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path: root/src/urubu/driver/lexer/lexer.go
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Diffstat (limited to 'src/urubu/driver/lexer/lexer.go')
-rw-r--r--src/urubu/driver/lexer/lexer.go335
1 files changed, 0 insertions, 335 deletions
diff --git a/src/urubu/driver/lexer/lexer.go b/src/urubu/driver/lexer/lexer.go
deleted file mode 100644
index 3f9712e..0000000
--- a/src/urubu/driver/lexer/lexer.go
+++ /dev/null
@@ -1,335 +0,0 @@
-package lexer
-
-import (
- "fmt"
- "io"
-)
-
-type ModeID int
-
-func (id ModeID) Int() int {
- return int(id)
-}
-
-type StateID int
-
-func (id StateID) Int() int {
- return int(id)
-}
-
-type KindID int
-
-func (id KindID) Int() int {
- return int(id)
-}
-
-type ModeKindID int
-
-func (id ModeKindID) Int() int {
- return int(id)
-}
-
-type LexSpec interface {
- InitialMode() ModeID
- Pop(mode ModeID, modeKind ModeKindID) bool
- Push(mode ModeID, modeKind ModeKindID) (ModeID, bool)
- ModeName(mode ModeID) string
- InitialState(mode ModeID) StateID
- NextState(mode ModeID, state StateID, v int) (StateID, bool)
- Accept(mode ModeID, state StateID) (ModeKindID, bool)
- KindIDAndName(mode ModeID, modeKind ModeKindID) (KindID, string)
-}
-
-// Token representes a token.
-type Token struct {
- // ModeID is an ID of a lex mode.
- ModeID ModeID
-
- // KindID is an ID of a kind. This is unique among all modes.
- KindID KindID
-
- // ModeKindID is an ID of a lexical kind. This is unique only within a mode.
- // Note that you need to use KindID field if you want to identify a kind across all modes.
- ModeKindID ModeKindID
-
- // BytePos is a byte position where a token appears.
- BytePos int
-
- // ByteLen is a length of a token.
- ByteLen int
-
- // Row is a row number where a token appears.
- Row int
-
- // Col is a column number where a token appears.
- // Note that Col is counted in code points, not bytes.
- Col int
-
- // Lexeme is a byte sequence matched a pattern of a lexical specification.
- Lexeme []byte
-
- // When this field is true, it means the token is the EOF token.
- EOF bool
-
- // When this field is true, it means the token is an error token.
- Invalid bool
-}
-
-type LexerOption func(l *Lexer) error
-
-// DisableModeTransition disables the active mode transition. Thus, even if the lexical specification has the push and pop
-// operations, the lexer doesn't perform these operations. When the lexical specification has multiple modes, and this option is
-// enabled, you need to call the Lexer.Push and Lexer.Pop methods to perform the mode transition. You can use the Lexer.Mode method
-// to know the current lex mode.
-func DisableModeTransition() LexerOption {
- return func(l *Lexer) error {
- l.passiveModeTran = true
- return nil
- }
-}
-
-type lexerState struct {
- srcPtr int
- row int
- col int
-}
-
-type Lexer struct {
- spec LexSpec
- src []byte
- state lexerState
- lastAcceptedState lexerState
- tokBuf []*Token
- modeStack []ModeID
- passiveModeTran bool
-}
-
-// NewLexer returns a new lexer.
-func NewLexer(spec LexSpec, src io.Reader, opts ...LexerOption) (*Lexer, error) {
- b, err := io.ReadAll(src)
- if err != nil {
- return nil, err
- }
- l := &Lexer{
- spec: spec,
- src: b,
- state: lexerState{
- srcPtr: 0,
- row: 0,
- col: 0,
- },
- lastAcceptedState: lexerState{
- srcPtr: 0,
- row: 0,
- col: 0,
- },
- modeStack: []ModeID{
- spec.InitialMode(),
- },
- passiveModeTran: false,
- }
- for _, opt := range opts {
- err := opt(l)
- if err != nil {
- return nil, err
- }
- }
-
- return l, nil
-}
-
-// Next returns a next token.
-func (l *Lexer) Next() (*Token, error) {
- if len(l.tokBuf) > 0 {
- tok := l.tokBuf[0]
- l.tokBuf = l.tokBuf[1:]
- return tok, nil
- }
-
- tok, err := l.nextAndTransition()
- if err != nil {
- return nil, err
- }
- if !tok.Invalid {
- return tok, nil
- }
- errTok := tok
- for {
- tok, err = l.nextAndTransition()
- if err != nil {
- return nil, err
- }
- if !tok.Invalid {
- break
- }
- errTok.ByteLen += tok.ByteLen
- errTok.Lexeme = append(errTok.Lexeme, tok.Lexeme...)
- }
- l.tokBuf = append(l.tokBuf, tok)
-
- return errTok, nil
-}
-
-func (l *Lexer) nextAndTransition() (*Token, error) {
- tok, err := l.next()
- if err != nil {
- return nil, err
- }
- if tok.EOF || tok.Invalid {
- return tok, nil
- }
- if l.passiveModeTran {
- return tok, nil
- }
- mode := l.Mode()
- if l.spec.Pop(mode, tok.ModeKindID) {
- err := l.PopMode()
- if err != nil {
- return nil, err
- }
- }
- if mode, ok := l.spec.Push(mode, tok.ModeKindID); ok {
- l.PushMode(mode)
- }
- // The checking length of the mode stack must be at after pop and push operations because those operations can be performed
- // at the same time. When the mode stack has just one element and popped it, the mode stack will be temporarily emptied.
- // However, since a push operation may be performed immediately after it, the lexer allows the stack to be temporarily empty.
- if len(l.modeStack) == 0 {
- return nil, fmt.Errorf("a mode stack must have at least one element")
- }
- return tok, nil
-}
-
-func (l *Lexer) next() (*Token, error) {
- mode := l.Mode()
- state := l.spec.InitialState(mode)
- buf := []byte{}
- startPos := l.state.srcPtr
- row := l.state.row
- col := l.state.col
- var tok *Token
- for {
- v, eof := l.read()
- if eof {
- if tok != nil {
- l.revert()
- return tok, nil
- }
- // When `buf` has unaccepted data and reads the EOF, the lexer treats the buffered data as an invalid token.
- if len(buf) > 0 {
- return &Token{
- ModeID: mode,
- ModeKindID: 0,
- BytePos: startPos,
- ByteLen: l.state.srcPtr - startPos,
- Lexeme: buf,
- Row: row,
- Col: col,
- Invalid: true,
- }, nil
- }
- return &Token{
- ModeID: mode,
- ModeKindID: 0,
- BytePos: startPos,
- Row: row,
- Col: col,
- EOF: true,
- }, nil
- }
- buf = append(buf, v)
- nextState, ok := l.spec.NextState(mode, state, int(v))
- if !ok {
- if tok != nil {
- l.revert()
- return tok, nil
- }
- return &Token{
- ModeID: mode,
- ModeKindID: 0,
- BytePos: startPos,
- ByteLen: l.state.srcPtr - startPos,
- Lexeme: buf,
- Row: row,
- Col: col,
- Invalid: true,
- }, nil
- }
- state = nextState
- if modeKindID, ok := l.spec.Accept(mode, state); ok {
- kindID, _ := l.spec.KindIDAndName(mode, modeKindID)
- tok = &Token{
- ModeID: mode,
- KindID: kindID,
- ModeKindID: modeKindID,
- BytePos: startPos,
- ByteLen: l.state.srcPtr - startPos,
- Lexeme: buf,
- Row: row,
- Col: col,
- }
- l.accept()
- }
- }
-}
-
-// Mode returns the current lex mode.
-func (l *Lexer) Mode() ModeID {
- return l.modeStack[len(l.modeStack)-1]
-}
-
-// PushMode adds a lex mode onto the mode stack.
-func (l *Lexer) PushMode(mode ModeID) {
- l.modeStack = append(l.modeStack, mode)
-}
-
-// PopMode removes a lex mode from the top of the mode stack.
-func (l *Lexer) PopMode() error {
- sLen := len(l.modeStack)
- if sLen == 0 {
- return fmt.Errorf("cannot pop a lex mode from a lex mode stack any more")
- }
- l.modeStack = l.modeStack[:sLen-1]
- return nil
-}
-
-func (l *Lexer) read() (byte, bool) {
- if l.state.srcPtr >= len(l.src) {
- return 0, true
- }
-
- b := l.src[l.state.srcPtr]
- l.state.srcPtr++
-
- // Count the token positions.
- // The driver treats LF as the end of lines and counts columns in code points, not bytes.
- // To count in code points, we refer to the First Byte column in the Table 3-6.
- //
- // Reference:
- // - [Table 3-6] https://www.unicode.org/versions/Unicode13.0.0/ch03.pdf > Table 3-6. UTF-8 Bit Distribution
- if b < 128 {
- // 0x0A is LF.
- if b == 0x0A {
- l.state.row++
- l.state.col = 0
- } else {
- l.state.col++
- }
- } else if b>>5 == 6 || b>>4 == 14 || b>>3 == 30 {
- l.state.col++
- }
-
- return b, false
-}
-
-// accept saves the current state.
-func (l *Lexer) accept() {
- l.lastAcceptedState = l.state
-}
-
-// revert reverts the lexer state to the last accepted state.
-//
-// We must not call this function consecutively.
-func (l *Lexer) revert() {
- l.state = l.lastAcceptedState
-}
generated by cgit v1.2.3 (git 2.49.0) at 2025-07-06 10:47:44 +0000