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.



1403
1404
1405
1406
1407
 
# File 'zlib.c', line 1403

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

#avail_in ⇒ Object

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



1363
1364
1365
1366
1367
1368
1369
 
# File 'zlib.c', line 1363

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

#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.



1336
1337
1338
1339
1340
1341
1342
 
# File 'zlib.c', line 1336

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

#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.



1350
1351
1352
1353
1354
1355
1356
1357
1358
 
# File 'zlib.c', line 1350

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;
}

#close ⇒ Object

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



1259
1260
1261
1262
1263
1264
 
# File 'zlib.c', line 1259

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

#closed? ⇒ Boolean

Returns true if the stream is closed.

Returns:

  • (Boolean) 


1421
1422
1423
1424
1425
1426
1427
 
# File 'zlib.c', line 1421

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

#data_type ⇒ Object

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



1394
1395
1396
1397
1398
 
# File 'zlib.c', line 1394

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

#end ⇒ Object

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



1259
1260
1261
1262
1263
1264
 
# File 'zlib.c', line 1259

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

#ended? ⇒ Boolean

Returns true if the stream is closed.

Returns:

  • (Boolean) 


1421
1422
1423
1424
1425
1426
1427
 
# File 'zlib.c', line 1421

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

#finish ⇒ String #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 ⇒ String

    Returns:

    • (String)
  • #finish {|chunk| ... } ⇒ nil

    Yields:

    • (chunk)

    Returns:

    • (nil) 


1286
1287
1288
1289
1290
1291
1292
1293
1294
 
# File 'zlib.c', line 1286

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.

Returns:

  • (Boolean) 


1412
1413
1414
1415
1416
 
# File 'zlib.c', line 1412

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

#flush_next_in ⇒ Object 



1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
 
# File 'zlib.c', line 1301

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

    Data_Get_Struct(obj, struct zstream, z);
    dst = zstream_detach_input(z);
    OBJ_INFECT(dst, obj);
    return dst;
}

#flush_next_out ⇒ String #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 ⇒ String

    Returns:

    • (String)
  • #flush_next_out {|chunk| ... } ⇒ nil

    Yields:

    • (chunk)

    Returns:

    • (nil) 


1322
1323
1324
1325
1326
1327
1328
1329
1330
 
# File 'zlib.c', line 1322

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

    Data_Get_Struct(obj, struct zstream, z);

    return zstream_detach_buffer(z);
}

#reset ⇒ Object

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



1270
1271
1272
1273
1274
1275
 
# File 'zlib.c', line 1270

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

#stream_end? ⇒ Boolean

Returns true if the stream is finished.

Returns:

  • (Boolean) 


1412
1413
1414
1415
1416
 
# File 'zlib.c', line 1412

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

#total_in ⇒ Object

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



1374
1375
1376
1377
1378
 
# File 'zlib.c', line 1374

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

#total_out ⇒ Object

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



1383
1384
1385
1386
1387
 
# File 'zlib.c', line 1383

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