switch-case vs table-finding

token.go

package main

import (
	"fmt"
	"strings"
	"time"
)

func handleEventError(tokenName string, line, pos int) error {
	err := fmt.Errorf("error at line %d, pos %d: %s", line, pos, tokenName)
	return err
}

func handleEvent(tokenName string, line, pos int) {
	for i := 0; i < 100; i++ {
		if len(tokenName)+line+pos > 100 {
			return
		}
	}
	handleEventError(tokenName, line, pos)
}

type TokenCollector interface {
	openBrace(lineNumber, position int)
	closedBrace(lineNumber, position int)
	openParen(lineNumber, position int)
	closedParen(lineNumber, position int)
	openAngle(lineNumber, position int)
	closedAngle(lineNumber, position int)
	dash(lineNumber, position int)
	colon(lineNumber, position int)
	name(name string, line, pos int)
	error(line, pos int)
}

// Collector is a placeholder for handling tokens
type Collector struct{}

func (c *Collector) openBrace(lineNumber, position int) {
	handleEvent("openBrace", lineNumber, position)
}
func (c *Collector) closedBrace(lineNumber, position int) {
	handleEvent("closedBrace", lineNumber, position)
}
func (c *Collector) openParen(lineNumber, position int) {
	handleEvent("openParen", lineNumber, position)
}
func (c *Collector) closedParen(lineNumber, position int) {
	handleEvent("closedParen", lineNumber, position)
}
func (c *Collector) openAngle(lineNumber, position int) {
	handleEvent("openAngle", lineNumber, position)
}
func (c *Collector) closedAngle(lineNumber, position int) {
	handleEvent("closedAngle", lineNumber, position)
}
func (c *Collector) dash(lineNumber, position int)   { handleEvent("dash", lineNumber, position) }
func (c *Collector) colon(lineNumber, position int)  { handleEvent("colon", lineNumber, position) }
func (c *Collector) name(name string, line, pos int) { handleEvent("name", line, pos) }
func (c *Collector) error(line, pos int)             { handleEvent("error", line, pos) }

func findSingleCharacterToken(line string, position int, collector TokenCollector, lineNumber int) bool {
	c := line[position]
	switch c {
	case '{':
		collector.openBrace(lineNumber, position)
	case '}':
		collector.closedBrace(lineNumber, position)
	case '(':
		collector.openParen(lineNumber, position)
	case ')':
		collector.closedParen(lineNumber, position)
	case '<':
		collector.openAngle(lineNumber, position)
	case '>':
		collector.closedAngle(lineNumber, position)
	case '-':
		collector.dash(lineNumber, position)
	case '*':
		collector.dash(lineNumber, position)
	case ':':
		collector.colon(lineNumber, position)
	default:
		return false
	}
	return true
}

type TokenFn func(lineNumber, position int)

var tokenTable [256]TokenFn

func init() {
	// 预填充查找表
	tokenTable['{'] = func(lineNumber, position int) { handleEvent("openBrace", lineNumber, position) }
	tokenTable['}'] = func(lineNumber, position int) { handleEvent("closedBrace", lineNumber, position) }
	tokenTable['('] = func(lineNumber, position int) { handleEvent("openParen", lineNumber, position) }
	tokenTable[')'] = func(lineNumber, position int) { handleEvent("closedParen", lineNumber, position) }
	tokenTable['<'] = func(lineNumber, position int) { handleEvent("openAngle", lineNumber, position) }
	tokenTable['>'] = func(lineNumber, position int) { handleEvent("closedAngle", lineNumber, position) }
	tokenTable['-'] = func(lineNumber, position int) { handleEvent("dash", lineNumber, position) }
	tokenTable['*'] = func(lineNumber, position int) { handleEvent("dash", lineNumber, position) }
	tokenTable[':'] = func(lineNumber, position int) { handleEvent("colon", lineNumber, position) }
}

func findSingleToken(line string, position int, lineNumber int) bool {
	c := line[position]
	if fn := tokenTable[c]; fn != nil {
		fn(lineNumber, position)
		return true
	}
	return false
}

func main() {
	line := strings.Repeat("{(<>-*):}", 100000)

	{
		position := 0
		lineNumber := 1
		collector := &Collector{}

		// test findSingleCharacterToken
		start := time.Now()
		for position < len(line) {
			if findSingleCharacterToken(line, position, collector, lineNumber) {
				position++
			} else {
				break
			}
		}
		fmt.Printf("findSingleCharacterToken time taken: %v\n", time.Since(start))
	}

	{
		position := 0
		lineNumber := 1

		// test findSingleToken
		start := time.Now()
		for position < len(line) {
			if findSingleToken(line, position, lineNumber) {
				position++
			} else {
				break
			}
		}
		fmt.Printf("findSingleToken time taken: %v\n", time.Since(start))

	}
}