public unsafe override int ReadForward(Stream s, byte[] bulk, BlockDBEntry *entriesPtr)
{
long pos = s.Position;
// Version 2 expects all chunks to be aligned to 4096 bytes
if (pos < BlockSize)
{
s.Position = BlockSize; pos = BlockSize;
}
long remaining = s.Length - pos;
if (remaining == 0)
{
return(0);
}
int bytes = (int)Math.Min(remaining, BlockSize);
int offset = bulk.Length - BlockSize;
// NOTE: bulk and entriesPtr point to same thing
// But we read into the end of the bulk array, thus the entriesPtr pointing
// to start of array never ends up overlapping with the data being read
BlockDBFile.ReadFully(s, bulk, offset, bytes);
return(DecompressChunk(bulk, offset, entriesPtr));
}
public unsafe override int ReadForward(Stream s, byte[] bulk, BlockDBEntry *entriesPtr)
{
long remaining = (s.Length - s.Position) / EntrySize;
int count = (int)Math.Min(remaining, BulkEntries);
if (count > 0)
{
BlockDBFile.ReadFully(s, bulk, 0, count * EntrySize);
}
return(count);
}
public override long CountEntries(Stream s)
{
byte[] data = new byte[8];
s.Position = 16;
BlockDBFile.ReadFully(s, data, 0, data.Length);
uint lo = (uint)ReadInt32(data, 0);
uint hi = (uint)ReadInt32(data, 4);
return((long)((ulong)lo | ((ulong)hi << 32)));
}
public unsafe override int ReadBackward(Stream s, byte[] bulk, BlockDBEntry *entriesPtr)
{
long pos = s.Position;
long remaining = (pos / EntrySize) - HeaderEntries;
int count = (int)Math.Min(remaining, BulkEntries);
if (count > 0)
{
pos -= count * EntrySize;
s.Position = pos;
BlockDBFile.ReadFully(s, bulk, 0, count * EntrySize);
s.Position = pos; // set correct position for next backward read
}
return(count);
}
public unsafe override int ReadBackward(Stream s, byte[] bulk, BlockDBEntry *entriesPtr)
{
long pos = s.Position;
if (pos > BlockSize)
{
int bytes = (int)Math.Min(pos - BlockSize, BlockSize);
int offset = bulk.Length - BlockSize;
pos -= bytes;
s.Position = pos;
BlockDBFile.ReadFully(s, bulk, offset, bytes);
s.Position = pos; // set correct position for next backward read
return(DecompressChunk(bulk, offset, entriesPtr));
}
return(0);
}