85 lines
1.9 KiB
Go
85 lines
1.9 KiB
Go
package torrent
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import (
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"math/rand"
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"sync"
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pp "github.com/anacrolix/torrent/peer_protocol"
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)
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// Piece priority describes the importance of obtaining a particular piece.
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type piecePriority byte
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const (
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PiecePriorityNone piecePriority = iota // Not wanted.
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PiecePriorityNormal // Wanted.
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PiecePriorityReadahead // May be required soon.
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PiecePriorityNext // Succeeds a piece where a read occurred.
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PiecePriorityNow // A read occurred in this piece.
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)
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type piece struct {
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// The completed piece SHA1 hash, from the metainfo "pieces" field.
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Hash pieceSum
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// Chunks we don't have. The offset and length can be determined by the
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// request chunkSize in use.
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PendingChunkSpecs []bool
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Hashing bool
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QueuedForHash bool
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EverHashed bool
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Event sync.Cond
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Priority piecePriority
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}
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func (p *piece) pendingChunk(cs chunkSpec) bool {
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if p.PendingChunkSpecs == nil {
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return false
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}
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return p.PendingChunkSpecs[chunkIndex(cs)]
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}
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func (p *piece) numPendingChunks() (ret int) {
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for _, pending := range p.PendingChunkSpecs {
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if pending {
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ret++
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}
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}
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return
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}
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func (p *piece) unpendChunkIndex(i int) {
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if p.PendingChunkSpecs == nil {
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return
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}
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p.PendingChunkSpecs[i] = false
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}
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func chunkIndexSpec(index int, pieceLength pp.Integer) chunkSpec {
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ret := chunkSpec{pp.Integer(index) * chunkSize, chunkSize}
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if ret.Begin+ret.Length > pieceLength {
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ret.Length = pieceLength - ret.Begin
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}
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return ret
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}
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func (p *piece) shuffledPendingChunkSpecs(pieceLength pp.Integer) (css []chunkSpec) {
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if p.numPendingChunks() == 0 {
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return
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}
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css = make([]chunkSpec, 0, p.numPendingChunks())
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for i, pending := range p.PendingChunkSpecs {
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if pending {
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css = append(css, chunkIndexSpec(i, pieceLength))
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}
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}
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if len(css) <= 1 {
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return
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}
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for i := range css {
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j := rand.Intn(i + 1)
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css[i], css[j] = css[j], css[i]
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}
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return
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}
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