/// <summary>
/// dekodiert nur den Header eines Blockes (benötigt mindestens 32 Bytes)
/// </summary>
/// <param name="buf">Buffer, welcher ausgelesen werden soll</param>
/// <param name="ofs">Startposition innerhalb des Buffers</param>
/// <param name="result">fertig gelesenes Ergebnis</param>
/// <returns>Größe des gesamten Blockes in Bytes</returns>
public static int DecodeQuick(byte[] buf, int ofs, out OsmBlob result)
{
/*****
* message BlobHeader
* {
* required string type = 1;
* optional bytes indexdata = 2;
* required int32 datasize = 3;
* }
*****/
int len = 0;
int blobHeaderLen;
len += ProtoBuf.ReadInt32Fix(buf, ofs + len, out blobHeaderLen);
result = new OsmBlob();
// --- required string type = 1; ---
string type;
if (buf[ofs + len++] != (1 << 3 | 2))
{
throw new PbfParseException();
}
len += ProtoBuf.ReadString(buf, ofs + len, out type);
// --- optional bytes indexdata = 2; ---
if (buf[ofs + len] == (2 << 3 | 2))
{
throw new NotImplementedException();
}
// --- required int32 datasize = 3; ---
if (buf[ofs + len++] != (3 << 3 | 0))
{
throw new PbfParseException();
}
ulong tmp;
len += ProtoBuf.ReadVarInt(buf, ofs + len, out tmp);
result.blobLen = len + (int)tmp;
if (len - sizeof(int) != blobHeaderLen)
{
throw new PbfParseException();
}
/*****
* message Blob
* {
* optional bytes raw = 1; // keine Kompression
* optional int32 raw_size = 2; // Nur gesetzt, wenn komprimiert, auf die unkomprimierte Größe
* optional bytes zlib_data = 3;
* // optional bytes lzma_data = 4; // GEPLANT.
* // optional bytes OBSOLETE_bzip2_data = 5; // Veraltet.
* }
*****/
// --- optional bytes raw = 1; ---
if (buf[ofs + len] == (1 << 3 | 2))
{
throw new NotSupportedException();
}
// --- optional int32 raw_size = 2; ---
if (buf[ofs + len] == (2 << 3 | 0))
{
len++;
len += ProtoBuf.ReadVarInt(buf, ofs + len, out tmp);
result.rawSize = (int)tmp;
}
// --- optional bytes zlib_data = 3; ---
if (buf[ofs + len] == (3 << 3 | 2))
{
len++;
len += ProtoBuf.ReadVarInt(buf, ofs + len, out tmp);
result.zlibOfs = len;
result.zlibLen = (int)tmp;
len += (int)tmp;
}
else
{
// --- optional bytes lzma_data = 4; ---
if (buf[ofs + len] == (4 << 3 | 2))
{
throw new NotSupportedException();
}
// --- optional bytes OBSOLETE_bzip2_data = 5; ---
if (buf[ofs + len] == (5 << 3 | 2))
{
throw new NotSupportedException();
}
}
if (len != result.blobLen)
{
throw new PbfParseException();
}
switch (type)
{
case "OSMHeader": break;
case "OSMData": break;
default: throw new Exception("unknown Type: " + type);
}
return(len);
}