Class: Zstdlib::Deflate

Inherits:
ZStream show all
Defined in:
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.



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# File 'ext/zstdlib/ruby/zlib-2.6/zstdlib.c', line 1555

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



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# File 'ext/zstdlib/ruby/zlib-2.6/zstdlib.c', line 1635

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_end, (VALUE)&z);

    OBJ_INFECT(dst, src);
    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.



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# File 'ext/zstdlib/ruby/zlib-2.6/zstdlib.c', line 1722

static VALUE
rb_deflate_addstr(VALUE obj, VALUE src)
{
    OBJ_INFECT(obj, 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.



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# File 'ext/zstdlib/ruby/zlib-2.6/zstdlib.c', line 1700

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);
    OBJ_INFECT(obj, src);
    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.



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# File 'ext/zstdlib/ruby/zlib-2.6/zstdlib.c', line 1745

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.



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# File 'ext/zstdlib/ruby/zlib-2.6/zstdlib.c', line 1581

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+.



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# File 'ext/zstdlib/ruby/zlib-2.6/zstdlib.c', line 1773

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)



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# File 'ext/zstdlib/ruby/zlib-2.6/zstdlib.c', line 1818

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

    OBJ_INFECT(obj, dic);
    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;
}