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Joe Tsai 9d0c86b6ec util/deephash: remove unnecessary formatting for structs and slices (#2571) ... The index for every struct field or slice element and the number of fields for the struct is unncessary. The hashing of Go values is unambiguous because every type (except maps) encodes in a parsable manner. So long as we know the type information, we could theoretically decode every value (except for maps). At a high level: * numbers are encoded as fixed-width records according to precision. * strings (and AppendTo output) are encoded with a fixed-width length, followed by the contents of the buffer. * slices are prefixed by a fixed-width length, followed by the encoding of each value. So long as we know the type of each element, we could theoretically decode each element. * arrays are encoded just like slices, but elide the length since it is determined from the Go type. * maps are encoded first with a byte indicating whether it is a cycle. If a cycle, it is followed by a fixed-width index for the pointer, otherwise followed by the SHA-256 hash of its contents. The encoding of maps is not decodeable, but a SHA-256 hash is sufficient to avoid ambiguities. * interfaces are encoded first with a byte indicating whether it is nil. If not nil, it is followed by a fixed-width index for the type, and then the encoding for the underlying value. Having the type be encoded first ensures that the value could theoretically be decoded next. * pointers are encoded first with a byte indicating whether it is 1) nil, 2) a cycle, or 3) newly seen. If a cycle, it is followed by a fixed-width index for the pointer. If newly seen, it is followed by the encoding for the pointed-at value. Removing unnecessary details speeds up hashing: name old time/op new time/op delta Hash-8 76.0µs ± 1% 55.8µs ± 2% -26.62% (p=0.000 n=10+10) HashMapAcyclic-8 61.9µs ± 0% 62.0µs ± 0% ~ (p=0.666 n=9+9) TailcfgNode-8 10.2µs ± 1% 7.5µs ± 1% -26.90% (p=0.000 n=10+9) HashArray-8 1.07µs ± 1% 0.70µs ± 1% -34.67% (p=0.000 n=10+9) Signed-off-by: Joe Tsai <joetsai@digital-static.net>		3 years ago
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cibuild	wgengine/magicsock: increase legacy ping timeout again	3 years ago
cmpver	util/cmpver: move into OSS from corp repo.	3 years ago
deephash	util/deephash: remove unnecessary formatting for structs and slices (#2571)	3 years ago
dnsname	util/dnsname: make ToFQDN take exactly 0 or 1 allocs for everything.	3 years ago
endian	util/endian: add Native variable to get the platform's native binary.ByteOrder	4 years ago
groupmember	cmd/tailscale/web: add support for QNAP	3 years ago
jsonutil	util/jsonutil: new package	4 years ago
lineread	util/lineread: add docs to Reader	4 years ago
osshare	ipn/ipnlocal: add file sharing to windows shell	3 years ago
pidowner	util/pidowner: add missing copyright header	4 years ago
racebuild	util/racebuild: add package to export a race-is-enabled const	4 years ago
systemd	util/systemd: explicitly check for os.ErrNotExist from sdnotify	3 years ago
uniq	util/uniq: add new package	4 years ago
winutil	net/dns: do not run wsl.exe as LocalSystem	3 years ago