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Class: DBM

Relationships & Source Files
Super Chains via Extension / Inclusion / Inheritance
Instance Chain:
self, Enumerable
Inherits: Object
Defined in: ext/dbm/dbm.c

Overview

Introduction

The DBM class provides a wrapper to a Unix-style dbm or Database Manager library.

Dbm databases do not have tables or columns; they are simple key-value data stores, like a Ruby Hash except not resident in RAM. Keys and values must be strings.

The exact library used depends on how Ruby was compiled. It could be any of the following:

  • The original ndbm library is released in 4.3BSD. It is based on dbm library in Unix Version 7 but has different API to support multiple databases in a process.

  • Berkeley DB versions 1 thru 6, also known as BDB and Sleepycat DB, now owned by Oracle Corporation.

  • Berkeley DB 1.x, still found in 4.4BSD derivatives (FreeBSD, OpenBSD, etc).

  • / gdbm, the GNU implementation of dbm.

  • qdbm, another open source reimplementation of dbm.

All of these dbm implementations have their own Ruby interfaces available, which provide richer (but varying) APIs.

Cautions

Before you decide to use DBM, there are some issues you should consider:

  • Each implementation of dbm has its own file format. Generally, dbm libraries will not read each other's files. This makes dbm files a bad choice for data exchange.

  • Even running the same OS and the same dbm implementation, the database file format may depend on the CPU architecture. For example, files may not be portable between PowerPC and 386, or between 32 and 64 bit Linux.

  • Different versions of Berkeley DB use different file formats. A change to the OS may therefore break DBM access to existing files.

  • Data size limits vary between implementations. Original Berkeley DB was limited to 2GB of data. Dbm libraries also sometimes limit the total size of a key/value pair, and the total size of all the keys that hash to the same value. These limits can be as little as 512 bytes. That said, gdbm and recent versions of Berkeley DB do away with these limits.

Given the above cautions, DBM is not a good choice for long term storage of important data. It is probably best used as a fast and easy alternative to a Hash for processing large amounts of data.

Example

require 'dbm'
db = DBM.open('rfcs', 0666, DBM::WRCREAT)
db['822'] = 'Standard for the Format of ARPA Internet Text Messages'
db['1123'] = 'Requirements for Internet Hosts - Application and Support'
db['3068'] = 'An Anycast Prefix for 6to4 Relay Routers'
puts db['822']

Constant Summary

  • NEWDB =

    Indicates that dbm_open() should open the database in read/write mode, create it if it does not already exist, and delete all contents if it does already exist.

    # File 'ext/dbm/dbm.c', line 1108
    INT2FIX(O_RDWR|O_CREAT|O_TRUNC|RUBY_DBM_RW_BIT)
  • READER =

    Indicates that dbm_open() should open the database in read-only mode

    # File 'ext/dbm/dbm.c', line 1094
    INT2FIX(O_RDONLY|RUBY_DBM_RW_BIT)
  • VERSION =
    • “ndbm (4.3BSD)”

    • “Berkeley DB 4.8.30: (April 9, 2010)”

    • “Berkeley DB (unknown)” (4.4BSD, maybe)

    • “GDBM version 1.8.3. 10/15/2002 (built Jul 1 2011 12:32:45)”

    • “QDBM 1.8.78”

    # File 'ext/dbm/dbm.c', line 1154
    Identifies ndbm library version.
    
    Examples
  • WRCREAT =

    Indicates that dbm_open() should open the database in read/write mode, and create it if it does not already exist

    # File 'ext/dbm/dbm.c', line 1102
    INT2FIX(O_RDWR|O_CREAT|RUBY_DBM_RW_BIT)
  • WRITER =

    Indicates that dbm_open() should open the database in read/write mode

    # File 'ext/dbm/dbm.c', line 1097
    INT2FIX(O_RDWR|RUBY_DBM_RW_BIT)

Class Method Summary

Instance Attribute Summary

Instance Method Summary

Constructor Details

.new(filename[, mode[, flags]]) ⇒ DBM

Open a dbm database with the specified name, which can include a directory path. Any file extensions needed will be supplied automatically by the dbm library. For example, Berkeley DB appends '.db', and GNU gdbm uses two physical files with extensions '.dir' and '.pag'.

The mode should be an integer, as for Unix chmod.

Flags should be one of READER, WRITER, WRCREAT or NEWDB.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 143

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

    TypedData_Get_Struct(obj, struct dbmdata, &dbm_type, dbmp);
    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);

    FilePathValue(file);

    /*
     * Note:
     * gdbm 1.10 works with O_CLOEXEC.  gdbm 1.9.1 silently ignore it.
     */
#ifndef O_CLOEXEC
#   define O_CLOEXEC 0
#endif

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

    if (dbm) {
	/*
	 * History of dbm_pagfno() and dbm_dirfno() in ndbm and its compatibles.
	 * (dbm_pagfno() and dbm_dirfno() is not standardized.)
	 *
	 * 1986: 4.3BSD provides ndbm.
	 *       It provides dbm_pagfno() and dbm_dirfno() as macros.
	 * 1991: gdbm-1.5 provides them as functions.
	 *       They returns a same descriptor.
	 *       (Earlier releases may have the functions too.)
	 * 1991: Net/2 provides Berkeley DB.
	 *       It doesn't provide dbm_pagfno() and dbm_dirfno().
	 * 1992: 4.4BSD Alpha provides Berkeley DB with dbm_dirfno() as a function.
	 *       dbm_pagfno() is a macro as DBM_PAGFNO_NOT_AVAILABLE.
	 * 1997: Berkeley DB 2.0 is released by Sleepycat Software, Inc.
	 *       It defines dbm_pagfno() and dbm_dirfno() as macros.
	 * 2011: gdbm-1.9 creates a separate dir file.
	 *       dbm_pagfno() and dbm_dirfno() returns different descriptors.
	 */
#if defined(HAVE_DBM_PAGFNO)
        rb_fd_fix_cloexec(dbm_pagfno(dbm));
#endif
#if defined(HAVE_DBM_DIRFNO)
        rb_fd_fix_cloexec(dbm_dirfno(dbm));
#endif

#if defined(RUBYDBM_DB_HEADER) && defined(HAVE_TYPE_DBC)
	/* Disable Berkeley DB error messages such as:
	 * DB->put: attempt to modify a read-only database */
        ((DBC*)dbm)->dbp->set_errfile(((DBC*)dbm)->dbp, NULL);
#endif
    }

    if (!dbm) {
	if (mode == -1) return Qnil;
	rb_sys_fail_str(file);
    }

    if (dbmp->di_dbm)
	dbm_close(dbmp->di_dbm);
    dbmp->di_dbm = dbm;
    dbmp->di_size = -1;

    return obj;
}

Class Method Details

.open(filename[, mode[, flags]]) ⇒ DBM .open(filename[, mode[, flags]]) {|dbm| ... }

Open a dbm database and yields it if a block is given. See also .new.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 246

static VALUE
fdbm_s_open(int argc, VALUE *argv, VALUE klass)
{
    VALUE obj = fdbm_alloc(klass);

    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;
}

Instance Attribute Details

#closed?Boolean (readonly)

Returns true if the database is closed, false otherwise.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 110

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

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

    return Qfalse;
}

#empty?Boolean (readonly)

Returns true if the database is empty, false otherwise.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 706

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

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

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

Instance Method Details

#[](key) ⇒ string value?

Return a value from the database by locating the key string provided. If the key is not found, returns nil.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 296

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

#store(key, value) ⇒ value #[]=(key, value)
Also known as: #store

Stores the specified string value in the database, indexed via the string key provided.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 646

static VALUE
fdbm_store(VALUE obj, VALUE keystr, VALUE 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_PTR(keystr);
    key.dsize = RSTRING_DSIZE(keystr);

    val.dptr = RSTRING_PTR(valstr);
    val.dsize = RSTRING_DSIZE(valstr);

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

    return valstr;
}

#clear

Deletes all data from the database.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 546

static VALUE
fdbm_clear(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;
}

#close

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 92

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

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

    return Qnil;
}

#delete(key)

Deletes an entry from the database.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 422

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

    fdbm_modify(obj);
    ExportStringValue(keystr);
    len = RSTRING_LEN(keystr);
    if (TOO_LONG(len)) goto not_found;
    key.dptr = RSTRING_PTR(keystr);
    key.dsize = (DSIZE_TYPE)len;

    GetDBM2(obj, dbmp, dbm);

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

    /* need to save value before dbm_delete() */
    valstr = rb_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;
}

#reject! {|key, value| ... } ⇒ self #delete_if {|key, value| ... } ⇒ self

Alias for #reject!.

#each_pair {|key, value| ... } ⇒ self Also known as: #each_pair

Calls the block once for each [key, value] pair in the database. Returns self.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 782

static VALUE
fdbm_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 = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	keystr = rb_str_new(key.dptr, key.dsize);
	valstr = rb_str_new(val.dptr, val.dsize);
	rb_yield(rb_assoc_new(keystr, valstr));
	GetDBM2(obj, dbmp, dbm);
    }

    return obj;
}

#each_key {|key| ... } ⇒ self

Calls the block once for each key string in the database. Returns self.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 758

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

    RETURN_ENUMERATOR(obj, 0, 0);

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

#each_pair {|key, value| ... } ⇒ self #each_pair {|key, value| ... } ⇒ self

Alias for #each.

#each_value {|value| ... } ⇒ self

Calls the block once for each value string in the database. Returns self.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 734

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

    RETURN_ENUMERATOR(obj, 0, 0);

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

#fetch(key[, ifnone]) ⇒ value

Return a value from the database by locating the key string provided. If the key is not found, returns ifnone. If ifnone is not given, raises IndexError.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 310

static VALUE
fdbm_fetch_m(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;
}

#include?(key) ⇒ Boolean #has_key?(key) ⇒ Boolean #member?(key) ⇒ Boolean #key?(key) ⇒ Boolean

Alias for #key?.

#has_value?(value) ⇒ Boolean #value?(value) ⇒ Boolean

Alias for #value?.

#include?(key) ⇒ Boolean #has_key?(key) ⇒ Boolean #member?(key) ⇒ Boolean #key?(key) ⇒ Boolean

Alias for #key?.

#index(value)

This method is for internal use only.
[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 353

static VALUE
fdbm_index(VALUE hash, VALUE value)
{
    rb_warn("DBM#index is deprecated; use DBM#key");
    return fdbm_key(hash, value);
}

#invertHash

Returns a Hash (not a DBM database) created by using each value in the database as a key, with the corresponding key as its value.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 573

static VALUE
fdbm_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 = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	keystr = rb_str_new(key.dptr, key.dsize);
	valstr = rb_str_new(val.dptr, val.dsize);
	rb_hash_aset(hash, valstr, keystr);
    }
    return hash;
}

#key(value) ⇒ String

Returns the key for the specified value.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 329

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

    ExportStringValue(valstr);
    len = RSTRING_LEN(valstr);
    if (TOO_LONG(len)) return Qnil;

    GetDBM2(obj, dbmp, dbm);
    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	if ((long)val.dsize == RSTRING_LEN(valstr) &&
	    memcmp(val.dptr, RSTRING_PTR(valstr), val.dsize) == 0) {
	    return rb_str_new(key.dptr, key.dsize);
	}
    }
    return Qnil;
}

#include?(key) ⇒ Boolean #has_key?(key) ⇒ Boolean #member?(key) ⇒ Boolean #key?(key) ⇒ Boolean
Also known as: #include?, #has_key?, #member?

Returns true if the database contains the specified key, false otherwise.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 862

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

    ExportStringValue(keystr);
    len = RSTRING_LEN(keystr);
    if (TOO_LONG(len)) return Qfalse;
    key.dptr = RSTRING_PTR(keystr);
    key.dsize = (DSIZE_TYPE)len;

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

#keysArray

Returns an array of all the string keys in the database.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 811

static VALUE
fdbm_keys(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_str_new(key.dptr, key.dsize));
    }

    return ary;
}

#lengthInteger #sizeInteger
Also known as: #size

Returns the number of entries in the database.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 681

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

    return INT2FIX(i);
}

#include?(key) ⇒ Boolean #has_key?(key) ⇒ Boolean #member?(key) ⇒ Boolean #key?(key) ⇒ Boolean

Alias for #key?.

#reject {|key, value| ... } ⇒ Hash

Converts the contents of the database to an in-memory Hash, then calls Hash#reject with the specified code block, returning a new Hash.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 973

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

#reject! {|key, value| ... } ⇒ self #delete_if {|key, value| ... } ⇒ self
Also known as: #delete_if

Deletes all entries for which the code block returns true. Returns self.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 498

static VALUE
fdbm_delete_if(VALUE obj)
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;
    VALUE keystr, valstr;
    VALUE ret, ary = rb_ary_tmp_new(0);
    int status = 0;
    long i, 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_str_new(key.dptr, key.dsize);
	OBJ_FREEZE(keystr);
	valstr = rb_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);
	key.dptr = RSTRING_PTR(keystr);
	key.dsize = (DSIZE_TYPE)RSTRING_LEN(keystr);
	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_LEN(ary);
    rb_ary_clear(ary);

    return obj;
}

#replace(obj)

Replaces the contents of the database with the contents of the specified object. Takes any object which implements the each_pair method, including Hash and DBM objects.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 630

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

#select {|key, value| ... } ⇒ Array

Returns a new array consisting of the [key, value] pairs for which the code block returns true.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 367

static VALUE
fdbm_select(VALUE obj)
{
    VALUE new = rb_ary_new();
    datum key, val;
    DBM *dbm;
    struct dbmdata *dbmp;

    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_str_new(key.dptr, key.dsize),
			     rb_str_new(val.dptr, val.dsize));
	v = rb_yield(assoc);
	if (RTEST(v)) {
	    rb_ary_push(new, assoc);
	}
	GetDBM2(obj, dbmp, dbm);
    }

    return new;
}

#shiftArray, value

Removes a [key, value] pair from the database, and returns it. If the database is empty, returns nil. The order in which values are removed/returned is not guaranteed.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 468

static VALUE
fdbm_shift(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_str_new(key.dptr, key.dsize);
    valstr = rb_str_new(val.dptr, val.dsize);
    dbm_delete(dbm, key);

    return rb_assoc_new(keystr, valstr);
}

#lengthInteger #sizeInteger

Alias for #length.

#store(key, value) ⇒ value #[]=(key, value)

Alias for #[]=.

#to_aArray

Converts the contents of the database to an array of [key, value] arrays, and returns it.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 921

static VALUE
fdbm_to_a(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_str_new(key.dptr, key.dsize),
				      rb_str_new(val.dptr, val.dsize)));
    }

    return ary;
}

#to_hashHash

Converts the contents of the database to an in-memory Hash object, and returns it.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 947

static VALUE
fdbm_to_hash(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_str_new(key.dptr, key.dsize),
		           rb_str_new(val.dptr, val.dsize));
    }

    return hash;
}

#update(obj)

Updates the database with multiple values from the specified object. Takes any object which implements the each_pair method, including Hash and DBM objects.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 615

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

#has_value?(value) ⇒ Boolean #value?(value) ⇒ Boolean
Also known as: #has_value?

Returns true if the database contains the specified string value, false otherwise.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 890

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

    ExportStringValue(valstr);
    len = RSTRING_LEN(valstr);
    if (TOO_LONG(len)) return Qfalse;
    val.dptr = RSTRING_PTR(valstr);
    val.dsize = (DSIZE_TYPE)len;

    GetDBM2(obj, dbmp, dbm);
    for (key = dbm_firstkey(dbm); key.dptr; key = dbm_nextkey(dbm)) {
	val = dbm_fetch(dbm, key);
	if ((DSIZE_TYPE)val.dsize == (DSIZE_TYPE)RSTRING_LEN(valstr) &&
	    memcmp(val.dptr, RSTRING_PTR(valstr), val.dsize) == 0)
	    return Qtrue;
    }
    return Qfalse;
}

#valuesArray

Returns an array of all the string values in the database.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 835

static VALUE
fdbm_values(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_str_new(val.dptr, val.dsize));
    }

    return ary;
}

#values_at(key, ...) ⇒ Array

Returns an array containing the values associated with the given keys.

[ GitHub ]

  
# File 'ext/dbm/dbm.c', line 397

static VALUE
fdbm_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, fdbm_fetch(obj, argv[i], Qnil));
    }

    return new;
}