405 lines
7.9 KiB
Go
405 lines
7.9 KiB
Go
// Copyright © 2016 Abcum Ltd
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package sql
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import (
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"bufio"
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"bytes"
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"encoding/json"
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"io"
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"strconv"
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"strings"
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"time"
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)
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// Scanner represents a lexical scanner.
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type Scanner struct {
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r *bufio.Reader
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}
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// NewScanner returns a new instance of Scanner.
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func NewScanner(r io.Reader) *Scanner {
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return &Scanner{r: bufio.NewReader(r)}
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}
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// Scan returns the next token and literal value.
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func (s *Scanner) Scan() (tok Token, lit string) {
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// Read the next rune.
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ch := s.read()
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// If we see whitespace then consume all contiguous whitespace.
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if isWhitespace(ch) {
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s.unread()
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return s.scanWhitespace()
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}
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// If we see a letter then consume as an string.
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if isLetter(ch) {
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s.unread()
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return s.scanIdent()
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}
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// If we see a number then consume as a number.
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if isNumber(ch) {
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s.unread()
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return s.scanNumber()
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}
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// Otherwise read the individual character.
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switch ch {
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case eof:
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return EOF, ""
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case '*':
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return ALL, string(ch)
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case '@':
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return EAT, string(ch)
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case ',':
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return COMMA, string(ch)
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case '.':
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chn := s.read()
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s.unread()
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if isNumber(chn) {
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return s.scanNumber()
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}
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return DOT, string(ch)
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case '"':
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s.unread()
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return s.scanString()
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case '\'':
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s.unread()
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return s.scanString()
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case '`':
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s.unread()
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return s.scanQuoted()
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case '{':
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s.unread()
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return s.scanSpecial()
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case '[':
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s.unread()
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return s.scanSpecial()
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case ':':
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return COLON, string(ch)
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case ';':
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return SEMICOLON, string(ch)
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case '(':
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return LPAREN, string(ch)
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case ')':
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return RPAREN, string(ch)
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case '=':
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return EQ, string(ch)
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case '+':
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if chn := s.read(); chn == '=' {
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return INC, "+="
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}
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s.unread()
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return ADD, string(ch)
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case '-':
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if chn := s.read(); chn == '=' {
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return DEC, "-="
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}
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s.unread()
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return SUB, string(ch)
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case '!':
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if chn := s.read(); chn == '=' {
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return NEQ, "!="
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}
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s.unread()
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case '<':
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if chn := s.read(); chn == '=' {
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return LTE, "<="
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}
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s.unread()
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return LT, string(ch)
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case '>':
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if chn := s.read(); chn == '=' {
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return GTE, ">="
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}
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s.unread()
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return GT, string(ch)
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}
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return ILLEGAL, string(ch)
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}
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// scanWhitespace consumes the current rune and all contiguous whitespace.
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func (s *Scanner) scanWhitespace() (tok Token, lit string) {
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// Create a buffer and read the current character into it.
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var buf bytes.Buffer
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buf.WriteRune(s.read())
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// Read every subsequent whitespace character into the buffer.
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// Non-whitespace characters and EOF will cause the loop to exit.
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for {
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if ch := s.read(); ch == eof {
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break
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} else if !isWhitespace(ch) {
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s.unread()
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break
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} else {
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buf.WriteRune(ch)
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}
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}
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return WS, buf.String()
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}
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// scanIdent consumes the current rune and all contiguous ident runes.
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func (s *Scanner) scanIdent() (tok Token, lit string) {
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// Create a buffer and read the current character into it.
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var buf bytes.Buffer
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buf.WriteRune(s.read())
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// Read every subsequent ident character into the buffer.
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// Non-ident characters and EOF will cause the loop to exit.
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for {
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if ch := s.read(); ch == eof {
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break
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} else if !isIdentChar(ch) {
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s.unread()
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break
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} else {
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buf.WriteRune(ch)
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}
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}
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// If the string matches a keyword then return that keyword.
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if tok := keywords[strings.ToUpper(buf.String())]; tok > 0 {
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return tok, buf.String()
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}
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// Otherwise return as a regular identifier.
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return IDENT, buf.String()
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}
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func (s *Scanner) scanQuoted() (Token, string) {
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tok, lit := s.scanString()
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if is(tok, STRING) {
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return IDENT, lit
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}
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return tok, lit
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}
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func (s *Scanner) scanString() (tok Token, lit string) {
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tok = STRING
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var buf bytes.Buffer
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char := s.read()
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for {
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if ch := s.read(); ch == char {
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break
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} else if ch == eof {
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return ILLEGAL, buf.String()
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} else if ch == '\n' {
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tok = REGION
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buf.WriteRune(ch)
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} else if ch == '\\' {
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chn := s.read()
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if chn == 'n' {
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buf.WriteRune('\n')
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} else if chn == '\\' {
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buf.WriteRune('\\')
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} else if chn == '"' {
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buf.WriteRune('"')
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} else if chn == '\'' {
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buf.WriteRune('\'')
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} else if chn == '`' {
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buf.WriteRune('`')
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} else {
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return ILLEGAL, buf.String()
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}
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} else {
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buf.WriteRune(ch)
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}
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}
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return tok, buf.String()
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}
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func (s *Scanner) scanNumber() (tok Token, lit string) {
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tok = NUMBER
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// Create a buffer and read the current character into it.
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var buf bytes.Buffer
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buf.WriteRune(s.read())
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// Read every subsequent ident character into the buffer.
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// Non-ident characters and EOF will cause the loop to exit.
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for {
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if ch := s.read(); ch == eof {
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break
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} else if ch == '.' {
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if tok == DOUBLE {
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tok = IDENT
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}
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if tok == NUMBER {
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tok = DOUBLE
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}
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buf.WriteRune(ch)
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} else if ch == '+' {
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buf.WriteRune(ch)
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} else if ch == '-' {
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buf.WriteRune(ch)
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} else if ch == ':' {
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buf.WriteRune(ch)
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} else if ch == 'T' {
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buf.WriteRune(ch)
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} else if isLetter(ch) {
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tok = IDENT
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buf.WriteRune(ch)
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} else if !isNumber(ch) {
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s.unread()
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break
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} else {
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buf.WriteRune(ch)
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}
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}
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if _, err := time.Parse("2006-01-02", buf.String()); err == nil {
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return DATE, buf.String()
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}
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if _, err := time.Parse(time.RFC3339, buf.String()); err == nil {
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return TIME, buf.String()
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}
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if _, err := time.Parse(time.RFC3339Nano, buf.String()); err == nil {
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return NANO, buf.String()
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}
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return tok, buf.String()
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}
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func (s *Scanner) scanSpecial() (tok Token, lit string) {
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tok = IDENT
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var buf bytes.Buffer
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beg := s.read()
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end := beg
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if beg == '{' {
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end = '}'
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}
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if beg == '[' {
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end = ']'
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}
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for {
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if ch := s.read(); ch == end {
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break
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} else if ch == eof {
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return ILLEGAL, buf.String()
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} else if ch == '\n' {
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tok = REGION
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buf.WriteRune(ch)
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} else if ch == '\\' {
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chn := s.read()
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if chn == 'n' {
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tok = REGION
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buf.WriteRune('\n')
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} else if chn == '\\' {
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buf.WriteRune('\\')
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} else if chn == '"' {
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buf.WriteRune('"')
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} else if chn == '\'' {
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buf.WriteRune('\'')
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} else if chn == '`' {
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buf.WriteRune('`')
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} else {
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break
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}
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} else {
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buf.WriteRune(ch)
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}
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}
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var f interface{}
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j := []byte(string(beg) + buf.String() + string(end))
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err := json.Unmarshal(j, &f)
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if err == nil {
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return JSON, string(beg) + buf.String() + string(end)
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}
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return tok, buf.String()
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}
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// read reads the next rune from the bufferred reader.
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// Returns the rune(0) if an error occurs (or io.EOF is returned).
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func (s *Scanner) read() rune {
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ch, _, err := s.r.ReadRune()
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if err != nil {
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return eof
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}
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return ch
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}
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// unread places the previously read rune back on the reader.
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func (s *Scanner) unread() {
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_ = s.r.UnreadRune()
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}
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func number(lit string) (i int64) {
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i, _ = strconv.ParseInt(lit, 10, 64)
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return
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}
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// isWhitespace returns true if the rune is a space, tab, or newline.
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func isWhitespace(ch rune) bool {
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return ch == ' ' || ch == '\t' || ch == '\n'
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}
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// isLetter returns true if the rune is a letter.
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func isLetter(ch rune) bool {
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return (ch >= 'a' && ch <= 'z') || (ch >= 'A' && ch <= 'Z')
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}
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// isNumber returns true if the rune is a number.
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func isNumber(ch rune) bool {
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return (ch >= '0' && ch <= '9')
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}
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// isSeparator returns true if the rune is a separator expression.
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func isSeparator(ch rune) bool {
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return (ch == '.')
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}
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// isIdentChar returns true if the rune can be used in an unquoted identifier.
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func isIdentChar(ch rune) bool {
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return isLetter(ch) || isNumber(ch) || isSeparator(ch) || ch == '_'
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}
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// eof represents a marker rune for the end of the reader.
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var eof = rune(0)
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