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OBD Java API compatible with ELM327.
package com.github.pires.obd.utils;
/**
* Abstract CommandAvailabilityHelper class.
*
* @author pires
* @version $Id: $Id
* @since 1.0-RC12
*/
public abstract class CommandAvailabilityHelper {
/*
All around this class, integers are used where unsigned bytes should be used. Too bad they don't exist in Java.
Thank you Oracle.
*/
/**
* Digests the given string into an array of integers which can be used to check for command availability
*
* @param availabilityString An 8*n (where n is an integer) character string containing only numbers and uppercase letters from A to F
* @return An integer array containing the digested information
* @throws java.lang.IllegalArgumentException if any.
*/
public static int[] digestAvailabilityString(final String availabilityString) throws IllegalArgumentException {
//The string must have 8*n characters, n being an integer
if (availabilityString.length() % 8 != 0) {
throw new IllegalArgumentException("Invalid length for Availability String supplied: " + availabilityString);
}
//Each two characters of the string will be digested into one byte, thus the resulting array will
//have half the elements the string has
int[] availabilityArray = new int[availabilityString.length() / 2];
for (int i = 0, a = 0; i < availabilityArray.length; ++i, a += 2) {
//First character is more significant
availabilityArray[i] = 16 * parseHexChar(availabilityString.charAt(a)) + parseHexChar(availabilityString.charAt(a + 1));
}
return availabilityArray;
}
private static int parseHexChar(char hexChar) {
switch (hexChar) {
case '0':
return 0;
case '1':
return 1;
case '2':
return 2;
case '3':
return 3;
case '4':
return 4;
case '5':
return 5;
case '6':
return 6;
case '7':
return 7;
case '8':
return 8;
case '9':
return 9;
case 'A':
return 10;
case 'B':
return 11;
case 'C':
return 12;
case 'D':
return 13;
case 'E':
return 14;
case 'F':
return 15;
default:
throw new IllegalArgumentException("Invalid character [" + hexChar + "] supplied");
}
}
/**
* Implementation of {@link #isAvailable(String, int[])} isAvailable} which returns the specified safetyReturn boolean instead of
* throwing and exception in the event of supplying an availabilityString which doesn't include information about the specified command
*
* This is a direct call to {@link #isAvailable(String, int[], boolean)} with built-in String digestion
*
* @param commandPid a {@link java.lang.String} object.
* @param availabilityString a {@link java.lang.String} object.
* @param safetyReturn a boolean.
* @return a boolean.
*/
public static boolean isAvailable(final String commandPid, final String availabilityString, boolean safetyReturn) {
return isAvailable(commandPid, digestAvailabilityString(availabilityString), safetyReturn);
}
/**
* Checks whether the command identified by commandPid is available, as noted by availabilityString.
*
* This is a direct call to {@link com.github.pires.obd.utils.CommandAvailabilityHelper#isAvailable(String, int[])} with built-in String digestion
*
* @param commandPid a {@link java.lang.String} object.
* @param availabilityString a {@link java.lang.String} object.
* @return a boolean.
* @throws java.lang.IllegalArgumentException if any.
*/
public static boolean isAvailable(final String commandPid, final String availabilityString) throws IllegalArgumentException {
return isAvailable(commandPid, digestAvailabilityString(availabilityString));
}
/**
* Implementation of {@link #isAvailable(String, int[])} isAvailable} which returns the specified safetyReturn boolean instead of
* throwing and exception in the event of supplying an availabilityString which doesn't include information about the specified command
*
* @param commandPid a {@link java.lang.String} object.
* @param availabilityArray an array of int.
* @param safetyReturn a boolean.
* @return a boolean.
*/
public static boolean isAvailable(final String commandPid, final int[] availabilityArray, boolean safetyReturn) {
try {
return isAvailable(commandPid, availabilityArray);
} catch (IllegalArgumentException e) {
return safetyReturn;
}
}
/**
* Checks whether the command identified by commandPid is available, as noted by availabilityArray
*
* @param commandPid a {@link java.lang.String} object.
* @param availabilityArray an array of int.
* @return a boolean.
* @throws java.lang.IllegalArgumentException if any.
*/
public static boolean isAvailable(final String commandPid, final int[] availabilityArray) throws IllegalArgumentException {
//Command 00 is always supported
if (commandPid.equals("00"))
return true;
//Which byte from the array contains the info we want?
int cmdNumber = Integer.parseInt(commandPid, 16);
int arrayIndex = (cmdNumber - 1) / 8; //the -1 corrects the command code offset, as 00, 20, 40 are not the first commands in each response to be evaluated
if (arrayIndex > availabilityArray.length - 1)
throw new IllegalArgumentException("availabilityArray does not contain enough entries to check for command " + commandPid);
//Subtract 8 from cmdNumber until we have it in the 1-8 range
while (cmdNumber > 8) {
cmdNumber -= 8;
}
int requestedAvailability;
switch (cmdNumber) {
case 1:
requestedAvailability = 128;
break;
case 2:
requestedAvailability = 64;
break;
case 3:
requestedAvailability = 32;
break;
case 4:
requestedAvailability = 16;
break;
case 5:
requestedAvailability = 8;
break;
case 6:
requestedAvailability = 4;
break;
case 7:
requestedAvailability = 2;
break;
case 8:
requestedAvailability = 1;
break;
default:
throw new RuntimeException("This is not supposed to happen.");
}
return requestedAvailability == (requestedAvailability & availabilityArray[arrayIndex]);
}
}