Basic parser

Signed-off-by: CHatingPython <chatingpython@gmail.com>

furc/src/front/lexer.cpp

@@ -0,0 +1,77 @@
+#include "furc/front/lexer.hpp"
+
+#include <cctype>
+#include <unordered_map>
+
+namespace furc::front {
+
+lexer::lexer(std::string_view filename, std::string_view content)
+  : m_filename(filename), m_content(content) {}
+
+token_handle<> lexer::next_token() {
+    skip_spaces();
+
+    location location = current_location();
+
+    char ch = get();
+    switch (ch) {
+    case '(': return { location, token_t::Lparen, m_content.substr(m_cursor++, 1) };
+    case ')': return { location, token_t::Rparen, m_content.substr(m_cursor++, 1) };
+    case '{': return { location, token_t::Lbrace, m_content.substr(m_cursor++, 1) };
+    case '}': return { location, token_t::Rbrace, m_content.substr(m_cursor++, 1) };
+    case '[': return { location, token_t::Lbracket, m_content.substr(m_cursor++, 1) };
+    case ']': return { location, token_t::Rbracket, m_content.substr(m_cursor++, 1) };
+    case ';': return { location, token_t::Semicolon, m_content.substr(m_cursor++, 1) };
+    case ':': return { location, token_t::Colon, m_content.substr(m_cursor++, 1) };
+    case ',': return { location, token_t::Comma, m_content.substr(m_cursor++, 1) };
+    case '.': return { location, token_t::Dot, m_content.substr(m_cursor++, 1) };
+    case std::char_traits<char>::eof(): return { location, token_t::None };
+    default: {
+        if (std::isdigit(ch) != 0) {}
+
+        if (std::isalnum(ch) != 0 || ch == '_') {
+            std::size_t start = m_cursor++;
+            while (std::isalnum(get()) != 0 || get() == '_')
+                next();
+
+            std::string_view value = m_content.substr(start, m_cursor - start);
+
+            static std::unordered_map<std::string_view, keyword_token> s_keywords = {
+                { "func", keyword_token::Func },
+                { "return", keyword_token::Return },
+            };
+
+            if (auto it = s_keywords.find(value); it != s_keywords.end()) return { location, it->second, value };
+            return { location, token_t::Identifier, value };
+        }
+
+        return { location, error_token::UnexpectedCharacter, m_content.substr(m_cursor, 1) };
+    }
+    }
+}
+
+void lexer::next() {
+    if (m_cursor >= m_content.size()) return;
+    char ch = get();
+    ++m_cursor;
+    if (ch == '\n') {
+        ++m_row;
+        m_lineStart = m_cursor;
+    }
+}
+
+char lexer::get(std::size_t offset) const {
+    if (m_cursor + offset < m_content.size()) return m_content[m_cursor + offset];
+    return std::char_traits<char>::eof();
+}
+
+void lexer::skip_spaces() {
+    while (std::isspace(get()) != 0)
+        next();
+}
+
+location lexer::current_location() {
+    return { m_filename, m_row, m_cursor - m_lineStart };
+}
+
+} // namespace furc::front