class SDBM

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

Public Class Methods

new(filename, mode = 0666) click to toggle source

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_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;
}

open(filename, mode = 0666) click to toggle source

open(filename, mode = 0666) { |sdbm| ... }

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_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;
}

Public Instance Methods

sdbm[key] → value or nil click to toggle source

Returns the value in the database associated with the given key string.

If no value is found, returns nil.

static VALUE
fsdbm_aref(VALUE obj, VALUE keystr)
{
    return fsdbm_fetch(obj, keystr, Qnil);
}

sdbm[key] = value → value click to toggle source

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_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;
}

Also aliased as: store

clear → self click to toggle source

Deletes all data from the database.

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;
}

close → nil click to toggle source

Closes the database file.

Raises SDBMError if the database is already closed.

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

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

    return Qnil;
}

closed? → true or false click to toggle source

Returns true if the database is 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;
}

delete(key) → value or nil click to toggle source

delete(key) { |key, value| ... }

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(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;
}

delete_if { |key, value| ... } → self click to toggle source

Iterates over the key-value pairs in the database, deleting those for which the block returns true.

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;
}

Also aliased as: reject!

each click to toggle source

each { |key, value| ... }

Iterates over each key-value pair in the database.

If no block is given, returns an Enumerator.

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;
}

Also aliased as: each_pair

each_key click to toggle source

each_key { |key| ... }

Iterates over each key 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;
}

each_pair()

Iterates over each key-value pair in the database.

If no block is given, returns an Enumerator.

Alias for: each

each_value click to toggle source

each_value { |value| ... }

Iterates over each value 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;
}

empty? → true or false click to toggle source

Returns true if the database is empty.

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;
}

fetch(key) → value or nil click to toggle source

fetch(key) { |key| ... }

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_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;
}

has_key?(key) → true or false click to toggle source

Returns true if the database contains the given key.

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;
}

Also aliased as: include?, key?, member?

has_value?(key) → true or false click to toggle source

Returns true if the database contains the given value.

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;
}

Also aliased as: value?

include?(key) → true or false

Returns true if the database contains the given key.

Alias for: has_key?

invert → Hash click to toggle source

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_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;
}

key(value) → key click to toggle source

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_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;
}

key?(key) → true or false

Returns true if the database contains the given key.

Alias for: has_key?

keys → Array click to toggle source

Returns a new Array containing the keys in the database.

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;
}

length → integer click to toggle source

Returns the number of 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);
}

Also aliased as: size

member?(key) → true or false

Returns true if the database contains the given key.

Alias for: has_key?

reject { |key, value| ... } → Hash click to toggle source

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_reject(VALUE obj)
{
    return rb_hash_delete_if(fsdbm_to_hash(obj));
}

reject! { |key, value| ... } → self

Iterates over the key-value pairs in the database, deleting those for which the block returns true.

Alias for: delete_if

replace(pairs) → self click to toggle source

Empties the database, then inserts the given key-value pairs.

This method will work with any object which implements an each_pair method, such as a Hash.

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;
}

select { |key, value| ... } → Array click to toggle source

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_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;
}

shift → Array or nil click to toggle source

Removes a key-value pair from the database and returns them as an Array. If the database is empty, returns nil.

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);
}

size → integer

Returns the number of keys in the database.

Alias for: length

store(key, value) → value

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.

Alias for: []=

to_a → Array click to toggle source

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_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;
}

to_hash → Hash click to toggle source

Returns a new Hash containing each key-value pair in the database.

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;
}

update(pairs) → self click to toggle source

Insert or update key-value pairs.

This method will work with any object which implements an each_pair method, such as a Hash.

static VALUE
fsdbm_update(VALUE obj, VALUE other)
{
    rb_block_call(other, rb_intern("each_pair"), 0, 0, update_i, obj);
    return obj;
}

value?(key) → true or false

Returns true if the database contains the given value.

Alias for: has_value?

values → Array click to toggle source

Returns a new Array containing the values in the database.

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;
}

values_at(key, ...) → Array click to toggle source

Returns an Array of values corresponding to the given keys.

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;
}