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134 lines
3.8 KiB
Go
134 lines
3.8 KiB
Go
//
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// Written by Maxim Khitrov (November 2012)
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//
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package flowrate
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import (
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"errors"
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"io"
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)
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// ErrLimit is returned by the Writer when a non-blocking write is short due to
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// the transfer rate limit.
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var ErrLimit = errors.New("flowrate: flow rate limit exceeded")
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// Limiter is implemented by the Reader and Writer to provide a consistent
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// interface for monitoring and controlling data transfer.
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type Limiter interface {
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Done() int64
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Status() Status
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SetTransferSize(bytes int64)
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SetLimit(new int64) (old int64)
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SetBlocking(new bool) (old bool)
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}
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// Reader implements io.ReadCloser with a restriction on the rate of data
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// transfer.
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type Reader struct {
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io.Reader // Data source
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*Monitor // Flow control monitor
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limit int64 // Rate limit in bytes per second (unlimited when <= 0)
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block bool // What to do when no new bytes can be read due to the limit
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}
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// NewReader restricts all Read operations on r to limit bytes per second.
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func NewReader(r io.Reader, limit int64) *Reader {
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return &Reader{r, New(0, 0), limit, true}
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}
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// Read reads up to len(p) bytes into p without exceeding the current transfer
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// rate limit. It returns (0, nil) immediately if r is non-blocking and no new
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// bytes can be read at this time.
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func (r *Reader) Read(p []byte) (n int, err error) {
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p = p[:r.Limit(len(p), r.limit, r.block)]
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if len(p) > 0 {
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n, err = r.IO(r.Reader.Read(p))
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}
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return
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}
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// SetLimit changes the transfer rate limit to new bytes per second and returns
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// the previous setting.
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func (r *Reader) SetLimit(new int64) (old int64) {
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old, r.limit = r.limit, new
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return
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}
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// SetBlocking changes the blocking behavior and returns the previous setting. A
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// Read call on a non-blocking reader returns immediately if no additional bytes
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// may be read at this time due to the rate limit.
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func (r *Reader) SetBlocking(new bool) (old bool) {
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old, r.block = r.block, new
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return
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}
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// Close closes the underlying reader if it implements the io.Closer interface.
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func (r *Reader) Close() error {
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defer r.Done()
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if c, ok := r.Reader.(io.Closer); ok {
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return c.Close()
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}
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return nil
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}
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// Writer implements io.WriteCloser with a restriction on the rate of data
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// transfer.
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type Writer struct {
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io.Writer // Data destination
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*Monitor // Flow control monitor
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limit int64 // Rate limit in bytes per second (unlimited when <= 0)
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block bool // What to do when no new bytes can be written due to the limit
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}
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// NewWriter restricts all Write operations on w to limit bytes per second. The
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// transfer rate and the default blocking behavior (true) can be changed
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// directly on the returned *Writer.
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func NewWriter(w io.Writer, limit int64) *Writer {
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return &Writer{w, New(0, 0), limit, true}
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}
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// Write writes len(p) bytes from p to the underlying data stream without
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// exceeding the current transfer rate limit. It returns (n, ErrLimit) if w is
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// non-blocking and no additional bytes can be written at this time.
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func (w *Writer) Write(p []byte) (n int, err error) {
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var c int
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for len(p) > 0 && err == nil {
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s := p[:w.Limit(len(p), w.limit, w.block)]
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if len(s) > 0 {
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c, err = w.IO(w.Writer.Write(s))
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} else {
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return n, ErrLimit
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}
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p = p[c:]
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n += c
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}
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return
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}
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// SetLimit changes the transfer rate limit to new bytes per second and returns
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// the previous setting.
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func (w *Writer) SetLimit(new int64) (old int64) {
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old, w.limit = w.limit, new
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return
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}
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// SetBlocking changes the blocking behavior and returns the previous setting. A
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// Write call on a non-blocking writer returns as soon as no additional bytes
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// may be written at this time due to the rate limit.
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func (w *Writer) SetBlocking(new bool) (old bool) {
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old, w.block = w.block, new
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return
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}
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// Close closes the underlying writer if it implements the io.Closer interface.
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func (w *Writer) Close() error {
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defer w.Done()
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if c, ok := w.Writer.(io.Closer); ok {
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return c.Close()
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}
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return nil
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}
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