108 lines
2.0 KiB
Go
108 lines
2.0 KiB
Go
package main
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import (
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"bufio"
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"fmt"
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"io"
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"strings"
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)
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type lexer struct {
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r *bufio.Reader
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lineno int
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peek Token
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}
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func NewLexer(src io.Reader) *lexer {
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return &lexer{
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r: bufio.NewReader(src),
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lineno: 0,
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}
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}
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func (l *lexer) Peek() (Token, error) {
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tok, err := l.Next()
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if err != nil {
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return nil, err
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}
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l.peek = tok
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return tok, nil
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}
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func (l *lexer) Next() (Token, error) {
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if l.peek != nil {
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ret := l.peek
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l.peek = nil
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return ret, nil
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}
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//
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l.lineno++
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line, err := l.r.ReadString('\n')
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if err != nil {
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return nil, err
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}
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// Strip leading spaces
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line = strings.TrimLeft(line, " \t\r\n")
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// Strip trailing line-comments (;)
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line, _, _ = strings.Cut(line, `;`)
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if len(line) == 0 {
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// This line only contained comments
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// Continue to the next line
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return l.Next()
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}
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fields := strings.Fields(line)
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// FIXME commas!?
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switch strings.ToLower(fields[0]) {
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case "section":
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return SectionToken{fields[1]}, nil
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case "global":
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return LabelToken{strings.TrimRight(fields[1], `:`), true}, nil
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case "mov":
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for i, _ := range fields {
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fields[i] = strings.TrimRight(fields[i], `,`)
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}
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return MovInstrToken{fields[1:]}, nil
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case "syscall":
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return SyscallInstrToken{}, nil
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case "ret":
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return RetInstrToken{}, nil
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default:
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// If the field ends with `:`, it's a (local) label
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if strings.HasSuffix(fields[0], `:`) {
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return LabelToken{strings.TrimRight(fields[0], `:`), false}, nil
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}
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// If the field starts with `$`, it's a "variable"
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if strings.HasPrefix(fields[0], `$`) {
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// 1: =
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if fields[1] != `=` {
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return nil, fmt.Errorf("Invalid syntax at line %d (expected = in declaration)", l.lineno)
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}
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// 2: sizeclass
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// 3+++: literal initializer
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return DataVariableInstrToken{
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VarName: fields[0][1:],
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Sizeclass: fields[2],
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Value: strings.Join(fields[3:], " "), // FIXME consecutive spaces are ruined
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}, nil
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}
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}
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return nil, fmt.Errorf("Unknown token '%s' at line %d", fields[0], l.lineno)
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}
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