Class: Zlib::Inflate

Inherits:

ZStream

• Object
• ZStream
• Zlib::Inflate

Defined in:

ext/zlib/zlib.c,
ext/zlib/zlib.c

Overview

Zlib:Inflate is the class for decompressing compressed data. Unlike Zlib::Deflate, an instance of this class is not able to duplicate (clone, dup) itself.

Class Method Summary

• .inflate(src) ⇒ Object

  call-seq: Zlib.inflate(string) Zlib::Inflate.inflate(string).

Instance Method Summary

• #<<(string) ⇒ Object

  Inputs string into the inflate stream just like Zlib::Inflate#inflate, but returns the Zlib::Inflate object itself.

• #add_dictionary(dictionary) ⇒ Object

  call-seq: add_dictionary(string).

• #inflate(*args) ⇒ Object

  call-seq: inflate(deflate_string, buffer: nil) -> String inflate(deflate_string, buffer: nil) { |chunk| … } -> nil.

• #initialize(*args) ⇒ Object constructor

  call-seq: Zlib::Inflate.new(window_bits = Zlib::MAX_WBITS).

• #set_dictionary(dic) ⇒ Object

  Sets the preset dictionary and returns string.

• #sync(string) ⇒ Object

  Inputs string into the end of input buffer and skips data until a full flush point can be found.

• #sync_point? ⇒ Boolean

  Quoted verbatim from original documentation:.

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:

Zlib::Inflate.new(window_bits = Zlib::MAX_WBITS)

Creates a new inflate stream for decompression. window_bits sets the size of the history buffer and can have the following values:

0

Have inflate use the window size from the zlib header of the compressed stream.

(8..15)

Overrides the window size of the inflate header in the compressed stream. The window size must be greater than or equal to the window size of the compressed stream.

Greater than 15

Add 32 to window_bits to enable zlib and gzip decoding with automatic header detection, or add 16 to decode only the gzip format (a Zlib::DataError will be raised for a non-gzip stream).

(-8..-15)

Enables raw deflate mode which will not generate a check value, and will not look for any check values for comparison at the end of the stream.

This is for use with other formats that use the deflate compressed data format such as zip which provide their own check values.

Example

open "compressed.file" do |compressed_io|
  zi = Zlib::Inflate.new(Zlib::MAX_WBITS + 32)

  begin
    open "uncompressed.file", "w+" do |uncompressed_io|
      uncompressed_io << zi.inflate(compressed_io.read)
    end
  ensure
    zi.close
  end
end

# File 'ext/zlib/zlib.c', line 1992

static VALUE
rb_inflate_initialize(int argc, VALUE *argv, VALUE obj)
{
    struct zstream *z;
    VALUE wbits;
    int err;

    rb_scan_args(argc, argv, "01", &wbits);
    TypedData_Get_Struct(obj, struct zstream, &zstream_data_type, z);

    err = inflateInit2(&z->stream, ARG_WBITS(wbits));
    if (err != Z_OK) {
	raise_zlib_error(err, z->stream.msg);
    }
    ZSTREAM_READY(z);

    return obj;
}

Class Method Details

.inflate(src) ⇒ Object

call-seq:

Zlib.inflate(string)
Zlib::Inflate.inflate(string)

Decompresses string. Raises a Zlib::NeedDict exception if a preset dictionary is needed for decompression.

This method is almost equivalent to the following code:

def inflate(string)
  zstream = Zlib::Inflate.new
  buf = zstream.inflate(string)
  zstream.finish
  zstream.close
  buf
end

See also Zlib.deflate

# File 'ext/zlib/zlib.c', line 2045

static VALUE
rb_inflate_s_inflate(VALUE obj, VALUE src)
{
    struct zstream z;
    VALUE dst, args[2];
    int err;

    StringValue(src);
    zstream_init_inflate(&z);
    err = inflateInit(&z.stream);
    if (err != Z_OK) {
	raise_zlib_error(err, z.stream.msg);
    }
    ZSTREAM_READY(&z);

    args[0] = (VALUE)&z;
    args[1] = src;
    dst = rb_ensure(inflate_run, (VALUE)args, zstream_ensure_end, (VALUE)&z);

    return dst;
}

Instance Method Details

#<<(string) ⇒ Object

Inputs string into the inflate stream just like Zlib::Inflate#inflate, but returns the Zlib::Inflate object itself. The output from the stream is preserved in output buffer.

# File 'ext/zlib/zlib.c', line 2211

static VALUE
rb_inflate_addstr(VALUE obj, VALUE src)
{
    struct zstream *z = get_zstream(obj);

    if (ZSTREAM_IS_FINISHED(z)) {
	if (!NIL_P(src)) {
	    StringValue(src);
	    zstream_append_buffer2(z, src);
	}
    }
    else {
	do_inflate(z, src);
	if (ZSTREAM_IS_FINISHED(z)) {
	    zstream_passthrough_input(z);
	}
    }

    return obj;
}

#add_dictionary(dictionary) ⇒ Object

call-seq: add_dictionary(string)

Provide the inflate stream with a dictionary that may be required in the future. Multiple dictionaries may be provided. The inflate stream will automatically choose the correct user-provided dictionary based on the stream’s required dictionary.

# File 'ext/zlib/zlib.c', line 2089

static VALUE
rb_inflate_add_dictionary(VALUE obj, VALUE dictionary)
{
    VALUE dictionaries = rb_ivar_get(obj, id_dictionaries);
    VALUE checksum = do_checksum(1, &dictionary, adler32);

    rb_hash_aset(dictionaries, checksum, dictionary);

    return obj;
}

#inflate(*args) ⇒ Object

call-seq:

inflate(deflate_string, buffer: nil)                 -> String
inflate(deflate_string, buffer: nil) { |chunk| ... } -> nil

Inputs deflate_string into the inflate stream and returns the output from the stream. Calling this method, both the input and the output buffer of the stream are flushed. If string is nil, this method finishes the stream, just like Zlib::ZStream#finish.

If a block is given consecutive inflated chunks from the deflate_string are yielded to the block and nil is returned.

If a :buffer keyword argument is given and not nil:

• The :buffer keyword should be a String, and will used as the output buffer. Using this option can reuse the memory required during inflation.

• When not passing a block, the return value will be the same object as the :buffer keyword argument.

• When passing a block, the yielded chunks will be the same value as the :buffer keyword argument.

Raises a Zlib::NeedDict exception if a preset dictionary is needed to decompress. Set the dictionary by Zlib::Inflate#set_dictionary and then call this method again with an empty string to flush the stream:

inflater = Zlib::Inflate.new

begin
  out = inflater.inflate compressed
rescue Zlib::NeedDict
  # ensure the dictionary matches the stream's required dictionary
  raise unless inflater.adler == Zlib.adler32(dictionary)

  inflater.set_dictionary dictionary
  inflater.inflate ''
end

# ...

inflater.close

See also Zlib::Inflate.new

# File 'ext/zlib/zlib.c', line 2146

static VALUE
rb_inflate_inflate(int argc, VALUE* argv, VALUE obj)
{
    struct zstream *z = get_zstream(obj);
    VALUE dst, src, opts, buffer = Qnil;

    if (OPTHASH_GIVEN_P(opts)) {
        VALUE buf;
        rb_get_kwargs(opts, &id_buffer, 0, 1, &buf);
        if (buf != Qundef && buf != Qnil) {
            buffer = StringValue(buf);
        }
    }
    if (buffer != Qnil) {
        if (!(ZSTREAM_REUSE_BUFFER_P(z) && z->buf == buffer)) {
            long len = RSTRING_LEN(buffer);
            if (len >= ZSTREAM_AVAIL_OUT_STEP_MAX) {
                rb_str_modify(buffer);
            }
            else {
                len = ZSTREAM_AVAIL_OUT_STEP_MAX - len;
                rb_str_modify_expand(buffer, len);
            }
            rb_str_set_len(buffer, 0);
            z->flags |= ZSTREAM_REUSE_BUFFER;
            z->buf = buffer;
        }
    } else if (ZSTREAM_REUSE_BUFFER_P(z)) {
        z->flags &= ~ZSTREAM_REUSE_BUFFER;
        z->buf = Qnil;
    }
    rb_scan_args(argc, argv, "10", &src);

    if (ZSTREAM_IS_FINISHED(z)) {
	if (NIL_P(src)) {
	    dst = zstream_detach_buffer(z);
	}
	else {
	    StringValue(src);
	    zstream_append_buffer2(z, src);
	    if (ZSTREAM_REUSE_BUFFER_P(z)) {
                dst = rb_str_resize(buffer, 0);
            } else {
                dst = rb_str_new(0, 0);
            }
	}
    }
    else {
	do_inflate(z, src);
	dst = zstream_detach_buffer(z);
	if (ZSTREAM_IS_FINISHED(z)) {
	    zstream_passthrough_input(z);
	}
    }

    return dst;
}

#set_dictionary(dic) ⇒ Object

Sets the preset dictionary and returns string. This method is available just only after a Zlib::NeedDict exception was raised. See zlib.h for details.

# File 'ext/zlib/zlib.c', line 2279

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

    StringValue(src);
    err = inflateSetDictionary(&z->stream,
			       (Bytef*)RSTRING_PTR(src), RSTRING_LENINT(src));
    if (err != Z_OK) {
	raise_zlib_error(err, z->stream.msg);
    }

    return dic;
}

#sync(string) ⇒ Object

Inputs string into the end of input buffer and skips data until a full flush point can be found. If the point is found in the buffer, this method flushes the buffer and returns false. Otherwise it returns true and the following data of full flush point is preserved in the buffer.

# File 'ext/zlib/zlib.c', line 2240

static VALUE
rb_inflate_sync(VALUE obj, VALUE src)
{
    struct zstream *z = get_zstream(obj);

    StringValue(src);
    return zstream_sync(z, (Bytef*)RSTRING_PTR(src), RSTRING_LEN(src));
}

#sync_point? ⇒ Boolean

Quoted verbatim from original documentation:

What is this?

:)

Returns:

• (Boolean)

# File 'ext/zlib/zlib.c', line 2256

static VALUE
rb_inflate_sync_point_p(VALUE obj)
{
    struct zstream *z = get_zstream(obj);
    int err;

    err = inflateSyncPoint(&z->stream);
    if (err == 1) {
	return Qtrue;
    }
    if (err != Z_OK) {
	raise_zlib_error(err, z->stream.msg);
    }
    return Qfalse;
}