Writing archive

Rust async functions store every value needed after an await. Learn to measure future size, identify saved fields, and reduce it without boxing everything.

Third-party APIs should not become your product model. Learn how a stable internal representation contains provider changes and keeps integrations understandable.

I printed the address of every kind of variable in a C program and a Rust program and matched them with nm and readelf. A 16 MiB array of zeros costs nothing in the file, the same array with one byte set to 1 costs 16 MiB, and a Rust const has no address at all.

I killed a program 300 times while it saved a file. Writing in place left a cut file 233 times, without any power loss. A temp file, fsync and rename never did. Then I traced how sed, Python, cp, install and git save files.

I measured 1,000 rounds of a 4 KiB write followed by a sync on my laptop: about 540 microseconds for an append, 208 for an overwrite in place, a slowest round eleven times the median, and 3.6 microseconds on tmpfs, where fsync waits for nothing.