zstd decompression using "--patch-from" cost memory too high (when the dict is a big file)

[rongekuta]

Is your feature request related to a problem? Please describe.

zstd -d -M128MB --patch-from=d:/code-shared/apks/wzry_old.apk d:/code-shared/apks/wzry.diff -o d:/code-shared/apks/wzry_new_d.apk

when i use zstd (--patch-from) to decompress a patch file using a big dict, i find "-M#" option is not valid, the big dict is load to memory all, and cost too many memory. i search code for reason, and find: https://github.com/facebook/zstd/blob/v1.5.2/programs/fileio.c#L2019

these code cause "-M" memory limit is not work under "--patch-from" mode

Describe the solution you'd like decompression under a big dict with "--patch-from" is also be limited memory

Describe alternatives you've considered the big dict also be cache from file system, not load to memory totally

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