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<title>Specifications of QDBM for Ruby</title>
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<h1>Specifications of QDBM for Ruby</h1>
<div class="note">Copyright (C) 2000-2006 Mikio Hirabayashi</div>
<div class="note">Last Update: Thu, 26 Oct 2006 15:00:20 +0900</div>
<div class="navi">[<a href="rbapidoc/index.html">API</a>] [<a href="rbspex-ja.html" hreflang="ja">Japanese</a>]</div>
<hr />
<h2>Table of Contents</h2>
<ol>
<li><a href="#overview">Overview</a></li>
<li><a href="#installation">Installation</a></li>
<li><a href="#examples">Examples</a></li>
<li><a href="#bugs">Bugs</a></li>
</ol>
<hr />
<h2><a name="overview" id="overview" class="head">Overview</a></h2>
<p>QDBM provides API for Ruby. This encapsulates the basic API, the extended API and the advanced API of QDBM. These APIs are safe on multi thread environment of Ruby.</p>
<p>You call the constructor `new' of the class `Depot', `Curia' or `Villa' to open a database file or directory and get the handle. The method `close' is used in order to close the database. Although a finalizer is not used, an iterator of `new' method save you from neglecting to call `close'. 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 APIs for C are available. Each class has class constants which are `EANY' and its sub classes. They are thrown when each method fails.</p>
<p>Because these classes perform Mix-in of the module `Enumerable', you can use such methods as `find', `sort', and so on. Moreover, they implements such methods: `[]=', `[]', and so on like the class `Hash', you can use a database like a usual hash.</p>
<p>Although keys and values of storing records are treated as strings, binary data can be stored as they are. But, `Villa' can store any serializable and comparable objects. `Depot' realizes a hash database with a file. `Curia' realizes a hash database with a directory and multiple files. `Villa' realizes a B+ tree database with a file. `Depot' is fastest. `Curia' is most scalable. `Villa' provides cursor supporting ordering access.</p>
<p>When `put' overwriting an existing record is cancelled or `get' retrieving a missing record, failure of the operation is noticed by exception. If you dislike such behavior, set the `silent' flag to be true. Then, failure of the operation is noticed by the return value.</p>
<p>For more information about the APIs, read documents in the sub directory `<a href="rbapidoc/">rbapidoc</a>'.</p>
<hr />
<h2><a name="installation" id="installation" class="head">Installation</a></h2>
<p>Make sure that Ruby 1.6.5 or later version is installed and make sure that QDBM is installed under `/usr/local'.</p>
<p>Change the current working directory to the sub directory named `ruby'.</p>
<pre>cd ruby
</pre>
<p>Run the configuration script.</p>
<pre>./configure
</pre>
<p>Build programs.</p>
<pre>make
</pre>
<p>Perform self-diagnostic test.</p>
<pre>make check
</pre>
<p>Install programs. This operation must be carried out by the root user.</p>
<pre>make install
</pre>
<p>When a series of work finishes, `depot.rb', `mod_depot.so', `curia.rb', `mod_curia.so', `villa.rb', `mod_villa.so', and so on are installed under an appropriate directory according to the install directory of Ruby. Executable commands `rbdptest', `rbcrtest', and `rbvltest' will be installed in `/usr/local/bin'.</p>
<p>To uninstall them, execute the following command after `./configure'. This operation must be carried out by the root user.</p>
<pre>make uninstall
</pre>
<hr />
<h2><a name="examples" id="examples" class="head">Examples</a></h2>
<p>The following example stores and retrieves a phone number, using the name as the key.</p>
<pre>require 'depot'
NAME = "mikio"
NUMBER = "000-1234-5678"
DBNAME = "book"
def main
depot = nil
begin
# open the database
depot = Depot::new(DBNAME, Depot::OWRITER | Depot::OCREAT)
# store the record
depot.put(NAME, NUMBER)
# retrieve the record
printf("Name: %s\n", NAME)
printf("Number: %s\n", depot.get(NAME))
rescue Depot::EANY
printf("%s\n", $!)
return 1
ensure
# close the database
if(depot)
begin
depot.close()
rescue Depot::EANY
printf("%s\n", $!)
end
end
end
return 0
end
exit(main());
</pre>
<p>The following example is a transcription of the one above, using hash-like interface and iterator.</p>
<pre>require 'depot'
NAME = "mikio"
NUMBER = "000-1234-5678"
DBNAME = "book"
def main
begin
# open the database and close it automatically
Depot::new(DBNAME, Depot::OWRITER | Depot::OCREAT) do |depot|
# store the record
depot[NAME] = NUMBER
# retrieve the record
printf("Name: %s\n", NAME)
printf("Number: %s\n", depot[NAME])
end
rescue Depot::EANY
printf("%s\n", $!)
return 1
end
return 0
end
exit(main());
</pre>
<p>The following example performs forward matching search for strings, using the class `Villa'.</p>
<pre>require 'villa'
DBNAME = "words"
PREFIX = "apple"
def main
begin
# open the database and close it automatically
Villa::new(DBNAME, Villa::OWRITER | Villa::OCREAT) do |villa|
# store records
villa.put("applet", "little application", Villa::DDUP)
villa.put("aurora", "polar wonderwork", Villa::DDUP)
villa.put("apple", "delicious fruit", Villa::DDUP)
villa.put("amigo", "good friend", Villa::DDUP)
villa.put("apple", "big city", Villa::DDUP)
begin
# set the cursor at the top of candidates
villa.curjump(PREFIX)
# scan with the cursor
while(true)
key = villa.curkey()
(key.index(PREFIX) == 0) || break
val = villa.curval()
printf("%s: %s\n", key, val)
villa.curnext()
end
rescue Villa::ENOITEM
end
end
rescue Villa::EANY
printf("%s\n", $!)
return 1
end
return 0
end
exit(main());
</pre>
<hr />
<h2><a name="bugs" id="bugs" class="head">Bugs</a></h2>
<p>This API are subtly different from the interface of standard library `DBM'.</p>
<p>This API can be implemented more effectively by Ruby hackers.</p>
<p>For the sake of simplicity of interface, Curia for Ruby does not feature handling large objects.</p>
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