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112 lines
2.1 KiB
Go
112 lines
2.1 KiB
Go
package lexer
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import (
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"gitea.paas.celticinfo.fr/oabrivard/gojson/token"
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)
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type Lexer struct {
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input string
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position int
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readPosition int
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ch byte
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}
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func NewLexer(input string) *Lexer {
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l := &Lexer{input: input}
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l.readChar()
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return l
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}
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func (l *Lexer) NextToken() token.Token {
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var tok token.Token
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l.skipWhitespace()
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switch l.ch {
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case '{':
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tok = token.NewToken(token.BEGIN_OBJECT, l.ch)
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case '}':
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tok = token.NewToken(token.END_OBJECT, l.ch)
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case '[':
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tok = token.NewToken(token.BEGIN_ARRAY, l.ch)
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case ']':
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tok = token.NewToken(token.END_ARRAY, l.ch)
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case ':':
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tok = token.NewToken(token.NAME_SEPARATOR, l.ch)
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case ',':
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tok = token.NewToken(token.VALUE_SEPARATOR, l.ch)
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case '"':
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tok.Type = token.STRING
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tok.Value = l.readString()
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case 0:
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tok.Value = ""
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tok.Type = token.EOF
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default:
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if isDigit(l.ch) || l.ch == '-' {
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tok.Value = l.readNumber()
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tok.Type = token.NUMBER
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return tok
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} else if isLetter(l.ch) {
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tok.Value = l.readIdentifier()
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tok.Type = token.LookupIdent(tok.Value)
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return tok
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} else {
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tok = token.NewToken(token.ILLEGAL, l.ch)
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}
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}
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l.readChar()
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return tok
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}
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func (l *Lexer) readChar() {
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if l.readPosition >= len(l.input) {
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l.ch = 0
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} else {
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l.ch = l.input[l.readPosition]
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}
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l.position = l.readPosition
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l.readPosition++
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}
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func (l *Lexer) skipWhitespace() {
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for l.ch == ' ' || l.ch == '\t' || l.ch == '\n' || l.ch == '\r' {
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l.readChar()
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}
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}
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func (l *Lexer) readNumber() string {
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position := l.position
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for isDigit(l.ch) || l.ch == '.' || l.ch == '-' || l.ch == '+' || l.ch == 'e' || l.ch == 'E' {
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l.readChar()
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}
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return l.input[position:l.position]
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}
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func isDigit(ch byte) bool {
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return '0' <= ch && ch <= '9'
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}
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func (l *Lexer) readString() string {
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position := l.position + 1
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for {
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l.readChar()
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if l.ch == '"' || l.ch == 0 {
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break
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}
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}
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return l.input[position:l.position]
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}
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func (l *Lexer) readIdentifier() string {
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position := l.position
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for isLetter(l.ch) {
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l.readChar()
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}
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return l.input[position:l.position]
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}
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func isLetter(ch byte) bool {
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return ('a' <= ch && ch <= 'z') || ('A' <= ch && ch <= 'Z') || ch == '_'
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}
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