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import sqlalchemy
import sqlalchemy.types as sqltypes
from sqlalchemy.sql import and_
from sqlalchemy.schema import UniqueConstraint
from sqlalchemy.sql.expression import bindparam
from pymodbus.exceptions import NotImplementedException
from pymodbus.interfaces import IModbusSlaveContext
#---------------------------------------------------------------------------#
# Logging
#---------------------------------------------------------------------------#
import logging;
_logger = logging.getLogger(__name__)
#---------------------------------------------------------------------------#
# Context
#---------------------------------------------------------------------------#
class DatabaseSlaveContext(IModbusSlaveContext):
'''
This creates a modbus data model with each data access
stored in its own personal block
'''
def __init__(self, *args, **kwargs):
''' Initializes the datastores
:param kwargs: Each element is a ModbusDataBlock
'''
self.table = kwargs.get('table', 'pymodbus')
self.database = kwargs.get('database', 'sqlite:///pymodbus.db')
self.__db_create(self.table, self.database)
def __str__(self):
''' Returns a string representation of the context
:returns: A string representation of the context
'''
return "Modbus Slave Context"
def reset(self):
''' Resets all the datastores to their default values '''
self._metadata.drop_all()
self.__db_create(self.table, self.database)
raise NotImplementedException() # TODO drop table?
def validate(self, fx, address, count=1):
''' Validates the request to make sure it is in range
:param fx: The function we are working with
:param address: The starting address
:param count: The number of values to test
:returns: True if the request in within range, False otherwise
'''
address = address + 1 # section 4.4 of specification
_logger.debug("validate[%d] %d:%d" % (fx, address, count))
return self.__validate(self.decode(fx), address, count)
def getValues(self, fx, address, count=1):
''' Validates the request to make sure it is in range
:param fx: The function we are working with
:param address: The starting address
:param count: The number of values to retrieve
:returns: The requested values from a:a+c
'''
address = address + 1 # section 4.4 of specification
_logger.debug("get-values[%d] %d:%d" % (fx, address, count))
return self.__get(self.decode(fx), address, count)
def setValues(self, fx, address, values):
''' Sets the datastore with the supplied values
:param fx: The function we are working with
:param address: The starting address
:param values: The new values to be set
'''
address = address + 1 # section 4.4 of specification
_logger.debug("set-values[%d] %d:%d" % (fx, address, len(values)))
self.__set(self.decode(fx), address, values)
#--------------------------------------------------------------------------#
# Sqlite Helper Methods
#--------------------------------------------------------------------------#
def __db_create(self, table, database):
''' A helper method to initialize the database and handles
:param table: The table name to create
:param database: The database uri to use
'''
self._engine = sqlalchemy.create_engine(database, echo=False)
self._metadata = sqlalchemy.MetaData(self._engine)
self._table = sqlalchemy.Table(table, self._metadata,
sqlalchemy.Column('type', sqltypes.String(1)),
sqlalchemy.Column('index', sqltypes.Integer),
sqlalchemy.Column('value', sqltypes.Integer),
UniqueConstraint('type', 'index', name='key'))
self._table.create(checkfirst=True)
self._connection = self._engine.connect()
def __get(self, type, offset, count):
'''
:param type: The key prefix to use
:param offset: The address offset to start at
:param count: The number of bits to read
:returns: The resulting values
'''
query = self._table.select(and_(
self._table.c.type == type,
self._table.c.index >= offset,
self._table.c.index <= offset + count))
query = query.order_by(self._table.c.index.asc())
result = self._connection.execute(query).fetchall()
return [row.value for row in result]
def __build_set(self, type, offset, values, p=''):
''' A helper method to generate the sql update context
:param type: The key prefix to use
:param offset: The address offset to start at
:param values: The values to set
'''
result = []
for index, value in enumerate(values):
result.append({
p + 'type' : type,
p + 'index' : offset + index,
'value' : value
})
return result
def __set(self, type, offset, values):
'''
:param key: The type prefix to use
:param offset: The address offset to start at
:param values: The values to set
'''
context = self.__build_set(type, offset, values)
query = self._table.insert()
result = self._connection.execute(query, context)
return result.rowcount == len(values)
def __update(self, type, offset, values):
'''
:param type: The type prefix to use
:param offset: The address offset to start at
:param values: The values to set
'''
context = self.__build_set(type, offset, values, p='x_')
query = self._table.update().values(name='value')
query = query.where(and_(
self._table.c.type == bindparam('x_type'),
self._table.c.index == bindparam('x_index')))
result = self._connection.execute(query, context)
return result.rowcount == len(values)
def __validate(self, key, offset, count):
'''
:param key: The key prefix to use
:param offset: The address offset to start at
:param count: The number of bits to read
:returns: The result of the validation
'''
query = self._table.select(and_(
self._table.c.type == type,
self._table.c.index >= offset,
self._table.c.index <= offset + count))
result = self._connection.execute(query)
return result.rowcount == count
|
