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Class: Zlib::GzipReader

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Class Chain:
self, GzipFile
Instance Chain:
self, Enumerable, GzipFile
Inherits: Zlib::GzipFile
Defined in: ext/zlib/zlib.c,
ext/zlib/zlib.c

Overview

GzipReader is the class for reading a gzipped file. GzipReader should be used as an IO, or -IO-like, object.

Zlib::GzipReader.open('hoge.gz') {|gz|
  print gz.read
}

File.open('hoge.gz') do |f|
  gz = Zlib::GzipReader.new(f)
  print gz.read
  gz.close
end

Method Catalogue

The following methods in GzipReader are just like their counterparts in IO, but they raise Error or GzipFile::Error exception if an error was found in the gzip file.

Be careful of the footer of the gzip file. A gzip file has the checksum of pre-compressed data in its footer. GzipReader checks all uncompressed data against that checksum at the following cases, and if it fails, raises GzipFile::NoFooter, GzipFile::CRCError, or GzipFile::LengthError exception.

  • When an reading request is received beyond the end of file (the end of compressed data). That is, when Zlib::GzipReader#read, Zlib::GzipReader#gets, or some other methods for reading returns nil.

  • When GzipFile#close method is called after the object reaches the end of file.

  • When #unused method is called after the object reaches the end of file.

The rest of the methods are adequately described in their own documentation.

Class Method Summary

GzipFile - Inherited

.wrap

Creates a GzipReader or GzipWriter associated with io, passing in any necessary extra options, and executes the block with the newly created object just like File.open.

Instance Attribute Summary

  • #lineno rw

    The line number of the last row read from this file.

  • #lineno=(lineno) rw

    Specify line number of the last row read from this file.

  • #eof (also: #eof?) readonly

    Returns true or false whether the stream has reached the end.

  • #eof? readonly

    Alias for #eof.

GzipFile - Inherited

#sync

Same as IO#sync
#sync=

Same as IO.
#closed?

Same as IO#closed?

Instance Method Summary

GzipFile - Inherited

#close

Closes the GzipFile object.
#comment

Returns comments recorded in the gzip file header, or nil if the comments is not present.
#crc

Returns CRC value of the uncompressed data.
#finish

Closes the GzipFile object.
#level

Returns compression level.
#mtime

Returns last modification time recorded in the gzip file header.
#orig_name

Returns original filename recorded in the gzip file header, or nil if original filename is not present.
#os_code

Returns OS code number recorded in the gzip file header.
#to_io

Same as IO.

Constructor Details

.new(io, options = {})

Creates a GzipReader object associated with io. The GzipReader object reads gzipped data from io, and parses/decompresses it. The io must have a #read method that behaves same as the IO#read.

The options hash may be used to set the encoding of the data. :external_encoding, :internal_encoding and :encoding may be set as in IO.new.

If the gzip file header is incorrect, raises an GzipFile::Error exception.

Class Method Details

.open(filename) {|gz| ... }

Opens a file specified by filename as a gzipped file, and returns a GzipReader object associated with that file. Further details of this method are in .new and ZLib::GzipFile.wrap.

Instance Attribute Details

#eof (readonly) Also known as: #eof?

Returns true or false whether the stream has reached the end.

#eof? (readonly)

Alias for #eof.

#lineno (rw)

The line number of the last row read from this file.

#lineno=(lineno) (rw)

Specify line number of the last row read from this file.

Instance Method Details

#bytes

This is a deprecated alias for #each_byte.

#each(*args) Also known as: #each_line

See GzipReader documentation for a description.

#each_byte

See GzipReader documentation for a description.

#each_char

See GzipReader documentation for a description.

#each_line(*args)

Alias for #each.

#external_encoding

See GzipReader documentation for a description.

#getbyte

See GzipReader documentation for a description.

#getc

See GzipReader documentation for a description.

#gets(*args)

See GzipReader documentation for a description.

#lines(*args)

This is a deprecated alias for #each_line.

#pos Also known as: #tell

Total number of output bytes output so far.

#read(*args)

See GzipReader documentation for a description.

#readbyte

See GzipReader documentation for a description.

#readchar

See GzipReader documentation for a description.

#readline(*args)

See GzipReader documentation for a description.

#readlines(*args)

See GzipReader documentation for a description.

#readpartial(maxlen [, outbuf]) ⇒ String, outbuf

Reads at most maxlen bytes from the gziped stream but it blocks only if gzipreader has no data immediately available. If the optional outbuf argument is present, it must reference a String, which will receive the data. It raises EOFError on end of file.

#rewind

Resets the position of the file pointer to the point created the GzipReader object. The associated IO object needs to respond to the seek method.

#tell

Alias for #pos.

#ungetbyte(ch)

See GzipReader documentation for a description.

#ungetc(s)

See GzipReader documentation for a description.

#unused

Returns the rest of the data which had read for parsing gzip format, or nil if the whole gzip file is not parsed yet.