Reducing DCtx Size for Embedded Systems (like esp32) about zstd

[Cyan4973]

The bulk of the decompression state memory budget is taken by the literals buffer.
For such special case, it's possible to reduce it considerably by modifying the build variable ZSTD_DECODER_INTERNAL_BUFFER at compilation time.
This is documented in https://github.com/facebook/zstd/tree/dev/lib#modular-build.
Be aware that reducing the size of the literals buffer tends to impact decompression speed negatively, but the cost is reasonable, and that's probably the better choice for your memory-constrained scenario.

[olokelo]

Thanks for quick response. Setting ZSTD_DECODER_INTERNAL_BUFFER to 4096 reduced DCtx size to 34368 bytes which is perfectly acceptable. I've looked at modular build yet somehow I missed this setting, thanks again.