Parse3339

Parse3339 is a fast RFC 3339 time stamp parser written in pure Swift.

RFC 3339 specifies the commonly used subset of ISO 8601 suitable for time stamps. This parser restricts the subset even further. The following are the formats supported by Parse3339:

• 2023-07-09T13:14:00+03:00
• 2023-07-09T13:14:00.2+03:00
• 2023-07-09T13:14:00Z
• 2023-07-09T13:14:00.2Z

There's nothing to configure, and it's all in just file in case you want to copy it over instead of using it as a package.

Usage

import Parse3339

let s = "2023-07-09T13:14:00+03:00"
guard let parts = Parse3339::parse(s) else {
    return
}
let date = parts.date
print(date.timeIntervalSinceReferenceDate)
// output: 710590440.0

There are variants of parse for String, Substring and Span<UInt8>. By default parse parses the start of the string and allows trailing data. If you don't want to allow trailing data, you can specify requireFullConsumption:

Parse3339::parse(s, requireFullConsumption: true)

There's a helper function you can use with Foundation's JSONDecoder:

import Parse3339

let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .custom(Parse3339::parseFromDecoder(_:))

Parse3339 ships with Foundation integration (Date, DateComponents) enabled by default, but they can be disabled by disabling the WithFoundation trait. The parsing itself uses only Swift standard library types.

For Package.swift snippets and documentation, visit the Swift Package Index page.

Speed and memory usage

Parse3339 is pleasantly fast and stingy with memory usage. The package has benchmarks:

swift package benchmark

To measure parsing without date conversion, run the parser-only benchmarks:

swift package benchmark --filter 'Parse with Parse3339 \((String|Span) only\)' --metric wallClock --metric throughput --scale

These benchmarks use 8,192 timestamps with varying dates, fractional precision, and time zones. They measure the String and byte-span entry points separately.

There are also benchmarks that parse the same string using Foundation's DateFormatter, Foundation's ISO8601DateFormatter, Parse3339 creating a Date with Foundation's DateComponents and Calendar, and Parse3339 creating a Date with standard Unix functions.

Output from one run (macOS 27.0.1, MacBook Pro M5):

Parse with DateFormatter

Metric	p0	p25	p50	p75	p90	p99	p100	Samples
Free (total) *	1061	1061	1061	1061	1061	1061	1063	100000
Instructions (K) *	2161	2163	2163	2163	2163	2179	2421	100000
Malloc (bytes total) *	232713	232831	232831	232831	232831	232831	237065	100000
Malloc (total) *	1063	1063	1063	1063	1063	1063	1067	100000
Malloc / free Δ *	2	2	2	2	2	2	6	100000
Malloc / free Δ (bytes) *	99	99	99	99	99	99	4195	100000
Memory (resident peak) (M)	17	21	25	29	31	32	32	100000
Throughput (# / s) (K)	12	11	11	11	11	9	6	100000
Time (total CPU) (ns) *	87918	94271	94847	95423	96639	107711	176791	100000
Time (wall clock) (ns) *	86750	92927	93503	94079	95167	105663	178750	100000

Parse with ISO8601DateFormatter

Metric	p0	p25	p50	p75	p90	p99	p100	Samples
Free (total) *	1239	1239	1239	1239	1239	1239	1239	100000
Instructions (K) *	2642	2642	2642	2642	2642	2660	2857	100000
Malloc (bytes total) *	330588	330751	330751	330751	330751	330751	331004	100000
Malloc (total) *	1239	1239	1239	1239	1239	1239	1245	100000
Malloc / free Δ *	0	0	0	0	0	0	6	100000
Malloc / free Δ (bytes) *	0	0	0	0	0	0	416	100000
Memory (resident peak) (M)	15	16	16	16	16	16	16	100000
Throughput (# / s) (#)	9012	8415	8359	8303	8175	7439	5318	100000
Time (total CPU) (ns) *	112375	120319	121215	122047	123967	135807	177208	100000
Time (wall clock) (ns) *	110958	118847	119679	120575	122367	134527	188042	100000

Parse with Parse3339 (DateComponents)

Metric	p0	p25	p50	p75	p90	p99	p100	Samples
Free (total) *	1	1	1	1	1	1	1	100000
Instructions (K) *	6	6	6	6	6	7	60	100000
Malloc (bytes total) *	153	153	153	153	153	153	153	100000
Malloc (total) *	1	1	1	1	1	1	1	100000
Malloc / free Δ *	0	0	0	0	0	0	0	100000
Malloc / free Δ (bytes) *	0	0	0	0	0	0	0	100000
Memory (resident peak) (M)	13	13	13	13	13	13	13	100000
Throughput (# / s) (K)	1845	1500	1413	1413	1411	1144	54	100000
Time (total CPU) (ns) *	1749	1959	2000	2042	2083	2543	23667	100000
Time (wall clock) (ns) *	542	667	708	708	709	875	18584	100000

Parse with Parse3339 (Span only)

Metric	p0	p25	p50	p75	p90	p99	p100	Samples
Free (total) *	0	0	0	0	0	0	0	100000
Instructions *	464	464	464	464	464	464	503	100000
Malloc (bytes total) *	0	0	0	0	0	0	0	100000
Malloc (total) *	0	0	0	0	0	0	0	100000
Malloc / free Δ *	0	0	0	0	0	0	0	100000
Malloc / free Δ (bytes) *	0	0	0	0	0	0	0	100000
Memory (resident peak) (M)	12	13	13	13	13	13	13	100000
Throughput (# / s) (M)	89	82	82	82	81	67	25	100000
Time (total CPU) (ns) *	13	14	14	14	14	17	38	100000
Time (wall clock) (ns) *	11	12	12	12	12	15	40	100000

Parse with Parse3339 (String only)

Metric	p0	p25	p50	p75	p90	p99	p100	Samples
Free (total) *	0	0	0	0	0	0	0	100000
Instructions *	525	525	525	525	525	525	573	100000
Malloc (bytes total) *	0	0	0	0	0	0	0	100000
Malloc (total) *	0	0	0	0	0	0	0	100000
Malloc / free Δ *	0	0	0	0	0	0	0	100000
Malloc / free Δ (bytes) *	0	0	0	0	0	0	0	100000
Memory (resident peak) (M)	12	13	13	13	13	13	13	100000
Throughput (# / s) (M)	68	62	62	61	60	51	16	100000
Time (total CPU) (ns) *	16	17	18	18	18	22	57	100000
Time (wall clock) (ns) *	15	16	16	16	17	20	62	100000

Parse with Parse3339 (Unix time)

Metric	p0	p25	p50	p75	p90	p99	p100	Samples
Free (total) *	0	0	0	0	0	0	0	100000
Instructions (K) *	54	54	54	54	54	55	70	100000
Malloc (bytes total) *	0	0	0	0	0	0	0	100000
Malloc (total) *	0	0	0	0	0	0	0	100000
Malloc / free Δ *	0	0	0	0	0	0	0	100000
Malloc / free Δ (bytes) *	0	0	0	0	0	0	0	100000
Memory (resident peak) (M)	12	13	13	13	13	13	13	100000
Throughput (# / s) (K)	490	445	437	429	429	343	50	100000
Time (total CPU) (ns) *	3209	3583	3625	3667	3709	4583	19332	100000
Time (wall clock) (ns) *	2041	2251	2291	2333	2335	2917	20000	100000