libgo/go/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 changes the way errors are handled by a Reader. Normally, a
  41 // Reader returns an error (typically EOF) from the first Read call after the
  42 // last piece of data is read. DataErrReader wraps a Reader and changes its
  43 // behavior so the final error is returned along with the final data, instead
  44 // of in the first call after the final data.
  45 func DataErrReader(r io.Reader) io.Reader { return &dataErrReader{r, nil, make([]byte, 1024)} }
  46
  47 type dataErrReader struct {
  48         r      io.Reader
  49         unread []byte
  50         data   []byte
  51 }
  52
  53 func (r *dataErrReader) Read(p []byte) (n int, err error) {
  54         // loop because first call needs two reads:
  55         // one to get data and a second to look for an error.
  56         for {
  57                 if len(r.unread) == 0 {
  58                         n1, err1 := r.r.Read(r.data)
  59                         r.unread = r.data[0:n1]
  60                         err = err1
  61                 }
  62                 if n > 0 || err != nil {
  63                         break
  64                 }
  65                 n = copy(p, r.unread)
  66                 r.unread = r.unread[n:]
  67         }
  68         return
  69 }
  70
  71 var ErrTimeout = errors.New("timeout")
  72
  73 // TimeoutReader returns ErrTimeout on the second read
  74 // with no data.  Subsequent calls to read succeed.
  75 func TimeoutReader(r io.Reader) io.Reader { return &timeoutReader{r, 0} }
  76
  77 type timeoutReader struct {
  78         r     io.Reader
  79         count int
  80 }
  81
  82 func (r *timeoutReader) Read(p []byte) (int, error) {
  83         r.count++
  84         if r.count == 2 {
  85                 return 0, ErrTimeout
  86         }
  87         return r.r.Read(p)
  88 }