SDBM provides a simple file-based key-value store, which can only store String keys and values.
Note that Ruby comes with the source code for SDBM, while the DBM and GDBM standard libraries rely on external libraries and headers.
Examples
Insert values:
require 'sdbm' SDBM.open 'my_database' do |db| db['apple'] = 'fruit' db['pear'] = 'fruit' db['carrot'] = 'vegetable' db['tomato'] = 'vegetable' end
Bulk update:
require 'sdbm' SDBM.open 'my_database' do |db| db.update('peach' => 'fruit', 'tomato' => 'fruit') end
Retrieve values:
require 'sdbm' SDBM.open 'my_database' do |db| db.each do |key, value| puts "Key: #{key}, Value: #{value}" end end
Outputs:
Key: apple, Value: fruit Key: pear, Value: fruit Key: carrot, Value: vegetable Key: peach, Value: fruit Key: tomato, Value: fruit
static VALUE
fsdbm_initialize(int argc, VALUE *argv, VALUE obj)
{
VALUE file, vmode;
DBM *dbm;
struct dbmdata *dbmp;
int mode;
TypedData_Get_Struct(obj, struct dbmdata, &sdbm_type, dbmp);
if (rb_scan_args(argc, argv, "11", &file, &vmode) == 1) {
mode = 0666; /* default value */
}
else if (NIL_P(vmode)) {
mode = -1; /* return nil if DB not exist */
}
else {
mode = NUM2INT(vmode);
}
FilePathValue(file);
dbm = 0;
if (mode >= 0)
dbm = sdbm_open(RSTRING_PTR(file), O_RDWR|O_CREAT, mode);
if (!dbm)
dbm = sdbm_open(RSTRING_PTR(file), O_RDWR, 0);
if (!dbm)
dbm = sdbm_open(RSTRING_PTR(file), O_RDONLY, 0);
if (!dbm) {
if (mode == -1) return Qnil;
rb_sys_fail_str(file);
}
if (dbmp->di_dbm)
sdbm_close(dbmp->di_dbm);
dbmp->di_dbm = dbm;
dbmp->di_size = -1;
return obj;
}
Creates a new database handle by opening the given filename. SDBM actually uses two physical files, with extensions ‘.dir’ and ‘.pag’. These extensions will automatically be appended to the filename.
If the file does not exist, a new file will be created using the given mode, unless mode is explicitly set to nil. In the latter case, no database will be created.
If the file exists, it will be opened in read/write mode. If this fails, it will be opened in read-only mode.
static VALUE
fsdbm_s_open(int argc, VALUE *argv, VALUE klass)
{
VALUE obj = fsdbm_alloc(klass);
if (NIL_P(fsdbm_initialize(argc, argv, obj))) {
return Qnil;
}
if (rb_block_given_p()) {
return rb_ensure(rb_yield, obj, fsdbm_close, obj);
}
return obj;
}
If called without a block, this is the same as SDBM.new.
If a block is given, the new database will be passed to the block and will be safely closed after the block has executed.
Example:
require 'sdbm' SDBM.open('my_database') do |db| db['hello'] = 'world' end
static VALUE
fsdbm_aref(VALUE obj, VALUE keystr)
{
return fsdbm_fetch(obj, keystr, Qnil);
}
Returns the value in the database associated with the given key string.
If no value is found, returns nil.
static VALUE
fsdbm_store(VALUE obj, VALUE keystr, VALUE valstr)
{
datum key, val;
struct dbmdata *dbmp;
DBM *dbm;
if (valstr == Qnil) {
fsdbm_delete(obj, keystr);
return Qnil;
}
fdbm_modify(obj);
ExportStringValue(keystr);
ExportStringValue(valstr);
key.dptr = RSTRING_PTR(keystr);
key.dsize = RSTRING_LENINT(keystr);
val.dptr = RSTRING_PTR(valstr);
val.dsize = RSTRING_LENINT(valstr);
GetDBM2(obj, dbmp, dbm);
dbmp->di_size = -1;
if (sdbm_store(dbm, key, val, DBM_REPLACE)) {
#ifdef HAVE_DBM_CLAERERR
sdbm_clearerr(dbm);
#endif
if (errno == EPERM) rb_sys_fail(0);
rb_raise(rb_eDBMError, "sdbm_store failed");
}
return valstr;
}
Stores a new value in the database with the given key as an index.
If the key already exists, this will update the value associated with the key.
Returns the given value.
static VALUE
fsdbm_clear(VALUE obj)
{
datum key;
struct dbmdata *dbmp;
DBM *dbm;
fdbm_modify(obj);
GetDBM2(obj, dbmp, dbm);
dbmp->di_size = -1;
while (key = sdbm_firstkey(dbm), key.dptr) {
if (sdbm_delete(dbm, key)) {
rb_raise(rb_eDBMError, "sdbm_delete failed");
}
}
dbmp->di_size = 0;
return obj;
}
Deletes all data from the database.
static VALUE
fsdbm_close(VALUE obj)
{
struct dbmdata *dbmp;
GetDBM(obj, dbmp);
sdbm_close(dbmp->di_dbm);
dbmp->di_dbm = 0;
return Qnil;
}
Closes the database file.
Raises SDBMError if the database is already closed.
static VALUE
fsdbm_closed(VALUE obj)
{
struct dbmdata *dbmp;
TypedData_Get_Struct(obj, struct dbmdata, &sdbm_type, dbmp);
if (dbmp->di_dbm == 0)
return Qtrue;
return Qfalse;
}
Returns true if the database is closed.
static VALUE
fsdbm_delete(VALUE obj, VALUE keystr)
{
datum key, value;
struct dbmdata *dbmp;
DBM *dbm;
VALUE valstr;
fdbm_modify(obj);
ExportStringValue(keystr);
key.dptr = RSTRING_PTR(keystr);
key.dsize = RSTRING_LENINT(keystr);
GetDBM2(obj, dbmp, dbm);
dbmp->di_size = -1;
value = sdbm_fetch(dbm, key);
if (value.dptr == 0) {
if (rb_block_given_p()) return rb_yield(keystr);
return Qnil;
}
/* need to save value before sdbm_delete() */
valstr = rb_external_str_new(value.dptr, value.dsize);
if (sdbm_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;
}
Deletes the key-value pair corresponding to the given key. If the key exists, the deleted value will be returned, otherwise nil.
If a block is provided, the deleted key and value will be passed to the block as arguments. If the key does not exist in the database, the value will be nil.
static VALUE
fsdbm_delete_if(VALUE obj)
{
datum key, val;
struct dbmdata *dbmp;
DBM *dbm;
VALUE keystr, valstr;
VALUE ret, ary = rb_ary_new();
long i;
int status = 0, n;
fdbm_modify(obj);
GetDBM2(obj, dbmp, dbm);
n = dbmp->di_size;
dbmp->di_size = -1;
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
val = sdbm_fetch(dbm, key);
keystr = rb_external_str_new(key.dptr, key.dsize);
valstr = rb_external_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_LEN(ary); i++) {
keystr = RARRAY_AREF(ary, i);
ExportStringValue(keystr);
key.dptr = RSTRING_PTR(keystr);
key.dsize = RSTRING_LENINT(keystr);
if (sdbm_delete(dbm, key)) {
rb_raise(rb_eDBMError, "sdbm_delete failed");
}
}
if (status) rb_jump_tag(status);
if (n > 0) dbmp->di_size = n - RARRAY_LENINT(ary);
return obj;
}
Iterates over the key-value pairs in the database, deleting those for which the block returns true.
static VALUE
fsdbm_each_pair(VALUE obj)
{
datum key, val;
DBM *dbm;
struct dbmdata *dbmp;
VALUE keystr, valstr;
RETURN_ENUMERATOR(obj, 0, 0);
GetDBM2(obj, dbmp, dbm);
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
val = sdbm_fetch(dbm, key);
keystr = rb_external_str_new(key.dptr, key.dsize);
valstr = rb_external_str_new(val.dptr, val.dsize);
rb_yield(rb_assoc_new(keystr, valstr));
GetDBM2(obj, dbmp, dbm);
}
return obj;
}
Iterates over each key-value pair in the database.
If no block is given, returns an Enumerator.
static VALUE
fsdbm_each_key(VALUE obj)
{
datum key;
struct dbmdata *dbmp;
DBM *dbm;
RETURN_ENUMERATOR(obj, 0, 0);
GetDBM2(obj, dbmp, dbm);
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
rb_yield(rb_external_str_new(key.dptr, key.dsize));
GetDBM2(obj, dbmp, dbm);
}
return obj;
}
Iterates over each key in the database.
If no block is given, returns an Enumerator.
static VALUE
fsdbm_each_value(VALUE obj)
{
datum key, val;
struct dbmdata *dbmp;
DBM *dbm;
RETURN_ENUMERATOR(obj, 0, 0);
GetDBM2(obj, dbmp, dbm);
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
val = sdbm_fetch(dbm, key);
rb_yield(rb_external_str_new(val.dptr, val.dsize));
GetDBM2(obj, dbmp, dbm);
}
return obj;
}
Iterates over each value in the database.
If no block is given, returns an Enumerator.
static VALUE
fsdbm_empty_p(VALUE obj)
{
datum key;
struct dbmdata *dbmp;
DBM *dbm;
GetDBM(obj, dbmp);
if (dbmp->di_size < 0) {
dbm = dbmp->di_dbm;
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
return Qfalse;
}
}
else {
if (dbmp->di_size)
return Qfalse;
}
return Qtrue;
}
Returns true if the database is empty.
static VALUE
fsdbm_fetch_m(int argc, VALUE *argv, VALUE obj)
{
VALUE keystr, valstr, ifnone;
rb_scan_args(argc, argv, "11", &keystr, &ifnone);
valstr = fsdbm_fetch(obj, keystr, ifnone);
if (argc == 1 && !rb_block_given_p() && NIL_P(valstr))
rb_raise(rb_eIndexError, "key not found");
return valstr;
}
Returns the value in the database associated with the given key string.
If a block is provided, the block will be called when there is no value associated with the given key. The key will be passed in as an argument to the block.
If no block is provided and no value is associated with the given key, then an IndexError will be raised.
static VALUE
fsdbm_has_key(VALUE obj, VALUE keystr)
{
datum key, val;
struct dbmdata *dbmp;
DBM *dbm;
ExportStringValue(keystr);
key.dptr = RSTRING_PTR(keystr);
key.dsize = RSTRING_LENINT(keystr);
GetDBM2(obj, dbmp, dbm);
val = sdbm_fetch(dbm, key);
if (val.dptr) return Qtrue;
return Qfalse;
}
Returns true if the database contains the given key.
static VALUE
fsdbm_has_value(VALUE obj, VALUE valstr)
{
datum key, val;
struct dbmdata *dbmp;
DBM *dbm;
ExportStringValue(valstr);
val.dptr = RSTRING_PTR(valstr);
val.dsize = RSTRING_LENINT(valstr);
GetDBM2(obj, dbmp, dbm);
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
val = sdbm_fetch(dbm, key);
if (val.dsize == RSTRING_LENINT(valstr) &&
memcmp(val.dptr, RSTRING_PTR(valstr), val.dsize) == 0)
return Qtrue;
}
return Qfalse;
}
Returns true if the database contains the given value.
static VALUE
fsdbm_invert(VALUE obj)
{
datum key, val;
struct dbmdata *dbmp;
DBM *dbm;
VALUE keystr, valstr;
VALUE hash = rb_hash_new();
GetDBM2(obj, dbmp, dbm);
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
val = sdbm_fetch(dbm, key);
keystr = rb_external_str_new(key.dptr, key.dsize);
valstr = rb_external_str_new(val.dptr, val.dsize);
rb_hash_aset(hash, valstr, keystr);
}
return hash;
}
Returns a Hash in which the key-value pairs have been inverted.
Example:
require 'sdbm' SDBM.open 'my_database' do |db| db.update('apple' => 'fruit', 'spinach' => 'vegetable') db.invert #=> {"fruit" => "apple", "vegetable" => "spinach"} end
static VALUE
fsdbm_key(VALUE obj, VALUE valstr)
{
datum key, val;
struct dbmdata *dbmp;
DBM *dbm;
ExportStringValue(valstr);
val.dptr = RSTRING_PTR(valstr);
val.dsize = RSTRING_LENINT(valstr);
GetDBM2(obj, dbmp, dbm);
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
val = sdbm_fetch(dbm, key);
if (val.dsize == RSTRING_LEN(valstr) &&
memcmp(val.dptr, RSTRING_PTR(valstr), val.dsize) == 0)
return rb_external_str_new(key.dptr, key.dsize);
}
return Qnil;
}
Returns the key associated with the given value. If more than one key corresponds to the given value, then the first key to be found will be returned. If no keys are found, nil will be returned.
static VALUE
fsdbm_keys(VALUE obj)
{
datum key;
struct dbmdata *dbmp;
DBM *dbm;
VALUE ary;
GetDBM2(obj, dbmp, dbm);
ary = rb_ary_new();
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
rb_ary_push(ary, rb_external_str_new(key.dptr, key.dsize));
}
return ary;
}
Returns a new Array containing the keys in the database.
static VALUE
fsdbm_length(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 = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
i++;
}
dbmp->di_size = i;
return INT2FIX(i);
}
Returns the number of keys in the database.
static VALUE
fsdbm_reject(VALUE obj)
{
return rb_hash_delete_if(fsdbm_to_hash(obj));
}
Creates a new Hash using the key-value pairs from the database, then calls Hash#reject with the given block, which returns a Hash with only the key-value pairs for which the block returns false.
static VALUE
fsdbm_replace(VALUE obj, VALUE other)
{
fsdbm_clear(obj);
rb_block_call(other, rb_intern("each_pair"), 0, 0, update_i, obj);
return obj;
}
static VALUE
fsdbm_select(VALUE obj)
{
VALUE new = rb_ary_new();
datum key, val;
DBM *dbm;
struct dbmdata *dbmp;
GetDBM2(obj, dbmp, dbm);
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
VALUE assoc, v;
val = sdbm_fetch(dbm, key);
assoc = rb_assoc_new(rb_external_str_new(key.dptr, key.dsize),
rb_external_str_new(val.dptr, val.dsize));
v = rb_yield(assoc);
if (RTEST(v)) {
rb_ary_push(new, assoc);
}
GetDBM2(obj, dbmp, dbm);
}
return new;
}
Returns a new Array of key-value pairs for which the block returns true.
Example:
require 'sdbm' SDBM.open 'my_database' do |db| db['apple'] = 'fruit' db['pear'] = 'fruit' db['spinach'] = 'vegetable' veggies = db.select do |key, value| value == 'vegetable' end #=> [["apple", "fruit"], ["pear", "fruit"]] end
static VALUE
fsdbm_shift(VALUE obj)
{
datum key, val;
struct dbmdata *dbmp;
DBM *dbm;
VALUE keystr, valstr;
fdbm_modify(obj);
GetDBM2(obj, dbmp, dbm);
key = sdbm_firstkey(dbm);
if (!key.dptr) return Qnil;
val = sdbm_fetch(dbm, key);
keystr = rb_external_str_new(key.dptr, key.dsize);
valstr = rb_external_str_new(val.dptr, val.dsize);
sdbm_delete(dbm, key);
if (dbmp->di_size >= 0) {
dbmp->di_size--;
}
return rb_assoc_new(keystr, valstr);
}
Removes a key-value pair from the database and returns them as an Array. If the database is empty, returns nil.
static VALUE
fsdbm_to_a(VALUE obj)
{
datum key, val;
struct dbmdata *dbmp;
DBM *dbm;
VALUE ary;
GetDBM2(obj, dbmp, dbm);
ary = rb_ary_new();
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
val = sdbm_fetch(dbm, key);
rb_ary_push(ary, rb_assoc_new(rb_external_str_new(key.dptr, key.dsize),
rb_external_str_new(val.dptr, val.dsize)));
}
return ary;
}
Returns a new Array containing each key-value pair in the database.
Example:
require 'sdbm' SDBM.open 'my_database' do |db| db.update('apple' => 'fruit', 'spinach' => 'vegetable') db.to_a #=> [["apple", "fruit"], ["spinach", "vegetable"]] end
static VALUE
fsdbm_to_hash(VALUE obj)
{
datum key, val;
struct dbmdata *dbmp;
DBM *dbm;
VALUE hash;
GetDBM2(obj, dbmp, dbm);
hash = rb_hash_new();
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
val = sdbm_fetch(dbm, key);
rb_hash_aset(hash, rb_external_str_new(key.dptr, key.dsize),
rb_external_str_new(val.dptr, val.dsize));
}
return hash;
}
Returns a new Hash containing each key-value pair in the database.
static VALUE
fsdbm_update(VALUE obj, VALUE other)
{
rb_block_call(other, rb_intern("each_pair"), 0, 0, update_i, obj);
return obj;
}
static VALUE
fsdbm_values(VALUE obj)
{
datum key, val;
struct dbmdata *dbmp;
DBM *dbm;
VALUE ary;
GetDBM2(obj, dbmp, dbm);
ary = rb_ary_new();
for (key = sdbm_firstkey(dbm); key.dptr; key = sdbm_nextkey(dbm)) {
val = sdbm_fetch(dbm, key);
rb_ary_push(ary, rb_external_str_new(val.dptr, val.dsize));
}
return ary;
}
Returns a new Array containing the values in the database.
static VALUE
fsdbm_values_at(int argc, VALUE *argv, VALUE obj)
{
VALUE new = rb_ary_new2(argc);
int i;
for (i=0; i<argc; i++) {
rb_ary_push(new, fsdbm_fetch(obj, argv[i], Qnil));
}
return new;
}
Returns an Array of values corresponding to the given keys.