add: top level parser

4 files changed, 149 insertions, 0 deletions

diff --git a/src/parser/ast.c b/src/parser/ast.c
new file mode 100644
index 0000000..979dff0
--- /dev/null
+++ b/src/parser/ast.c
@@ -0,0 +1,33 @@
+#include <stdlib.h>
+
+#include "parser/ast.h"
+
+struct Program create_program(void)
+{
+	struct Program program;
+	program.consts = NULL;
+	program.const_count = 0;
+	program.const_capacity = 0;
+	return program;
+}
+
+void free_program(struct Program* program)
+{
+	free(program->consts);
+	program->consts = NULL;
+	program->const_count = 0;
+	program->const_capacity = 0;
+}
+
+void add_const(struct Program* program, struct ConstDecl decl)
+{
+	if (program->const_count == program->const_capacity)
+	{
+		size_t capacity = program->const_capacity < 8 ? 8 : program->const_capacity * 2;
+		program->consts = realloc(program->consts, capacity * sizeof(struct ConstDecl));
+		program->const_capacity = capacity;
+	}
+
+	program->consts[program->const_count] = decl;
+	program->const_count += 1;
+}
diff --git a/src/parser/ast.h b/src/parser/ast.h
new file mode 100644
index 0000000..7079305
--- /dev/null
+++ b/src/parser/ast.h
@@ -0,0 +1,22 @@
+#pragma once
+
+#include <stddef.h>
+
+#include "lexer/lexer.h"
+
+struct ConstDecl
+{
+	struct Token name;
+	struct Token value;
+};
+
+struct Program
+{
+	struct ConstDecl* consts;
+	size_t const_count;
+	size_t const_capacity;
+};
+
+struct Program create_program(void);
+void free_program(struct Program* program);
+void add_const(struct Program* program, struct ConstDecl decl);
diff --git a/src/parser/parser.c b/src/parser/parser.c
new file mode 100644
index 0000000..5845ad4
--- /dev/null
+++ b/src/parser/parser.c
@@ -0,0 +1,86 @@
+#include <stdio.h>
+
+#include "parser/parser.h"
+
+struct Parser
+{
+	struct Lexer* lexer;
+	struct Token current;
+	struct Token previous;
+	bool had_error;
+};
+
+static void advance_parser(struct Parser* parser)
+{
+	parser->previous = parser->current;
+	parser->current = scan_token(parser->lexer);
+}
+
+static bool check(struct Parser* parser, enum TokenType type)
+{
+	return parser->current.type == type;
+}
+
+static void error_at(struct Parser* parser, struct Token token, const char* message)
+{
+	fprintf(stderr, "error: line %u: %s\n", token.line, message);
+	parser->had_error = true;
+}
+
+static bool consume(struct Parser* parser, enum TokenType type, const char* message)
+{
+	if (check(parser, type))
+	{
+		advance_parser(parser);
+		return true;
+	}
+
+	error_at(parser, parser->current, message);
+	return false;
+}
+
+static bool parse_const(struct Parser* parser, struct Program* program)
+{
+	struct ConstDecl decl;
+
+	if (!consume(parser, TOKEN_IDENTIFIER, "expected constant name after 'const'"))
+		return false;
+	decl.name = parser->previous;
+
+	if (!consume(parser, TOKEN_EQUAL, "expected '=' after constant name"))
+		return false;
+
+	if (!consume(parser, TOKEN_INTEGER, "expected integer value after '='"))
+		return false;
+	decl.value = parser->previous;
+
+	add_const(program, decl);
+	return true;
+}
+
+bool parse_program(struct Lexer* lexer, struct Program* out)
+{
+	struct Parser parser;
+	parser.lexer = lexer;
+	parser.had_error = false;
+	advance_parser(&parser);
+
+	*out = create_program();
+
+	while (!check(&parser, TOKEN_EOF))
+	{
+		if (check(&parser, TOKEN_CONST))
+		{
+			advance_parser(&parser);
+			if (!parse_const(&parser, out))
+				return false;
+		}
+		else
+		{
+			error_at(&parser, parser.current, "expected a top-level declaration");
+			return false;
+		}
+	}
+
+	return !parser.had_error;
+}
diff --git a/src/parser/parser.h b/src/parser/parser.h
new file mode 100644
index 0000000..82d306a
--- /dev/null
+++ b/src/parser/parser.h
@@ -0,0 +1,8 @@
+#pragma once
+
+#include <stdbool.h>
+
+#include "lexer/lexer.h"
+#include "parser/ast.h"
+
+bool parse_program(struct Lexer* lexer, struct Program* out);