dbm.c   [plain text]

/************************************************

  dbm.c -

  $Author: knu $
  $Date: 2008-05-19 00:02:36 +0900 (Mon, 19 May 2008) $
  created at: Mon Jan 24 15:59:52 JST 1994

  Copyright (C) 1995-2001 Yukihiro Matsumoto

************************************************/

#include "ruby.h"

#ifdef HAVE_CDEFS_H
# include <cdefs.h>
#endif
#ifdef HAVE_SYS_CDEFS_H
# include <sys/cdefs.h>
#endif
#include DBM_HDR
#include <fcntl.h>
#include <errno.h>

static VALUE rb_cDBM, rb_eDBMError;

#define RUBY_DBM_RW_BIT 0x20000000

struct dbmdata {
    int  di_size;
    DBM *di_dbm;
};

static void
closed_dbm()
{
    rb_raise(rb_eDBMError, "closed DBM file");
}

#define GetDBM(obj, dbmp) {\
    Data_Get_Struct(obj, struct dbmdata, dbmp);\
    if (dbmp == 0) closed_dbm();\
    if (dbmp->di_dbm == 0) closed_dbm();\
}

#define GetDBM2(obj, data, dbm) {\
    GetDBM(obj, data);\
    (dbm) = dbmp->di_dbm;\
}

static void
free_dbm(dbmp)
    struct dbmdata *dbmp;
{
    if (dbmp) {
	if (dbmp->di_dbm) dbm_close(dbmp->di_dbm);
	free(dbmp);
    }
}

static VALUE
fdbm_close(obj)
    VALUE obj;
{
    struct dbmdata *dbmp;

    GetDBM(obj, dbmp);
    dbm_close(dbmp->di_dbm);
    dbmp->di_dbm = 0;

    return Qnil;
}

static VALUE
fdbm_closed(obj)
    VALUE obj;
{
    struct dbmdata *dbmp;

    Data_Get_Struct(obj, struct dbmdata, dbmp);
    if (dbmp == 0)
	return Qtrue;
    if (dbmp->di_dbm == 0)
	return Qtrue;

    return Qfalse;
}

static VALUE fdbm_alloc _((VALUE));
static VALUE
fdbm_alloc(klass)
    VALUE klass;
{
    return Data_Wrap_Struct(klass, 0, free_dbm, 0);
}

static VALUE
fdbm_initialize(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE file, vmode, vflags;
    DBM *dbm;
    struct dbmdata *dbmp;
    int mode, flags = 0;

    if (rb_scan_args(argc, argv, "12", &file, &vmode, &vflags) == 1) {
	mode = 0666;		/* default value */
    }
    else if (NIL_P(vmode)) {
	mode = -1;		/* return nil if DB not exist */
    }
    else {
	mode = NUM2INT(vmode);
    }

    if (!NIL_P(vflags))
        flags = NUM2INT(vflags);

    SafeStringValue(file);

    if (flags & RUBY_DBM_RW_BIT) {
        flags &= ~RUBY_DBM_RW_BIT;
        dbm = dbm_open(RSTRING(file)->ptr, flags, mode);
    }
    else {
        dbm = 0;
        if (mode >= 0) {
            dbm = dbm_open(RSTRING(file)->ptr, O_RDWR|O_CREAT, mode);
        }
        if (!dbm) {
            dbm = dbm_open(RSTRING(file)->ptr, O_RDWR, 0);
        }
        if (!dbm) {
            dbm = dbm_open(RSTRING(file)->ptr, O_RDONLY, 0);
        }
    }

    if (!dbm) {
	if (mode == -1) return Qnil;
	rb_sys_fail(RSTRING(file)->ptr);
    }

    dbmp = ALLOC(struct dbmdata);
    DATA_PTR(obj) = dbmp;
    dbmp->di_dbm = dbm;
    dbmp->di_size = -1;

    return obj;
}

static VALUE
fdbm_s_open(argc, argv, klass)
    int argc;
    VALUE *argv;
    VALUE klass;
{
    VALUE obj = Data_Wrap_Struct(klass, 0, free_dbm, 0);

    if (NIL_P(fdbm_initialize(argc, argv, obj))) {
	return Qnil;
    }

    if (rb_block_given_p()) {
        return rb_ensure(rb_yield, obj, fdbm_close, obj);
    }

    return obj;
}

static VALUE
fdbm_fetch(obj, keystr, ifnone)
    VALUE obj, keystr, ifnone;
{
    datum key, value;
    struct dbmdata *dbmp;
    DBM *dbm;

    StringValue(keystr);
    key.dptr = RSTRING(keystr)->ptr;
    key.dsize = RSTRING(keystr)->len;

    GetDBM2(obj, dbmp, dbm);
    value = dbm_fetch(dbm, key);
    if (value.dptr == 0) {
	if (ifnone == Qnil && rb_block_given_p())
	    return rb_yield(rb_tainted_str_new(key.dptr, key.dsize));
	return ifnone;
    }
    return rb_tainted_str_new(value.dptr, value.dsize);
}

static VALUE
fdbm_aref(obj, keystr)
    VALUE obj, keystr;
{
    return fdbm_fetch(obj, keystr, Qnil);
}

static VALUE
fdbm_fetch_m(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE keystr, valstr, ifnone;

    rb_scan_args(argc, argv, "11", &keystr, &ifnone);
    valstr = fdbm_fetch(obj, keystr, ifnone);
    if (argc == 1 && !rb_block_given_p() && NIL_P(valstr))
	rb_raise(rb_eIndexError, "key not found");

    return valstr;
}

static VALUE
fdbm_index(obj, valstr)
    VALUE obj, valstr;
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;

    StringValue(valstr);
    val.dptr = RSTRING(valstr)->ptr;
    val.dsize = RSTRING(valstr)->len;

    GetDBM2(obj, dbmp, dbm);
    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	if (val.dsize == RSTRING(valstr)->len &&
	    memcmp(val.dptr, RSTRING(valstr)->ptr, val.dsize) == 0) {
	    return rb_tainted_str_new(key.dptr, key.dsize);
	}
    }
    return Qnil;
}

static VALUE
fdbm_indexes(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE new;
    int i;

    new = rb_ary_new2(argc);
    for (i=0; i<argc; i++) {
	rb_ary_push(new, fdbm_fetch(obj, argv[i], Qnil));
    }

    return new;
}

static VALUE
fdbm_select(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE new = rb_ary_new2(argc);
    int i;

    if (rb_block_given_p()) {
        datum key, val;
        DBM *dbm;
        struct dbmdata *dbmp;

	if (argc > 0) {
	    rb_raise(rb_eArgError, "wrong number arguments(%d for 0)", argc);
	}
        GetDBM2(obj, dbmp, dbm);
        for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
            VALUE assoc, v;
            val = dbm_fetch(dbm, key);
            assoc = rb_assoc_new(rb_tainted_str_new(key.dptr, key.dsize),
                                 rb_tainted_str_new(val.dptr, val.dsize));
	    v = rb_yield(assoc);
	    if (RTEST(v)) {
		rb_ary_push(new, assoc);
	    }
	    GetDBM2(obj, dbmp, dbm);
	}
    }
    else {
	rb_warn("DBM#select(index..) is deprecated; use DBM#values_at");

        for (i=0; i<argc; i++) {
            rb_ary_push(new, fdbm_fetch(obj, argv[i], Qnil));
        }
    }

    return new;
}

static VALUE
fdbm_values_at(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE new = rb_ary_new2(argc);
    int i;

    for (i=0; i<argc; i++) {
        rb_ary_push(new, fdbm_fetch(obj, argv[i], Qnil));
    }

    return new;
}

static void
fdbm_modify(obj)
    VALUE obj;
{
    rb_secure(4);
    if (OBJ_FROZEN(obj)) rb_error_frozen("DBM");
}

static VALUE
fdbm_delete(obj, keystr)
    VALUE obj, keystr;
{
    datum key, value;
    struct dbmdata *dbmp;
    DBM *dbm;
    VALUE valstr;

    fdbm_modify(obj);
    StringValue(keystr);
    key.dptr = RSTRING(keystr)->ptr;
    key.dsize = RSTRING(keystr)->len;

    GetDBM2(obj, dbmp, dbm);
    value = dbm_fetch(dbm, key);
    if (value.dptr == 0) {
	if (rb_block_given_p()) return rb_yield(keystr);
	return Qnil;
    }

    /* need to save value before dbm_delete() */
    valstr = rb_tainted_str_new(value.dptr, value.dsize);

    if (dbm_delete(dbm, key)) {
	dbmp->di_size = -1;
	rb_raise(rb_eDBMError, "dbm_delete failed");
    }
    else if (dbmp->di_size >= 0) {
	dbmp->di_size--;
    }
    return valstr;
}

static VALUE
fdbm_shift(obj)
    VALUE obj;
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;
    VALUE keystr, valstr;

    fdbm_modify(obj);
    GetDBM2(obj, dbmp, dbm);
    dbmp->di_size = -1;

    key = dbm_firstkey(dbm); 
    if (!key.dptr) return Qnil;
    val = dbm_fetch(dbm, key);
    keystr = rb_tainted_str_new(key.dptr, key.dsize);
    valstr = rb_tainted_str_new(val.dptr, val.dsize);
    dbm_delete(dbm, key);

    return rb_assoc_new(keystr, valstr);
}

static VALUE
fdbm_delete_if(obj)
    VALUE obj;
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;
    VALUE keystr, valstr;
    VALUE ret, ary = rb_ary_new();
    int i, status = 0, n;

    fdbm_modify(obj);
    GetDBM2(obj, dbmp, dbm);
    n = dbmp->di_size;
    dbmp->di_size = -1;

    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	keystr = rb_tainted_str_new(key.dptr, key.dsize);
	valstr = rb_tainted_str_new(val.dptr, val.dsize);
        ret = rb_protect(rb_yield, rb_assoc_new(rb_str_dup(keystr), valstr), &status);
        if (status != 0) break;
	if (RTEST(ret)) rb_ary_push(ary, keystr);
	GetDBM2(obj, dbmp, dbm);
    }

    for (i = 0; i < RARRAY(ary)->len; i++) {
	keystr = RARRAY(ary)->ptr[i];
	StringValue(keystr);
	key.dptr = RSTRING(keystr)->ptr;
	key.dsize = RSTRING(keystr)->len;
	if (dbm_delete(dbm, key)) {
	    rb_raise(rb_eDBMError, "dbm_delete failed");
	}
    }
    if (status) rb_jump_tag(status);
    if (n > 0) dbmp->di_size = n - RARRAY(ary)->len;

    return obj;
}

static VALUE
fdbm_clear(obj)
    VALUE obj;
{
    datum key;
    struct dbmdata *dbmp;
    DBM *dbm;

    fdbm_modify(obj);
    GetDBM2(obj, dbmp, dbm);
    dbmp->di_size = -1;
    while (key = dbm_firstkey(dbm), key.dptr) {
	if (dbm_delete(dbm, key)) {
	    rb_raise(rb_eDBMError, "dbm_delete failed");
	}
    }
    dbmp->di_size = 0;

    return obj;
}

static VALUE
fdbm_invert(obj)
    VALUE obj;
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;
    VALUE keystr, valstr;
    VALUE hash = rb_hash_new();

    GetDBM2(obj, dbmp, dbm);
    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	keystr = rb_tainted_str_new(key.dptr, key.dsize);
	valstr = rb_tainted_str_new(val.dptr, val.dsize);
	rb_hash_aset(hash, valstr, keystr);
    }
    return hash;
}

static VALUE each_pair _((VALUE));

static VALUE
each_pair(obj)
    VALUE obj;
{
    return rb_funcall(obj, rb_intern("each_pair"), 0, 0);
}

static VALUE fdbm_store _((VALUE,VALUE,VALUE));

static VALUE
update_i(pair, dbm)
    VALUE pair, dbm;
{
    Check_Type(pair, T_ARRAY);
    if (RARRAY(pair)->len < 2) {
	rb_raise(rb_eArgError, "pair must be [key, value]");
    }
    fdbm_store(dbm, RARRAY(pair)->ptr[0], RARRAY(pair)->ptr[1]);
    return Qnil;
}

static VALUE
fdbm_update(obj, other)
    VALUE obj, other;
{
    rb_iterate(each_pair, other, update_i, obj);
    return obj;
}

static VALUE
fdbm_replace(obj, other)
    VALUE obj, other;
{
    fdbm_clear(obj);
    rb_iterate(each_pair, other, update_i, obj);
    return obj;
}

static VALUE
fdbm_store(obj, keystr, valstr)
    VALUE obj, keystr, valstr;
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;

    fdbm_modify(obj);
    keystr = rb_obj_as_string(keystr);
    valstr = rb_obj_as_string(valstr);

    key.dptr = RSTRING(keystr)->ptr;
    key.dsize = RSTRING(keystr)->len;

    val.dptr = RSTRING(valstr)->ptr;
    val.dsize = RSTRING(valstr)->len;

    GetDBM2(obj, dbmp, dbm);
    dbmp->di_size = -1;
    if (dbm_store(dbm, key, val, DBM_REPLACE)) {
#ifdef HAVE_DBM_CLEARERR
	dbm_clearerr(dbm);
#endif
	if (errno == EPERM) rb_sys_fail(0);
	rb_raise(rb_eDBMError, "dbm_store failed");
    }

    return valstr;
}

static VALUE
fdbm_length(obj)
    VALUE obj;
{
    datum key;
    struct dbmdata *dbmp;
    DBM *dbm;
    int i = 0;

    GetDBM2(obj, dbmp, dbm);
    if (dbmp->di_size > 0) return INT2FIX(dbmp->di_size);

    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	i++;
    }
    dbmp->di_size = i;

    return INT2FIX(i);
}

static VALUE
fdbm_empty_p(obj)
    VALUE obj;
{
    datum key;
    struct dbmdata *dbmp;
    DBM *dbm;
    int i = 0;

    GetDBM2(obj, dbmp, dbm);
    if (dbmp->di_size < 0) {
	dbm = dbmp->di_dbm;

	for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	    i++;
	}
    }
    else {
	i = dbmp->di_size;
    }
    if (i == 0) return Qtrue;
    return Qfalse;
}

static VALUE
fdbm_each_value(obj)
    VALUE obj;
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;

    GetDBM2(obj, dbmp, dbm);
    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	rb_yield(rb_tainted_str_new(val.dptr, val.dsize));
	GetDBM2(obj, dbmp, dbm);
    }
    return obj;
}

static VALUE
fdbm_each_key(obj)
    VALUE obj;
{
    datum key;
    struct dbmdata *dbmp;
    DBM *dbm;

    GetDBM2(obj, dbmp, dbm);
    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	rb_yield(rb_tainted_str_new(key.dptr, key.dsize));
	GetDBM2(obj, dbmp, dbm);
    }
    return obj;
}

static VALUE
fdbm_each_pair(obj)
    VALUE obj;
{
    datum key, val;
    DBM *dbm;
    struct dbmdata *dbmp;
    VALUE keystr, valstr;

    GetDBM2(obj, dbmp, dbm);

    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	keystr = rb_tainted_str_new(key.dptr, key.dsize);
	valstr = rb_tainted_str_new(val.dptr, val.dsize);
	rb_yield(rb_assoc_new(keystr, valstr));
	GetDBM2(obj, dbmp, dbm);
    }

    return obj;
}

static VALUE
fdbm_keys(obj)
    VALUE obj;
{
    datum key;
    struct dbmdata *dbmp;
    DBM *dbm;
    VALUE ary;

    GetDBM2(obj, dbmp, dbm);

    ary = rb_ary_new();
    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	rb_ary_push(ary, rb_tainted_str_new(key.dptr, key.dsize));
    }

    return ary;
}

static VALUE
fdbm_values(obj)
    VALUE obj;
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;
    VALUE ary;

    GetDBM2(obj, dbmp, dbm);
    ary = rb_ary_new();
    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	rb_ary_push(ary, rb_tainted_str_new(val.dptr, val.dsize));
    }

    return ary;
}

static VALUE
fdbm_has_key(obj, keystr)
    VALUE obj, keystr;
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;

    StringValue(keystr);
    key.dptr = RSTRING(keystr)->ptr;
    key.dsize = RSTRING(keystr)->len;

    GetDBM2(obj, dbmp, dbm);
    val = dbm_fetch(dbm, key);
    if (val.dptr) return Qtrue;
    return Qfalse;
}

static VALUE
fdbm_has_value(obj, valstr)
    VALUE obj, valstr;
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;

    StringValue(valstr);
    val.dptr = RSTRING(valstr)->ptr;
    val.dsize = RSTRING(valstr)->len;

    GetDBM2(obj, dbmp, dbm);
    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	if (val.dsize == RSTRING(valstr)->len &&
	    memcmp(val.dptr, RSTRING(valstr)->ptr, val.dsize) == 0)
	    return Qtrue;
    }
    return Qfalse;
}

static VALUE
fdbm_to_a(obj)
    VALUE obj;
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;
    VALUE ary;

    GetDBM2(obj, dbmp, dbm);
    ary = rb_ary_new();
    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	rb_ary_push(ary, rb_assoc_new(rb_tainted_str_new(key.dptr, key.dsize),
				      rb_tainted_str_new(val.dptr, val.dsize)));
    }

    return ary;
}

static VALUE
fdbm_to_hash(obj)
    VALUE obj;
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;
    VALUE hash;

    GetDBM2(obj, dbmp, dbm);
    hash = rb_hash_new();
    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	rb_hash_aset(hash, rb_tainted_str_new(key.dptr, key.dsize),
		           rb_tainted_str_new(val.dptr, val.dsize));
    }

    return hash;
}

static VALUE
fdbm_reject(obj)
    VALUE obj;
{
    return rb_hash_delete_if(fdbm_to_hash(obj));
}

void
Init_dbm()
{
    rb_cDBM = rb_define_class("DBM", rb_cObject);
    rb_eDBMError = rb_define_class("DBMError", rb_eStandardError);
    rb_include_module(rb_cDBM, rb_mEnumerable);

    rb_define_alloc_func(rb_cDBM, fdbm_alloc);
    rb_define_singleton_method(rb_cDBM, "open", fdbm_s_open, -1);

    rb_define_method(rb_cDBM, "initialize", fdbm_initialize, -1);
    rb_define_method(rb_cDBM, "close", fdbm_close, 0);
    rb_define_method(rb_cDBM, "closed?", fdbm_closed, 0);
    rb_define_method(rb_cDBM, "[]", fdbm_aref, 1);
    rb_define_method(rb_cDBM, "fetch", fdbm_fetch_m, -1);
    rb_define_method(rb_cDBM, "[]=", fdbm_store, 2);
    rb_define_method(rb_cDBM, "store", fdbm_store, 2);
    rb_define_method(rb_cDBM, "index",  fdbm_index, 1);
    rb_define_method(rb_cDBM, "indexes",  fdbm_indexes, -1);
    rb_define_method(rb_cDBM, "indices",  fdbm_indexes, -1);
    rb_define_method(rb_cDBM, "select",  fdbm_select, -1);
    rb_define_method(rb_cDBM, "values_at", fdbm_values_at, -1);
    rb_define_method(rb_cDBM, "length", fdbm_length, 0);
    rb_define_method(rb_cDBM, "size", fdbm_length, 0);
    rb_define_method(rb_cDBM, "empty?", fdbm_empty_p, 0);
    rb_define_method(rb_cDBM, "each", fdbm_each_pair, 0);
    rb_define_method(rb_cDBM, "each_value", fdbm_each_value, 0);
    rb_define_method(rb_cDBM, "each_key", fdbm_each_key, 0);
    rb_define_method(rb_cDBM, "each_pair", fdbm_each_pair, 0);
    rb_define_method(rb_cDBM, "keys", fdbm_keys, 0);
    rb_define_method(rb_cDBM, "values", fdbm_values, 0);
    rb_define_method(rb_cDBM, "shift", fdbm_shift, 0);
    rb_define_method(rb_cDBM, "delete", fdbm_delete, 1);
    rb_define_method(rb_cDBM, "delete_if", fdbm_delete_if, 0);
    rb_define_method(rb_cDBM, "reject!", fdbm_delete_if, 0);
    rb_define_method(rb_cDBM, "reject", fdbm_reject, 0);
    rb_define_method(rb_cDBM, "clear", fdbm_clear, 0);
    rb_define_method(rb_cDBM,"invert", fdbm_invert, 0);
    rb_define_method(rb_cDBM,"update", fdbm_update, 1);
    rb_define_method(rb_cDBM,"replace", fdbm_replace, 1);

    rb_define_method(rb_cDBM, "include?", fdbm_has_key, 1);
    rb_define_method(rb_cDBM, "has_key?", fdbm_has_key, 1);
    rb_define_method(rb_cDBM, "member?", fdbm_has_key, 1);
    rb_define_method(rb_cDBM, "has_value?", fdbm_has_value, 1);
    rb_define_method(rb_cDBM, "key?", fdbm_has_key, 1);
    rb_define_method(rb_cDBM, "value?", fdbm_has_value, 1);

    rb_define_method(rb_cDBM, "to_a", fdbm_to_a, 0);
    rb_define_method(rb_cDBM, "to_hash", fdbm_to_hash, 0);

    /* flags for dbm_open() */
    rb_define_const(rb_cDBM, "READER",  INT2FIX(O_RDONLY|RUBY_DBM_RW_BIT));
    rb_define_const(rb_cDBM, "WRITER",  INT2FIX(O_RDWR|RUBY_DBM_RW_BIT));
    rb_define_const(rb_cDBM, "WRCREAT", INT2FIX(O_RDWR|O_CREAT|RUBY_DBM_RW_BIT));
    rb_define_const(rb_cDBM, "NEWDB",   INT2FIX(O_RDWR|O_CREAT|O_TRUNC|RUBY_DBM_RW_BIT));

#ifdef DB_VERSION_STRING
    rb_define_const(rb_cDBM, "VERSION",  rb_str_new2(DB_VERSION_STRING));
#else
    rb_define_const(rb_cDBM, "VERSION",  rb_str_new2("unknown"));
#endif
}