Kamaelia.ReadFileAdaptor.ReadFileAdaptor

class ReadFileAdaptor(Axon.Component.component)

An instance of this class is a read file adaptor component. It's constructor arguments are all optional. If no arguments are provided, then the default is to read from stdin, one line at a time, as fast as possible. Note that this will cause the outbox to fill at the same rate as stdin can provide data. (Be wary of memory constraints this will cause!)

Arguments & meaning:

filename="filename" - the name of the file to read. If you want stdin, do not provide a filename! If you want the output from a command, also leave this blank...
command="command" - the name of the command you want the output from. Leave the filename blank if you use this!
readmode - possible values:

"bitrate" - read at a specified bitrate. "line" - read on a line by line basis "block" - read the file on a block by block basis.
If bitrate mode is set, you should set bitrate= to your desired bitrate (unless you want 64Kbit/s), and chunkrate= to your desired chunkrate (unless you want 24 fps). You are expected to be able to handle the bit rate you request!
If block mode is set then you should set readsize (size of the block in bytes), and steptime (how often you want bytes). If steptime is set to zero, you will read blocks at the speed the source device can provide them. (be wary of memory constraints)

After setting the ReadFileAdaptor in motion, you can then hook it into your linkages like any other component.

Its interfaces are:

inboxes=["inbox"] - not actually read at present
outboxes=["outbox"]) - When data is read, it is made available here.

Inboxes

control : Secondary inbox often used for signals. The closest analogy is unix signals
inbox : Default inbox for bulk data. Used in a pipeline much like stdin

Outboxes

outbox : Default data out outbox, used in a pipeline much like stdout
signal : The default signal based outbox - kinda like stderr, but more for sending singal type signals

Methods defined here

Warning!

You should be using the inbox/outbox interface, not these methods (except construction). This documentation is designed as a roadmap as to their functionalilty for maintainers and new component developers.

init(self, filename, command, readmode, readsize, steptime, bitrate, chunkrate, debug)

Standard constructor, see class docs for details

closeDownComponent(self)

#!!!! Called at component exit...: Closes the file handle

getDataByteLen(self)

This method attempts to read data of a specific block size from: the file handle. If null, the file is EOF. This method is never called directly. If the readmode is block or bitrate, then the attribute self.getData is set to this function, and then this function is called using self.getData(). The reason for this indirection is to make it so that the check for which readmode we are in is done once, and once only

getDataReadline(self)

This method attempts to read a line of data from the file handle.: If null, the file is EOF. As with getDataByteLen, this method is never called directly. If the readmode is readline (or ""), then the attribute self.getData is set to this function, and then this function is called using self.getData(). Same reason for indirection as above.

initialiseComponent(self)

Opens the appropriate file handle

mainBody(self)

We check whether it's time to perform a new read, if it is, we: read some data. If we get some data, we put it in out outbox "outbox", and to stdout (if debugging). If we had an error state (eg EOF), we return 0, stopping this component, otherwise we return 1 to live for another line/block.

Feedback

Got a problem with the documentation? Something unclear, could be clearer? Want to help with improving? Constructive criticism, preferably in the form of suggested rewording is very welcome.

Please leave the feedback here, in reply to the documentation thread in the Kamaelia blog.

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