/// <summary>
/// Decode a Qap1-encoded Sexp
/// </summary>
/// <param name="data">The byte stream in which the Sexp is encoded</param>
/// <param name="start">At which index of data does the Sexp begin?</param>
/// <returns>The decoded Sexp.</returns>
private static Sexp DecodeSexp(byte[] data, ref long start)
{
// pull sexp type
byte xt = data[start];
// calculate length of payload
var lengthBuf = new byte[8];
Array.Copy(data, start + 1, lengthBuf, 0, 3);
start += 4;
if ((xt & XtLarge) == XtLarge)
{
Array.Copy(data, start, lengthBuf, 3, 4);
start += 4;
xt -= XtLarge;
}
var length = ( long )BitConverter.ToUInt64(lengthBuf, 0);
// has attributes? process first
SexpTaggedList attrs = null;
if ((xt & XtHasAttr) == XtHasAttr)
{
xt -= XtHasAttr;
long oldstart = start;
attrs = ( SexpTaggedList )DecodeSexp(data, ref start);
length -= start - oldstart;
}
long end = start + length;
Sexp result;
switch (xt)
{
case XtNull:
{
if (length != 0)
{
throw new RserveException("Attempting to decode an SexpNull, but it is followed by data when it shouldn't be.");
}
result = new SexpNull();
}
break;
case XtSymName:
{
// keep all characters up to the first null
var symnNamBuf = new byte[length];
Array.Copy(data, start, symnNamBuf, 0, length);
string res = Encoding.UTF8.GetString(symnNamBuf);
result = new SexpSymname(res.Split('\x00')[0]);
}
break;
case XtArrayInt:
{
var res = new int[length / 4];
var intBuf = new byte[4];
for (long i = 0; i < length; i += 4)
{
Array.Copy(data, start + i, intBuf, 0, 4);
res[i / 4] = BitConverter.ToInt32(intBuf, 0);
}
// is date or just an integer?
if ((attrs != null) && (attrs.ContainsKey("class") && attrs["class"].AsStrings.Contains("Date")))
{
result = new SexpArrayDate(res);
}
else
{
result = new SexpArrayInt(res);
}
}
break;
case XtArrayBool:
{
if (length < 4)
{
throw new RserveException("Decoding an SexpArrayBool where data doesn't seem to contain a data length field.");
}
var boolLengthBuf = new byte[4];
Array.Copy(data, start, boolLengthBuf, 0, 4);
var datalength = BitConverter.ToInt32(boolLengthBuf, 0);
if (datalength > length - 4)
{
throw new RserveException("Decoding an SexpArrayBool where transmitted data field too short for number of entries.");
}
var res = new bool?[datalength];
for (int i = 0; i < datalength; i++)
{
// R logical is false if 0, true if 1, and NA if 2
switch (data[start + i + 4])
{
case 0:
res[i] = false;
break;
case 1:
res[i] = true;
break;
case 2:
res[i] = null;
break;
default:
throw new RserveException("Decoding an SexpArrayBool and found an element in the array that is not an R bool: " + data[start + i + 4]);
}
}
result = new SexpArrayBool(res);
}
break;
case XtArrayDouble:
{
var res = new double[length / 8];
var doubleBuf = new byte[8];
for (long i = 0; i < length; i += 8)
{
Array.Copy(data, start + i, doubleBuf, 0, 8);
res[i / 8] = BitConverter.ToDouble(doubleBuf, 0);
}
// is date or just a double?
if ((attrs != null) && (attrs.ContainsKey("class") && attrs["class"].AsStrings.Contains("Date")))
{
result = new SexpArrayDate(res.Select(Convert.ToInt32));
}
else
{
result = new SexpArrayDouble(res);
}
}
break;
case XtArrayString:
{
var res = new List <string>();
long i = 0;
for (long j = 0; j < length; j++)
{
if (data[start + j] != 0)
{
continue;
}
if ((j == i + 1) && (data[start + i] == 255))
{
res.Add(null);
}
else
{
if (data[start + i] == 255)
{
i++;
}
var stringBuf = new byte[j - i];
Array.Copy(data, start + i, stringBuf, 0, j - i);
res.Add(Encoding.UTF8.GetString(stringBuf));
}
i = j + 1;
}
result = new SexpArrayString(res);
}
break;
case XtListNoTag:
case XtLangNoTag:
case XtVector:
result = new SexpList();
while (start < end)
{
result.Add(DecodeSexp(data, ref start));
}
break;
case XtLangTag:
case XtListTag:
result = new SexpTaggedList();
while (start < end)
{
Sexp val = DecodeSexp(data, ref start);
Sexp key = DecodeSexp(data, ref start);
result.Add(key.IsNull ? String.Empty : key.AsString, val);
}
break;
case XtRaw:
{
var d = new byte[length];
Array.Copy(data, start, d, 0, length);
result = new SexpQap1Raw(xt, d);
}
break;
default:
throw new RserveException("Cannot decode an Sexp because the type is not recognized: " + xt);
}
if (start > end)
{
throw new RserveException("When decoding an Sexp, more data consumed than provided.");
}
start = end;
if (attrs != null)
{
foreach (var a in attrs.AsSexpDictionary)
{
result.Attributes.Add(a.Key, a.Value);
}
}
return(result);
}
/// <summary>
/// Decode a Qap1-encoded Sexp
/// </summary>
/// <param name="data">The byte stream in which the Sexp is encoded</param>
/// <param name="start">At which index of data does the Sexp begin?</param>
/// <returns>The decoded Sexp.</returns>
private static Sexp DecodeSexp( byte[] data , ref long start )
{
// pull sexp type
byte xt = data[ start ];
// calculate length of payload
var lengthBuf = new byte[ 8 ];
Array.Copy( data , start + 1 , lengthBuf , 0 , 3 );
start += 4;
if ( ( xt & XtLarge ) == XtLarge )
{
Array.Copy( data , start , lengthBuf , 3 , 4 );
start += 4;
xt -= XtLarge;
}
var length = ( long )BitConverter.ToUInt64( lengthBuf , 0 );
// has attributes? process first
SexpTaggedList attrs = null;
if ( ( xt & XtHasAttr ) == XtHasAttr )
{
xt -= XtHasAttr;
long oldstart = start;
attrs = ( SexpTaggedList )DecodeSexp( data , ref start );
length -= start - oldstart;
}
long end = start + length;
Sexp result;
switch ( xt )
{
case XtNull:
{
if ( length != 0 )
{
throw new RserveException( "Attempting to decode an SexpNull, but it is followed by data when it shouldn't be." );
}
result = new SexpNull();
}
break;
case XtSymName:
{
// keep all characters up to the first null
var symnNamBuf = new byte[ length ];
Array.Copy( data , start , symnNamBuf , 0 , length );
string res = Encoding.UTF8.GetString( symnNamBuf );
result = new SexpSymname( res.Split( '\x00' )[ 0 ] );
}
break;
case XtArrayInt:
{
var res = new int[ length / 4 ];
var intBuf = new byte[ 4 ];
for ( long i = 0 ; i < length ; i += 4 )
{
Array.Copy( data , start + i , intBuf , 0 , 4 );
res[ i / 4 ] = BitConverter.ToInt32( intBuf , 0 );
}
// is date or just an integer?
if ( ( attrs != null ) && ( attrs.ContainsKey( "class" ) && attrs[ "class" ].AsStrings.Contains( "Date" ) ) )
{
result = new SexpArrayDate( res );
}
else
{
result = new SexpArrayInt( res );
}
}
break;
case XtArrayBool:
{
if ( length < 4 )
{
throw new RserveException( "Decoding an SexpArrayBool where data doesn't seem to contain a data length field." );
}
var boolLengthBuf = new byte[ 4 ];
Array.Copy( data , start , boolLengthBuf , 0 , 4 );
var datalength = BitConverter.ToInt32( boolLengthBuf , 0 );
if ( datalength > length - 4 )
{
throw new RserveException( "Decoding an SexpArrayBool where transmitted data field too short for number of entries." );
}
var res = new bool?[ datalength ];
for ( int i = 0 ; i < datalength ; i++ )
{
// R logical is false if 0, true if 1, and NA if 2
switch ( data[ start + i + 4 ] )
{
case 0:
res[ i ] = false;
break;
case 1:
res[ i ] = true;
break;
case 2:
res[ i ] = null;
break;
default:
throw new RserveException( "Decoding an SexpArrayBool and found an element in the array that is not an R bool: " + data[ start + i + 4 ] );
}
}
result = new SexpArrayBool( res );
}
break;
case XtArrayDouble:
{
var res = new double[ length / 8 ];
var doubleBuf = new byte[ 8 ];
for ( long i = 0 ; i < length ; i += 8 )
{
Array.Copy( data , start + i , doubleBuf , 0 , 8 );
res[ i / 8 ] = BitConverter.ToDouble( doubleBuf , 0 );
}
// is date or just a double?
if ( ( attrs != null ) && ( attrs.ContainsKey( "class" ) && attrs[ "class" ].AsStrings.Contains( "Date" ) ) )
{
result = new SexpArrayDate( res.Select( Convert.ToInt32 ) );
}
else
{
result = new SexpArrayDouble( res );
}
}
break;
case XtArrayString:
{
var res = new List<string>();
long i = 0;
for ( long j = 0 ; j < length ; j++ )
{
if ( data[ start + j ] != 0 )
{
continue;
}
if ( ( j == i + 1 ) && ( data[ start + i ] == 255 ) )
{
res.Add( null );
}
else
{
if ( data[ start + i ] == 255 )
{
i++;
}
var stringBuf = new byte[ j - i ];
Array.Copy( data , start + i , stringBuf , 0 , j - i );
res.Add( Encoding.UTF8.GetString( stringBuf ) );
}
i = j + 1;
}
result = new SexpArrayString( res );
}
break;
case XtListNoTag:
case XtLangNoTag:
case XtVector:
result = new SexpList();
while ( start < end )
{
result.Add( DecodeSexp( data , ref start ) );
}
break;
case XtLangTag:
case XtListTag:
result = new SexpTaggedList();
while ( start < end )
{
Sexp val = DecodeSexp( data , ref start );
Sexp key = DecodeSexp( data , ref start );
result.Add( key.IsNull ? String.Empty : key.AsString , val );
}
break;
case XtRaw:
{
var d = new byte[ length ];
Array.Copy( data , start , d , 0 , length );
result = new SexpQap1Raw( xt , d );
}
break;
default:
throw new RserveException( "Cannot decode an Sexp because the type is not recognized: " + xt );
}
if ( start > end )
{
throw new RserveException( "When decoding an Sexp, more data consumed than provided." );
}
start = end;
if ( attrs != null )
{
foreach ( var a in attrs.AsSexpDictionary )
{
result.Attributes.Add( a.Key , a.Value );
}
}
return result;
}
