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)
{
volatile VALUE file;
VALUE vmode;
DBM *dbm;
struct dbmdata *dbmp;
int mode;
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);
}
dbmp = ALLOC(struct dbmdata);
DATA_PTR(obj) = dbmp;
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 == 0)
return Qtrue;
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.