Specification of QDBM for Perl

Copyright (C) 2000-2003 Mikio Hirabayashi
Last Update: Sun, 04 May 2003 07:11:37 +0900
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Table of Contents

  1. Overview
  2. Installation
  3. Examples
  4. Bugs

Overview

QDBM provides API for Perl. This encapsulates the basic API and the extended API of QDBM. These APIs are implemented with the APIs for C called with XS language. There are two kinds of interfaces to handle a database: using methods directly and using tying functions with a hash.

In case of using methods, you call the constructor `new' of the class `Depot' or `Curia' to open a database file or directory and get the handle. The method `close' is used in order to close the database. If the instance is destroyed without closing the database explicitly, the destructor closes the database. The method `put' is used in order to store a record. The method `out' is used in order to delete a record. The method `get' is used in order to retrieve a record. Besides, most operations like ones of the basic API and the extended API for C is available.

Although keys and values of storing records are treated as strings, binary data can be stored as they are. `Depot' realizes a database with a file. `Curia' realizes a database with a directory and multiple files. Although the formar is faster, the latter is more scalable.

In case of using tying functions, you call the `tie' function whose parameter is the same as ones of the constructor. After tying, operations with the tied hash perform as operations to the binded database. You use the `untie' function to close the database.

For more information about the APIs, read documents in the sub directory `papidoc'.


Installation

Make sure that Perl 5.6.0 or later version is installed and make sure that QDBM is installed under `/usr/local'.

Change the current working directory to the subdirectory named `perl'.

cd perl

Run the configuration script.

./configure

Build programs.

make

Perform self-diagnostic test.

make check

Install programs. This operation must be carried out by the root user.

make install

When a series of work finishes, `Depot.so', `Depot.pm', `Curia.so', `Curia.pm' and so on are installed under an appropriate directory according to the install directory of Perl. Executable commands `pdptest' and `pcrtest' will be installed in `/usr/local/bin'.


Examples

The following example stores and retrieves a phone number, using the name as the key.

use Depot;

use constant NAME => "mikio";
use constant NUMBER => "000-1234-5678";
use constant DBNAME => "book";

sub main {
    my($depot, $val);

    # open the record
    if(!($depot = new Depot(&DBNAME, Depot::OWRITER | Depot::OCREAT))){
        printf(STDERR "new failed: %s\n", $Depot::errmsg);
        return 1;
    }

    # store the record
    if(!$depot->put(&NAME, &NUMBER)){
        printf(STDERR "put failed: %s\n", $Depot::errmsg);
    }

    # retrieve the record
    if(!($val = $depot->get(&NAME))){
        printf(STDERR "get failed: %s\n", $Depot::errmsg);
    } else {
        printf("Name: %s\n", &NAME);
        printf("Number: %s\n", $val);
    }

    # close the database
    if(!$depot->close()){
        printf(STDERR "close failed: %s\n", $Depot::errmsg);
        return 1;
    }

    return 0;
}

exit(main());

The following example is a transcription of the one above, using tying functions.

use Depot;

use constant NAME => "mikio";
use constant NUMBER => "000-1234-5678";
use constant DBNAME => "book";

sub main {
    my(%hash, $val);

    # open the database
    if(!tie(%hash, "Depot", &DBNAME, Depot::OWRITER | Depot::OCREAT)){
        printf(STDERR "tie failed: %s\n", $Depot::errmsg);
        return 1;
    }

    # store the record
    if(!($hash{&NAME} = &NUMBER)){
        printf(STDERR "store failed: %s\n", $Depot::errmsg);
    }

    # retrieve the record
    if(!($val = $hash{&NAME})){
        printf(STDERR "fetch failed: %s\n", $Depot::errmsg);
    } else {
        printf("Name: %s\n", &NAME);
        printf("Number: %s\n", $val);
    }

    # close the record
    if(!untie(%hash)){
        printf(STDERR "untie failed: %s\n", $Depot::errmsg);
        return 1;
    }

    return 0;
}

exit(main());

Bugs

So far, this API is not associated with AnyDBM_File.

This API can be implemented more effectively by Perl hackers.

For the sake of simplicity of interface, Curia for Perl does not feature handling large objects.