ISO 8601 parsing/formatting for RelativeDuration (#14)

* implement iso 8601 parser for RelativeDuration

* implement iso 8601 formatter for RelativeDuration

* document iso 8601 parser and formatter

* support nanoseconds in duration parser

* use correct integer types in RelativeDuration parser

* check for integer overflow in RelativeDuration parser

* use u32 to represent nanos, to follow chrono::Duration::new signature

* support nanoseconds in RelativeDuration formatter

* simplify format_spec and improve efficiency

* make divmod clearer in RelativeDuration::to_iso_8601

* more test cases for RelativeDuration iso parse/format

* add benchmarks for RelativeDuration format/parse

* fix quirks of nanosecond handling in RelativeDuration parsing/formatting

* add property tests for RelativeDuration parser and formatter

Cargo.toml

@@ -17,7 +17,12 @@ version = "0.2.6"
 [dev-dependencies]
 criterion = "0.3"
 chrono-tz = "0.8.3"
+proptest = "1.4.0"
 
 [[bench]]
 name = "delta"
 harness = false
+
+[[bench]]
+name = "relative_duration"
+harness = false

benches/relative_duration.rs

@@ -0,0 +1,53 @@
+use criterion::{black_box, criterion_group, criterion_main, Criterion};
+
+use chronoutil::RelativeDuration;
+
+fn relative_duration_format_benchmark(c: &mut Criterion) {
+    let durations = [
+        "P1M",
+        "P1Y1M1W1DT1H1M1S",
+        "P99999999Y11M30DT23H59M59.999999999S",
+    ]
+    .iter()
+    .map(|s| RelativeDuration::from_iso_8601(s).unwrap())
+    .collect::<Vec<RelativeDuration>>();
+
+    let mut g = c.benchmark_group("relative_duration_format");
+
+    g.bench_function("one_specifier", |b| {
+        b.iter(|| black_box(durations[0]).to_iso_8601())
+    });
+    g.bench_function("all_specifiers", |b| {
+        b.iter(|| black_box(durations[1]).to_iso_8601())
+    });
+    g.bench_function("long_specifiers", |b| {
+        b.iter(|| black_box(durations[2]).to_iso_8601())
+    });
+}
+
+fn relative_duration_parse_benchmark(c: &mut Criterion) {
+    let durations = [
+        "P1M",
+        "P1Y1M1W1DT1H1M1S",
+        "P99999999Y11M30DT23H59M59.999999999S",
+    ];
+
+    let mut g = c.benchmark_group("relative_duration_parse");
+
+    g.bench_function("one_specifier", |b| {
+        b.iter(|| RelativeDuration::from_iso_8601(black_box(durations[0])))
+    });
+    g.bench_function("all_specifiers", |b| {
+        b.iter(|| RelativeDuration::from_iso_8601(black_box(durations[1])))
+    });
+    g.bench_function("long_specifiers", |b| {
+        b.iter(|| RelativeDuration::from_iso_8601(black_box(durations[2])))
+    });
+}
+
+criterion_group!(
+    benches,
+    relative_duration_format_benchmark,
+    relative_duration_parse_benchmark
+);
+criterion_main!(benches);

src/relative_duration.rs

@@ -6,6 +6,8 @@ use chrono::{Date, DateTime, Duration, NaiveDate, NaiveDateTime, TimeZone};
 
 use super::delta::shift_months;
 
+mod parse;
+
 /// Relative time duration extending Chrono's Duration.
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug, Hash)]
 pub struct RelativeDuration {