Why Does Golang\'s `flate` Produce Different Compression Output Than Python\'s `zlib`?

Difference in Compression Output between Golang's zlib and Python's zlib

To troubleshoot the differing compression results observed between Python's zlib and Golang's flate, it is important to note that they use different underlying implementations.

In Python, zlib is utilized, which is a DEFLATE-based library that outputs data in zlib format. On the other hand, Golang employs flate, a DEFLATE implementation.

Cause of the Output Discrepancy

The observed discrepancy stems from the fifth byte in the output: Python's zlib sets it to 0, while Golang's flate sets it to 4. This difference arises because Python's zlib is configured to flush the buffer after compressing the first string, effectively truncating the output.

To replicate Python's behavior in Golang, developers can replace Close() with Flush() in the compressor:

<code class="go">func compress(source string) []byte {
    buf := new(bytes.Buffer)
    w, _ := flate.NewWriter(buf, 7)
    w.Write([]byte(source))
    w.Flush()

    return buf.Bytes()
}</code>

Compatibility vs. Identical Output

However, it is critical to recognize that even after adjusting Golang's function to match Python's, the resulting byte-for-byte matches are not guaranteed. Compatibility between compression libraries is ensured, but identical output may not be achievable.

The discrepancies arise from the inherent differences in library implementations and the specific parameters used during compression. Therefore, relying on byte-for-byte equality between different libraries is inadvisable.

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