protected SerializationInfo(Type objType, IFormatterConverter converter)
{
Type = objType;
Converter = converter;
// create an instance of the object to get missing values from the field initializers.
object instance = STDFFormatterServices.GetUninitializedObject(Type);
FieldInfo[] fields = STDFFormatterServices.GetSerializeableFields(Type);
Info = new SerializationInfoEntry[fields.Length];
for (int i = 0; i < fields.Length; i++)
{
var field = fields[i];
object value = field.GetValue(instance);
string itemCountField = (field.GetCustomAttribute <STDFAttribute>() ??
field.GetCustomAttribute <STDFOptionalAttribute>())?.ItemCountProperty;
var entry = new SerializationInfoEntry()
{
Index = i,
Name = field.Name,
Type = field.FieldType,
IsOptional = field.GetCustomAttribute <STDFOptionalAttribute>() != null,
IsSet = false,
ItemCountIndex = Array.FindIndex(fields, x => x.Name == itemCountField),
Value = value,
MissingValue = value
};
Info[i] = entry;
}
}
protected virtual void SerializeValue(int index, object currentValue, object originalValue = null)
{
SerializationInfoEntry entry = CurrentInfo.GetEntry(index);
object missingValue = entry.MissingValue;
object defaultValue = CurrentDefaults?.GetValue(index);
// if field is not an optional field, then no further checking required,
// just return the value as is
if (entry.IsOptional)
{
// logic to determine what value to serialize
//
// Truth table:
//
// OM = Original = missing value
// DV = Current = default value
// MV = Current = missing value
//
// O D M
// M V V Action
// - - - -----------------------------------
// 0 0 0 Write current value
// 0 0 1 Write missing value
// 0 1 0 Write current value
// 0 1 1 Write missing value
// 1 0 0 Write current value
// 1 0 1 Write missing value
// 1 1 0 Write missing value
// 1 1 1 Write missing value
int writeFlag = 0b000;
writeFlag |= IsEqual(originalValue, missingValue) ? 0b100 : 0b000;
writeFlag |= IsEqual(currentValue, defaultValue) ? 0b010 : 0b000;
writeFlag |= IsEqual(currentValue, missingValue) ? 0b001 : 0b000;
switch (writeFlag)
{
case 0b000: // original value != missing && current value (!= default && != missing)
case 0b010: // original value != missing && current value (== default && != missing)
case 0b100: // original value == missing) && current value (!= default && != missing)
entry.Value = currentValue;
entry.IsMissingValue = false;
break;
default: // all other combinations, return the missing value.
entry.Value = missingValue;
entry.IsMissingValue = true;
break;
}
}
else
{
entry.Value = currentValue;
entry.IsMissingValue = IsEqual(currentValue, missingValue);
}
}
protected virtual object DeserializeValue(int index)
{
SerializationInfoEntry entry = CurrentInfo.GetEntry(index);
object currentValue = entry.Value;
object missingValue = entry.MissingValue;
object defaultValue = CurrentDefaults?.GetValue(index);
// if field is not an optional field, then no further checking required,
// just return the value as read from the instream (or initialized with missing value)
if (entry.IsOptional)
{
// logic to determine which value to deserialize to (as read, missing, or default value)
//
// Truth table:
//
// NV = Value is null
// MV = Value is missing value
// DV = Value is default value
//
// N M D
// V V V Action
// - - - -----------------------------------
// 0 0 0 Return value as read
// 0 0 1 Return value as read
// 0 1 0 Return default value
// 0 1 1 Return default value
// 1 0 0 Return value as read
// 1 0 1 Return value as read
// 1 1 0 Return default value
// 1 1 1 Return default value
int writeFlag = currentValue == null ? 0b100 : 0b000;
writeFlag |= IsEqual(currentValue, missingValue) ? 0b010 : 0b000;
writeFlag |= IsEqual(currentValue, defaultValue) ? 0b001 : 0b000;
switch (writeFlag)
{
case 0b000: // as read value (!= null && != missing && != default)
case 0b001: // as read value (!= null && != missing && == default)
case 0b100: // as read value (== null && != missing && != default)
case 0b101: // as read value (== null && != missing && == default)
return(currentValue);
default: // all other combinations, return the default value.
return(defaultValue);
}
}
return(currentValue);
}