Use standard library to compare bytes in parseDateTime

[zihengCat]

Description

• Use a pre-allocated time.Time in function parseDateTime.
• Use standard library to compare bytes, no need for a variable base.
• Add more comments.

Checklist

• Code compiles correctly
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary
• Added myself / the copyright holder to the AUTHORS file

[zihengCat]

CI reports a unit test case fail, but seems nothing so serious.

driver_test.go:2618: FIXME: it sometime fails with "expected driver.ErrBadConn, got sql: connection is already closed" on windows and macOS

[zihengCat]

@shogo82148
Hi, take a review pls. :)

[methane]

• Use a pre-allocated time.Time in function parseDateTime.

Why?

[zihengCat]

@methane
Well, I write a BenchmarkParseDateTime based on utils_test.go to compare the difference between pre-allocated time.Time and instant constructed time.Time. It seems nothing so particular, Go compiler optimization done things very well!

So, I would like to remove the global pre-allocated time.Time variable. Thanks!

goos: linux
goarch: amd64
cpu: Intel(R) Core(TM) i7-4770HQ CPU @ 2.20GHz
BenchmarkParseDateTime/parse_invalid_time-UTC-2                  8174274               309.7 ns/op            80 B/op          4 allocs/op
BenchmarkParseDateTime/parse_year-UTC-2                         20757028               104.4 ns/op            48 B/op          2 allocs/op
BenchmarkParseDateTime/parse_month-UTC-2                        21054753               108.4 ns/op            48 B/op          2 allocs/op
BenchmarkParseDateTime/parse_"-"_after_parsed_year-UTC-2                 9021055               256.7 ns/op            72 B/op          3 allocs/op
BenchmarkParseDateTime/parse_"-"_after_parsed_month-UTC-2                8705283               292.0 ns/op            72 B/op          3 allocs/op
BenchmarkParseDateTime/parse_"_"_after_parsed_date-UTC-2                 8441883               284.0 ns/op            72 B/op          3 allocs/op
BenchmarkParseDateTime/parse_":"_after_parsed_date-UTC-2                 8025570               310.6 ns/op            72 B/op          3 allocs/op
BenchmarkParseDateTime/parse_":"_after_parsed_hour-UTC-2                 7832512               290.5 ns/op            72 B/op          3 allocs/op
BenchmarkParseDateTime/parse_"."_after_parsed_sec-UTC-2                  7848106               294.3 ns/op            72 B/op          3 allocs/op
BenchmarkParseDateTime/parse_invalid_time-test-2                         8227734               283.6 ns/op            80 B/op          4 allocs/op
BenchmarkParseDateTime/parse_year-test-2                                20994528               101.9 ns/op            48 B/op          2 allocs/op
BenchmarkParseDateTime/parse_month-test-2                               20942578               108.0 ns/op            48 B/op          2 allocs/op
BenchmarkParseDateTime/parse_"-"_after_parsed_year-test-2                8922724               255.9 ns/op            72 B/op          3 allocs/op
BenchmarkParseDateTime/parse_"-"_after_parsed_month-test-2               8598964               270.3 ns/op            72 B/op          3 allocs/op
BenchmarkParseDateTime/parse_"_"_after_parsed_date-test-2                8464677               276.1 ns/op            72 B/op          3 allocs/op
BenchmarkParseDateTime/parse_":"_after_parsed_date-test-2                8322849               289.1 ns/op            72 B/op          3 allocs/op
BenchmarkParseDateTime/parse_":"_after_parsed_hour-test-2                7467320               321.1 ns/op            72 B/op          3 allocs/op
BenchmarkParseDateTime/parse_"."_after_parsed_sec-test-2                 7823634               316.3 ns/op            72 B/op          3 allocs/op
PASS
ok      command-line-arguments  46.934s

Benchmark Report

[zihengCat]

@methane
Please take another look. :)

[methane]

Why?
Do you expect performance improvement? or readability improvement?

[zihengCat]

Both actually. No need for a constant variable base here.