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 does not support inter-process file locking.
     6  //go:build !js
     7  
     8  package lockedfile_test
     9  
    10  import (
    11  	"bytes"
    12  	"encoding/binary"
    13  	"math/rand"
    14  	"path/filepath"
    15  	"testing"
    16  	"time"
    17  
    18  	"cmd/go/internal/lockedfile"
    19  )
    20  
    21  func isPowerOf2(x int) bool {
    22  	return x > 0 && x&(x-1) == 0
    23  }
    24  
    25  func roundDownToPowerOf2(x int) int {
    26  	if x <= 0 {
    27  		panic("nonpositive x")
    28  	}
    29  	bit := 1
    30  	for x != bit {
    31  		x = x &^ bit
    32  		bit <<= 1
    33  	}
    34  	return x
    35  }
    36  
    37  func TestTransform(t *testing.T) {
    38  	dir, remove := mustTempDir(t)
    39  	defer remove()
    40  	path := filepath.Join(dir, "blob.bin")
    41  
    42  	const maxChunkWords = 8 << 10
    43  	buf := make([]byte, 2*maxChunkWords*8)
    44  	for i := uint64(0); i < 2*maxChunkWords; i++ {
    45  		binary.LittleEndian.PutUint64(buf[i*8:], i)
    46  	}
    47  	if err := lockedfile.Write(path, bytes.NewReader(buf[:8]), 0666); err != nil {
    48  		t.Fatal(err)
    49  	}
    50  
    51  	var attempts int64 = 128
    52  	if !testing.Short() {
    53  		attempts *= 16
    54  	}
    55  	const parallel = 32
    56  
    57  	var sem = make(chan bool, parallel)
    58  
    59  	for n := attempts; n > 0; n-- {
    60  		sem <- true
    61  		go func() {
    62  			defer func() { <-sem }()
    63  
    64  			time.Sleep(time.Duration(rand.Intn(100)) * time.Microsecond)
    65  			chunkWords := roundDownToPowerOf2(rand.Intn(maxChunkWords) + 1)
    66  			offset := rand.Intn(chunkWords)
    67  
    68  			err := lockedfile.Transform(path, func(data []byte) (chunk []byte, err error) {
    69  				chunk = buf[offset*8 : (offset+chunkWords)*8]
    70  
    71  				if len(data)&^7 != len(data) {
    72  					t.Errorf("read %d bytes, but each write is an integer multiple of 8 bytes", len(data))
    73  					return chunk, nil
    74  				}
    75  
    76  				words := len(data) / 8
    77  				if !isPowerOf2(words) {
    78  					t.Errorf("read %d 8-byte words, but each write is a power-of-2 number of words", words)
    79  					return chunk, nil
    80  				}
    81  
    82  				u := binary.LittleEndian.Uint64(data)
    83  				for i := 1; i < words; i++ {
    84  					next := binary.LittleEndian.Uint64(data[i*8:])
    85  					if next != u+1 {
    86  						t.Errorf("wrote sequential integers, but read integer out of sequence at offset %d", i)
    87  						return chunk, nil
    88  					}
    89  					u = next
    90  				}
    91  
    92  				return chunk, nil
    93  			})
    94  
    95  			if err != nil {
    96  				t.Errorf("unexpected error from Transform: %v", err)
    97  			}
    98  		}()
    99  	}
   100  
   101  	for n := parallel; n > 0; n-- {
   102  		sem <- true
   103  	}
   104  }
   105
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