/// <summary>
/// Create an instance by specified byte array and start position.
/// </summary>
/// <returns>An System.Array that contains all array members.</returns>
public override object Parse(ElementInstance parent, Stream stream, long stopAt)
{
Debug.Assert(DataElement != null);
int len = EvalLength(parent, stream, stopAt);
ArrayList list = new ArrayList();
for (int i = 0; i < len; i++)
{
list.Add(DataElement.Parse(parent, stream, stopAt));
}
ArrayInstance inst = new ArrayInstance(parent, DataElement, list.ToArray());
return inst;
}
public StructInstance(ElementInstance parent, Element[] elements)
: base(parent)
{
_elements = elements;
}
public ElementInstance(ElementInstance parent)
{
_parent = parent;
}
public ArrayInstance(ElementInstance parent, Element type, Object[] elements)
: base(parent)
{
this.Type = type;
this.Elements = elements;
}
private int EvalLength(ElementInstance parent, Stream stream, long stopAt)
{
int len = 0;
if (Length == null)
{
Debug.Assert(stopAt >= stream.Position);
len = (int)((stopAt - stream.Position) / DataElement.Size);
}
else
{
try
{
len = Convert.ToInt32(Length);
}
catch (FormatException)
{
IConvertible evalLen = parent.Eval(Length) as IConvertible;
if (evalLen != null)
{
len = evalLen.ToInt32(null);
}
}
}
return len;
}
/// <summary>
/// Create an instance by specified byte array and start position.
/// </summary>
public override object Parse(ElementInstance parent, Stream stream, long stopAt)
{
StructInstance inst = new StructInstance(parent, Elements);
if (Elements != null)
{
foreach (Element elem in Elements)
{
if (elem.EvalCondition(inst))
{
if (stream.Position >= stopAt)
{
break; // don't read beyond boundary.
}
object elemInst = elem.Parse(inst, stream, stopAt);
// Elements that don't have a name will not be added directly
if (elem.Name != null && elem.Name != string.Empty)
{
inst[elem.Name] = elemInst;
}
}
}
}
return inst;
}
private void AddBitFields(ElementInstance parent, int data)
{
if (BitsFields != null && parent is StructInstance)
{
foreach (BitsField f in BitsFields)
{
Debug.Assert(f.length >= 1);
int mask = (1 << f.length) - 1;
int bits = (data >> f.offset) & mask;
((StructInstance) parent)[f.name] = bits;
}
}
}
public override object Parse(ElementInstance parent, Stream stream, long stopAt)
{
char type = DataType[0];
char prefix = Char.ToLower(type);
int size = Size;
string dataType = DataType.ToLower();
if (prefix == 'b') // byte
{
if (size <= 1)
{
int b = stream.ReadByte();
AddBitFields(parent, b);
return b;
}
else
{
byte[] data = new byte[size];
stream.Read( data, 0, size);
return data;
}
}
else if (prefix == 's') // fixed-length string
{
byte[] data = new byte[size];
stream.Read( data, 0, size);
string s = Encoding.UTF8.GetString(data, 0, size);
// a workaround for '\0'-stuffed stream
if (s.IndexOf('\0') >= 0)
{
s = s.Substring( 0, s.IndexOf("\0"));
}
return s;
}
else if (prefix == 'z') // zero-ended string
{
size = (int) (stopAt - stream.Position);
byte[] data = new byte[size];
stream.Read( data, 0, size);
int z = Array.IndexOf(data, 0, 0, size);
if (z < 0)
z = data.Length;
string s = Encoding.UTF8.GetString(data, 0, z);
return s;
}
// vluimsbf8: Variable length code unsigned integer, most significant bit first.
// The size of vluimsbf8 is a multiple of one byte. The first bit (Ext) of each
// byte specifies if set to 1 that another byte is present for this vluimsbf8 code
// word. The unsigned integer is encoded by the concatenation of the seven least
// significant bits of each byte belonging to this vluimsbf8 code word.
else if (prefix == 'v')
{
int i = 0;
int b = 0x80;
int bytes = 0;
for (; (b & 0x80) != 0; bytes++)
{
b = stream.ReadByte();
i = i << 7 | (b & 0x7f);
}
if (type == 'v' && bytes > 1)
{
return Util.EndianFlip(i, bytes);
}
return i;
}
else if ("iuf".IndexOf(prefix) >= 0) // signed/unsigned integer
{
byte[] data = new byte[size];
stream.Read( data, 0, size);
if (size == 8)
{
long i = data[0] | data[1] << 8 | data[2] << 16 | data[3] << 24 |
data[4] << 32 | data[5] << 40 | data[6] << 48 | data[7] << 56;
return i;
}
else if (size == 4 || size == 3)
{
int i;
if (size == 4)
{
i = data[0] | data[1] << 8 | data[2] << 16 | data[3] << 24;
}
else
{
i = data[0] | data[1] << 8 | data[2] << 16;
}
// Big-indian integer is identified by upper case 'I'
if (type == 'I')
{
return Util.EndianFlip(i, size);
}
// Big-indian unsigned integer is identified by upper case 'U'
else if (type == 'U')
{
return Util.EndianFlip((uint) i, size);
}
else if (type == 'u')
{
return (uint) i;
}
return i;
}
else if (size == 2)
{
short i = (short) (data[0] | data[1] << 8);
if (type == 'I')
{
return (short) Util.EndianFlip((int) i, size);
}
else if (type == 'U')
{
return (ushort) Util.EndianFlip(((uint) i), size);
}
else if (type == 'u')
{
return (ushort) i;
}
return i;
}
else
{
Debug.Assert( false, "Invalid field size!");
}
}
return null;
}
/// <summary> /// To construct instance from specified stream. /// </summary> /// <param name="parent"></param> /// <param name="stream"></param> /// <param name="stopAt"></param> /// <returns></returns> public abstract object Parse(ElementInstance parent, Stream stream, long stopAt);
/// <summary>
/// Evaluate bool expression
/// </summary>
/// <param name="inst"></param>
/// <returns></returns>
public bool EvalCondition(ElementInstance inst)
{
if (Condition != null)
{
try
{
BoolExprLexer lexer = new BoolExprLexer(new StringReader(Condition));
BoolExprParser parser = new BoolExprParser(lexer);
ConditionEvaluator treeParser = new ConditionEvaluator();
parser.expression();
antlr.collections.AST ast = parser.getAST();
treeParser.Instance = inst;
return treeParser.expression(ast);
}
catch (Exception ex)
{
Debug.Write(ex);
return false;
}
}
return true;
}
