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.
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.
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.
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.
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.
For more information about the APIs, read documents in the sub directory `rbapidoc'.
Make sure that Ruby 1.6.5 or later version is installed and make sure that QDBM is installed under `/usr/local'.
Change the current working directory to the sub directory named `ruby'.
cd ruby
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.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'.
To uninstall them, execute the following command after `./configure'. This operation must be carried out by the root user.
make uninstall
The following example stores and retrieves a phone number, using the name as the key.
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());
The following example is a transcription of the one above, using hash-like interface and iterator.
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());
The following example performs forward matching search for strings, using the class `Villa'.
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());
This API are subtly different from the interface of standard library `DBM'.
This API can be implemented more effectively by Ruby hackers.
For the sake of simplicity of interface, Curia for Ruby does not feature handling large objects.