# class DBM

## 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']

### Constants

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.

READER

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

VERSION

  Identifies ndbm library version.

  Examples:

  - “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”

WRCREAT

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

WRITER

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

### Public Class Methods

new(filename[, mode[, flags]]) → dbm click to toggle source

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`.

    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;
    }

open(filename[, mode[, flags]]) → dbm click to toggle source
open(filename[, mode[, flags]]) {|dbm| block}

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

    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;
    }

### Public Instance Methods

dbm[key] → string value or nil click to toggle source

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

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

dbm[key] = value click to toggle source

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

    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 click to toggle source

Deletes all data from the database.

    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 click to toggle source

Closes the database.

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

        GetDBM(obj, dbmp);
        dbm_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, false otherwise.

    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;
    }

delete(key) click to toggle source

Deletes an entry from the database.

    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;
    }

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

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

    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;
    }

each_pair {|key,value| block} → self click to toggle source

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

    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| block} → self click to toggle source

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

    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| block} → self click to toggle source

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

    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_value {|value| block} → self click to toggle source

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

    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;
    }

empty? click to toggle source

Returns true if the database is empty, false otherwise.

    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;
    }

fetch(key[, ifnone]) → value click to toggle source

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`.

    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;
    }

has_key?(key) → boolean click to toggle source

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

    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;
    }

has_value?(value) → boolean click to toggle source

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

    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;
    }

include?(key) → boolean click to toggle source

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

    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;
    }

invert → hash click to toggle source

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.

    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 click to toggle source

Returns the key for the specified value.

    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;
    }

key?(key) → boolean click to toggle source

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

    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;
    }

keys → array click to toggle source

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

    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;
    }

length → integer click to toggle source

Returns the number of entries in the database.

    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);
    }

member?(key) → boolean click to toggle source

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

    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;
    }

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

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

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

reject! {|key, value| block} → self click to toggle source

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

    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) click to toggle source

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.

    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| block} → array click to toggle source

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

    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;
    }

shift() → [key, value] click to toggle source

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.

    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);
    }

size → integer click to toggle source

Returns the number of entries in the database.

    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);
    }

store(key, value) → value click to toggle source

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

    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;
    }

to_a → array click to toggle source

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

    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_hash → hash click to toggle source

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

    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) click to toggle source

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

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

value?(value) → boolean click to toggle source

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

    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;
    }

values → array click to toggle source

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

    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 click to toggle source

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

    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;
    }