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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package iotest implements Readers and Writers useful mainly for testing.
package iotest
import (
"errors"
"io"
)
// OneByteReader returns a Reader that implements
// each non-empty Read by reading one byte from r.
func OneByteReader(r io.Reader) io.Reader { return &oneByteReader{r} }
type oneByteReader struct {
r io.Reader
}
func (r *oneByteReader) Read(p []byte) (int, error) {
if len(p) == 0 {
return 0, nil
}
return r.r.Read(p[0:1])
}
// HalfReader returns a Reader that implements Read
// by reading half as many requested bytes from r.
func HalfReader(r io.Reader) io.Reader { return &halfReader{r} }
type halfReader struct {
r io.Reader
}
func (r *halfReader) Read(p []byte) (int, error) {
return r.r.Read(p[0 : (len(p)+1)/2])
}
// DataErrReader changes the way errors are handled by a Reader. Normally, a
// Reader returns an error (typically EOF) from the first Read call after the
// last piece of data is read. DataErrReader wraps a Reader and changes its
// behavior so the final error is returned along with the final data, instead
// of in the first call after the final data.
func DataErrReader(r io.Reader) io.Reader { return &dataErrReader{r, nil, make([]byte, 1024)} }
type dataErrReader struct {
r io.Reader
unread []byte
data []byte
}
func (r *dataErrReader) Read(p []byte) (n int, err error) {
// loop because first call needs two reads:
// one to get data and a second to look for an error.
for {
if len(r.unread) == 0 {
n1, err1 := r.r.Read(r.data)
r.unread = r.data[0:n1]
err = err1
}
if n > 0 || err != nil {
break
}
n = copy(p, r.unread)
r.unread = r.unread[n:]
}
return
}
// ErrTimeout is a fake timeout error.
var ErrTimeout = errors.New("timeout")
// TimeoutReader returns ErrTimeout on the second read
// with no data. Subsequent calls to read succeed.
func TimeoutReader(r io.Reader) io.Reader { return &timeoutReader{r, 0} }
type timeoutReader struct {
r io.Reader
count int
}
func (r *timeoutReader) Read(p []byte) (int, error) {
r.count++
if r.count == 2 {
return 0, ErrTimeout
}
return r.r.Read(p)
}
// ErrReader returns an io.Reader that returns 0, err from all Read calls.
func ErrReader(err error) io.Reader {
return &alwaysErrReader{err: err}
}
type alwaysErrReader struct {
err error
}
func (aer *alwaysErrReader) Read(p []byte) (int, error) {
return 0, aer.err
}
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