Source file src/pkg/testing/iotest/reader.go

     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	// Package iotest implements Readers and Writers useful mainly for testing.
     6	package iotest
     7	
     8	import (
     9		"errors"
    10		"io"
    11	)
    12	
    13	// OneByteReader returns a Reader that implements
    14	// each non-empty Read by reading one byte from r.
    15	func OneByteReader(r io.Reader) io.Reader { return &oneByteReader{r} }
    16	
    17	type oneByteReader struct {
    18		r io.Reader
    19	}
    20	
    21	func (r *oneByteReader) Read(p []byte) (int, error) {
    22		if len(p) == 0 {
    23			return 0, nil
    24		}
    25		return r.r.Read(p[0:1])
    26	}
    27	
    28	// HalfReader returns a Reader that implements Read
    29	// by reading half as many requested bytes from r.
    30	func HalfReader(r io.Reader) io.Reader { return &halfReader{r} }
    31	
    32	type halfReader struct {
    33		r io.Reader
    34	}
    35	
    36	func (r *halfReader) Read(p []byte) (int, error) {
    37		return r.r.Read(p[0 : (len(p)+1)/2])
    38	}
    39	
    40	// DataErrReader returns a Reader that returns the final
    41	// error with the last data read, instead of by itself with
    42	// zero bytes of data.
    43	func DataErrReader(r io.Reader) io.Reader { return &dataErrReader{r, nil, make([]byte, 1024)} }
    44	
    45	type dataErrReader struct {
    46		r      io.Reader
    47		unread []byte
    48		data   []byte
    49	}
    50	
    51	func (r *dataErrReader) Read(p []byte) (n int, err error) {
    52		// loop because first call needs two reads:
    53		// one to get data and a second to look for an error.
    54		for {
    55			if len(r.unread) == 0 {
    56				n1, err1 := r.r.Read(r.data)
    57				r.unread = r.data[0:n1]
    58				err = err1
    59			}
    60			if n > 0 || err != nil {
    61				break
    62			}
    63			n = copy(p, r.unread)
    64			r.unread = r.unread[n:]
    65		}
    66		return
    67	}
    68	
    69	var ErrTimeout = errors.New("timeout")
    70	
    71	// TimeoutReader returns ErrTimeout on the second read
    72	// with no data.  Subsequent calls to read succeed.
    73	func TimeoutReader(r io.Reader) io.Reader { return &timeoutReader{r, 0} }
    74	
    75	type timeoutReader struct {
    76		r     io.Reader
    77		count int
    78	}
    79	
    80	func (r *timeoutReader) Read(p []byte) (int, error) {
    81		r.count++
    82		if r.count == 2 {
    83			return 0, ErrTimeout
    84		}
    85		return r.r.Read(p)
    86	}