transform_test.go

Documentation: cmd/go/internal/lockedfile

     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  	dir, remove := mustTempDir(t)
    40  	defer remove()
    41  	path := filepath.Join(dir, "blob.bin")
    42  
    43  	const maxChunkWords = 8 << 10
    44  	buf := make([]byte, 2*maxChunkWords*8)
    45  	for i := uint64(0); i < 2*maxChunkWords; i++ {
    46  		binary.LittleEndian.PutUint64(buf[i*8:], i)
    47  	}
    48  	if err := lockedfile.Write(path, bytes.NewReader(buf[:8]), 0666); err != nil {
    49  		t.Fatal(err)
    50  	}
    51  
    52  	var attempts int64 = 128
    53  	if !testing.Short() {
    54  		attempts *= 16
    55  	}
    56  	const parallel = 32
    57  
    58  	var sem = make(chan bool, parallel)
    59  
    60  	for n := attempts; n > 0; n-- {
    61  		sem <- true
    62  		go func() {
    63  			defer func() { <-sem }()
    64  
    65  			time.Sleep(time.Duration(rand.Intn(100)) * time.Microsecond)
    66  			chunkWords := roundDownToPowerOf2(rand.Intn(maxChunkWords) + 1)
    67  			offset := rand.Intn(chunkWords)
    68  
    69  			err := lockedfile.Transform(path, func(data []byte) (chunk []byte, err error) {
    70  				chunk = buf[offset*8 : (offset+chunkWords)*8]
    71  
    72  				if len(data)&^7 != len(data) {
    73  					t.Errorf("read %d bytes, but each write is an integer multiple of 8 bytes", len(data))
    74  					return chunk, nil
    75  				}
    76  
    77  				words := len(data) / 8
    78  				if !isPowerOf2(words) {
    79  					t.Errorf("read %d 8-byte words, but each write is a power-of-2 number of words", words)
    80  					return chunk, nil
    81  				}
    82  
    83  				u := binary.LittleEndian.Uint64(data)
    84  				for i := 1; i < words; i++ {
    85  					next := binary.LittleEndian.Uint64(data[i*8:])
    86  					if next != u+1 {
    87  						t.Errorf("wrote sequential integers, but read integer out of sequence at offset %d", i)
    88  						return chunk, nil
    89  					}
    90  					u = next
    91  				}
    92  
    93  				return chunk, nil
    94  			})
    95  
    96  			if err != nil {
    97  				t.Errorf("unexpected error from Transform: %v", err)
    98  			}
    99  		}()
   100  	}
   101  
   102  	for n := parallel; n > 0; n-- {
   103  		sem <- true
   104  	}
   105  }
   106
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