github.com/cockroachdb/cockroach@v20.2.0-alpha.1+incompatible/pkg/util/sysutil/large_file_naive.go (about)

     1  // Copyright 2018 The Cockroach Authors.
     2  //
     3  // Use of this software is governed by the Business Source License
     4  // included in the file licenses/BSL.txt.
     5  //
     6  // As of the Change Date specified in that file, in accordance with
     7  // the Business Source License, use of this software will be governed
     8  // by the Apache License, Version 2.0, included in the file
     9  // licenses/APL.txt.
    10  
    11  // +build !linux
    12  
    13  package sysutil
    14  
    15  import (
    16  	"os"
    17  
    18  	"github.com/cockroachdb/errors"
    19  )
    20  
    21  // CreateLargeFile creates a large file at the given path with bytes size. On
    22  // Linux, it uses the fallocate syscall to efficiently create the file. On other
    23  // platforms, it naively writes the specified number of bytes, which can take a
    24  // long time when the number of bytes is large.
    25  func CreateLargeFile(path string, bytes int64) error {
    26  	f, err := os.Create(path)
    27  	if err != nil {
    28  		return errors.Wrapf(err, "failed to create file %s", path)
    29  	}
    30  	defer f.Close()
    31  	sixtyFourMB := make([]byte, 64<<20)
    32  	for bytes > 0 {
    33  		z := sixtyFourMB
    34  		if bytes < int64(len(z)) {
    35  			z = sixtyFourMB[:bytes]
    36  		}
    37  		if _, err := f.Write(z); err != nil {
    38  			return err
    39  		}
    40  		bytes -= int64(len(z))
    41  	}
    42  	return f.Sync()
    43  }