Started implementing lexer in lexer.cpp

The implementation for tokenise_symbol is already a lot nicer to look
at and add to due to string/string_view operator overloading of ==.
Furthermore, error handling through pair<> instead of making some
custom structure which essentially does the same thing is already
making me happy for this rewrite.

1 files changed, 215 insertions, 0 deletions

diff --git a/asm/lexer.cpp b/asm/lexer.cpp
new file mode 100644
index 0000000..0024b05
--- /dev/null
+++ b/asm/lexer.cpp
@@ -0,0 +1,215 @@
+/* Copyright (C) 2024 Aryadev Chavali
+
+ * You may distribute and modify this code under the terms of the GPLv2
+ * license.  You should have received a copy of the GPLv2 license with
+ * this file.  If not, please write to: aryadev@aryadevchavali.com.
+
+ * Created: 2024-04-14
+ * Author: Aryadev Chavali
+ * Description: Lexer for assembly language
+ */
+
+#include <lib/inst.h>
+
+#include <algorithm>
+#include <tuple>
+
+#include "./lexer.hpp"
+
+using std::string_view, std::pair, std::make_pair;
+
+constexpr auto VALID_SYMBOL =
+    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.:()%#$";
+
+bool is_char_in_s(char c, const char *s)
+{
+  return string_view(s).find(c) != string::npos;
+}
+
+bool initial_match(string_view src, string_view match)
+{
+  return (src.size() > match.size() && src.substr(0, match.size()) == match);
+}
+
+pair<token_t, lerr_t> tokenise_symbol(string_view &source, size_t &column)
+{
+  auto end = source.find_first_not_of(VALID_SYMBOL);
+  if (end == string::npos)
+    end = source.size() - 1;
+  string sym{source.substr(0, end)};
+  source.remove_prefix(end);
+  std::transform(sym.begin(), sym.end(), sym.begin(), ::toupper);
+
+  token_t t{};
+
+  if (initial_match(sym, "%CONST"))
+  {
+    t = token_t(token_type_t::PP_CONST, sym.substr(6));
+  }
+  else if (sym == "%USE")
+  {
+    t.type = token_type_t::PP_USE;
+  }
+  else if (sym == "%END")
+  {
+    t.type = token_type_t::PP_END;
+  }
+  else if (sym[0] == '%')
+  {
+    return make_pair(t, lerr_t::INVALID_PREPROCESSOR_DIRECTIVE);
+  }
+  else if (sym.size() > 1 && sym[0] == '$')
+  {
+    t = token_t(token_type_t::PP_REFERENCE, sym.substr(1));
+  }
+  else if (sym == "NOOP")
+  {
+    t.type = token_type_t::NOOP;
+  }
+  else if (sym == "HALT")
+  {
+    t.type = token_type_t::HALT;
+  }
+  else if (initial_match(sym, "PUSH.REG."))
+  {
+    t = token_t(token_type_t::PUSH_REG, sym.substr(9));
+  }
+  else if (initial_match(sym, "PUSH."))
+  {
+    t = token_t(token_type_t::PUSH, sym.substr(5));
+  }
+  else if (initial_match(sym, "POP."))
+  {
+    t = token_t(token_type_t::POP, sym.substr(4));
+  }
+  else if (initial_match(sym, "MOV."))
+  {
+    t = token_t(token_type_t::MOV, sym.substr(4));
+  }
+  else if (initial_match(sym, "DUP."))
+  {
+    t = token_t(token_type_t::DUP, sym.substr(4));
+  }
+  else if (initial_match(sym, "MALLOC.STACK."))
+  {
+    t = token_t(token_type_t::MALLOC_STACK, sym.substr(13));
+  }
+  else if (initial_match(sym, "MALLOC."))
+  {
+    t = token_t(token_type_t::MALLOC, sym.substr(7));
+  }
+  else if (initial_match(sym, "MSET.STACK."))
+  {
+    t = token_t(token_type_t::MSET_STACK, sym.substr(11));
+  }
+  else if (initial_match(sym, "MSET."))
+  {
+    t = token_t(token_type_t::MSET, sym.substr(5));
+  }
+  else if (initial_match(sym, "MGET.STACK."))
+  {
+    t = token_t(token_type_t::MGET_STACK, sym.substr(11));
+  }
+  else if (initial_match(sym, "MGET."))
+  {
+    t = token_t(token_type_t::MGET, sym.substr(5));
+  }
+  else if (sym == "MDELETE")
+  {
+    t.type = token_type_t::MDELETE;
+  }
+  else if (sym == "MSIZE")
+  {
+    t.type = token_type_t::MSIZE;
+  }
+  else if (initial_match(sym, "NOT."))
+  {
+    t = token_t(token_type_t::NOT, sym.substr(4));
+  }
+  else if (initial_match(sym, "OR."))
+  {
+    t = token_t(token_type_t::OR, sym.substr(3));
+  }
+  else if (initial_match(sym, "AND."))
+  {
+    t = token_t(token_type_t::AND, sym.substr(4));
+  }
+  else if (initial_match(sym, "XOR."))
+  {
+    t = token_t(token_type_t::XOR, sym.substr(4));
+  }
+  else if (initial_match(sym, "EQ."))
+  {
+    t = token_t(token_type_t::EQ, sym.substr(3));
+  }
+  else if (initial_match(sym, "LTE."))
+  {
+    t = token_t(token_type_t::LTE, sym.substr(4));
+  }
+  else if (initial_match(sym, "LT."))
+  {
+    t = token_t(token_type_t::LT, sym.substr(3));
+  }
+  else if (initial_match(sym, "GTE."))
+  {
+    t = token_t(token_type_t::GTE, sym.substr(4));
+  }
+  else if (initial_match(sym, "GT."))
+  {
+    t = token_t(token_type_t::GT, sym.substr(3));
+  }
+  else if (initial_match(sym, "SUB."))
+  {
+    t = token_t(token_type_t::SUB, sym.substr(4));
+  }
+  else if (initial_match(sym, "PLUS."))
+  {
+    t = token_t(token_type_t::PLUS, sym.substr(5));
+  }
+  else if (initial_match(sym, "MULT."))
+  {
+    t = token_t(token_type_t::MULT, sym.substr(5));
+  }
+  else if (initial_match(sym, "PRINT."))
+  {
+    t = token_t(token_type_t::PRINT, sym.substr(6));
+  }
+  else if (sym == "JUMP.ABS")
+  {
+    t.type = token_type_t::JUMP_ABS;
+  }
+  else if (sym == "JUMP.STACK")
+  {
+    t.type = token_type_t::JUMP_STACK;
+  }
+  else if (initial_match(sym, "JUMP.IF."))
+  {
+    t = token_t(token_type_t::JUMP_IF, sym.substr(8));
+  }
+  else if (sym == "CALL.STACK")
+  {
+    t.type = token_type_t::CALL_STACK;
+  }
+  else if (sym == "CALL")
+  {
+    t.type = token_type_t::CALL;
+  }
+  else if (sym == "RET")
+  {
+    t.type = token_type_t::RET;
+  }
+  else if (sym == "GLOBAL")
+  {
+    t.type = token_type_t::GLOBAL;
+  }
+  else
+  {
+    t.type = token_type_t::SYMBOL;
+  }
+
+  if (t.content == "")
+    t.content = sym;
+  t.column = column;
+  column += sym.size();
+  return make_pair(t, lerr_t::OK);
+}