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Gzip compression is a widely used data compression method that reduces the size of files or data streams, making them faster to transfer and more efficient to store. It is commonly used to compress web content like HTML, CSS, JavaScript, and other resources to improve website loading times. Here's how gzip compression works:
Data Segmentation: The data to be compressed is divided into smaller blocks or chunks. These chunks can be individual files or sections of a larger data stream.
Deflation: The compression process begins by applying the DEFLATE algorithm. DEFLATE is a combination of two other algorithms: Huffman coding and LZ77 (Lempel-Ziv 1977). LZ77 is used for identifying repeated strings in the data, while Huffman coding is employed to create variable-length codes to represent frequently occurring symbols more efficiently.
Finding Repeated Strings: The LZ77 algorithm scans the data and identifies repeated substrings (sequences of characters) within the same data block. Instead of encoding each occurrence of the substring separately, LZ77 represents the substring as a "pointer" to a previous occurrence, saving space.
Creating Huffman Codes: After identifying repeated strings, the DEFLATE algorithm creates Huffman codes based on the frequency of occurrence of each symbol (characters or codes). More frequent symbols get shorter codes, while less frequent symbols get longer codes, resulting in better compression.
Data Encoding: The data is then encoded using the Huffman codes, which replace the original symbols with variable-length codes based on their frequency in the data.
Metadata Addition: Gzip also adds some metadata to the compressed data, such as information about the original file name, timestamp, and other optional fields.
Gzip Format: The compressed data and metadata are wrapped in the Gzip file format, which includes headers, CRC (Cyclic Redundancy Check) checksums for integrity verification, and a trailer.
When a web client (like a browser) requests content from a server, it includes an "Accept-Encoding" header in the request. If the server supports gzip compression and the client indicates that it accepts gzip-encoded content, the server will compress the requested resources using gzip before sending them back to the client. The server includes the "Content-Encoding: gzip" header in the response to inform the client that the content is compressed.
Upon receiving the compressed data, the client (browser) decompresses it using the reverse process. It reads the gzip headers, extracts the compressed data, applies the DEFLATE algorithm in reverse to reconstruct the original data, and finally renders the content for the user.
Overall, gzip compression is an effective way to reduce the size of files or data streams, leading to faster website loading times and improved network efficiency