Zlib::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 Zlib::GzipReader are just like their counterparts in IO, but they raise Zlib::Error or Zlib::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 Zlib::GzipFile::NoFooter, Zlib::GzipFile::CRCError, or Zlib::GzipFile::LengthError exception.

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

  • When Zlib::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.

Methods
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Included Modules
Class Public methods
Zlib::GzipReader.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 Zlib::GzipFile::Error exception.

static VALUE
rb_gzreader_initialize(int argc, VALUE *argv, VALUE obj)
{
    VALUE io, opt = Qnil;
    struct gzfile *gz;
    int err;

    TypedData_Get_Struct(obj, struct gzfile, &gzfile_data_type, gz);
    rb_scan_args(argc, argv, "1:", &io, &opt);

    /* this is undocumented feature of zlib */
    err = inflateInit2(&gz->z.stream, -MAX_WBITS);
    if (err != Z_OK) {
        raise_zlib_error(err, gz->z.stream.msg);
    }
    gz->io = io;
    ZSTREAM_READY(&gz->z);
    gzfile_read_header(gz);
    rb_gzfile_ecopts(gz, opt);

    if (rb_respond_to(io, id_path)) {
        gz->path = rb_funcall(gz->io, id_path, 0);
        rb_define_singleton_method(obj, "path", rb_gzfile_path, 0);
    }

    return obj;
}
Zlib::GzipReader.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.

static VALUE
rb_gzreader_s_open(int argc, VALUE *argv, VALUE klass)
{
    return gzfile_s_open(argc, argv, klass, "rb");
}
Instance Public methods
bytes()

This is a deprecated alias for each_byte.

static VALUE
rb_gzreader_bytes(VALUE obj)
{
    rb_warn("Zlib::GzipReader#bytes is deprecated; use #each_byte instead");
    if (!rb_block_given_p())
        return rb_enumeratorize(obj, ID2SYM(rb_intern("each_byte")), 0, 0);
    return rb_gzreader_each_byte(obj);
}
each(*args)

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_each(int argc, VALUE *argv, VALUE obj)
{
    VALUE str;

    RETURN_ENUMERATOR(obj, 0, 0);

    while (!NIL_P(str = gzreader_gets(argc, argv, obj))) {
        rb_yield(str);
    }
    return obj;
}
each_byte()

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_each_byte(VALUE obj)
{
    VALUE c;

    RETURN_ENUMERATOR(obj, 0, 0);

    while (!NIL_P(c = rb_gzreader_getbyte(obj))) {
        rb_yield(c);
    }
    return Qnil;
}
each_char()

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_each_char(VALUE obj)
{
    VALUE c;

    RETURN_ENUMERATOR(obj, 0, 0);

    while (!NIL_P(c = rb_gzreader_getc(obj))) {
        rb_yield(c);
    }
    return Qnil;
}
each_line(*args)

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_each(int argc, VALUE *argv, VALUE obj)
{
    VALUE str;

    RETURN_ENUMERATOR(obj, 0, 0);

    while (!NIL_P(str = gzreader_gets(argc, argv, obj))) {
        rb_yield(str);
    }
    return obj;
}
eof()

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

static VALUE
rb_gzfile_eof_p(VALUE obj)
{
    struct gzfile *gz = get_gzfile(obj);
    return GZFILE_IS_FINISHED(gz) ? Qtrue : Qfalse;
}
eof?()

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

static VALUE
rb_gzfile_eof_p(VALUE obj)
{
    struct gzfile *gz = get_gzfile(obj);
    return GZFILE_IS_FINISHED(gz) ? Qtrue : Qfalse;
}
external_encoding()

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_external_encoding(VALUE self)
{
    return rb_enc_from_encoding(get_gzfile(self)->enc);
}
getbyte()

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_getbyte(VALUE obj)
{
    struct gzfile *gz = get_gzfile(obj);
    VALUE dst;

    dst = gzfile_read(gz, 1);
    if (!NIL_P(dst)) {
        dst = INT2FIX((unsigned int)(RSTRING_PTR(dst)[0]) & 0xff);
    }
    return dst;
}
getc()

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_getc(VALUE obj)
{
    struct gzfile *gz = get_gzfile(obj);

    return gzfile_getc(gz);
}
gets(*args)

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_gets(int argc, VALUE *argv, VALUE obj)
{
    VALUE dst;
    dst = gzreader_gets(argc, argv, obj);
    if (!NIL_P(dst)) {
        rb_lastline_set(dst);
    }
    return dst;
}
lineno()

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

static VALUE
rb_gzfile_lineno(VALUE obj)
{
    return INT2NUM(get_gzfile(obj)->lineno);
}
lineno=(p1)

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

static VALUE
rb_gzfile_set_lineno(VALUE obj, VALUE lineno)
{
    struct gzfile *gz = get_gzfile(obj);
    gz->lineno = NUM2INT(lineno);
    return lineno;
}
lines(*args)

This is a deprecated alias for each_line.

static VALUE
rb_gzreader_lines(int argc, VALUE *argv, VALUE obj)
{
    rb_warn("Zlib::GzipReader#lines is deprecated; use #each_line instead");
    if (!rb_block_given_p())
        return rb_enumeratorize(obj, ID2SYM(rb_intern("each_line")), argc, argv);
    return rb_gzreader_each(argc, argv, obj);
}
pos()

Total number of output bytes output so far.

static VALUE
rb_gzfile_total_out(VALUE obj)
{
    struct gzfile *gz = get_gzfile(obj);
    uLong total_out = gz->z.stream.total_out;
    long buf_filled = gz->z.buf_filled;

    if (total_out >= (uLong)buf_filled) {
        return rb_uint2inum(total_out - buf_filled);
    } else {
        return LONG2FIX(-(buf_filled - (long)total_out));
    }
}
read(p1 = v1)

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_read(int argc, VALUE *argv, VALUE obj)
{
    struct gzfile *gz = get_gzfile(obj);
    VALUE vlen;
    long len;

    rb_scan_args(argc, argv, "01", &vlen);
    if (NIL_P(vlen)) {
        return gzfile_read_all(gz);
    }

    len = NUM2INT(vlen);
    if (len < 0) {
        rb_raise(rb_eArgError, "negative length %ld given", len);
    }
    return gzfile_read(gz, len);
}
readbyte()

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_readbyte(VALUE obj)
{
    VALUE dst;
    dst = rb_gzreader_getbyte(obj);
    if (NIL_P(dst)) {
        rb_raise(rb_eEOFError, "end of file reached");
    }
    return dst;
}
readchar()

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_readchar(VALUE obj)
{
    VALUE dst;
    dst = rb_gzreader_getc(obj);
    if (NIL_P(dst)) {
        rb_raise(rb_eEOFError, "end of file reached");
    }
    return dst;
}
readline(*args)

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_readline(int argc, VALUE *argv, VALUE obj)
{
    VALUE dst;
    dst = rb_gzreader_gets(argc, argv, obj);
    if (NIL_P(dst)) {
        rb_raise(rb_eEOFError, "end of file reached");
    }
    return dst;
}
readlines(*args)

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_readlines(int argc, VALUE *argv, VALUE obj)
{
    VALUE str, dst;
    dst = rb_ary_new();
    while (!NIL_P(str = gzreader_gets(argc, argv, obj))) {
        rb_ary_push(dst, str);
    }
    return dst;
}
gzipreader.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.

static VALUE
rb_gzreader_readpartial(int argc, VALUE *argv, VALUE obj)
{
    struct gzfile *gz = get_gzfile(obj);
    VALUE vlen, outbuf;
    long len;

    rb_scan_args(argc, argv, "11", &vlen, &outbuf);

    len = NUM2INT(vlen);
    if (len < 0) {
        rb_raise(rb_eArgError, "negative length %ld given", len);
    }
    if (!NIL_P(outbuf))
        Check_Type(outbuf, T_STRING);
    return gzfile_readpartial(gz, len, outbuf);
}
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.

static VALUE
rb_gzreader_rewind(VALUE obj)
{
    struct gzfile *gz = get_gzfile(obj);
    gzfile_reader_rewind(gz);
    return INT2FIX(0);
}
tell()

Total number of output bytes output so far.

static VALUE
rb_gzfile_total_out(VALUE obj)
{
    struct gzfile *gz = get_gzfile(obj);
    uLong total_out = gz->z.stream.total_out;
    long buf_filled = gz->z.buf_filled;

    if (total_out >= (uLong)buf_filled) {
        return rb_uint2inum(total_out - buf_filled);
    } else {
        return LONG2FIX(-(buf_filled - (long)total_out));
    }
}
ungetbyte(p1)

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_ungetbyte(VALUE obj, VALUE ch)
{
    struct gzfile *gz = get_gzfile(obj);
    gzfile_ungetbyte(gz, NUM2CHR(ch));
    return Qnil;
}
ungetc(p1)

See Zlib::GzipReader documentation for a description.

static VALUE
rb_gzreader_ungetc(VALUE obj, VALUE s)
{
    struct gzfile *gz;

    if (FIXNUM_P(s))
        return rb_gzreader_ungetbyte(obj, s);
    gz = get_gzfile(obj);
    StringValue(s);
    if (gz->enc2 && gz->enc2 != rb_ascii8bit_encoding()) {
        s = rb_str_conv_enc(s, rb_enc_get(s), gz->enc2);
    }
    gzfile_ungets(gz, (const Bytef*)RSTRING_PTR(s), RSTRING_LEN(s));
    RB_GC_GUARD(s);
    return Qnil;
}
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.

static VALUE
rb_gzreader_unused(VALUE obj)
{
    struct gzfile *gz;
    TypedData_Get_Struct(obj, struct gzfile, &gzfile_data_type, gz);
    return gzfile_reader_get_unused(gz);
}