task_share.Share Class Reference

An item which holds data to be shared between tasks. More...

Inheritance diagram for task_share.Share:

Public Member Functions
	__init__ (self, type_code, thread_protect=True, name=None)
	Create a shared data item used to transfer data between tasks.
	put (self, data, in_ISR=False)
	Write an item of data into the share.
	get (self, in_ISR=False)
	Read an item of data from the share.
	__repr__ (self)
	Puts diagnostic information about the share into a string.
Public Member Functions inherited from task_share.BaseShare
	__init__ (self, type_code, thread_protect=True, name=None)
	Create a base queue object when called by a child class initializer.

Static Public Attributes
int	ser_num = 0
	A counter used to give serial numbers to shares for diagnostic use.

Protected Attributes
	_buffer = array.array (type_code, [0])
str	_name
Protected Attributes inherited from task_share.BaseShare
	_type_code = type_code
	_thread_protect = thread_protect

Detailed Description

An item which holds data to be shared between tasks.

This class implements a shared data item which can be protected against data corruption by pre-emptive multithreading. Multithreading which can corrupt shared data includes the use of ordinary interrupts as well as the use of pre-emptive multithreading such as by a Real-Time Operating System (RTOS).

An example of the creation and use of a share is as follows:

import task_share
 
# This share holds a signed short (16-bit) integer
my_share = task_share.Queue ('h', name="My Share")
 
# Somewhere in one task, put data into the share
my_share.put (some_data)
 
# In another task, read data from the share
something = my_share.get ()

Constructor & Destructor Documentation

__init__()

task_share.Share.__init__	(		self,
			type_code,
			thread_protect = True,
			name = None )

Create a shared data item used to transfer data between tasks.

This method allocates memory in which the shared data will be buffered.

Each share can only carry data of one particular type which must be chosen from the following list. The data type is specified by a one-letter type code which is given as for the Python array.array type, which can be any of the following:

b (signed char)	B (unsigned char)	8 bit integers
h (signed short)	H (unsigned short)	16 bit integers
i (signed int)	I (unsigned int)	32 bit integers (probably)
l (signed long)	L (unsigned long)	32 bit integers
q (signed long long)	Q (unsigned long long)	64 bit integers
f (float)	d (double-precision float)

Parameters

type_code	The type of data items which the share can hold
thread_protect	True if mutual exclusion protection is used
name	A short name for the share, default ShareN where N is a serial number for the share

Member Function Documentation

__repr__()

task_share.Share.__repr__

(

self

)

Puts diagnostic information about the share into a string.

Shares are pretty simple, so we just put the name and type.

get()

task_share.Share.get	(		self,
			in_ISR = False )

Read an item of data from the share.

If thread protection is enabled, interrupts are disabled during the time that the data is being read so as to prevent data corruption by changes in the data as it is being read.

Parameters

in_ISR

Set this to True if calling from within an ISR

put()

task_share.Share.put	(		self,
			data,
			in_ISR = False )

Write an item of data into the share.

This method puts data into the share; any old data is overwritten. This code disables interrupts during the writing so as to prevent data corrupting by an interrupt service routine which might access the same data.

Parameters

data	The data to be put into this share
in_ISR	Set this to True if calling from within an ISR

Member Data Documentation

_buffer

task_share.Share._buffer = array.array (type_code, [0])

protected

_name

task_share.Share._name

protected

Initial value:

=  None \
            else 'Share' + str (Share.ser_num)

ser_num

int task_share.Share.ser_num = 0

static

A counter used to give serial numbers to shares for diagnostic use.

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The documentation for this class was generated from the following file:

• src/task_share.py