Last Updated: 9/25/2001

A_TempFile

Purpose

License

Description

Dependencies

Limitations

Performance Considerations

To Do

Usage

Class Methods

Instance Methods

Testing

A_Debug Usage

 

Purpose:

You can export values into this class and then iterate over those values. This works exactly like an Array except when the specified amount of memory is used up the values are written to disk. If the all data fits in the specified memory size, then this class works exactly like an Array. The class was created to allow my to put large amounts of data from the A_BTree, A_Table, and A_Index classes and then iterate over them. This class takes into account the fact that all the data may not fit in memory.

 

Description:

The temporary file used will have an extension of .tmp. This is a rows in, rows out kind of class. The rows are returned in the exact same order they are put in. If you want to order the data, see the A_FileSort class.

 

Dependencies:

• a_debug.rb - this provides debugging messages for all of my Ruby code. See a_debug.html for more details.

 

Limitations:

• None

 

Performance Considerations:

• If you have a lot of memory to spare, set the buffer size to a much larger value like 32M. Please keep in mind that a multi-user system supporting ArunaDB, there could be several of these and other large memory consuming classes currently being used. The amount of memory to use for sorting is dependent to how much memory you have and how many users are connected at the same time.

 

To Do:

• I would like to rewrite this use the A_Buffer class rather than the Array class.
• Add support for multiple out files in multiple directories.

 

 Usage:

tmp = A_TempFile.new()

tmp.write(['hello world', 'Test this 1', 2])

tmp.write(['hello world3', 'Test this 1', 2])

tmp.write(['hello world', 'Test this 3', 2])

tmp.each {|data| print "#{data.join(',')}\n"}

tmp.close()

 

Class Methods:

A_TempFile.version()

Returns the version of this class.

A_TempFile.buffer_size=(new_size)

Allows you set the memory size in bytes of the buffer. This value is used to determine if the buffer is full and should written to disk. This value applies to all temp files. The default value is 500K.

A_TempFile.buffer_size()

Returns the currently defined size of the buffer used for temp files.

A_TempFile.new(path=nil)

Creates a new object.

• path - is the path where the temp file is created. '/tmp' is the default.

 

Instance Methods:

close()

Close this temp file and all opened temporary files.

each()

Iterate over all rows in the temp file. Yields(data).

write(data)

Write this data to the temp file.

• data - can be any Ruby object that works with Marshal.dump and Marshal.load.

 

Testing: 

tst_a_tempfile.rb - this script performs basic testing for the A_TempFile class. To run this tests type:

ruby -I.. tst_a_tempfile.rb

 

A_Debug Usage:

7 - prints high level stuff like creating and opening an A_TempFile object

71 - prints information about reading and writing blocks of data to and from disk.