static VALUE
rb_zlib_adler32(int argc, VALUE *argv, VALUE klass)
{
    return do_checksum(argc, argv, adler32);
}

static VALUE
rb_zlib_adler32_combine(VALUE klass, VALUE adler1, VALUE adler2, VALUE len2)
{
    return ULONG2NUM(
        adler32_combine(NUM2ULONG(adler1), NUM2ULONG(adler2), NUM2LONG(len2)));
}

static VALUE
rb_zlib_crc32(int argc, VALUE *argv, VALUE klass)
{
    return do_checksum(argc, argv, crc32);
}

static VALUE
rb_zlib_crc32_combine(VALUE klass, VALUE crc1, VALUE crc2, VALUE len2)
{
    return ULONG2NUM(
        crc32_combine(NUM2ULONG(crc1), NUM2ULONG(crc2), NUM2LONG(len2)));
}

static VALUE
rb_zlib_crc_table(VALUE obj)
{
#if !defined(HAVE_TYPE_Z_CRC_T)
    /* z_crc_t is defined since zlib-1.2.7. */
    typedef unsigned long z_crc_t;
#endif
    const z_crc_t *crctbl;
    VALUE dst;
    int i;

    crctbl = get_crc_table();
    dst = rb_ary_new2(256);

    for (i = 0; i < 256; i++) {
        rb_ary_push(dst, rb_uint2inum(crctbl[i]));
    }
    return dst;
}

static VALUE
rb_deflate_s_deflate(int argc, VALUE *argv, VALUE klass)
{
    struct zstream z;
    VALUE src, level, dst, args[2];
    int err, lev;

    rb_scan_args(argc, argv, "11", &src, &level);

    lev = ARG_LEVEL(level);
    StringValue(src);
    zstream_init_deflate(&z);
    err = deflateInit(&z.stream, lev);
    if (err != Z_OK) {
        raise_zlib_error(err, z.stream.msg);
    }
    ZSTREAM_READY(&z);

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

    return dst;
}

static VALUE
zlib_gunzip(VALUE klass, VALUE src)
{
    struct gzfile gz0;
    struct gzfile *gz = &gz0;
    int err;

    StringValue(src);

    gzfile_init(gz, &inflate_funcs, zlib_gunzip_end);
    err = inflateInit2(&gz->z.stream, -MAX_WBITS);
    if (err != Z_OK) {
        raise_zlib_error(err, gz->z.stream.msg);
    }
    gz->io = Qundef;
    gz->z.input = src;
    ZSTREAM_READY(&gz->z);
    return rb_ensure(zlib_gunzip_run, (VALUE)gz, zlib_gzip_ensure, (VALUE)gz);
}

static VALUE
zlib_s_gzip(int argc, VALUE *argv, VALUE klass)
{
    struct gzfile gz0;
    struct gzfile *gz = &gz0;
    int err;
    VALUE src, opts, level=Qnil, strategy=Qnil, args[2];

    if (OPTHASH_GIVEN_P(opts)) {
        ID keyword_ids[2];
        VALUE kwargs[2];
        keyword_ids[0] = id_level;
        keyword_ids[1] = id_strategy;
        rb_get_kwargs(opts, keyword_ids, 0, 2, kwargs);
        if (kwargs[0] != Qundef) {
            level = kwargs[0];
        }
        if (kwargs[1] != Qundef) {
            strategy = kwargs[1];
        }
    }
    rb_scan_args(argc, argv, "10", &src);
    StringValue(src);
    gzfile_init(gz, &deflate_funcs, zlib_gzip_end);
    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) {
        zlib_gzip_end(gz);
        raise_zlib_error(err, gz->z.stream.msg);
    }
    ZSTREAM_READY(&gz->z);
    args[0] = (VALUE)gz;
    args[1] = src;
    return rb_ensure(zlib_gzip_run, (VALUE)args, zlib_gzip_ensure, (VALUE)gz);
}

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;
}

static VALUE
rb_zlib_version(VALUE klass)
{
    return rb_str_new2(zlibVersion());
}