Reserve parser storage upfront

[dduan]

Estimate key/value and node counts from input size and reserve parser arrays before tokenization. Cut dynamic array growth and copy churn in hot parse 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	66	66	67	70	84	142	7311
pull_request	65	66	66	67	70	85	151	7284
Δ	0	0	0	0	0	1	9	-27
Improvement %	0	0	0	0	0	-1	-6	-27

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

Retains *	p0	p25	p50	p75	p90	p99	p100	Samples
main	604	604	605	605	605	605	605	7311
pull_request	604	604	604	604	604	604	604	7284
Δ	0	0	-1	-1	-1	-1	-1	-27
Improvement %	0	0	0	0	0	0	0	-27

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	6122	6263	6303	6355	6435	9799	20558	10000
pull_request	5420	5543	5583	5631	5703	7123	25278	10000
Δ	-702	-720	-720	-724	-732	-2676	4720	0
Improvement %	11	11	11	11	11	27	-23	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	264	264	265	265	265	265	265	4
pull_request	264	264	265	266	266	266	266	4
Δ	0	0	0	1	1	1	1	0
Improvement %	0	0	0	0	0	0	0	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	8876	8929	8946	8962	9003	9265	9447	111
pull_request	8833	8864	8880	8897	8921	9150	9397	112
Δ	-43	-65	-66	-65	-82	-115	-50	1
Improvement %	0	1	1	1	1	1	1	1

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	112
Δ	0	0	0	0	0	0	0	1
Improvement %	0	0	0	0	0	0	0	1

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	162	163	164	172	173	173	173	6
pull_request	157	157	158	158	159	159	159	7
Δ	-5	-6	-6	-14	-14	-14	-14	1
Improvement %	3	4	4	8	8	8	8	1

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	6
pull_request	150	150	150	150	150	150	150	7
Δ	0	0	0	0	0	0	0	1
Improvement %	0	0	0	0	0	0	0	1

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	17	17	17	18	18	19	19	58
pull_request	16	16	16	17	17	18	18	61
Δ	-1	-1	-1	-1	-1	-1	-1	3
Improvement %	6	6	6	6	6	5	5	3

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	58
pull_request	133	134	134	134	134	134	134	61
Δ	0	0	0	0	0	0	0	3
Improvement %	0	0	0	0	0	0	0	3

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	2696	2716	2724	2736	2759	2861	3251	359
pull_request	2663	2687	2697	2705	2716	2800	3409	363
Δ	-33	-29	-27	-31	-43	-61	158	4
Improvement %	1	1	1	1	2	2	-5	4

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	359
pull_request	3138	3139	3139	3139	3139	3139	3139	363
Δ	0	0	0	0	0	0	0	4
Improvement %	0	0	0	0	0	0	0	4