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Source file src/io/io_test.go

Documentation: io

  // Copyright 2009 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  package io_test
  
  import (
  	"bytes"
  	"errors"
  	"fmt"
  	. "io"
  	"strings"
  	"testing"
  )
  
  // An version of bytes.Buffer without ReadFrom and WriteTo
  type Buffer struct {
  	bytes.Buffer
  	ReaderFrom // conflicts with and hides bytes.Buffer's ReaderFrom.
  	WriterTo   // conflicts with and hides bytes.Buffer's WriterTo.
  }
  
  // Simple tests, primarily to verify the ReadFrom and WriteTo callouts inside Copy, CopyBuffer and CopyN.
  
  func TestCopy(t *testing.T) {
  	rb := new(Buffer)
  	wb := new(Buffer)
  	rb.WriteString("hello, world.")
  	Copy(wb, rb)
  	if wb.String() != "hello, world." {
  		t.Errorf("Copy did not work properly")
  	}
  }
  
  func TestCopyBuffer(t *testing.T) {
  	rb := new(Buffer)
  	wb := new(Buffer)
  	rb.WriteString("hello, world.")
  	CopyBuffer(wb, rb, make([]byte, 1)) // Tiny buffer to keep it honest.
  	if wb.String() != "hello, world." {
  		t.Errorf("CopyBuffer did not work properly")
  	}
  }
  
  func TestCopyBufferNil(t *testing.T) {
  	rb := new(Buffer)
  	wb := new(Buffer)
  	rb.WriteString("hello, world.")
  	CopyBuffer(wb, rb, nil) // Should allocate a buffer.
  	if wb.String() != "hello, world." {
  		t.Errorf("CopyBuffer did not work properly")
  	}
  }
  
  func TestCopyReadFrom(t *testing.T) {
  	rb := new(Buffer)
  	wb := new(bytes.Buffer) // implements ReadFrom.
  	rb.WriteString("hello, world.")
  	Copy(wb, rb)
  	if wb.String() != "hello, world." {
  		t.Errorf("Copy did not work properly")
  	}
  }
  
  func TestCopyWriteTo(t *testing.T) {
  	rb := new(bytes.Buffer) // implements WriteTo.
  	wb := new(Buffer)
  	rb.WriteString("hello, world.")
  	Copy(wb, rb)
  	if wb.String() != "hello, world." {
  		t.Errorf("Copy did not work properly")
  	}
  }
  
  // Version of bytes.Buffer that checks whether WriteTo was called or not
  type writeToChecker struct {
  	bytes.Buffer
  	writeToCalled bool
  }
  
  func (wt *writeToChecker) WriteTo(w Writer) (int64, error) {
  	wt.writeToCalled = true
  	return wt.Buffer.WriteTo(w)
  }
  
  // It's preferable to choose WriterTo over ReaderFrom, since a WriterTo can issue one large write,
  // while the ReaderFrom must read until EOF, potentially allocating when running out of buffer.
  // Make sure that we choose WriterTo when both are implemented.
  func TestCopyPriority(t *testing.T) {
  	rb := new(writeToChecker)
  	wb := new(bytes.Buffer)
  	rb.WriteString("hello, world.")
  	Copy(wb, rb)
  	if wb.String() != "hello, world." {
  		t.Errorf("Copy did not work properly")
  	} else if !rb.writeToCalled {
  		t.Errorf("WriteTo was not prioritized over ReadFrom")
  	}
  }
  
  type zeroErrReader struct {
  	err error
  }
  
  func (r zeroErrReader) Read(p []byte) (int, error) {
  	return copy(p, []byte{0}), r.err
  }
  
  type errWriter struct {
  	err error
  }
  
  func (w errWriter) Write([]byte) (int, error) {
  	return 0, w.err
  }
  
  // In case a Read results in an error with non-zero bytes read, and
  // the subsequent Write also results in an error, the error from Write
  // is returned, as it is the one that prevented progressing further.
  func TestCopyReadErrWriteErr(t *testing.T) {
  	er, ew := errors.New("readError"), errors.New("writeError")
  	r, w := zeroErrReader{err: er}, errWriter{err: ew}
  	n, err := Copy(w, r)
  	if n != 0 || err != ew {
  		t.Errorf("Copy(zeroErrReader, errWriter) = %d, %v; want 0, writeError", n, err)
  	}
  }
  
  func TestCopyN(t *testing.T) {
  	rb := new(Buffer)
  	wb := new(Buffer)
  	rb.WriteString("hello, world.")
  	CopyN(wb, rb, 5)
  	if wb.String() != "hello" {
  		t.Errorf("CopyN did not work properly")
  	}
  }
  
  func TestCopyNReadFrom(t *testing.T) {
  	rb := new(Buffer)
  	wb := new(bytes.Buffer) // implements ReadFrom.
  	rb.WriteString("hello")
  	CopyN(wb, rb, 5)
  	if wb.String() != "hello" {
  		t.Errorf("CopyN did not work properly")
  	}
  }
  
  func TestCopyNWriteTo(t *testing.T) {
  	rb := new(bytes.Buffer) // implements WriteTo.
  	wb := new(Buffer)
  	rb.WriteString("hello, world.")
  	CopyN(wb, rb, 5)
  	if wb.String() != "hello" {
  		t.Errorf("CopyN did not work properly")
  	}
  }
  
  type noReadFrom struct {
  	w Writer
  }
  
  func (w *noReadFrom) Write(p []byte) (n int, err error) {
  	return w.w.Write(p)
  }
  
  type wantedAndErrReader struct{}
  
  func (wantedAndErrReader) Read(p []byte) (int, error) {
  	return len(p), errors.New("wantedAndErrReader error")
  }
  
  func TestCopyNEOF(t *testing.T) {
  	// Test that EOF behavior is the same regardless of whether
  	// argument to CopyN has ReadFrom.
  
  	b := new(bytes.Buffer)
  
  	n, err := CopyN(&noReadFrom{b}, strings.NewReader("foo"), 3)
  	if n != 3 || err != nil {
  		t.Errorf("CopyN(noReadFrom, foo, 3) = %d, %v; want 3, nil", n, err)
  	}
  
  	n, err = CopyN(&noReadFrom{b}, strings.NewReader("foo"), 4)
  	if n != 3 || err != EOF {
  		t.Errorf("CopyN(noReadFrom, foo, 4) = %d, %v; want 3, EOF", n, err)
  	}
  
  	n, err = CopyN(b, strings.NewReader("foo"), 3) // b has read from
  	if n != 3 || err != nil {
  		t.Errorf("CopyN(bytes.Buffer, foo, 3) = %d, %v; want 3, nil", n, err)
  	}
  
  	n, err = CopyN(b, strings.NewReader("foo"), 4) // b has read from
  	if n != 3 || err != EOF {
  		t.Errorf("CopyN(bytes.Buffer, foo, 4) = %d, %v; want 3, EOF", n, err)
  	}
  
  	n, err = CopyN(b, wantedAndErrReader{}, 5)
  	if n != 5 || err != nil {
  		t.Errorf("CopyN(bytes.Buffer, wantedAndErrReader, 5) = %d, %v; want 5, nil", n, err)
  	}
  
  	n, err = CopyN(&noReadFrom{b}, wantedAndErrReader{}, 5)
  	if n != 5 || err != nil {
  		t.Errorf("CopyN(noReadFrom, wantedAndErrReader, 5) = %d, %v; want 5, nil", n, err)
  	}
  }
  
  func TestReadAtLeast(t *testing.T) {
  	var rb bytes.Buffer
  	testReadAtLeast(t, &rb)
  }
  
  // A version of bytes.Buffer that returns n > 0, err on Read
  // when the input is exhausted.
  type dataAndErrorBuffer struct {
  	err error
  	bytes.Buffer
  }
  
  func (r *dataAndErrorBuffer) Read(p []byte) (n int, err error) {
  	n, err = r.Buffer.Read(p)
  	if n > 0 && r.Buffer.Len() == 0 && err == nil {
  		err = r.err
  	}
  	return
  }
  
  func TestReadAtLeastWithDataAndEOF(t *testing.T) {
  	var rb dataAndErrorBuffer
  	rb.err = EOF
  	testReadAtLeast(t, &rb)
  }
  
  func TestReadAtLeastWithDataAndError(t *testing.T) {
  	var rb dataAndErrorBuffer
  	rb.err = fmt.Errorf("fake error")
  	testReadAtLeast(t, &rb)
  }
  
  func testReadAtLeast(t *testing.T, rb ReadWriter) {
  	rb.Write([]byte("0123"))
  	buf := make([]byte, 2)
  	n, err := ReadAtLeast(rb, buf, 2)
  	if err != nil {
  		t.Error(err)
  	}
  	n, err = ReadAtLeast(rb, buf, 4)
  	if err != ErrShortBuffer {
  		t.Errorf("expected ErrShortBuffer got %v", err)
  	}
  	if n != 0 {
  		t.Errorf("expected to have read 0 bytes, got %v", n)
  	}
  	n, err = ReadAtLeast(rb, buf, 1)
  	if err != nil {
  		t.Error(err)
  	}
  	if n != 2 {
  		t.Errorf("expected to have read 2 bytes, got %v", n)
  	}
  	n, err = ReadAtLeast(rb, buf, 2)
  	if err != EOF {
  		t.Errorf("expected EOF, got %v", err)
  	}
  	if n != 0 {
  		t.Errorf("expected to have read 0 bytes, got %v", n)
  	}
  	rb.Write([]byte("4"))
  	n, err = ReadAtLeast(rb, buf, 2)
  	want := ErrUnexpectedEOF
  	if rb, ok := rb.(*dataAndErrorBuffer); ok && rb.err != EOF {
  		want = rb.err
  	}
  	if err != want {
  		t.Errorf("expected %v, got %v", want, err)
  	}
  	if n != 1 {
  		t.Errorf("expected to have read 1 bytes, got %v", n)
  	}
  }
  
  func TestTeeReader(t *testing.T) {
  	src := []byte("hello, world")
  	dst := make([]byte, len(src))
  	rb := bytes.NewBuffer(src)
  	wb := new(bytes.Buffer)
  	r := TeeReader(rb, wb)
  	if n, err := ReadFull(r, dst); err != nil || n != len(src) {
  		t.Fatalf("ReadFull(r, dst) = %d, %v; want %d, nil", n, err, len(src))
  	}
  	if !bytes.Equal(dst, src) {
  		t.Errorf("bytes read = %q want %q", dst, src)
  	}
  	if !bytes.Equal(wb.Bytes(), src) {
  		t.Errorf("bytes written = %q want %q", wb.Bytes(), src)
  	}
  	if n, err := r.Read(dst); n != 0 || err != EOF {
  		t.Errorf("r.Read at EOF = %d, %v want 0, EOF", n, err)
  	}
  	rb = bytes.NewBuffer(src)
  	pr, pw := Pipe()
  	pr.Close()
  	r = TeeReader(rb, pw)
  	if n, err := ReadFull(r, dst); n != 0 || err != ErrClosedPipe {
  		t.Errorf("closed tee: ReadFull(r, dst) = %d, %v; want 0, EPIPE", n, err)
  	}
  }
  
  func TestSectionReader_ReadAt(t *testing.T) {
  	dat := "a long sample data, 1234567890"
  	tests := []struct {
  		data   string
  		off    int
  		n      int
  		bufLen int
  		at     int
  		exp    string
  		err    error
  	}{
  		{data: "", off: 0, n: 10, bufLen: 2, at: 0, exp: "", err: EOF},
  		{data: dat, off: 0, n: len(dat), bufLen: 0, at: 0, exp: "", err: nil},
  		{data: dat, off: len(dat), n: 1, bufLen: 1, at: 0, exp: "", err: EOF},
  		{data: dat, off: 0, n: len(dat) + 2, bufLen: len(dat), at: 0, exp: dat, err: nil},
  		{data: dat, off: 0, n: len(dat), bufLen: len(dat) / 2, at: 0, exp: dat[:len(dat)/2], err: nil},
  		{data: dat, off: 0, n: len(dat), bufLen: len(dat), at: 0, exp: dat, err: nil},
  		{data: dat, off: 0, n: len(dat), bufLen: len(dat) / 2, at: 2, exp: dat[2 : 2+len(dat)/2], err: nil},
  		{data: dat, off: 3, n: len(dat), bufLen: len(dat) / 2, at: 2, exp: dat[5 : 5+len(dat)/2], err: nil},
  		{data: dat, off: 3, n: len(dat) / 2, bufLen: len(dat)/2 - 2, at: 2, exp: dat[5 : 5+len(dat)/2-2], err: nil},
  		{data: dat, off: 3, n: len(dat) / 2, bufLen: len(dat)/2 + 2, at: 2, exp: dat[5 : 5+len(dat)/2-2], err: EOF},
  		{data: dat, off: 0, n: 0, bufLen: 0, at: -1, exp: "", err: EOF},
  		{data: dat, off: 0, n: 0, bufLen: 0, at: 1, exp: "", err: EOF},
  	}
  	for i, tt := range tests {
  		r := strings.NewReader(tt.data)
  		s := NewSectionReader(r, int64(tt.off), int64(tt.n))
  		buf := make([]byte, tt.bufLen)
  		if n, err := s.ReadAt(buf, int64(tt.at)); n != len(tt.exp) || string(buf[:n]) != tt.exp || err != tt.err {
  			t.Fatalf("%d: ReadAt(%d) = %q, %v; expected %q, %v", i, tt.at, buf[:n], err, tt.exp, tt.err)
  		}
  	}
  }
  
  func TestSectionReader_Seek(t *testing.T) {
  	// Verifies that NewSectionReader's Seeker behaves like bytes.NewReader (which is like strings.NewReader)
  	br := bytes.NewReader([]byte("foo"))
  	sr := NewSectionReader(br, 0, int64(len("foo")))
  
  	for _, whence := range []int{SeekStart, SeekCurrent, SeekEnd} {
  		for offset := int64(-3); offset <= 4; offset++ {
  			brOff, brErr := br.Seek(offset, whence)
  			srOff, srErr := sr.Seek(offset, whence)
  			if (brErr != nil) != (srErr != nil) || brOff != srOff {
  				t.Errorf("For whence %d, offset %d: bytes.Reader.Seek = (%v, %v) != SectionReader.Seek = (%v, %v)",
  					whence, offset, brOff, brErr, srErr, srOff)
  			}
  		}
  	}
  
  	// And verify we can just seek past the end and get an EOF
  	got, err := sr.Seek(100, SeekStart)
  	if err != nil || got != 100 {
  		t.Errorf("Seek = %v, %v; want 100, nil", got, err)
  	}
  
  	n, err := sr.Read(make([]byte, 10))
  	if n != 0 || err != EOF {
  		t.Errorf("Read = %v, %v; want 0, EOF", n, err)
  	}
  }
  
  func TestSectionReader_Size(t *testing.T) {
  	tests := []struct {
  		data string
  		want int64
  	}{
  		{"a long sample data, 1234567890", 30},
  		{"", 0},
  	}
  
  	for _, tt := range tests {
  		r := strings.NewReader(tt.data)
  		sr := NewSectionReader(r, 0, int64(len(tt.data)))
  		if got := sr.Size(); got != tt.want {
  			t.Errorf("Size = %v; want %v", got, tt.want)
  		}
  	}
  }
  

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