Class: Zlib::ZStream

Inherits:
Object
  • Object
show all
Defined in:
zlib.c,
zlib.c

Overview

Zlib::ZStream is the abstract class for the stream which handles the compressed data. The operations are defined in the subclasses: Zlib::Deflate for compression, and Zlib::Inflate for decompression.

An instance of Zlib::ZStream has one stream (struct zstream in the source) and two variable-length buffers which associated to the input (next_in) of the stream and the output (next_out) of the stream. In this document, “input buffer” means the buffer for input, and “output buffer” means the buffer for output.

Data input into an instance of Zlib::ZStream are temporally stored into the end of input buffer, and then data in input buffer are processed from the beginning of the buffer until no more output from the stream is produced (i.e. until avail_out > 0 after processing). During processing, output buffer is allocated and expanded automatically to hold all output data.

Some particular instance methods consume the data in output buffer and return them as a String.

Here is an ascii art for describing above:

+================ an instance of Zlib::ZStream ================+
||                                                            ||
||     +--------+          +-------+          +--------+      ||
||  +--| output |<---------|zstream|<---------| input  |<--+  ||
||  |  | buffer |  next_out+-------+next_in   | buffer |   |  ||
||  |  +--------+                             +--------+   |  ||
||  |                                                      |  ||
+===|======================================================|===+
    |                                                      |
    v                                                      |
"output data"                                         "input data"

If an error occurs during processing input buffer, an exception which is a subclass of Zlib::Error is raised. At that time, both input and output buffer keep their conditions at the time when the error occurs.

Method Catalogue

Many of the methods in this class are fairly low-level and unlikely to be of interest to users. In fact, users are unlikely to use this class directly; rather they will be interested in Zlib::Inflate and Zlib::Deflate.

The higher level methods are listed below.

  • #total_in

  • #total_out

  • #data_type

  • #adler

  • #reset

  • #finish

  • #finished?

  • #close

  • #closed?

Direct Known Subclasses

Deflate, Inflate

Instance Method Summary collapse

Instance Method Details

#adler ⇒ Object

Returns the adler-32 checksum.



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# File 'zlib.c', line 1088

static VALUE
rb_zstream_adler(obj)
VALUE obj;

#avail_in ⇒ Object

Returns bytes of data in the input buffer. Normally, returns 0.



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# File 'zlib.c', line 1044

static VALUE
rb_zstream_avail_in(obj)
VALUE obj;

#avail_out ⇒ Object

Returns number of bytes of free spaces in output buffer. Because the free space is allocated automatically, this method returns 0 normally.



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# File 'zlib.c', line 1015

static VALUE
rb_zstream_avail_out(obj)
VALUE obj;

#avail_out= ⇒ Object

Allocates size bytes of free space in the output buffer. If there are more than size bytes already in the buffer, the buffer is truncated. Because free space is allocated automatically, you usually don’t need to use this method.



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# File 'zlib.c', line 1030

static VALUE
rb_zstream_set_avail_out(obj, size)
VALUE obj, size;

#close ⇒ Object

Closes the stream. All operations on the closed stream will raise an exception.



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# File 'zlib.c', line 941

static VALUE
rb_zstream_end(obj)
VALUE obj;

#closed? ⇒ Boolean

Returns true if the stream is closed.

Returns:

  • (Boolean) 


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# File 'zlib.c', line 1108

static VALUE
rb_zstream_closed_p(obj)
VALUE obj;

#data_type ⇒ Object

Guesses the type of the data which have been inputed into the stream. The returned value is either Zlib::BINARY, Zlib::ASCII, or Zlib::UNKNOWN.



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# File 'zlib.c', line 1078

static VALUE
rb_zstream_data_type(obj)
VALUE obj;

#end ⇒ Object

Closes the stream. All operations on the closed stream will raise an exception.



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# File 'zlib.c', line 941

static VALUE
rb_zstream_end(obj)
VALUE obj;

#ended? ⇒ Boolean

Returns true if the stream is closed.

Returns:

  • (Boolean) 


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# File 'zlib.c', line 1108

static VALUE
rb_zstream_closed_p(obj)
VALUE obj;

#finish ⇒ Object

Finishes the stream and flushes output buffer. See Zlib::Deflate#finish and Zlib::Inflate#finish for details of this behavior.



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# File 'zlib.c', line 965

static VALUE
rb_zstream_finish(obj)
VALUE obj;

#finished? ⇒ Boolean

Returns true if the stream is finished.

Returns:

  • (Boolean) 


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# File 'zlib.c', line 1098

static VALUE
rb_zstream_finished_p(obj)
VALUE obj;

#flush_next_in ⇒ Object

Flushes input buffer and returns all data in that buffer.



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# File 'zlib.c', line 982

static VALUE
rb_zstream_flush_next_in(obj)
VALUE obj;

#flush_next_out ⇒ Object

Flushes output buffer and returns all data in that buffer.



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# File 'zlib.c', line 998

static VALUE
rb_zstream_flush_next_out(obj)
VALUE obj;

#reset ⇒ Object

Resets and initializes the stream. All data in both input and output buffer are discarded.



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# File 'zlib.c', line 953

static VALUE
rb_zstream_reset(obj)
VALUE obj;

#stream_end? ⇒ Boolean

Returns true if the stream is finished.

Returns:

  • (Boolean) 


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# File 'zlib.c', line 1098

static VALUE
rb_zstream_finished_p(obj)
VALUE obj;

#total_in ⇒ Object

Returns the total bytes of the input data to the stream. FIXME



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# File 'zlib.c', line 1056

static VALUE
rb_zstream_total_in(obj)
VALUE obj;

#total_out ⇒ Object

Returns the total bytes of the output data from the stream. FIXME



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# File 'zlib.c', line 1066

static VALUE
rb_zstream_total_out(obj)
VALUE obj;