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

#adlerObject

Returns the adler-32 checksum.


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# File 'zlib.c', line 1418

static VALUE
rb_zstream_adler(VALUE obj)
{
  return rb_uint2inum(get_zstream(obj)->stream.adler);
}

#avail_inObject

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


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# File 'zlib.c', line 1378

static VALUE
rb_zstream_avail_in(VALUE obj)
{
    struct zstream *z;
    TypedData_Get_Struct(obj, struct zstream, &zstream_data_type, z);
    return INT2FIX(NIL_P(z->input) ? 0 : (int)(RSTRING_LEN(z->input)));
}

#avail_outObject

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 1351

static VALUE
rb_zstream_avail_out(VALUE obj)
{
    struct zstream *z;
    TypedData_Get_Struct(obj, struct zstream, &zstream_data_type, z);
    return rb_uint2inum(z->stream.avail_out);
}

#avail_out=(size) ⇒ 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 1365

static VALUE
rb_zstream_set_avail_out(VALUE obj, VALUE size)
{
    struct zstream *z = get_zstream(obj);

    Check_Type(size, T_FIXNUM);
    zstream_expand_buffer_into(z, FIX2INT(size));
    return size;
}

#closeObject

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


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# File 'zlib.c', line 1274

static VALUE
rb_zstream_end(VALUE obj)
{
    zstream_end(get_zstream(obj));
    return Qnil;
}

#closed?Boolean

Returns true if the stream is closed.


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# File 'zlib.c', line 1436

static VALUE
rb_zstream_closed_p(VALUE obj)
{
    struct zstream *z;
    TypedData_Get_Struct(obj, struct zstream, &zstream_data_type, z);
    return ZSTREAM_IS_READY(z) ? Qfalse : Qtrue;
}

#data_typeObject

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


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# File 'zlib.c', line 1409

static VALUE
rb_zstream_data_type(VALUE obj)
{
    return INT2FIX(get_zstream(obj)->stream.data_type);
}

#endObject

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


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# File 'zlib.c', line 1274

static VALUE
rb_zstream_end(VALUE obj)
{
    zstream_end(get_zstream(obj));
    return Qnil;
}

#ended?Boolean

Returns true if the stream is closed.


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# File 'zlib.c', line 1436

static VALUE
rb_zstream_closed_p(VALUE obj)
{
    struct zstream *z;
    TypedData_Get_Struct(obj, struct zstream, &zstream_data_type, z);
    return ZSTREAM_IS_READY(z) ? Qfalse : Qtrue;
}

#finishString #finish {|chunk| ... } ⇒ nil

Finishes the stream and flushes output buffer. If a block is given each chunk is yielded to the block until the input buffer has been flushed to the output buffer.

Overloads:

  • #finish {|chunk| ... } ⇒ nil

    Yields:

    • (chunk)

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# File 'zlib.c', line 1301

static VALUE
rb_zstream_finish(VALUE obj)
{
    struct zstream *z = get_zstream(obj);

    zstream_run(z, (Bytef*)"", 0, Z_FINISH);

    return zstream_detach_buffer(z);
}

#finished?Boolean

Returns true if the stream is finished.


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# File 'zlib.c', line 1427

static VALUE
rb_zstream_finished_p(VALUE obj)
{
    return ZSTREAM_IS_FINISHED(get_zstream(obj)) ? Qtrue : Qfalse;
}

#flush_next_inObject


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# File 'zlib.c', line 1316

static VALUE
rb_zstream_flush_next_in(VALUE obj)
{
    struct zstream *z;
    VALUE dst;

    TypedData_Get_Struct(obj, struct zstream, &zstream_data_type, z);
    dst = zstream_detach_input(z);
    OBJ_INFECT(dst, obj);
    return dst;
}

#flush_next_outString #flush_next_out {|chunk| ... } ⇒ nil

Flushes output buffer and returns all data in that buffer. If a block is given each chunk is yielded to the block until the current output buffer has been flushed.

Overloads:

  • #flush_next_out {|chunk| ... } ⇒ nil

    Yields:

    • (chunk)

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# File 'zlib.c', line 1337

static VALUE
rb_zstream_flush_next_out(VALUE obj)
{
    struct zstream *z;

    TypedData_Get_Struct(obj, struct zstream, &zstream_data_type, z);

    return zstream_detach_buffer(z);
}

#resetObject

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


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# File 'zlib.c', line 1285

static VALUE
rb_zstream_reset(VALUE obj)
{
    zstream_reset(get_zstream(obj));
    return Qnil;
}

#stream_end?Boolean

Returns true if the stream is finished.


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# File 'zlib.c', line 1427

static VALUE
rb_zstream_finished_p(VALUE obj)
{
    return ZSTREAM_IS_FINISHED(get_zstream(obj)) ? Qtrue : Qfalse;
}

#total_inObject

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


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# File 'zlib.c', line 1389

static VALUE
rb_zstream_total_in(VALUE obj)
{
    return rb_uint2inum(get_zstream(obj)->stream.total_in);
}

#total_outObject

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


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# File 'zlib.c', line 1398

static VALUE
rb_zstream_total_out(VALUE obj)
{
    return rb_uint2inum(get_zstream(obj)->stream.total_out);
}