tree 2a67360dee3975f337fa7e3a7c1053bca0c2db00
parent 00e50dc9c1830e440bb7d0d2f4a4da39c67d0c26
author Herbie Ong <herbie@google.com> 1555398843 -0700
committer Herbie Ong <herbie@google.com> 1555460773 +0000

internal/encoding/{json,text}: improve string parsing

Previous calls to indexNeedEscape with a type conversion from []byte
to string incurs allocation.

Make 2 different calls instead, one for string and one for bytes.

Type converting string to []byte does not incur extra allocation,
however, the benchmark results still show it to be slower by ~3% for
textpb and 6+% for jsonpb, hence decided to go with 2 separate calls
instead.

Results over current head:
name          old time/op    new time/op    delta
TextEncode-4    18.1ms ± 2%    18.3ms ± 2%     ~     (p=0.065 n=10+9)
TextDecode-4     233ms ± 3%     102ms ± 1%  -56.34%  (p=0.000 n=9+10)
JSONEncode-4    10.4ms ± 2%    10.5ms ± 0%   +0.56%  (p=0.019 n=9+9)
JSONDecode-4     870ms ± 2%     354ms ± 4%  -59.33%  (p=0.000 n=9+10)

name          old alloc/op   new alloc/op   delta
TextEncode-4    28.9MB ± 0%    28.9MB ± 0%   +0.00%  (p=0.000 n=10+9)
TextDecode-4    1.16GB ± 0%    0.03GB ± 0%  -97.44%  (p=0.000 n=9+10)
JSONEncode-4    3.94MB ± 0%    3.94MB ± 0%   +0.00%  (p=0.000 n=10+10)
JSONDecode-4    3.35GB ± 0%    0.01GB ± 0%  -99.83%  (p=0.000 n=10+10)

name          old allocs/op  new allocs/op  delta
TextEncode-4     73.5k ± 0%     73.5k ± 0%     ~     (all equal)
TextDecode-4      278k ± 0%      255k ± 0%   -8.26%  (p=0.000 n=9+10)
JSONEncode-4     63.8k ± 0%     63.8k ± 0%     ~     (all equal)
JSONDecode-4      247k ± 0%      210k ± 0%  -14.92%  (p=0.000 n=10+10)

Change-Id: Ibc64e9a7827ec1fffa213eb79f60497950203700
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/172239
Reviewed-by: Joe Tsai <thebrokentoaster@gmail.com>