Flatten key lookup pointer loops

[dduan]

Reduce overhead in Parser key lookup by removing nested withUnsafeBufferPointer closures in matchKeyValue/matchKeyArray/matchKeyTable.

Each matcher now opens one buffer pointer for backing storage and scans borrowed index lists with simple index-based loops and pointer advances.

Behavior is unchanged; this targets instruction count in repeated table/key lookup paths.

[github-actions]

Comparing results between 'main' and 'pull_request'

Host 'runnervmkj6or' with 4 'x86_64' processors with 15 GB memory, running:
#18~24.04.1-Ubuntu SMP Sat Jun 28 04:46:03 UTC 2025

TOMLDecoderBenchmarks

Decode toml.io example metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (μs) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	65	65	66	66	70	85	147	7344
pull_request	64	65	65	66	69	82	115	7360
Δ	-1	0	-1	0	-1	-3	-32	16
Improvement %	2	0	2	0	1	4	22	16

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	605	605	605	606	606	606	606	7344
pull_request	604	604	604	604	604	604	604	7360
Δ	-1	-1	-1	-2	-2	-2	-2	16
Improvement %	0	0	0	0	0	0	0	16

Parse toml.io example metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ns) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	5651	5783	5823	5871	5963	10351	31248	10000
pull_request	5530	5651	5691	5731	5803	9351	30156	10000
Δ	-121	-132	-132	-140	-160	-1000	-1092	0
Improvement %	2	2	2	2	3	10	3	0

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	13	14	14	14	14	14	14	10000
pull_request	13	14	14	14	14	14	14	10000
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

decode canada.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	263	263	264	264	266	266	266	4
pull_request	267	267	268	269	269	269	269	4
Δ	4	4	4	5	3	3	3	0
Improvement %	-2	-2	-2	-2	-1	-1	-1	0

Retains: results within specified thresholds, fold down for details.

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	1674	1674	1674	1674	1674	1674	1674	4
pull_request	1674	1674	1674	1674	1674	1674	1674	4
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

decode twitter.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (μs) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	8897	8921	8937	8962	8995	9265	9455	111
pull_request	8737	8782	8790	8815	8864	9093	9370	113
Δ	-160	-139	-147	-147	-131	-172	-85	2
Improvement %	2	2	2	2	1	2	1	2

Retains: results within specified thresholds, fold down for details.

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	68	68	68	68	68	68	68	111
pull_request	68	68	68	68	68	68	68	113
Δ	0	0	0	0	0	0	0	2
Improvement %	0	0	0	0	0	0	0	2

parse GitHub events archive metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	156	157	159	164	166	166	166	7
pull_request	153	153	154	154	155	155	155	7
Δ	-3	-4	-5	-10	-11	-11	-11	0
Improvement %	2	3	3	6	7	7	7	0

Retains: results within specified thresholds, fold down for details.

Retains (K) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	150	150	150	150	150	150	150	7
pull_request	150	150	150	150	150	150	150	7
Δ	0	0	0	0	0	0	0	0
Improvement %	0	0	0	0	0	0	0	0

parse canada.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (ms) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	16	16	16	18	29	31	31	53
pull_request	16	16	17	17	17	18	18	60
Δ	0	0	1	-1	-12	-13	-13	7
Improvement %	0	0	-6	6	41	42	42	7

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	133	134	134	134	134	134	134	53
pull_request	133	134	134	134	134	134	134	60
Δ	0	0	0	0	0	0	0	7
Improvement %	0	0	0	0	0	0	0	7

parse twitter.toml metrics

Time (wall clock): results within specified thresholds, fold down for details.

Time (wall clock) (μs) *	p0	p25	p50	p75	p90	p99	p100	Samples
main	2662	2679	2685	2695	3359	6500	6780	332
pull_request	2625	2638	2644	2654	2666	2867	3383	370
Δ	-37	-41	-41	-41	-693	-3633	-3397	38
Improvement %	1	2	2	2	21	56	50	38

Retains: results within specified thresholds, fold down for details.

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	3138	3139	3139	3139	3139	3139	3139	332
pull_request	3138	3139	3139	3139	3139	3139	3139	370
Δ	0	0	0	0	0	0	0	38
Improvement %	0	0	0	0	0	0	0	38