Phobos provides a wrapper for the common zlib/gzip/DEFLATE compression algorithm. This algorithm is used in the .zip files, the .png images, the HTTP protocol, the common gzip utility, and more. With std.zlib, we can both compress and decompress data easily.
Let's compress and decompress data by executing the following steps:
- Import
std.zlib. - Create an instance of
CompressorUnCompress, depending on what direction you want to go. - Call the
compressoruncompressmethods for each block of data, concatenating the pieces together as they are made. - Call
flushto get the last block of data.
The code is as follows:
void main() {
import std.zlib, std.file;
auto compressor = new Compress(HeaderFormat.gzip);
void[] compressedData;
compressedData ~= compressor.compress("Hello, ");
compressedData ~= compressor.compress("world!");
compressedData ~= compressor.flush();
std.file.write("compressed.gz", compressedData);
}Running the program will create a file, compressed.gz, which can be unzipped to become a text file with Hello, world!.
The std.zlib module doesn't follow exactly the same pattern as std.digest (the implementation of std.zlib was written before ranges were incorporated into Phobos), but it is a very simple API. It works with one block of data at a time, returning the compressed or uncompressed block. When finished, the flush method clears any partial blocks, returning the final piece of data.
There are also convenience functions, compress and uncompress, that can perform the operation in a single function call if you have all the data available as a single array at once.