/// <summary>
/// <P>Performs the unsigned debit, subtracting the debit amount from
/// the user's balance and storing the new, unsigned account data on the
/// user's iButton. The debit amount can be set using
/// <code>transaction.setParameter(SHADebit.DEBIT_AMOUNT, 50)</code>,
/// where the value is in units of cents (i.e. for 1 dollar, use 100).</P>
///
/// <P><B>Flow of action: </B>
/// <ul>
/// <li> Read the account data from user </li>
/// <li> Extract account balance </li>
/// <li> Assert balance greater than debit amount </li>
/// <li> Debit money from balance </li>
/// <li> Insert the new balance </li>
/// <li> Write the account data to the user </li>
/// </ul></P>
///
/// <P>If previous steps have been executed, all "Read" commands on
/// the user are reading from cached data.</P>
/// </summary>
/// <param name="user"> SHAiButtonUser upon which the transaction occurs.
/// </param>
/// <returns> <code>true</code> if and only if the user has enough in the
/// account balance to perform the requested debit AND the account data
/// has been written to the button.
/// </returns>
/// <seealso cref= SHAiButtonUser#readAccountData(byte[],int) </seealso>
/// <seealso cref= SHAiButtonUser#writeAccountData(byte[],int) </seealso>
/// <seealso cref= #getLastError() </seealso>
public override bool executeTransaction(SHAiButtonUser user, bool verifySuccess)
{
lock (this)
{
//clear any error
this.lastError = NO_ERROR;
//init local vars
//holds the working copy of account data
byte[] accountData = this.executeTransaction_accountData;
//holds the backup copy of account data before writing
byte[] oldAcctData = this.executeTransaction_oldAcctData;
//holds the account data read back for checking
byte[] newAcctData = this.executeTransaction_newAcctData;
//just make the transaction ID a random number, so it changes
int transID = rand.Next();
//if verifyUser was called, this is a read of cached data
user.readAccountData(accountData, 0);
//before we update the account data array at all, let's make a backup copy
Array.Copy(accountData, 0, oldAcctData, 0, 32);
//get the user's balance from accountData
int balance = -1;
if (accountData[I_FILE_LENGTH] == RECORD_A_LENGTH)
{
balance = Convert.toInt(accountData, I_BALANCE_A, 3);
}
else if (accountData[I_FILE_LENGTH] == RECORD_B_LENGTH)
{
balance = Convert.toInt(accountData, I_BALANCE_B, 3);
}
//if there are insufficient funds
if (this.debitAmount > balance)
{
this.lastError = USER_BAD_ACCOUNT_DATA;
return(false);
}
//update the user's balance
this.userBalance = (balance - this.debitAmount);
// attempt to update the page
bool success = false;
try
{
success = writeTransactionData(user, transID, this.userBalance, accountData);
}
catch (System.Exception)
{ // sink
}
//if write didn't succeeded or if we need to perform
//a verification step anyways, let's double-check what
//the user has on the button.
if (verifySuccess || !success)
{
OneWireEventSource.Log.Debug("attempting to re-write transaction data: ");
OneWireEventSource.Log.Debug("cur Data: " + Convert.toHexString(accountData));
OneWireEventSource.Log.Debug("old data: " + Convert.toHexString(oldAcctData));
bool dataOK = false;
int cnt = MAX_RETRY_CNT;
do
{
try
{
// let's refresh the page
user.refreshDevice();
//calling verify user re-issues a challenge-response
//and reloads the cached account data in the user object.
if (verifyUser(user))
{
//compare the user's account data against the working
//copy and the backup copy.
if (user.readAccountData(newAcctData, 0))
{
OneWireEventSource.Log.Debug("new data: " + Convert.toHexString(newAcctData));
bool isOld = true;
bool isCur = true;
for (int i = 0; i < 32 && (isOld || isCur); i++)
{
//match the backup
isOld = isOld && (newAcctData[i] == oldAcctData[i]);
//match the working copy
isCur = isCur && (newAcctData[i] == accountData[i]);
}
if (isOld)
{
//if it matches the backup copy, we didn't write anything
//and the data is still okay, but we didn't do a debit
dataOK = true;
success = false;
}
else if (isCur)
{
dataOK = true;
success = true;
}
else
{
int cnt2 = MAX_RETRY_CNT;
do
{
//iBUTTON DATA IS TOTALLY HOSED
//keep trying to get account data on the button
try
{
success = writeTransactionData(user, transID, this.userBalance, accountData);
}
catch (OneWireIOException owioe)
{
if (cnt2 == 0)
{
throw owioe;
}
}
catch (OneWireException owe)
{
if (cnt2 == 0)
{
throw owe;
}
}
} while (((cnt2 -= 1) > 0) && !success);
}
}
}
}
catch (OneWireIOException owioe)
{
if (cnt == 0)
{
throw owioe;
}
}
catch (OneWireException owe)
{
if (cnt == 0)
{
throw owe;
}
}
} while (!dataOK && ((cnt -= 1) > 0)); //TODO
if (!dataOK)
{
//couldn't fix the data after 255 retries
IOHelper.writeLine("Catastrophic Failure!");
success = false;
}
}
return(success);
}
}
/// <summary>
/// <P>Verifies user's account data. Account data is "verified" if and
/// only if the account balance is greater than zero. No digital
/// signature is checked by this transaction.</P>
///
/// <P><B>Flow of action: </B>
/// <ul>
/// <li> Read the account data from user </li>
/// <li> Extract account balance </li>
/// <li> Debit money from balance </li>
/// <li> Insert the new balance </li>
/// <li> Write the account data to the user </li>
/// </ul></P>
///
/// <P>If previous steps have been executed, all "Read" commands on
/// the user are reading from cached data.</P>
/// </summary>
/// <param name="user"> SHAiButtonUser upon which the transaction occurs.
/// </param>
/// <returns> <code>true</code> if and only if the account balance is
/// greater than zero.
/// </returns>
/// <seealso cref= SHAiButtonUser#readAccountData(byte[],int) </seealso>
/// <seealso cref= #getLastError() </seealso>
public override bool verifyTransactionData(SHAiButtonUser user)
{
lock (this)
{
//clear any error
this.lastError = NO_ERROR;
byte[] accountData = this.verifyData_accountData;
//if verifyUser was called, this is a read of cached data
user.readAccountData(accountData, 0);
// verify the A-B data scheme is valid
bool validPtr = false, validA = false, validB = false;
byte fileLength = accountData[I_FILE_LENGTH];
int crc16 = CRC16.compute(accountData, 0, fileLength + 3, user.AccountPageNumber);
if (fileLength == RECORD_A_LENGTH || fileLength == RECORD_B_LENGTH)
{
validPtr = true;
}
// was the crc of the file correct?
if (crc16 == 0xB001)
{
// if the header points to a valid record, we're done
if (validPtr)
{
// nothing more to check for DS1961S/DS2432, since
// it carries no signed data, we're finished
return(true);
}
// header points to neither record A nor B, but
// crc is absolutely correct. that can only mean
// we're looking at something that is the wrong
// size from what was expected, but apparently is
// exactly what was meant to be written. I'm done.
this.lastError = USER_BAD_ACCOUNT_DATA;
return(false);
}
// restore the other header information
accountData[I_DATA_TYPE_CODE] = 0x01;
accountData[I_CONVERSION_FACTOR + 0] = 0x8B;
accountData[I_CONVERSION_FACTOR + 1] = 0x48;
// zero-out the don't care bytes
accountData[I_DONT_CARE] = 0x00;
accountData[I_DONT_CARE + 1] = 0x00;
accountData[I_DONT_CARE + 2] = 0x00;
accountData[I_DONT_CARE + 3] = 0x00;
// lets try Record A and check the crc
accountData[I_FILE_LENGTH] = RECORD_A_LENGTH;
crc16 = CRC16.compute(accountData, 0, RECORD_A_LENGTH + 3, user.AccountPageNumber);
if (crc16 == 0xB001)
{
validA = true;
}
// lets try Record B and check the crc
accountData[I_FILE_LENGTH] = RECORD_B_LENGTH;
crc16 = CRC16.compute(accountData, 0, RECORD_B_LENGTH + 3, user.AccountPageNumber);
if (crc16 == 0xB001)
{
validB = true;
}
if (validA && validB)
{
OneWireEventSource.Log.Debug("Both A and B are valid");
// Both A & B are valid! And we know that we can only
// get here if the pointer or the header was not valid.
// That means that B was the last updated one but the
// header got hosed and the debit was not finished...
// which means A is the last known good value, let's go with A.
accountData[I_FILE_LENGTH] = RECORD_A_LENGTH;
}
else if (validA)
{
OneWireEventSource.Log.Debug("A is valid not B");
// B is invalid, A is valid. Means A is the last updated one,
// but B is the last known good value. The header was not updated
// to point to A before debit was aborted. Let's go with B
accountData[I_FILE_LENGTH] = RECORD_B_LENGTH;
}
else if (validB)
{
OneWireEventSource.Log.Debug("B is valid not A - impossible");
// A is invalid, B is valid. Should never ever happen. Something
// got completely hosed. What should happen here?
this.lastError = USER_BAD_ACCOUNT_DATA;
return(false);
}
else
{
OneWireEventSource.Log.Debug("Neither record has valid CRC");
// neither record contains a valid CRC. What should happen here?
// probably got weak bit in ptr record, no telling which way to go
this.lastError = USER_BAD_ACCOUNT_DATA;
return(false);
}
//get the user's balance from accountData
int balance = -1;
if (accountData[I_FILE_LENGTH] == RECORD_A_LENGTH)
{
balance = Convert.toInt(accountData, I_BALANCE_A, 3);
}
else if (accountData[I_FILE_LENGTH] == RECORD_B_LENGTH)
{
balance = Convert.toInt(accountData, I_BALANCE_B, 3);
}
if (balance < 0)
{
this.lastError = USER_BAD_ACCOUNT_DATA;
return(false);
}
this.userBalance = balance;
int cnt = MAX_RETRY_CNT;
do
{
if (user.refreshDevice() && writeTransactionData(user, -1, balance, accountData))
{
break;
}
} while (--cnt > 0);
return(false);
}
}
