forked from hardcoresushi/DroidFS
56 lines
1.1 KiB
Go
56 lines
1.1 KiB
Go
package cryptocore
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import (
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"bytes"
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"log"
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"sync"
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)
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// Number of bytes to prefetch.
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// 512 looks like a good compromise between throughput and latency - see
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// randsize_test.go for numbers.
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const prefetchN = 512
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func init() {
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randPrefetcher.refill = make(chan []byte)
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go randPrefetcher.refillWorker()
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}
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type randPrefetcherT struct {
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sync.Mutex
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buf bytes.Buffer
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refill chan []byte
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}
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func (r *randPrefetcherT) read(want int) (out []byte) {
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out = make([]byte, want)
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r.Lock()
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// Note: don't use defer, it slows us down!
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have, err := r.buf.Read(out)
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if have == want && err == nil {
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r.Unlock()
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return out
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}
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// Buffer was empty -> re-fill
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fresh := <-r.refill
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if len(fresh) != prefetchN {
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log.Panicf("randPrefetcher: refill: got %d bytes instead of %d", len(fresh), prefetchN)
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}
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r.buf.Reset()
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r.buf.Write(fresh)
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have, err = r.buf.Read(out)
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if have != want || err != nil {
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log.Panicf("randPrefetcher could not satisfy read: have=%d want=%d err=%v", have, want, err)
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}
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r.Unlock()
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return out
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}
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func (r *randPrefetcherT) refillWorker() {
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for {
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r.refill <- RandBytes(prefetchN)
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}
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}
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var randPrefetcher randPrefetcherT
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