Joe Tsai b9b8cecbfc encoding/json: simplify folded name logic ... The folded name logic (despite all attempts to optimize it) was fundamentally an O(n) operation where every field in a struct needed to be linearly scanned in order to find a match. This made unmashaling of unknown fields always O(n). Instead of optimizing the comparison for each field, make it such that we can look up a name in O(1). We accomplish this by maintaining a map keyed by pre-folded names, which we can pre-calculate when processing the struct type. Using a stack-allocated buffer, we can fold the input name and look up its presence in the map. Also, instead of mapping from names to indexes, map directly to a pointer to the field information. The memory cost of this is the same and avoids an extra slice index. The new logic is both simpler and faster. Performance: name old time/op new time/op delta CodeDecoder 2.47ms ± 4% 2.42ms ± 2% -1.83% (p=0.022 n=10+9) UnicodeDecoder 259ns ± 2% 248ns ± 1% -4.32% (p=0.000 n=10+10) DecoderStream 150ns ± 1% 149ns ± 1% ~ (p=0.516 n=10+10) CodeUnmarshal 3.13ms ± 2% 3.09ms ± 2% -1.37% (p=0.022 n=10+9) CodeUnmarshalReuse 2.50ms ± 1% 2.45ms ± 1% -1.96% (p=0.001 n=8+9) UnmarshalString 67.1ns ± 5% 64.5ns ± 5% -3.90% (p=0.005 n=10+10) UnmarshalFloat64 60.1ns ± 4% 58.4ns ± 2% -2.89% (p=0.002 n=10+8) UnmarshalInt64 51.0ns ± 4% 49.2ns ± 1% -3.53% (p=0.001 n=10+8) Issue10335 80.7ns ± 2% 79.2ns ± 1% -1.82% (p=0.016 n=10+8) Issue34127 28.6ns ± 3% 28.8ns ± 3% ~ (p=0.388 n=9+10) Unmapped 177ns ± 2% 177ns ± 2% ~ (p=0.956 n=10+10) Change-Id: I478b2b958f5a63a69c9a991a39cd5ffb43244a2a Reviewed-on: https://go-review.googlesource.com/c/go/+/471196 Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Run-TryBot: Joseph Tsai <joetsai@digital-static.net> Auto-Submit: Joseph Tsai <joetsai@digital-static.net> TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com> Reviewed-by: Than McIntosh <thanm@google.com> Reviewed-by: Daniel Martí <mvdan@mvdan.cc>		2023-02-27 17:37:27 +00:00
..
ascii85	encoding: use strings.Builder	2022-09-06 15:46:20 +00:00
asn1	all: remove redundant type conversion	2022-10-06 04:37:00 +00:00
base32	all: remove redundant type conversion	2022-10-06 04:37:00 +00:00
base64	encoding: use strings.Builder	2022-09-06 15:46:20 +00:00
binary	src: rename unexported errors by adding prefix err	2023-02-16 23:09:19 +00:00
csv	encoding/csv: use proper doc comment for Deprecated notes	2022-12-02 16:30:23 +00:00
gob	encoding/gob: use reflect.Value.SetZero	2023-02-27 15:31:13 +00:00
hex	Revert "hex: fix panic in Decode when len(src) > 2*len(dst)"	2023-02-21 15:35:11 +00:00
json	encoding/json: simplify folded name logic	2023-02-27 17:37:27 +00:00
pem	all: use strings.Builder where appropriate	2022-09-29 22:56:00 +00:00
xml	encoding/xml: allow overriding by empty namespace	2023-01-31 18:23:50 +00:00
encoding.go