How to Compress and Decompress Files in Golang
The Gzip and Zlib algorithms are popularly used to compress and decompress files. Gzip is primarily used for compressing single files, while Zlib mainly compresses data streams. The algorithms use the Deflate Compression Algorithm for compression, although Gzip provides additional features including error checking and file metadata.
Gzip has provided better compression ratios than Zlib. However, Gzip requires more processing power to compress and decompress data. In most cases, you should use Gzip for compressing files and Zlib for compressing data streams.
Go provides the functionality for compressing data, including files through thecompresspackage.
The Compress Package
Thecompresspackage supports compressing data through thecompress/gzipandcompress/zlibpackages, amongst other functionalities.
Thegzippackage supports compressing and decompressing the gzip file format data, including read and write operations as specified inRFC 1952. While thezlibpackage helps with compressing and decompressing data in the zlib format.
You can importgzipandzlibfrom thecompresspackage using theimportkeyword.
Compressing and Decompressing Files With Gzip
Gzip is a file format and a software application for file compression and decompression. Gzip uses the Lempel-Ziv-Markov chain algorithm (LZ77) to compress data, and the algorithm is often used for compressing text files, such as HTML, CSS, or JavaScript files.
The process of compressing files with thegzippackage is simple and intuitive. You’ll need to open the file, create a gzipped file, create a gzip writer, and copy the original file’s contents to the gzip writer before the flush operation that ensures the writing process is complete.
Run thisbash commandin the terminal of your working directory on Unix systems to create a sample text file and then insert text in the file.
After creating the file and inserting the text, you’re able to import thegzip,io,andospackages for the compression operation.
Here is how you can use thecompress/gzippackage to compress a text file.
TheOpenfunction of theospackage opens the text file, and theClosefunction closes the file with adeferstatement. TheCreatefunction creates a gzipped file, and theNewWriterfunction of thegzippackage writes the content of the text file to the gzip file using theCopyfunction of theiopackage.
TheFlushmethod of thegzipWriterinstance flushes the gzip writer once all the data is available on the zipped file.
You can retrieve the original file from a gzipped file through a decompression process. The process of decompressing a file is similar; you’ll open the file and create a gzip file reader, then create a new file to hold the uncompressed data before copying the contents to the new file.
TheOpenfunction of theospackage opens the gzipped file, and theNewReaderfunction of thegzippackage reads the zipped file. TheCreatefunction of theospackage creates a new text file. TheCopyfunction copies the contents of thegzipReaderto theuncompressedFile.
Compressing and Decompressing Data With Zlib
Zlib is a library for data compression and decompression; the library also uses the LZ77 algorithm. Zlib is written in C and is widely used as the basis for other compression libraries and software. Unlikegzip,zlibis a library, andzlibdoes not include afile format. However, it is often used to compress data stored in container formats, such as PNG or HTTP.
The process of compressing with zlib is the same as for gzip. You’ll create a zlib file, configure a writer, open the original file, and copy the contents to the compressed file.
TheCreatemethod creates the zlib file, and theNewWriterLevelfunction creates a writer for the file with the specified option (in this case, theBestCompressionoption). TheOpenmethod of theospackage opens the text file, and theCopyfunction of theiopackage copies the content of the text file to the zlib file in the compression process.
To decompress the zlib file, you’ll need to open the compressed file, create a new zlib reader, and then finally copy the content of the reader to standard output.
The main function opens the zlib file with theospackage’sOpenfunction, and theNewReaderfunction of thezlibpackage reads the zlib file into a reader instance. TheCopymethod of theiopackage copies the content from the reader to the standard output (in this case, the console).
Use These Tools for File Compression
Writing code for file compression is handy for automating tasks and compressing several files. If you only need to compress a few files, it’s possible to resort to using applications like WinRar, WinZip, Express Zip, and Bandizip.
Have to squish down a file, and fast? Try these programs to crunch down on those megabytes for easy sending.
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