mmap创建超过既定文件大小的memory-mapped file

本文主要是介绍mmap创建超过既定文件大小的memory-mapped file，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

• 问题

  mmap针对Windows和Unix的版本在具体实现上有所不同，对于Windows版本，当length参数比file本身size大的时候，会自动扩展file为指定length大小；而Unix版本不支持自动扩展，即length只能小于等于size of file，如果超出size，则会报错。

• 解决方案

  The unix version of mmap doesn’t grow the file automatically, but can just write zeros to the file by yourself:

  size = 1073741824   # bytes in 1GiB
  self.file = open("/path/demo.csv", "w+b")
  self.file.write("\0" * size)
  self.file.flush()
  self.mm = mmap.mmap(self.file.fileno(), size, access= mmap.ACCESS_WRITE)
  

  But this takes too long to finish, it can be improved by :

  with open("file.to.create", "wb") as out:out.seek((1024 * 1024 * 1024) - 1)out.write('\0')
  

• Reference

1. Why can’t I create a new file with mmap of known size?
2. create file of particular size in python

这篇关于mmap创建超过既定文件大小的memory-mapped file的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！

---