In the digital age, the storage and transfer of files is essential for the day-to-day operations of businesses. However, compressed files in the server often can't be viewed or previewed directly, which is inconvenient for users. In order to solve this problem, the development of an online decompression function has become particularly important. Next, we will introduce an open-source library that can realize online decompression - Libarchive.
什么是Libarchive？
Libarchive is an open-source C library that is specifically designed to work with many types of archives. It supports a wide range of formats, including but not limited to tar, zip, 7zip, and ISO images. Libarchive is a comprehensive feature that not only reads and writes archives, but also decompresses, compresses, encrypts, and signs files.
In addition, Libarchive's cross-platform nature allows it to run on multiple operating systems, including Windows, Linux, and Mac. Thanks to its efficient internal IO model, Libarchive maintains excellent performance when working with large archives.
How do I compile Libarchive?
To get the source code for Libarchive, you can visit its repository (https://github.com/libarchive/libarchive) on GitHub. In the project, read the documentation Read.md to learn about the documentation that supports CMakeLists.txt build process.
Using the CMAKE GUI tool, you can configure CMakeLists.txt as a Visual Studio project. As part of this process, you may need to configure a number of dependencies, including:
- 压缩算法依赖库:LZ4、LZO、LZMA、Zstandard、Bzip2
- 加密依赖库：Mbed TLS、GNU Nettle、OpenSSL
Depending on the specific needs of the project, you can add the corresponding dependencies. For example, if you need to support the zip format, add the ZLIB library; If you want 7zip format, then add the LZMA library. In addition, you can also use the make install command to install the dependent library when compiling it, so that the corresponding library can be automatically found during the CMAKE configuration process.
After you generate a Visual Studio project, you can directly compile and generate a dynamic link library (DLL) and a static link library (.lib). If you need to do static linking, you can add a macro definition LZMA_API_STATIC to the archive.h header file. For the case that you need to run in a Windows 8 or earlier environment, you need to set the _WIN32_WINNT and WINVER to the corresponding lower version values in the config.h file.
Libarchive的代码集成
When using Libarchive, you need to use two basic types of objects, struct archive and struct archive_entry. The struct archive represents an instance of the original compressed file, while the struct archive_entry represents a single instance of the file in the compressed file. The approximate invocation process in libarchive is as follows:
- Call the archive_xxx_new function to create an archive object.
- Use the support or set function to set the properties of the archive object and determine whether the format for decompression is supported.
- Call the open function to open the compressed file.
- Loop through archive content: Retrieves a new archive_entry to extract the data from the compressed file from the archive_entry.
- At the end, use the close and free functions to release the archive object.
Precautions
When you use Libarchive to extract a file, you may encounter the problem that the file name is obtained as empty or garbled. The solution to this problem is to call the setlocale(LC_CTYPE,") function to ensure that the file name is displayed correctly.
Through the above introduction, we can see that Libarchive is a powerful and flexible open-source library, which provides great convenience for working with archived files. Whether you need to read archive files during development or provide users with an online decompression service, Libarchive is an option worth considering.
summary
Raysync (privatized deployment solution, can also be connected to the public cloud, enterprises and social organization users can apply for a free trial) through the integration of Libarchive, on Windows, Linux and other platforms to achieve online decompression function, providing enterprises with a powerful and secure online decompression solution for large file transfer system. This not only meets the data processing needs of enterprises in diverse scenarios, but also provides solid technical support for the long-term development of enterprises. In the next article, we will further explore how Raysync uses Libarchive to achieve efficient and intelligent file transfer and management.