void readHeader() throws Exception {
byte[] header = new byte[this.headersize];
// this.fromfile.Seek(this.seekStart, System.IO.SeekOrigin.Begin);
this.fromfile.seek(this.seekStart);
// this.fromfile.Read(header, 0, this.headersize);
this.fromfile.read(header, 0, this.headersize);
int index = 0;
// check prefix
// foreach (byte b in HEADERPREFIX)
for (int i = 0; i < HEADERPREFIX.length; i++) {
byte b = HEADERPREFIX[i];
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 byte[] GetChunk(long HeadBufferNumber) throws Exception {
// get the head, interpret the length
// byte buffertype;
// long NextBufferNumber;
// byte[] buffer = this.ParseBuffer(HeadBufferNumber, out buffertype, out NextBufferNumber);
ParseBuffer P = new ParseBuffer(HeadBufferNumber);
byte buffertype = P.type;
long NextBufferNumber = P.NextBufferNumber;
byte[] buffer = P.payload;
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);
for (int i = 0; i < firstLength; i++) {
result[i] = buffer[BufferFile.INTSTORAGE + i];
}
int stored = firstLength;
while (stored < length) {
// get the next buffer
long thisBufferNumber = NextBufferNumber;
// buffer = this.ParseBuffer(thisBufferNumber, out buffertype, out NextBufferNumber);
P = new ParseBuffer(thisBufferNumber);
buffer = P.payload;
buffertype = P.type;
NextBufferNumber = P.NextBufferNumber;
int nextLength = this.buffersize;
if (length - stored < nextLength) {
nextLength = length - stored;
}
// Array.Copy(buffer, 0, result, stored, nextLength);
for (int i = 0; i < nextLength; i++) {
result[stored + i] = buffer[i];
}
stored += nextLength;
}
return result;
}
