Source file src/io/multi_test.go

Documentation: io

     1  // Copyright 2010 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 io_test
     6  
     7  import (
     8  	"bytes"
     9  	"crypto/sha1"
    10  	"errors"
    11  	"fmt"
    12  	. "io"
    13  	"runtime"
    14  	"strings"
    15  	"testing"
    16  	"time"
    17  )
    18  
    19  func TestMultiReader(t *testing.T) {
    20  	var mr Reader
    21  	var buf []byte
    22  	nread := 0
    23  	withFooBar := func(tests func()) {
    24  		r1 := strings.NewReader("foo ")
    25  		r2 := strings.NewReader("")
    26  		r3 := strings.NewReader("bar")
    27  		mr = MultiReader(r1, r2, r3)
    28  		buf = make([]byte, 20)
    29  		tests()
    30  	}
    31  	expectRead := func(size int, expected string, eerr error) {
    32  		nread++
    33  		n, gerr := mr.Read(buf[0:size])
    34  		if n != len(expected) {
    35  			t.Errorf("#%d, expected %d bytes; got %d",
    36  				nread, len(expected), n)
    37  		}
    38  		got := string(buf[0:n])
    39  		if got != expected {
    40  			t.Errorf("#%d, expected %q; got %q",
    41  				nread, expected, got)
    42  		}
    43  		if gerr != eerr {
    44  			t.Errorf("#%d, expected error %v; got %v",
    45  				nread, eerr, gerr)
    46  		}
    47  		buf = buf[n:]
    48  	}
    49  	withFooBar(func() {
    50  		expectRead(2, "fo", nil)
    51  		expectRead(5, "o ", nil)
    52  		expectRead(5, "bar", nil)
    53  		expectRead(5, "", EOF)
    54  	})
    55  	withFooBar(func() {
    56  		expectRead(4, "foo ", nil)
    57  		expectRead(1, "b", nil)
    58  		expectRead(3, "ar", nil)
    59  		expectRead(1, "", EOF)
    60  	})
    61  	withFooBar(func() {
    62  		expectRead(5, "foo ", nil)
    63  	})
    64  }
    65  
    66  func TestMultiWriter(t *testing.T) {
    67  	sink := new(bytes.Buffer)
    68  	// Hide bytes.Buffer's WriteString method:
    69  	testMultiWriter(t, struct {
    70  		Writer
    71  		fmt.Stringer
    72  	}{sink, sink})
    73  }
    74  
    75  func TestMultiWriter_String(t *testing.T) {
    76  	testMultiWriter(t, new(bytes.Buffer))
    77  }
    78  
    79  // Test that a multiWriter.WriteString calls results in at most 1 allocation,
    80  // even if multiple targets don't support WriteString.
    81  func TestMultiWriter_WriteStringSingleAlloc(t *testing.T) {
    82  	var sink1, sink2 bytes.Buffer
    83  	type simpleWriter struct { // hide bytes.Buffer's WriteString
    84  		Writer
    85  	}
    86  	mw := MultiWriter(simpleWriter{&sink1}, simpleWriter{&sink2})
    87  	allocs := int(testing.AllocsPerRun(1000, func() {
    88  		WriteString(mw, "foo")
    89  	}))
    90  	if allocs != 1 {
    91  		t.Errorf("num allocations = %d; want 1", allocs)
    92  	}
    93  }
    94  
    95  type writeStringChecker struct{ called bool }
    96  
    97  func (c *writeStringChecker) WriteString(s string) (n int, err error) {
    98  	c.called = true
    99  	return len(s), nil
   100  }
   101  
   102  func (c *writeStringChecker) Write(p []byte) (n int, err error) {
   103  	return len(p), nil
   104  }
   105  
   106  func TestMultiWriter_StringCheckCall(t *testing.T) {
   107  	var c writeStringChecker
   108  	mw := MultiWriter(&c)
   109  	WriteString(mw, "foo")
   110  	if !c.called {
   111  		t.Error("did not see WriteString call to writeStringChecker")
   112  	}
   113  }
   114  
   115  func testMultiWriter(t *testing.T, sink interface {
   116  	Writer
   117  	fmt.Stringer
   118  }) {
   119  	sha1 := sha1.New()
   120  	mw := MultiWriter(sha1, sink)
   121  
   122  	sourceString := "My input text."
   123  	source := strings.NewReader(sourceString)
   124  	written, err := Copy(mw, source)
   125  
   126  	if written != int64(len(sourceString)) {
   127  		t.Errorf("short write of %d, not %d", written, len(sourceString))
   128  	}
   129  
   130  	if err != nil {
   131  		t.Errorf("unexpected error: %v", err)
   132  	}
   133  
   134  	sha1hex := fmt.Sprintf("%x", sha1.Sum(nil))
   135  	if sha1hex != "01cb303fa8c30a64123067c5aa6284ba7ec2d31b" {
   136  		t.Error("incorrect sha1 value")
   137  	}
   138  
   139  	if sink.String() != sourceString {
   140  		t.Errorf("expected %q; got %q", sourceString, sink.String())
   141  	}
   142  }
   143  
   144  // writerFunc is an Writer implemented by the underlying func.
   145  type writerFunc func(p []byte) (int, error)
   146  
   147  func (f writerFunc) Write(p []byte) (int, error) {
   148  	return f(p)
   149  }
   150  
   151  // Test that MultiWriter properly flattens chained multiWriters.
   152  func TestMultiWriterSingleChainFlatten(t *testing.T) {
   153  	pc := make([]uintptr, 1000) // 1000 should fit the full stack
   154  	n := runtime.Callers(0, pc)
   155  	var myDepth = callDepth(pc[:n])
   156  	var writeDepth int // will contain the depth from which writerFunc.Writer was called
   157  	var w Writer = MultiWriter(writerFunc(func(p []byte) (int, error) {
   158  		n := runtime.Callers(1, pc)
   159  		writeDepth += callDepth(pc[:n])
   160  		return 0, nil
   161  	}))
   162  
   163  	mw := w
   164  	// chain a bunch of multiWriters
   165  	for i := 0; i < 100; i++ {
   166  		mw = MultiWriter(w)
   167  	}
   168  
   169  	mw = MultiWriter(w, mw, w, mw)
   170  	mw.Write(nil) // don't care about errors, just want to check the call-depth for Write
   171  
   172  	if writeDepth != 4*(myDepth+2) { // 2 should be multiWriter.Write and writerFunc.Write
   173  		t.Errorf("multiWriter did not flatten chained multiWriters: expected writeDepth %d, got %d",
   174  			4*(myDepth+2), writeDepth)
   175  	}
   176  }
   177  
   178  func TestMultiWriterError(t *testing.T) {
   179  	f1 := writerFunc(func(p []byte) (int, error) {
   180  		return len(p) / 2, ErrShortWrite
   181  	})
   182  	f2 := writerFunc(func(p []byte) (int, error) {
   183  		t.Errorf("MultiWriter called f2.Write")
   184  		return len(p), nil
   185  	})
   186  	w := MultiWriter(f1, f2)
   187  	n, err := w.Write(make([]byte, 100))
   188  	if n != 50 || err != ErrShortWrite {
   189  		t.Errorf("Write = %d, %v, want 50, ErrShortWrite", n, err)
   190  	}
   191  }
   192  
   193  // Test that MultiReader copies the input slice and is insulated from future modification.
   194  func TestMultiReaderCopy(t *testing.T) {
   195  	slice := []Reader{strings.NewReader("hello world")}
   196  	r := MultiReader(slice...)
   197  	slice[0] = nil
   198  	data, err := ReadAll(r)
   199  	if err != nil || string(data) != "hello world" {
   200  		t.Errorf("ReadAll() = %q, %v, want %q, nil", data, err, "hello world")
   201  	}
   202  }
   203  
   204  // Test that MultiWriter copies the input slice and is insulated from future modification.
   205  func TestMultiWriterCopy(t *testing.T) {
   206  	var buf bytes.Buffer
   207  	slice := []Writer{&buf}
   208  	w := MultiWriter(slice...)
   209  	slice[0] = nil
   210  	n, err := w.Write([]byte("hello world"))
   211  	if err != nil || n != 11 {
   212  		t.Errorf("Write(`hello world`) = %d, %v, want 11, nil", n, err)
   213  	}
   214  	if buf.String() != "hello world" {
   215  		t.Errorf("buf.String() = %q, want %q", buf.String(), "hello world")
   216  	}
   217  }
   218  
   219  // readerFunc is an Reader implemented by the underlying func.
   220  type readerFunc func(p []byte) (int, error)
   221  
   222  func (f readerFunc) Read(p []byte) (int, error) {
   223  	return f(p)
   224  }
   225  
   226  // callDepth returns the logical call depth for the given PCs.
   227  func callDepth(callers []uintptr) (depth int) {
   228  	frames := runtime.CallersFrames(callers)
   229  	more := true
   230  	for more {
   231  		_, more = frames.Next()
   232  		depth++
   233  	}
   234  	return
   235  }
   236  
   237  // Test that MultiReader properly flattens chained multiReaders when Read is called
   238  func TestMultiReaderFlatten(t *testing.T) {
   239  	pc := make([]uintptr, 1000) // 1000 should fit the full stack
   240  	n := runtime.Callers(0, pc)
   241  	var myDepth = callDepth(pc[:n])
   242  	var readDepth int // will contain the depth from which fakeReader.Read was called
   243  	var r Reader = MultiReader(readerFunc(func(p []byte) (int, error) {
   244  		n := runtime.Callers(1, pc)
   245  		readDepth = callDepth(pc[:n])
   246  		return 0, errors.New("irrelevant")
   247  	}))
   248  
   249  	// chain a bunch of multiReaders
   250  	for i := 0; i < 100; i++ {
   251  		r = MultiReader(r)
   252  	}
   253  
   254  	r.Read(nil) // don't care about errors, just want to check the call-depth for Read
   255  
   256  	if readDepth != myDepth+2 { // 2 should be multiReader.Read and fakeReader.Read
   257  		t.Errorf("multiReader did not flatten chained multiReaders: expected readDepth %d, got %d",
   258  			myDepth+2, readDepth)
   259  	}
   260  }
   261  
   262  // byteAndEOFReader is a Reader which reads one byte (the underlying
   263  // byte) and EOF at once in its Read call.
   264  type byteAndEOFReader byte
   265  
   266  func (b byteAndEOFReader) Read(p []byte) (n int, err error) {
   267  	if len(p) == 0 {
   268  		// Read(0 bytes) is useless. We expect no such useless
   269  		// calls in this test.
   270  		panic("unexpected call")
   271  	}
   272  	p[0] = byte(b)
   273  	return 1, EOF
   274  }
   275  
   276  // This used to yield bytes forever; issue 16795.
   277  func TestMultiReaderSingleByteWithEOF(t *testing.T) {
   278  	got, err := ReadAll(LimitReader(MultiReader(byteAndEOFReader('a'), byteAndEOFReader('b')), 10))
   279  	if err != nil {
   280  		t.Fatal(err)
   281  	}
   282  	const want = "ab"
   283  	if string(got) != want {
   284  		t.Errorf("got %q; want %q", got, want)
   285  	}
   286  }
   287  
   288  // Test that a reader returning (n, EOF) at the end of a MultiReader
   289  // chain continues to return EOF on its final read, rather than
   290  // yielding a (0, EOF).
   291  func TestMultiReaderFinalEOF(t *testing.T) {
   292  	r := MultiReader(bytes.NewReader(nil), byteAndEOFReader('a'))
   293  	buf := make([]byte, 2)
   294  	n, err := r.Read(buf)
   295  	if n != 1 || err != EOF {
   296  		t.Errorf("got %v, %v; want 1, EOF", n, err)
   297  	}
   298  }
   299  
   300  func TestMultiReaderFreesExhaustedReaders(t *testing.T) {
   301  	var mr Reader
   302  	closed := make(chan struct{})
   303  	// The closure ensures that we don't have a live reference to buf1
   304  	// on our stack after MultiReader is inlined (Issue 18819).  This
   305  	// is a work around for a limitation in liveness analysis.
   306  	func() {
   307  		buf1 := bytes.NewReader([]byte("foo"))
   308  		buf2 := bytes.NewReader([]byte("bar"))
   309  		mr = MultiReader(buf1, buf2)
   310  		runtime.SetFinalizer(buf1, func(*bytes.Reader) {
   311  			close(closed)
   312  		})
   313  	}()
   314  
   315  	buf := make([]byte, 4)
   316  	if n, err := ReadFull(mr, buf); err != nil || string(buf) != "foob" {
   317  		t.Fatalf(`ReadFull = %d (%q), %v; want 3, "foo", nil`, n, buf[:n], err)
   318  	}
   319  
   320  	runtime.GC()
   321  	select {
   322  	case <-closed:
   323  	case <-time.After(5 * time.Second):
   324  		t.Fatal("timeout waiting for collection of buf1")
   325  	}
   326  
   327  	if n, err := ReadFull(mr, buf[:2]); err != nil || string(buf[:2]) != "ar" {
   328  		t.Fatalf(`ReadFull = %d (%q), %v; want 2, "ar", nil`, n, buf[:n], err)
   329  	}
   330  }
   331  
   332  func TestInterleavedMultiReader(t *testing.T) {
   333  	r1 := strings.NewReader("123")
   334  	r2 := strings.NewReader("45678")
   335  
   336  	mr1 := MultiReader(r1, r2)
   337  	mr2 := MultiReader(mr1)
   338  
   339  	buf := make([]byte, 4)
   340  
   341  	// Have mr2 use mr1's []Readers.
   342  	// Consume r1 (and clear it for GC to handle) and consume part of r2.
   343  	n, err := ReadFull(mr2, buf)
   344  	if got := string(buf[:n]); got != "1234" || err != nil {
   345  		t.Errorf(`ReadFull(mr2) = (%q, %v), want ("1234", nil)`, got, err)
   346  	}
   347  
   348  	// Consume the rest of r2 via mr1.
   349  	// This should not panic even though mr2 cleared r1.
   350  	n, err = ReadFull(mr1, buf)
   351  	if got := string(buf[:n]); got != "5678" || err != nil {
   352  		t.Errorf(`ReadFull(mr1) = (%q, %v), want ("5678", nil)`, got, err)
   353  	}
   354  }
   355  

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