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misc.go
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misc.go
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package torrent
import (
"crypto"
"errors"
"fmt"
"time"
"github.com/michaeldye/torrent/metainfo"
pp "github.com/michaeldye/torrent/peer_protocol"
)
const (
pieceHash = crypto.SHA1
maxRequests = 250 // Maximum pending requests we allow peers to send us.
defaultChunkSize = 0x4000 // 16KiB
// Peer ID client identifier prefix. We'll update this occasionally to
// reflect changes to client behaviour that other clients may depend on.
// Also see `extendedHandshakeClientVersion`.
bep20 = "-GT0001-"
nominalDialTimeout = time.Second * 30
minDialTimeout = 5 * time.Second
)
type (
InfoHash [20]byte
pieceSum [20]byte
)
func (ih InfoHash) AsString() string {
return string(ih[:])
}
func (ih InfoHash) HexString() string {
return fmt.Sprintf("%x", ih[:])
}
func lastChunkSpec(pieceLength, chunkSize pp.Integer) (cs chunkSpec) {
cs.Begin = (pieceLength - 1) / chunkSize * chunkSize
cs.Length = pieceLength - cs.Begin
return
}
type chunkSpec struct {
Begin, Length pp.Integer
}
type request struct {
Index pp.Integer
chunkSpec
}
func newRequest(index, begin, length pp.Integer) request {
return request{index, chunkSpec{begin, length}}
}
var (
// Requested data not yet available.
errDataNotReady = errors.New("data not ready")
)
// The size in bytes of a metadata extension piece.
func metadataPieceSize(totalSize int, piece int) int {
ret := totalSize - piece*(1<<14)
if ret > 1<<14 {
ret = 1 << 14
}
return ret
}
type superer interface {
Super() interface{}
}
// Returns ok if there's a parent, and it's not nil.
func super(child interface{}) (parent interface{}, ok bool) {
s, ok := child.(superer)
if !ok {
return
}
parent = s.Super()
ok = parent != nil
return
}
// Return the request that would include the given offset into the torrent data.
func torrentOffsetRequest(torrentLength, pieceSize, chunkSize, offset int64) (
r request, ok bool) {
if offset < 0 || offset >= torrentLength {
return
}
r.Index = pp.Integer(offset / pieceSize)
r.Begin = pp.Integer(offset % pieceSize / chunkSize * chunkSize)
r.Length = pp.Integer(chunkSize)
pieceLeft := pp.Integer(pieceSize - int64(r.Begin))
if r.Length > pieceLeft {
r.Length = pieceLeft
}
torrentLeft := torrentLength - int64(r.Index)*pieceSize - int64(r.Begin)
if int64(r.Length) > torrentLeft {
r.Length = pp.Integer(torrentLeft)
}
ok = true
return
}
func torrentRequestOffset(torrentLength, pieceSize int64, r request) (off int64) {
off = int64(r.Index)*pieceSize + int64(r.Begin)
if off < 0 || off >= torrentLength {
panic("invalid request")
}
return
}
func validateInfo(info *metainfo.Info) error {
if len(info.Pieces)%20 != 0 {
return errors.New("pieces has invalid length")
}
if int((info.TotalLength()+info.PieceLength-1)/info.PieceLength) != info.NumPieces() {
return errors.New("piece count and file lengths are at odds")
}
return nil
}
func chunkIndexSpec(index int, pieceLength, chunkSize pp.Integer) chunkSpec {
ret := chunkSpec{pp.Integer(index) * chunkSize, chunkSize}
if ret.Begin+ret.Length > pieceLength {
ret.Length = pieceLength - ret.Begin
}
return ret
}