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 // The iotest package implements Readers and Writers
   6 // useful only for testing.
   7 package iotest
   8
   9 import (
  10         "io"
  11         "os"
  12 )
  13
  14 // OneByteReader returns a Reader that implements
  15 // each non-empty Read by reading one byte from r.
  16 func OneByteReader(r io.Reader) io.Reader { return &oneByteReader{r} }
  17
  18 type oneByteReader struct {
  19         r io.Reader
  20 }
  21
  22 func (r *oneByteReader) Read(p []byte) (int, os.Error) {
  23         if len(p) == 0 {
  24                 return 0, nil
  25         }
  26         return r.r.Read(p[0:1])
  27 }
  28
  29 // HalfReader returns a Reader that implements Read
  30 // by reading half as many requested bytes from r.
  31 func HalfReader(r io.Reader) io.Reader { return &halfReader{r} }
  32
  33 type halfReader struct {
  34         r io.Reader
  35 }
  36
  37 func (r *halfReader) Read(p []byte) (int, os.Error) {
  38         return r.r.Read(p[0 : (len(p)+1)/2])
  39 }
  40
  41
  42 // DataErrReader returns a Reader that returns the final
  43 // error with the last data read, instead of by itself with
  44 // zero bytes of 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 os.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 {
  63                         break
  64                 }
  65                 n = copy(p, r.unread)
  66                 r.unread = r.unread[n:]
  67         }
  68         return
  69 }