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