gobble's Introduction

gobble

gobble is a parser combinator library written in Go. It was inspired by the nom library written for Rust. Its aim is to allow users to build complex parsers, without compromising on speed, while abstracting away most of the parsing complexities.

Example

Hexadecimal color parser:

package main

import (
	"github.com/roblovelock/gobble/pkg/combinator"
	"github.com/roblovelock/gobble/pkg/combinator/branch"
	"github.com/roblovelock/gobble/pkg/combinator/sequence"
	"github.com/roblovelock/gobble/pkg/parser/ascii"
	"github.com/roblovelock/gobble/pkg/parser/bytes"
	"image/color"
	"strconv"
	"github.com/roblovelock/gobble/pkg/parser/strings"
)

var (
	hex       = bytes.TakeWhileMinMax(2, 2, ascii.IsHexDigit)
	rgbValue  = combinator.Map(hex, hexToUint8)
	rgbValues = sequence.Tuple(rgbValue, rgbValue, rgbValue)

	hexByte        = bytes.OneOf([]byte("0123456789abcdefABCDEF")...)
	shortRGBValue  = combinator.Map(hexByte, hexByteToUint8)
	shortRGBValues = sequence.Tuple(shortRGBValue, shortRGBValue, shortRGBValue)

	rgb = branch.Alt(rgbValues, shortRGBValues)

	colorValue = combinator.Map(rgb, func(rgb []uint8) (color.Color, error) {
		return color.RGBA{R: rgb[0], G: rgb[1], B: rgb[2], A: 255}, nil
	})

	hash        = bytes.Byte('#')
	colorParser = sequence.Preceded(hash, colorValue)
)

func hexToUint8(bytes []byte) (uint8, error) {
	i, err := strconv.ParseUint(string(bytes), 16, 8)
	return uint8(i), err
}

func hexByteToUint8(hexByte byte) (uint8, error) {
	return hexToUint8([]byte{hexByte, hexByte})
}

func Parse(in string) (color.Color, error) {
	return colorParser(strings.NewReader(in))
}