Скачать или смотреть How to Create a Sparse File Programmatically in C on Mac OS X

Learn how to create a sparse file in C on Mac OS X, understand the filesystem requirements, and discover alternatives for efficient file storage.
---
This video is based on the question https://stackoverflow.com/q/186077/ asked by the user 'robottobor' ( https://stackoverflow.com/u/10184/ ) and on the answer https://stackoverflow.com/a/186098/ provided by the user 'Colin Jensen' ( https://stackoverflow.com/u/9884/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

Visit these links for original content and any more details, such as alternate solutions, comments, revision history etc. For example, the original title of the Question was: How do I create a sparse file programmatically, in C, on Mac OS X?

Also, Content (except music) licensed under CC BY-SA https://meta.stackexchange.com/help/l...
The original Question post is licensed under the 'CC BY-SA 2.5' ( https://creativecommons.org/licenses/... ) license, and the original Answer post is licensed under the 'CC BY-SA 3.0' ( https://creativecommons.org/licenses/... ) license.

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Exploring Sparse Files in Mac OS X: A Guide for C Programmers

Creating a sparse file is an essential task for developers who want to optimize disk space usage. A sparse file is designed to allow the underlying filesystem to save space by not storing blocks of data that contain only zeros. But can you create a sparse file programmatically in C on Mac OS X? This post will delve into that question, examining both the feasibility of sparse file creation on Mac OS X and the state of the relevant filesystems.

What is a Sparse File?

A sparse file is a type of file that attempts to use less disk space when it contains large blocks of zeroed-out data. Essentially, unlike regular files where every byte is stored regardless of its content, a sparse file circumvents the storage of blocks filled entirely with zeros until data is actually written to those blocks. This feature can be particularly beneficial when dealing with large files that may have considerable amounts of empty space.

The Challenge on Mac OS X

If you are programming in C and want to create a sparse file on Mac OS X, it’s essential to first understand the filesystem constraints:

HFS+ Support: The default filesystem for Mac OS X is HFS+ (Hierarchical File System Plus). Unfortunately, HFS+ does not support sparse files.

UFS Removal: Although previous versions of Mac OS X supported UFS (Unix File System) volumes that could handle sparse files, that support has since been removed in favor of HFS+ and newer filesystems, leaving developers without native sparse file capabilities.

Implications for Developers

If you are working on a project intended to make use of sparse files, the lack of native support on macOS can limit your options.

No Special Requirements: Unlike some other operating systems, where developers must do additional configurations or special handling for sparse files, macOS's current filesystems are straightforward but lack this feature altogether.

Performance: On a positive note, there is no performance penalty for using sparse files on systems that support them, unlike some Windows systems.

Alternative Solutions

Given the current state of filesystems on Mac OS X, what can you do if you need to work with sparse files or reduce disk space usage? Here are some ideas:

Use Virtual Machines or Containers: If you require filesystem capabilities not available in macOS, consider setting up a Linux VM or container. Linux filesystems highly support sparse files that can handle this feature seamlessly.

File Compression: Look into file compression techniques which can help reduce the physical size on disk without requiring sparse file creation.

Check Future Updates: Keep an eye on macOS updates and changes to see if Apple introduces new filesystems that might support sparse files in the future.

Conclusion

Creating a sparse file programmatically in C on Mac OS X presents challenges due to the limitations of supported filesystems, particularly the lack of sparse file capabilities in HFS+. While options such as virtualization or compression exist for achieving similar outcomes, it’s essential to adapt your strategy based on these constraints. Always look for future developments in macOS that might provide new solutions for file management.

Armed with this understanding, you can make informed decisions about how to manage your storage needs effectively on Mac OS X.