zlib: Differences Between the `deflate` and `compress` Functions
compression, deflate, zlib
Solution
`compress()` is used to compress the data in a single call, and always compresses to the zlib format, which is deflate data with a two-byte header and a four-byte check value trailer. `compress()` is used by itself.
`deflate()` is used to compress data a chunk at a time, and/or to compress to other formats such as gzip-wrapped or raw, and with other options, such as memory levels and compression strategies.
You would use `compress()` if you have all the data available at once and enough memory to hold the result, and you want the default compression format, memory usage, and strategy. Otherwise, you would use `deflate()`.
deflate() is not used by itself. You need to use `deflateInit()` or `deflateInit2()` to initialize the `z_stream` structure used by `deflate()`. Then you call `deflate()` one or more times to take in data to compress and to make available the result. At the end, `deflateEnd()` is called to free the memory resources used in the structure. You can read the documentation in zlib.h and at http://zlib.net/zlib_how.html for more information.
Problem
What are the differences between the `deflate()` and `compress()` functions in zlib? I have looked through online examples and some used deflate while others used compress. How should I decide which situation I would use one over the other?