public Receipt Read()
{
var reader = new MyBinaryReader(_stream);
// Reading the lookup updates
int updateCount;
try
{
updateCount = reader.Read7BitEncodedInt();
}
catch (EndOfStreamException)
{
return(null);
}
for (int i = 0; i < updateCount; i++)
{
var flag = reader.Read7BitEncodedInt();
var isNewValue = ((flag & 1) == 1);
var valueType = flag >> 1; // discarding 1 bit
switch (valueType)
{
case 0: // GTINS
if (isNewValue)
{
_gtins.Add(reader.ReadString());
}
else
{
var oldIndex = reader.Read7BitEncodedInt();
var newIndex = reader.Read7BitEncodedInt();
_gtins.Swap(oldIndex, newIndex);
}
break;
case 1: // Prices
if (isNewValue)
{
_prices.Add(reader.ReadInt32());
}
else
{
var oldIndex = reader.Read7BitEncodedInt();
var newIndex = reader.Read7BitEncodedInt();
_prices.Swap(oldIndex, newIndex);
}
break;
case 2: // Discounts
if (isNewValue)
{
_discounts.Add(reader.ReadInt32());
}
else
{
var oldIndex = reader.Read7BitEncodedInt();
var newIndex = reader.Read7BitEncodedInt();
_discounts.Swap(oldIndex, newIndex);
}
break;
case 3: // VAT rates
if (isNewValue)
{
_vatRates.Add(reader.ReadInt32());
}
else
{
var oldIndex = reader.Read7BitEncodedInt();
var newIndex = reader.Read7BitEncodedInt();
_vatRates.Swap(oldIndex, newIndex);
}
break;
default:
throw new NotSupportedException();
}
}
// Reading the receipt content
var date = reader.ReadInt32().FromInt32ToDateTime();
var loyaltyCard = reader.ReadInt32();
var store = reader.ReadUInt16();
var receipt = new Receipt
{
Date = date,
LoyaltyCard = loyaltyCard,
Store = store
};
var itemCount = reader.Read7BitEncodedInt();
var items = new Item[itemCount];
for (int i = 0; i < itemCount; i++)
{
var gtinIndex = reader.Read7BitEncodedInt();
var priceIndex = reader.Read7BitEncodedInt();
var flag = reader.ReadByte();
var nonOneQuantity = ((flag & 1) == 1);
var nonZeroDiscount = ((flag & 2) == 2);
var vatRateIndex = flag >> 2; // discarding two bits
// fact: quantities equals to 1 amounts for 85% of the items.
var quantity = nonOneQuantity ? reader.Read7BitEncodedInt() : 1;
var discount = nonZeroDiscount ? reader.Read7BitEncodedInt() : 0;
items[i] = new Item
{
GTIN = _gtins[gtinIndex],
UnitPrice = _prices[priceIndex],
Quantity = quantity,
Discount = discount,
VatRate = _vatRates[vatRateIndex]
};
}
receipt.Items = items;
return(receipt);
}
public Receipt Read()
{
var reader = new MyBinaryReader(_stream);
// Reading the lookup updates
int updateCount;
try
{
updateCount = reader.Read7BitEncodedInt();
}
catch(EndOfStreamException)
{
return null;
}
for(int i = 0; i < updateCount; i++)
{
var flag = reader.Read7BitEncodedInt();
var isNewValue = ((flag & 1) == 1);
var valueType = flag >> 1; // discarding 1 bit
switch (valueType)
{
case 0: // GTINS
if(isNewValue)
{
_gtins.Add(reader.ReadString());
}
else
{
var oldIndex = reader.Read7BitEncodedInt();
var newIndex = reader.Read7BitEncodedInt();
_gtins.Swap(oldIndex, newIndex);
}
break;
case 1: // Prices
if(isNewValue)
{
_prices.Add(reader.ReadInt32());
}
else
{
var oldIndex = reader.Read7BitEncodedInt();
var newIndex = reader.Read7BitEncodedInt();
_prices.Swap(oldIndex, newIndex);
}
break;
case 2: // Discounts
if (isNewValue)
{
_discounts.Add(reader.ReadInt32());
}
else
{
var oldIndex = reader.Read7BitEncodedInt();
var newIndex = reader.Read7BitEncodedInt();
_discounts.Swap(oldIndex, newIndex);
}
break;
case 3: // VAT rates
if (isNewValue)
{
_vatRates.Add(reader.ReadInt32());
}
else
{
var oldIndex = reader.Read7BitEncodedInt();
var newIndex = reader.Read7BitEncodedInt();
_vatRates.Swap(oldIndex, newIndex);
}
break;
default:
throw new NotSupportedException();
}
}
// Reading the receipt content
var date = reader.ReadInt32().FromInt32ToDateTime();
var loyaltyCard = reader.ReadInt32();
var store = reader.ReadUInt16();
var receipt = new Receipt
{
Date = date,
LoyaltyCard = loyaltyCard,
Store = store
};
var itemCount = reader.Read7BitEncodedInt();
var items = new Item[itemCount];
for (int i = 0; i < itemCount; i++)
{
var gtinIndex = reader.Read7BitEncodedInt();
var priceIndex = reader.Read7BitEncodedInt();
var flag = reader.ReadByte();
var nonOneQuantity = ((flag & 1) == 1);
var nonZeroDiscount = ((flag & 2) == 2);
var vatRateIndex = flag >> 2; // discarding two bits
// fact: quantities equals to 1 amounts for 85% of the items.
var quantity = nonOneQuantity ? reader.Read7BitEncodedInt() : 1;
var discount = nonZeroDiscount ? reader.Read7BitEncodedInt() : 0;
items[i] = new Item
{
GTIN = _gtins[gtinIndex],
UnitPrice = _prices[priceIndex],
Quantity = quantity,
Discount = discount,
VatRate = _vatRates[vatRateIndex]
};
}
receipt.Items = items;
return receipt;
}