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 ================+
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|| +--------+ +-------+ +--------+ ||
|| +--| output |<---------|zstream|<---------| input |<--+ ||
|| | | buffer | next_out+-------+next_in | buffer | | ||
|| | +--------+ +--------+ | ||
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+===|======================================================|===+
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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 CatalogueMany 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.
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); }
Returns number of bytes of free spaces in output buffer. Because the free space is allocated automatically, this method returns 0 normally.
static VALUE rb_zstream_set_avail_out(VALUE obj, VALUE size) { struct zstream *z = get_zstream(obj); zstream_expand_buffer_into(z, FIX2INT(size)); return size; }
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.
Closes the stream. All operations on the closed stream will raise an exception.
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; }
Returns true if the stream is closed.
Closes the stream. All operations on the closed stream will raise an exception.
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); }
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.
static VALUE rb_zstream_finished_p(VALUE obj) { return ZSTREAM_IS_FINISHED(get_zstream(obj)) ? Qtrue : Qfalse; }
Returns true if the stream is finished.
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); }
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.
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