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parser.go
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parser.go
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package main
import (
"bufio"
"os"
"regexp"
"strings"
)
var (
ACommandRegex = regexp.MustCompile(`^@(.*)`)
CCommandRegex = regexp.MustCompile(`^([ADM]+=)?([\-\+\!\&\|01ADM]+)(;[JGELNMTQP]+)?\s*`)
LCommandRegex = regexp.MustCompile(`^\((.*)\)`)
)
type CommandType uint8
const (
INVALID_COMMAND CommandType = iota
A_COMMAND
C_COMMAND
L_COMMAND
)
type Parser struct {
Scanner *bufio.Scanner
CurrentLine string
}
func NewParser(filename string) (*Parser, error) {
f, err := os.Open(filename)
if err != nil {
return nil, err
}
scanner := bufio.NewScanner(f)
return &Parser{
Scanner: scanner,
}, nil
}
func (p *Parser) HasMoreCommands() bool {
hasMoreLine := p.Scanner.Scan()
if !hasMoreLine {
return false
}
line := p.Scanner.Text()
line = strings.TrimSpace(line)
if ACommandRegex.MatchString(line) || CCommandRegex.MatchString(line) || LCommandRegex.MatchString(line) {
p.CurrentLine = line
return true
}
return p.HasMoreCommands()
}
func (p *Parser) Advance() string {
return p.CurrentLine
}
func (p *Parser) CommandType() CommandType {
if ACommandRegex.MatchString(p.CurrentLine) {
return A_COMMAND
}
if CCommandRegex.MatchString(p.CurrentLine) {
return C_COMMAND
}
if LCommandRegex.MatchString(p.CurrentLine) {
return L_COMMAND
}
return INVALID_COMMAND
}
func (p *Parser) Symbol() string {
if p.CommandType() == A_COMMAND {
m := ACommandRegex.FindAllStringSubmatch(p.CurrentLine, -1)
return m[0][1]
}
if p.CommandType() == L_COMMAND {
m := LCommandRegex.FindAllStringSubmatch(p.CurrentLine, -1)
return m[0][1]
}
return ""
}
func (p *Parser) Dest() string {
return strings.TrimSuffix(p.cCommandSubstring(1), `=`)
}
func (p *Parser) Comp() string {
return p.cCommandSubstring(2)
}
func (p *Parser) Jump() string {
return strings.TrimPrefix(p.cCommandSubstring(3), `;`)
}
func (p *Parser) cCommandSubstring(n int) string {
if p.CommandType() == C_COMMAND {
m := CCommandRegex.FindAllStringSubmatch(p.CurrentLine, -1)
return m[0][n]
}
return ""
}