func NewPieceData(bitfield *bit_field.Bitfield, pieceLength, lastPieceLength int64) (p *PieceData) {
p = new(PieceData)
p.pieces = make(map[int64]*Piece, bitfield.Len())
p.peers = make(map[string]map[uint64]int64, ACTIVE_PEERS+INCOMING_PEERS)
p.bitfield = bitfield
p.pieceLength = pieceLength
p.lastPieceLength = lastPieceLength
return
}
func (pd *PieceData) SearchPiece(addr string, bitfield *bit_field.Bitfield) (rpiece int64, rblock int, err os.Error) {
// Check if peer has some of the active pieces to finish them
//log.Println("PieceData -> Searching for an already present piece")
for k, piece := range pd.pieces {
available := -1
for block, downloads := range piece.downloaderCount {
if downloads == 0 {
available = block
break
}
}
if available != -1 && bitfield.IsSet(k) {
// Send request piece k, block available
pd.Add(addr, k, available)
rpiece, rblock = k, available
return
}
}
//log.Println("PieceData -> No suitable piece found in active set")
// Check what piece we can request
totalPieces := pd.bitfield.Len()
bytes := bitfield.Bytes()
start := rand.Int63n(totalPieces)
// Search fordward
//log.Println("PieceData -> Searching fordwards")
for piece := pd.bitfield.FindNextPiece(start, bytes); piece != -1 && piece < totalPieces; piece = pd.bitfield.FindNextPiece(piece+1, bytes) {
//log.Println("PieceData -> Piece found, see if it's already in active piece set:", piece)
if _, ok := pd.pieces[piece]; !ok {
// Add new piece to set
pd.Add(addr, piece, 0)
rpiece, rblock = piece, 0
return
}
}
// Search backwards
//log.Println("PieceData -> Searching backwards")
for piece := pd.bitfield.FindNextPiece(0, bytes); piece != -1 && piece < start; piece = pd.bitfield.FindNextPiece(piece+1, bytes) {
//log.Println("PieceData -> Piece found, see if it's already in active piece set:", piece)
if _, ok := pd.pieces[piece]; !ok {
// Add new piece to set
pd.Add(addr, piece, 0)
rpiece, rblock = piece, 0
return
}
}
// If all pieces are taken, double up on an active piece
// if only 20% of pieces remaining
//log.Println("PieceData -> Trying to enter endgame mode")
if float64(pd.bitfield.Count())/float64(pd.bitfield.Len()) < 0.80 {
err = os.NewError("No available block found")
return
}
//log.Println("PieceData -> Doubling up on an active piece")
first := true
min := 0
for k, piece := range pd.pieces {
for block, downloads := range piece.downloaderCount {
if bitfield.IsSet(k) && !pd.CheckRequested(addr, k, block) {
if first && downloads != -1 {
rpiece, rblock, min = k, block, downloads
first = false
}
if downloads != -1 && downloads < min {
rpiece, rblock, min = k, block, downloads
}
}
}
}
if !first && min < MAX_PIECE_REQUESTS {
pd.Add(addr, rpiece, rblock)
return
}
err = os.NewError("No available block found")
return
}