class Zlib::GzipWriter

Zlib::GzipWriter is a class for writing gzipped files. GzipWriter should be used with an instance of IO, or IO-like, object.

Following two example generate the same result.

Zlib::GzipWriter.open('hoge.gz') do |gz|
  gz.write 'jugemu jugemu gokou no surikire...'
end

File.open('hoge.gz', 'w') do |f|
  gz = Zlib::GzipWriter.new(f)
  gz.write 'jugemu jugemu gokou no surikire...'
  gz.close
end

To make like gzip(1) does, run following:

orig = 'hoge.txt'
Zlib::GzipWriter.open('hoge.gz') do |gz|
  gz.mtime = File.mtime(orig)
  gz.orig_name = orig
  gz.write IO.binread(orig)
end

NOTE: Due to the limitation of Ruby’s finalizer, you must explicitly close GzipWriter objects by Zlib::GzipWriter#close etc. Otherwise, GzipWriter will be not able to write the gzip footer and will generate a broken gzip file.

Public Class Methods

Zlib::GzipWriter.new(io, level = nil, strategy = nil, options = {})

Creates a GzipWriter object associated with io. level and strategy should be the same as the arguments of Zlib::Deflate.new. The GzipWriter object writes gzipped data to io. io must respond to the write method that behaves the same as IO#write.

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.

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

    if (argc > 1) {
        opt = rb_check_convert_type(argv[argc-1], T_HASH, "Hash", "to_hash");
        if (!NIL_P(opt)) argc--;
    }

    rb_scan_args(argc, argv, "12", &io, &level, &strategy);
    TypedData_Get_Struct(obj, struct gzfile, &gzfile_data_type, gz);

    /* this is undocumented feature of zlib */
    gz->level = ARG_LEVEL(level);
    err = deflateInit2(&gz->z.stream, gz->level, Z_DEFLATED,
                       -MAX_WBITS, DEF_MEM_LEVEL, ARG_STRATEGY(strategy));
    if (err != Z_OK) {
        raise_zlib_error(err, gz->z.stream.msg);
    }
    gz->io = io;
    ZSTREAM_READY(&gz->z);
    rb_gzfile_ecopts(gz, opt);

    if (rb_respond_to(io, id_path)) {
        /* File#path may raise IOError in case when a path is unavailable */
        rb_rescue2(gzfile_initialize_path_partial, obj, NULL, Qnil, rb_eIOError, (VALUE)0);
    }

    return obj;
}

Zlib::GzipWriter.open(filename, level=nil, strategy=nil) { |gz| ... }

Opens a file specified by filename for writing gzip compressed data, and returns a GzipWriter object associated with that file. Further details of this method are found in Zlib::GzipWriter.new and Zlib::GzipFile.wrap.

static VALUE
rb_gzwriter_s_open(int argc, VALUE *argv, VALUE klass)
{
    return gzfile_s_open(argc, argv, klass, "wb");
}

Public Instance Methods

<< (p1)

Same as IO.

#define rb_gzwriter_addstr  rb_io_addstr

comment= (p1)

Specify the comment (str) in the gzip header.

static VALUE
rb_gzfile_set_comment(VALUE obj, VALUE str)
{
    struct gzfile *gz = get_gzfile(obj);
    VALUE s;
    char *p;

    if (gz->z.flags & GZFILE_FLAG_HEADER_FINISHED) {
        rb_raise(cGzError, "header is already written");
    }
    s = rb_str_dup(rb_str_to_str(str));
    p = memchr(RSTRING_PTR(s), '\0', RSTRING_LEN(s));
    if (p) {
        rb_str_resize(s, p - RSTRING_PTR(s));
    }
    gz->comment = s;
    return str;
}

flush(flush=nil)

Flushes all the internal buffers of the GzipWriter object. The meaning of flush is same as in Zlib::Deflate#deflate. Zlib::SYNC_FLUSH is used if flush is omitted. It is no use giving flush Zlib::NO_FLUSH.

static VALUE
rb_gzwriter_flush(int argc, VALUE *argv, VALUE obj)
{
    struct gzfile *gz = get_gzfile(obj);
    VALUE v_flush;
    int flush;

    rb_scan_args(argc, argv, "01", &v_flush);

    flush = FIXNUMARG(v_flush, Z_SYNC_FLUSH);
    if (flush != Z_NO_FLUSH) {  /* prevent Z_BUF_ERROR */
        zstream_run(&gz->z, (Bytef*)"", 0, flush);
    }

    gzfile_write_raw(gz);
    if (rb_respond_to(gz->io, id_flush)) {
        rb_funcall(gz->io, id_flush, 0);
    }
    return obj;
}

mtime= (p1)

Specify the modification time (mtime) in the gzip header. Using an Integer.

Setting the mtime in the gzip header does not effect the mtime of the file generated. Different utilities that expand the gzipped files may use the mtime header. For example the gunzip utility can use the ‘-N` flag which will set the resultant file’s mtime to the value in the header. By default many tools will set the mtime of the expanded file to the mtime of the gzipped file, not the mtime in the header.

If you do not set an mtime, the default value will be the time when compression started. Setting a value of 0 indicates no time stamp is available.

static VALUE
rb_gzfile_set_mtime(VALUE obj, VALUE mtime)
{
    struct gzfile *gz = get_gzfile(obj);
    VALUE val;

    if (gz->z.flags & GZFILE_FLAG_HEADER_FINISHED) {
        rb_raise(cGzError, "header is already written");
    }

    val = rb_Integer(mtime);
    gz->mtime = NUM2UINT(val);
    gz->z.flags |= GZFILE_FLAG_MTIME_IS_SET;

    return mtime;
}

orig_name= (p1)

Specify the original name (str) in the gzip header.

static VALUE
rb_gzfile_set_orig_name(VALUE obj, VALUE str)
{
    struct gzfile *gz = get_gzfile(obj);
    VALUE s;
    char *p;

    if (gz->z.flags & GZFILE_FLAG_HEADER_FINISHED) {
        rb_raise(cGzError, "header is already written");
    }
    s = rb_str_dup(rb_str_to_str(str));
    p = memchr(RSTRING_PTR(s), '\0', RSTRING_LEN(s));
    if (p) {
        rb_str_resize(s, p - RSTRING_PTR(s));
    }
    gz->orig_name = s;
    return str;
}

pos ()

Total number of input bytes read so far.

static VALUE
rb_gzfile_total_in(VALUE obj)
{
    return rb_uint2inum(get_gzfile(obj)->z.stream.total_in);
}

Also aliased as: tell

print (*args)

Same as IO.

#define rb_gzwriter_print  rb_io_print

printf (*args)

Same as IO.

#define rb_gzwriter_printf  rb_io_printf

putc (p1)

Same as IO.

static VALUE
rb_gzwriter_putc(VALUE obj, VALUE ch)
{
    struct gzfile *gz = get_gzfile(obj);
    char c = NUM2CHR(ch);

    gzfile_write(gz, (Bytef*)&c, 1);
    return ch;
}

puts (*args)

Same as IO.

#define rb_gzwriter_puts  rb_io_puts

tell ()

Total number of input bytes read so far.

Alias for: pos

write (*args)

Same as IO.

static VALUE
rb_gzwriter_write(int argc, VALUE *argv, VALUE obj)
{
    struct gzfile *gz = get_gzfile(obj);
    size_t total = 0;

    while (argc-- > 0) {
        VALUE str = *argv++;
        if (!RB_TYPE_P(str, T_STRING))
            str = rb_obj_as_string(str);
        if (gz->enc2 && gz->enc2 != rb_ascii8bit_encoding()) {
            str = rb_str_conv_enc(str, rb_enc_get(str), gz->enc2);
        }
        gzfile_write(gz, (Bytef*)RSTRING_PTR(str), RSTRING_LEN(str));
        total += RSTRING_LEN(str);
        RB_GC_GUARD(str);
    }
    return SIZET2NUM(total);
}