fastpostcode

fastpostcode

A fast postcode validator written in Go. Capable of validating every postcode in the United Kingdom in milliseconds.

The regular expressions for the matcher are from this stackoverflow answer. These were rewritten as ragel expressions and compiled into a Finite State Machine.

The trade-off for this performance is binary size, with the matcher being ~1600 lines of code. If you want an idiomatic Go implementation, the regex version is here.

Validating a postcode by its pattern catches invalid inputs, but there will be false positives. Validator is tested against all ~1.8 million postcodes.

See

• Postcodes_in_the_United_Kingdom
• speeding-up-regexp-matching-with-ragel
• ragel-cheat-sheet
• postcodes.io

Benchmarks

Benchmark_IsValid/fastpostcode_Valid           111773841	      10.7 ns/op
Benchmark_IsValid/fastpostcode_Invalid         150052951	      7.82 ns/op

Benchmark_IsValid/regex_Valid                	 4851324	       222 ns/op
Benchmark_IsValid/regex_Invalid               	  714759	      1516 ns/op

Example

package main

import (
	"fmt"
	"github.com/T-J-L/fastpostcode"
)

func main() {
	if fastpostcode.IsValid("SW1A 1AA") {
		fmt.Println("This looks like a valid postcode")
	}
}

License

fastpostcode is released under the MIT License.