io.dvlopt.linux.i2c.I2CTransaction Maven / Gradle / Ivy
/*
* Copyright 2018 Adam Helinski
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package io.dvlopt.linux.i2c ;
import com.sun.jna.Memory ;
import com.sun.jna.Pointer ;
import io.dvlopt.linux.i2c.I2CMessage ;
import io.dvlopt.linux.i2c.internal.NativeI2CIoctlData ;
import io.dvlopt.linux.i2c.internal.NativeI2CMessage ;
/**
* Class representing an I2C transaction for carrying out several uninterrupted IO operations.
*
* Sometimes, only one message per transaction is supported, which defeat the purpose of having
* transactions.
*/
public class I2CTransaction {
/**
* The maximum number of messages a single transaction can carry out in theory.
*/
public final static int MAX_LENGTH = 42 ;
Memory memory ;
Memory memoryMessages ;
private I2CMessage[] messages ;
/**
* How many messages this transaction holds.
*/
public final int length ;
/**
* Creates a new transaction.
*
* @param length The number of messages.
*
* @see #MAX_LENGTH
*/
public I2CTransaction( int length ) {
if ( length > MAX_LENGTH ) {
throw new IllegalArgumentException( "The requested number of messages is higher than what is supported" ) ;
}
this.memoryMessages = new Memory( length * NativeI2CMessage.SIZE ) ;
this.memoryMessages.clear() ;
this.memory = new Memory( NativeI2CIoctlData.SIZE ) ;
this.memory.setPointer( NativeI2CIoctlData.OFFSET_MESSAGES ,
this.memoryMessages ) ;
this.memory.setInt( NativeI2CIoctlData.OFFSET_LENGTH ,
length ) ;
this.messages = new I2CMessage[ length ] ;
for ( int i = 0 ;
i < length ;
i += 1 ) {
this.messages[ i ] = new I2CMessage( this.memoryMessages.share( i * NativeI2CMessage.SIZE ) ) ;
}
this.length = length ;
}
/**
* Retrieves a message from this transaction.
*
* @param index Which one.
*
* @return The relevant message.
*/
public I2CMessage getMessage( int index ) {
return this.messages[ index ] ;
}
}