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LibSQL: Introduce a SQL library with a tokenizer
LibSQL aims to be a SQLite clone for SerenityOS. Step 1 is creating a tokenizer to lex SQL tokens. This lexer is heavily influenced by the LibJS lexer.
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Userland/Libraries/LibSQL/Lexer.cpp
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306
Userland/Libraries/LibSQL/Lexer.cpp
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/*
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* Copyright (c) 2021, Tim Flynn <trflynn89@pm.me>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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*
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* 1. Redistributions of source code must retain the above copyright notice, this
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* list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright notice,
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* this list of conditions and the following disclaimer in the documentation
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* and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "Lexer.h"
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#include <AK/Debug.h>
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#include <ctype.h>
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namespace SQL {
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HashMap<String, TokenType> Lexer::s_keywords;
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HashMap<char, TokenType> Lexer::s_one_char_tokens;
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HashMap<String, TokenType> Lexer::s_two_char_tokens;
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Lexer::Lexer(StringView source)
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: m_source(source)
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{
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if (s_keywords.is_empty()) {
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#define __ENUMERATE_SQL_TOKEN(value, type, category) \
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if (TokenCategory::category == TokenCategory::Keyword) \
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s_keywords.set(value, TokenType::type);
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ENUMERATE_SQL_TOKENS
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#undef __ENUMERATE_SQL_TOKEN
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}
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if (s_one_char_tokens.is_empty()) {
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#define __ENUMERATE_SQL_TOKEN(value, type, category) \
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if (TokenCategory::category != TokenCategory::Keyword && StringView(value).length() == 1) \
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s_one_char_tokens.set(value[0], TokenType::type);
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ENUMERATE_SQL_TOKENS
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#undef __ENUMERATE_SQL_TOKEN
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}
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if (s_two_char_tokens.is_empty()) {
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#define __ENUMERATE_SQL_TOKEN(value, type, category) \
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if (TokenCategory::category != TokenCategory::Keyword && StringView(value).length() == 2) \
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s_two_char_tokens.set(value, TokenType::type);
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ENUMERATE_SQL_TOKENS
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#undef __ENUMERATE_SQL_TOKEN
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}
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consume();
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}
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Token Lexer::next()
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{
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bool found_invalid_comment = consume_whitespace_and_comments();
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size_t value_start = m_position;
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size_t value_start_line_number = m_line_number;
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size_t value_start_column_number = m_line_column;
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auto token_type = TokenType::Invalid;
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if (is_eof()) {
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token_type = found_invalid_comment ? TokenType::Invalid : TokenType::Eof;
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} else if (is_identifier_start()) {
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do {
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consume();
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} while (is_identifier_middle());
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if (auto it = s_keywords.find(m_source.substring_view(value_start - 1, m_position - value_start)); it != s_keywords.end()) {
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token_type = it->value;
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} else {
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token_type = TokenType::Identifier;
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}
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} else if (is_numeric_literal_start()) {
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token_type = TokenType::NumericLiteral;
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if (!consume_numeric_literal())
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token_type = TokenType::Invalid;
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} else {
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bool found_two_char_token = false;
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if (m_position < m_source.length()) {
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if (auto it = s_two_char_tokens.find(m_source.substring_view(m_position - 1, 2)); it != s_two_char_tokens.end()) {
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found_two_char_token = true;
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token_type = it->value;
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consume();
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consume();
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}
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}
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bool found_one_char_token = false;
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if (!found_two_char_token) {
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if (auto it = s_one_char_tokens.find(m_current_char); it != s_one_char_tokens.end()) {
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found_one_char_token = true;
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token_type = it->value;
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consume();
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}
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}
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if (!found_two_char_token && !found_one_char_token) {
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token_type = TokenType::Invalid;
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consume();
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}
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}
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Token token(token_type, m_source.substring_view(value_start - 1, m_position - value_start), value_start_line_number, value_start_column_number);
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if constexpr (SQL_DEBUG) {
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dbgln("------------------------------");
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dbgln("Token: {}", token.name());
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dbgln("Value: {}", token.value());
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dbgln("Line: {}, Column: {}", token.line_number(), token.line_column());
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dbgln("------------------------------");
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}
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return token;
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}
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void Lexer::consume()
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{
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auto did_reach_eof = [this] {
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if (m_position != m_source.length())
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return false;
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m_current_char = EOF;
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++m_line_column;
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++m_position;
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return true;
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};
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if (m_position > m_source.length())
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return;
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if (did_reach_eof())
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return;
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if (is_line_break()) {
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++m_line_number;
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m_line_column = 1;
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} else {
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++m_line_column;
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}
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m_current_char = m_source[m_position++];
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}
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bool Lexer::consume_whitespace_and_comments()
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{
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bool found_invalid_comment = false;
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while (true) {
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if (isspace(m_current_char)) {
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do {
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consume();
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} while (isspace(m_current_char));
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} else if (is_line_comment_start()) {
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consume();
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do {
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consume();
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} while (!is_eof() && !is_line_break());
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} else if (is_block_comment_start()) {
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consume();
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do {
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consume();
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} while (!is_eof() && !is_block_comment_end());
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if (is_eof())
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found_invalid_comment = true;
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consume(); // consume *
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if (is_eof())
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found_invalid_comment = true;
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consume(); // consume /
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} else {
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break;
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}
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}
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return found_invalid_comment;
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}
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bool Lexer::consume_numeric_literal()
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{
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// https://www.sqlite.org/draft/syntax/numeric-literal.html
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bool is_valid_numeric_literal = true;
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if (m_current_char == '0') {
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consume();
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if (m_current_char == '.') {
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consume();
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while (isdigit(m_current_char))
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consume();
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if (m_current_char == 'e' || m_current_char == 'E')
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is_valid_numeric_literal = consume_exponent();
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} else if (m_current_char == 'e' || m_current_char == 'E') {
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is_valid_numeric_literal = consume_exponent();
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} else if (m_current_char == 'x' || m_current_char == 'X') {
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is_valid_numeric_literal = consume_hexadecimal_number();
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} else if (isdigit(m_current_char)) {
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do {
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consume();
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} while (isdigit(m_current_char));
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}
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} else {
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do {
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consume();
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} while (isdigit(m_current_char));
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if (m_current_char == '.') {
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consume();
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while (isdigit(m_current_char))
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consume();
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}
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if (m_current_char == 'e' || m_current_char == 'E')
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is_valid_numeric_literal = consume_exponent();
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}
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return is_valid_numeric_literal;
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}
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bool Lexer::consume_exponent()
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{
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consume();
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if (m_current_char == '-' || m_current_char == '+')
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consume();
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if (!isdigit(m_current_char))
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return false;
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while (isdigit(m_current_char)) {
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consume();
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}
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return true;
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}
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bool Lexer::consume_hexadecimal_number()
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{
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consume();
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if (!isxdigit(m_current_char))
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return false;
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while (isxdigit(m_current_char))
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consume();
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return true;
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}
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bool Lexer::match(char a, char b) const
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{
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if (m_position >= m_source.length())
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return false;
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return m_current_char == a
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&& m_source[m_position] == b;
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}
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bool Lexer::is_identifier_start() const
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{
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return isalpha(m_current_char) || m_current_char == '_';
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}
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bool Lexer::is_identifier_middle() const
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{
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return is_identifier_start() || isdigit(m_current_char);
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}
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bool Lexer::is_numeric_literal_start() const
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{
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return isdigit(m_current_char) || (m_current_char == '.' && m_position < m_source.length() && isdigit(m_source[m_position]));
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}
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bool Lexer::is_line_comment_start() const
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{
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return match('-', '-');
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}
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bool Lexer::is_block_comment_start() const
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{
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return match('/', '*');
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}
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bool Lexer::is_block_comment_end() const
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{
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return match('*', '/');
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}
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bool Lexer::is_line_break() const
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{
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return m_current_char == '\n';
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}
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bool Lexer::is_eof() const
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{
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return m_current_char == EOF;
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}
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}
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