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throttle.go
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throttle.go
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package iokit
import (
"io"
"math"
"github.com/insolar/vanilla/throw"
)
type RateLimiter interface {
TakeQuota(max int64) int64
}
func RateLimitReader(r io.Reader, q RateLimiter) *RateLimitedReader {
switch {
case r == nil:
panic(throw.IllegalValue())
case q == nil:
panic(throw.IllegalValue())
}
return &RateLimitedReader{r, q}
}
func RateLimitWriter(w io.Writer, q RateLimiter) *RateLimitedWriter {
switch {
case w == nil:
panic(throw.IllegalValue())
case q == nil:
panic(throw.IllegalValue())
}
return &RateLimitedWriter{w, q}
}
var _ io.Reader = RateLimitedReader{}
var _ io.WriterTo = RateLimitedReader{}
type RateLimitedReader struct {
R io.Reader
Q RateLimiter
}
func (r RateLimitedReader) WriteTo(w io.Writer) (int64, error) {
return RateLimitedCopy(w, r.R, r.Q)
}
func (r RateLimitedReader) Read(p []byte) (int, error) {
return RateLimitedByteCopy(r.R.Read, p, r.Q)
}
func (r RateLimitedReader) Close() error {
if c, ok := r.R.(io.Closer); ok {
return c.Close()
}
return nil
}
var _ io.Writer = RateLimitedWriter{}
var _ io.ReaderFrom = RateLimitedWriter{}
type RateLimitedWriter struct {
W io.Writer
Q RateLimiter
}
func (r RateLimitedWriter) ReadFrom(rd io.Reader) (int64, error) {
return RateLimitedCopy(r.W, rd, r.Q)
}
func (r RateLimitedWriter) Write(p []byte) (int, error) {
return RateLimitedByteCopy(r.W.Write, p, r.Q)
}
func (r RateLimitedWriter) Close() error {
if c, ok := r.W.(io.Closer); ok {
return c.Close()
}
return nil
}
/****************************/
const rateLimitBlockMin = 4096
const rateLimitBlockMax = 32768 // don't set too high to avoid exhaustion of rate limiter
type quotaSizer struct {
v int64
}
func (p *quotaSizer) estimate() int64 {
switch {
case p.v < rateLimitBlockMin:
return rateLimitBlockMin
case p.v > rateLimitBlockMax:
return rateLimitBlockMax
}
return p.v
}
func (p *quotaSizer) update(n int64) {
if p.v < n {
p.v = n
} else {
p.v -= n
}
}
func RateLimitedCopy(writer io.Writer, reader io.Reader, q RateLimiter) (int64, error) {
if q == nil {
return io.Copy(writer, reader)
}
// io.LimitedReader is reused for multiple calls to io.Copy
sizer := quotaSizer{}
limited := io.LimitedReader{}
limited.R, sizer.v = traverseLimitReaders(reader, math.MaxInt64)
innerW, maxW := traverseLimitWriters(writer, math.MaxInt64)
switch {
case maxW == 0 || sizer.v == 0:
return 0, nil
case maxW < sizer.v:
sizer.v = maxW
case sizer.v == math.MaxInt64:
sizer.v = 0
}
for total := int64(0); ; {
limited.N += q.TakeQuota(sizer.estimate())
for limited.N > 0 {
// io.Copy will use io.ReaderFrom when available
n, err := io.Copy(innerW, &limited)
total += n
if err != nil {
updatedLimitReaders(reader, total)
updatedLimitWriters(writer, total)
return total, err
}
sizer.update(n)
}
}
}
func RateLimitedByteCopy(fn func([]byte) (int, error), p []byte, q RateLimiter) (int, error) {
if q == nil {
return fn(p)
}
total := 0
for len(p) > 0 {
for q := q.TakeQuota(int64(len(p))); q > 0; {
n, err := fn(p[:q])
if err != nil {
return total + n, err
}
total += n
p = p[n:]
q -= int64(n)
}
}
return total, nil
}
func RateLimitedBySize(n int64, q RateLimiter) error {
if q == nil {
return nil
}
for ; n > 0; n -= q.TakeQuota(n) {
}
return nil
}