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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 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	}
    89	

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