transform_test.go

     1  // Copyright 2019 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  // js and wasip1 do not support inter-process file locking.
     6  //
     7  //go:build !js && !wasip1
     8  
     9  package lockedfile_test
    10  
    11  import (
    12  	"bytes"
    13  	"encoding/binary"
    14  	"math/rand"
    15  	"path/filepath"
    16  	"testing"
    17  	"time"
    18  
    19  	"cmd/go/internal/lockedfile"
    20  )
    21  
    22  func isPowerOf2(x int) bool {
    23  	return x > 0 && x&(x-1) == 0
    24  }
    25  
    26  func roundDownToPowerOf2(x int) int {
    27  	if x <= 0 {
    28  		panic("nonpositive x")
    29  	}
    30  	bit := 1
    31  	for x != bit {
    32  		x = x &^ bit
    33  		bit <<= 1
    34  	}
    35  	return x
    36  }
    37  
    38  func TestTransform(t *testing.T) {
    39  	path := filepath.Join(t.TempDir(), "blob.bin")
    40  
    41  	const maxChunkWords = 8 << 10
    42  	buf := make([]byte, 2*maxChunkWords*8)
    43  	for i := uint64(0); i < 2*maxChunkWords; i++ {
    44  		binary.LittleEndian.PutUint64(buf[i*8:], i)
    45  	}
    46  	if err := lockedfile.Write(path, bytes.NewReader(buf[:8]), 0666); err != nil {
    47  		t.Fatal(err)
    48  	}
    49  
    50  	var attempts int64 = 128
    51  	if !testing.Short() {
    52  		attempts *= 16
    53  	}
    54  	const parallel = 32
    55  
    56  	var sem = make(chan bool, parallel)
    57  
    58  	for n := attempts; n > 0; n-- {
    59  		sem <- true
    60  		go func() {
    61  			defer func() { <-sem }()
    62  
    63  			time.Sleep(time.Duration(rand.Intn(100)) * time.Microsecond)
    64  			chunkWords := roundDownToPowerOf2(rand.Intn(maxChunkWords) + 1)
    65  			offset := rand.Intn(chunkWords)
    66  
    67  			err := lockedfile.Transform(path, func(data []byte) (chunk []byte, err error) {
    68  				chunk = buf[offset*8 : (offset+chunkWords)*8]
    69  
    70  				if len(data)&^7 != len(data) {
    71  					t.Errorf("read %d bytes, but each write is an integer multiple of 8 bytes", len(data))
    72  					return chunk, nil
    73  				}
    74  
    75  				words := len(data) / 8
    76  				if !isPowerOf2(words) {
    77  					t.Errorf("read %d 8-byte words, but each write is a power-of-2 number of words", words)
    78  					return chunk, nil
    79  				}
    80  
    81  				u := binary.LittleEndian.Uint64(data)
    82  				for i := 1; i < words; i++ {
    83  					next := binary.LittleEndian.Uint64(data[i*8:])
    84  					if next != u+1 {
    85  						t.Errorf("wrote sequential integers, but read integer out of sequence at offset %d", i)
    86  						return chunk, nil
    87  					}
    88  					u = next
    89  				}
    90  
    91  				return chunk, nil
    92  			})
    93  
    94  			if err != nil {
    95  				t.Errorf("unexpected error from Transform: %v", err)
    96  			}
    97  		}()
    98  	}
    99  
   100  	for n := parallel; n > 0; n-- {
   101  		sem <- true
   102  	}
   103  }
   104
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