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lex.go
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lex.go
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package arnoldc
import (
"bytes"
"fmt"
"io"
"os"
"strconv"
"strings"
"unicode"
)
//go:generate goyacc -c -cr -o parser.go parser.y
type ArnoldC struct {
input io.ReadSeeker
program Program // Our result object
err error // The last error to come out of the parser
Debug bool // Print debugging messages
// State
scannedInstruction bool
// Where are we in out input?
line int
offset int
currentByte byte
// TODO: Keep the current line in memory so we can add it to errors?
}
func New(input io.ReadSeeker) *ArnoldC {
return &ArnoldC{input: input, line: 1, Debug: false}
}
func (a *ArnoldC) Parse() (*Program, error) {
_ = yyParse(a)
if a.err != nil {
return nil, a.err
}
return &a.program, nil
}
func (a *ArnoldC) log(format string, args ...interface{}) {
if a.Debug {
fmt.Fprintf(os.Stderr, "Lexer: "+format+"\n", args...)
}
}
// Error satisfies yyLexer.
func (a *ArnoldC) Error(s string) {
a.err = fmt.Errorf("%s on line %d at character %d, %q", s, a.line, a.offset, a.currentByte)
}
// Lex satisfies yyLexer.
func (a *ArnoldC) Lex(lval *yySymType) int {
if !a.scannedInstruction {
return a.scanInstruction(lval)
}
return a.scanNormal(lval)
}
// Gets the next byte in the input.
func (a *ArnoldC) next() byte {
// TODO: Optimize this buffer creation.
// TODO: We can also scan like, 10 chars and walk them to eat up space and stuff.
var b []byte = make([]byte, 1)
_, err := a.input.Read(b)
if err != nil {
if err == io.EOF {
a.log("!! EOF")
}
// TODO: Set the non-EOF error contents somewhere?
return 0
}
a.offset++
a.currentByte = b[0]
return b[0]
}
// Seek input backwards one byte.
func (a *ArnoldC) backup() error {
a.log("<- backup")
_, err := a.input.Seek(-1, io.SeekCurrent)
if err == nil {
a.offset--
a.currentByte = 0
}
return err
}
func (a *ArnoldC) scanInstruction(lval *yySymType) int {
a.log("> scanInstruction")
buf := bytes.NewBuffer(nil)
for b := a.next(); ; b = a.next() {
a.log("%q %d", b, b)
switch {
case (unicode.IsUpper(rune(b)) || b == '\'' || b == ',' || unicode.IsSpace(rune(b))) && b != '\n':
buf.WriteByte(b)
default:
lval.str = strings.TrimSpace(buf.String())
if len(lval.str) == 0 {
if b == 0 {
return 0
}
continue
}
a.log("str = %q", lval.str)
if b != 0 {
a.backup()
}
a.scannedInstruction = true
tk, ok := instructions[lval.str]
if !ok {
a.log("!! Unknown Instruction")
// TODO: Store error.
return LexError
}
if '\n' == b {
a.line++
a.offset = 0
}
return tk
}
}
}
func (a *ArnoldC) scanNormal(lval *yySymType) int {
a.log("> scanNormal")
for b := a.next(); b != 0; b = a.next() {
a.log("%q %d", b, b)
switch {
case '\n' == b:
a.line++
a.offset = 0
a.scannedInstruction = false
return a.scanInstruction(lval)
case unicode.IsSpace(rune(b)):
continue
case b == '@':
return a.scanMacro(lval)
case b == '"':
return a.scanString(lval)
case unicode.IsDigit(rune(b)) || b == '-':
a.backup()
return a.scanInteger(lval)
case unicode.IsLetter(rune(b)):
a.backup()
return a.scanVariable(lval)
default:
return int(b)
}
}
return 0
}
func (a *ArnoldC) scanString(lval *yySymType) int {
a.log("> scanString")
buf := bytes.NewBuffer(nil)
for b := a.next(); b != 0; b = a.next() {
a.log("%q %d", b, b)
switch b {
case '"':
lval.str = buf.String()
a.log("str = %q", lval.str)
return String
default:
buf.WriteByte(b)
}
}
return LexError
}
func (a *ArnoldC) scanVariable(lval *yySymType) int {
a.log("> scanVariable")
buf := bytes.NewBuffer(nil)
for b := a.next(); ; b = a.next() {
a.log("%q %d", b, b)
switch {
case unicode.IsLetter(rune(b)) || unicode.IsDigit(rune(b)):
buf.WriteByte(b)
case b == '\n':
a.backup()
fallthrough
default:
lval.str = buf.String()
a.log("str = %q", lval.str)
return Variable
}
}
}
func (a *ArnoldC) scanMacro(lval *yySymType) int {
a.log("> scanMacro")
buf := bytes.NewBuffer(nil)
for b := a.next(); ; b = a.next() {
a.log("%q %d", b, b)
switch {
case unicode.IsLetter(rune(b)) || b == ' ':
buf.WriteByte(b)
case b == '\n':
a.backup()
fallthrough
default:
lval.str = buf.String()
a.log("str = %q", lval.str)
tk, ok := macros[lval.str]
if !ok {
a.log("!! Unknown Macro \"@%s\"", lval.str)
// TODO: Store error.
return LexError
}
return tk
}
}
}
func (a *ArnoldC) scanInteger(lval *yySymType) int {
a.log("> scanInteger")
buf := bytes.NewBuffer(nil)
for b := a.next(); ; b = a.next() {
a.log("%q %d", b, b)
// TODO: - should only be allowed for the first byte
if unicode.IsDigit(rune(b)) || b == '-' {
buf.WriteByte(b)
} else {
if 0 != b {
a.backup()
}
val, err := strconv.Atoi(buf.String())
if err != nil {
a.log("!! Invalid Integer")
// TODO: Store error.
return LexError
}
lval.integer = val
a.log("integer = %d", lval.integer)
return Integer
}
}
}