// reserveHashes reserves a set of hashes for the given peer, skipping previously
// failed ones.
//
// Note, this method expects the queue lock to be already held for writing. The
// reason the lock is not obtained in here is because the parameters already need
// to access the queue, so they already need a lock anyway.
func (q *queue) reserveHashes(p *peer, count int, taskQueue *prque.Prque, taskGen func(int), pendPool map[string]*fetchRequest, maxPending int) *fetchRequest {
// Short circuit if the peer's already downloading something (sanity check to
// not corrupt state)
if _, ok := pendPool[p.id]; ok {
return nil
}
// Calculate an upper limit on the hashes we might fetch (i.e. throttling)
allowance := maxPending
if allowance > 0 {
for _, request := range pendPool {
allowance -= len(request.Hashes)
}
}
// If there's a task generator, ask it to fill our task queue
if taskGen != nil && taskQueue.Size() < allowance {
taskGen(allowance - taskQueue.Size())
}
if taskQueue.Empty() {
return nil
}
// Retrieve a batch of hashes, skipping previously failed ones
send := make(map[common.Hash]int)
skip := make(map[common.Hash]int)
for proc := 0; (allowance == 0 || proc < allowance) && len(send) < count && !taskQueue.Empty(); proc++ {
hash, priority := taskQueue.Pop()
if p.Lacks(hash.(common.Hash)) {
skip[hash.(common.Hash)] = int(priority)
} else {
send[hash.(common.Hash)] = int(priority)
}
}
// Merge all the skipped hashes back
for hash, index := range skip {
taskQueue.Push(hash, float32(index))
}
// Assemble and return the block download request
if len(send) == 0 {
return nil
}
request := &fetchRequest{
Peer: p,
Hashes: send,
Time: time.Now(),
}
pendPool[p.id] = request
return request
}
// reserveHeaders reserves a set of data download operations for a given peer,
// skipping any previously failed ones. This method is a generic version used
// by the individual special reservation functions.
//
// Note, this method expects the queue lock to be already held for writing. The
// reason the lock is not obtained in here is because the parameters already need
// to access the queue, so they already need a lock anyway.
func (q *queue) reserveHeaders(p *peer, count int, taskPool map[common.Hash]*types.Header, taskQueue *prque.Prque,
pendPool map[string]*fetchRequest, donePool map[common.Hash]struct{}, isNoop func(*types.Header) bool) (*fetchRequest, bool, error) {
// Short circuit if the pool has been depleted, or if the peer's already
// downloading something (sanity check not to corrupt state)
if taskQueue.Empty() {
return nil, false, nil
}
if _, ok := pendPool[p.id]; ok {
return nil, false, nil
}
// Calculate an upper limit on the items we might fetch (i.e. throttling)
space := len(q.resultCache) - len(donePool)
for _, request := range pendPool {
space -= len(request.Headers)
}
// Retrieve a batch of tasks, skipping previously failed ones
send := make([]*types.Header, 0, count)
skip := make([]*types.Header, 0)
progress := false
for proc := 0; proc < space && len(send) < count && !taskQueue.Empty(); proc++ {
header := taskQueue.PopItem().(*types.Header)
// If we're the first to request this task, initialise the result container
index := int(header.Number.Int64() - int64(q.resultOffset))
if index >= len(q.resultCache) || index < 0 {
common.Report("index allocation went beyond available resultCache space")
return nil, false, errInvalidChain
}
if q.resultCache[index] == nil {
components := 1
if q.mode == FastSync && header.Number.Uint64() <= q.fastSyncPivot {
components = 2
}
q.resultCache[index] = &fetchResult{
Pending: components,
Header: header,
}
}
// If this fetch task is a noop, skip this fetch operation
if isNoop(header) {
donePool[header.Hash()] = struct{}{}
delete(taskPool, header.Hash())
space, proc = space-1, proc-1
q.resultCache[index].Pending--
progress = true
continue
}
// Otherwise unless the peer is known not to have the data, add to the retrieve list
if p.Lacks(header.Hash()) {
skip = append(skip, header)
} else {
send = append(send, header)
}
}
// Merge all the skipped headers back
for _, header := range skip {
taskQueue.Push(header, -float32(header.Number.Uint64()))
}
if progress {
// Wake WaitResults, resultCache was modified
q.active.Signal()
}
// Assemble and return the block download request
if len(send) == 0 {
return nil, progress, nil
}
request := &fetchRequest{
Peer: p,
Headers: send,
Time: time.Now(),
}
pendPool[p.id] = request
return request, progress, nil
}