void ReadHeader()
{
byte[] header = new byte[this.headersize];
this.fromfile.Seek(this.seekStart, System.IO.SeekOrigin.Begin);
this.fromfile.Read(header, 0, this.headersize);
int index = 0;
// check prefix
foreach (byte b in HEADERPREFIX)
{
if (header[index] != b)
{
throw new LinkedFileException("invalid header prefix");
}
index++;
}
// skip version (for now)
index++;
// read buffersize
this.buffersize = BufferFile.Retrieve(header, index);
index += BufferFile.INTSTORAGE;
this.FreeListHead = BufferFile.RetrieveLong(header, index);
this.SanityCheck();
this.headerDirty = false;
}
public void Load(byte[] serialization)
{
int index = 0;
int byteCount = serialization.Length;
if (this.values.Count != 0 || this.keys.Count != 0)
{
throw new BplusTreeException("load into nonempty xBucket not permitted");
}
while (index < byteCount)
{
// get key prefix and key
int keylength = BufferFile.Retrieve(serialization, index);
index += BufferFile.INTSTORAGE;
byte[] keybytes = new byte[keylength];
Array.Copy(serialization, index, keybytes, 0, keylength);
string keystring = BplusTree.BytesToString(keybytes);
index += keylength;
// get value prefix and value
int valuelength = BufferFile.Retrieve(serialization, index);
index += BufferFile.INTSTORAGE;
byte[] valuebytes = new byte[valuelength];
Array.Copy(serialization, index, valuebytes, 0, valuelength);
// record new key and value
this.keys.Add(keystring);
this.values.Add(valuebytes);
index += valuelength;
}
if (index != byteCount)
{
throw new BplusTreeException("bad byte count in serialization " + byteCount);
}
}
public byte[] GetChunk(long headBufferNumber)
{
// get the head, interpret the length
byte buffertype;
long nextBufferNumber;
byte[] buffer = this.ParseBuffer(headBufferNumber, out buffertype, out nextBufferNumber);
int length = BufferFile.Retrieve(buffer, 0);
if (length < 0)
{
throw new LinkedFileException("negative length block? must be garbage: " + length);
}
if (buffertype != HEAD)
{
throw new LinkedFileException("first buffer not marked HEAD");
}
byte[] result = new byte[length];
// read in the data from the first buffer
int firstLength = this.buffersize - BufferFile.INTSTORAGE;
if (firstLength > length)
{
firstLength = length;
}
Array.Copy(buffer, BufferFile.INTSTORAGE, result, 0, firstLength);
int stored = firstLength;
while (stored < length)
{
// get the next buffer
long thisBufferNumber = nextBufferNumber;
buffer = this.ParseBuffer(thisBufferNumber, out buffertype, out nextBufferNumber);
int nextLength = this.buffersize;
if (length - stored < nextLength)
{
nextLength = length - stored;
}
Array.Copy(buffer, 0, result, stored, nextLength);
stored += nextLength;
}
return(result);
}