2.7/zstdlib.c', line 1708

static VALUE
rb_deflate_deflate(int argc, VALUE *argv, VALUE obj)
{
    struct zstream *z = get_zstream(obj);
    VALUE src, flush;

    rb_scan_args(argc, argv, "11", &src, &flush);
    do_deflate(z, src, ARG_FLUSH(flush));

    return zstream_detach_buffer(z);
}

#flush(*args) ⇒ Object

call-seq: flush(flush = Zstdlib::SYNC_FLUSH) -> String flush(flush = Zstdlib::SYNC_FLUSH) { |chunk| ... } -> nil

This method is equivalent to deflate('', flush). This method is just provided to improve the readability of your Ruby program. If a block is given chunks of deflate output are yielded to the block until the buffer is flushed.

See Zstdlib::Deflate#deflate for detail on the +flush+ constants NO_FLUSH, SYNC_FLUSH, FULL_FLUSH and FINISH.



1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
 
# File 'ext/zstdlib/ruby/zlib-2.7/zstdlib.c', line 1751

static VALUE
rb_deflate_flush(int argc, VALUE *argv, VALUE obj)
{
    struct zstream *z = get_zstream(obj);
    VALUE v_flush;
    int flush;

    rb_scan_args(argc, argv, "01", &v_flush);
    flush = FIXNUMARG(v_flush, Z_SYNC_FLUSH);
    if (flush != Z_NO_FLUSH) {  /* prevent Z_BUF_ERROR */
  zstream_run(z, (Bytef*)"", 0, flush);
    }

    return zstream_detach_buffer(z);
}

#initialize_copy(orig) ⇒ Object

Duplicates the deflate stream.



1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
 
# File 'ext/zstdlib/ruby/zlib-2.7/zstdlib.c', line 1590

static VALUE
rb_deflate_init_copy(VALUE self, VALUE orig)
{
    struct zstream *z1, *z2;
    int err;

    TypedData_Get_Struct(self, struct zstream, &zstream_data_type, z1);
    z2 = get_zstream(orig);

    if (z1 == z2) return self;
    err = deflateCopy(&z1->stream, &z2->stream);
    if (err != Z_OK) {
  raise_zlib_error(err, 0);
    }
    z1->input = NIL_P(z2->input) ? Qnil : rb_str_dup(z2->input);
    z1->buf   = NIL_P(z2->buf)   ? Qnil : rb_str_dup(z2->buf);
    z1->flags = z2->flags;

    return self;
}

#params(v_level, v_strategy) ⇒ Object

call-seq: params(level, strategy)

Changes the parameters of the deflate stream to allow changes between different types of data that require different types of compression. Any unprocessed data is flushed before changing the params.

See Zstdlib::Deflate.new for a description of +level+ and +strategy+.



1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
 
# File 'ext/zstdlib/ruby/zlib-2.7/zstdlib.c', line 1779

static VALUE
rb_deflate_params(VALUE obj, VALUE v_level, VALUE v_strategy)
{
    struct zstream *z = get_zstream(obj);
    int level, strategy;
    int err;
    uInt n;
    long filled;

    level = ARG_LEVEL(v_level);
    strategy = ARG_STRATEGY(v_strategy);

    n = z->stream.avail_out;
    err = deflateParams(&z->stream, level, strategy);
    filled = n - z->stream.avail_out;
    while (err == Z_BUF_ERROR) {
  rb_warning("deflateParams() returned Z_BUF_ERROR");
  zstream_expand_buffer(z);
  rb_str_set_len(z->buf, RSTRING_LEN(z->buf) + filled);
  n = z->stream.avail_out;
  err = deflateParams(&z->stream, level, strategy);
  filled = n - z->stream.avail_out;
    }
    if (err != Z_OK) {
  raise_zlib_error(err, z->stream.msg);
    }
    rb_str_set_len(z->buf, RSTRING_LEN(z->buf) + filled);

    return Qnil;
}

#set_dictionary(dic) ⇒ Object

call-seq: set_dictionary(string)

Sets the preset dictionary and returns +string+. This method is available just only after Zstdlib::Deflate.new or Zstdlib::ZStream#reset method was called. See zlib.h for details.

Can raise errors of Z_STREAM_ERROR if a parameter is invalid (such as NULL dictionary) or the stream state is inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the expected one (incorrect adler32 value)



1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
 
# File 'ext/zstdlib/ruby/zlib-2.7/zstdlib.c', line 1824

static VALUE
rb_deflate_set_dictionary(VALUE obj, VALUE dic)
{
    struct zstream *z = get_zstream(obj);
    VALUE src = dic;
    int err;

    StringValue(src);
    err = deflateSetDictionary(&z->stream,
             (Bytef*)RSTRING_PTR(src), RSTRING_LENINT(src));
    if (err != Z_OK) {
  raise_zlib_error(err, z->stream.msg);
    }

    return dic;
}