smcc/ccompiler/frontend/parser/ast/stmt.c

#include "../parser.h"
#include "ast.h"

ast_node_t* parse_stmt(parser_t* parser) {
    tok_buf_t* tokbuf = &parser->tokbuf;
    flush_peek_tok(tokbuf);
    tok_type_t ttype = peek_tok_type(tokbuf);
    ast_node_t* node = new_ast_node();
    switch (ttype) {
    case TOKEN_IF: {
        /**
         * if (exp) stmt
         * if (exp) stmt else stmt
         */
        pop_tok(tokbuf);

        expect_pop_tok(tokbuf, TOKEN_L_PAREN);
        node->if_stmt.cond = parse_expr(parser);
        flush_peek_tok(tokbuf);
        expect_pop_tok(tokbuf, TOKEN_R_PAREN);

        node->if_stmt.if_stmt = parse_stmt(parser);
        ttype = peek_tok_type(tokbuf);
        if (ttype == TOKEN_ELSE) {
            pop_tok(tokbuf);
            node->if_stmt.else_stmt = parse_stmt(parser);
        } else {
            node->if_stmt.else_stmt = NULL;
        }
        node->type = NT_STMT_IF;
        break;
    }
    case TOKEN_SWITCH: {
        /**
         * switch (exp) stmt
         */
        pop_tok(tokbuf);

        expect_pop_tok(tokbuf, TOKEN_L_PAREN);
        node->switch_stmt.cond = parse_expr(parser);
        expect_pop_tok(tokbuf, TOKEN_R_PAREN);

        node->switch_stmt.body = parse_stmt(parser);
        node->type = NT_STMT_SWITCH;
        break;
    }
    case TOKEN_WHILE: {
        /**
         * while (exp) stmt
         */
        pop_tok(tokbuf);
        
        expect_pop_tok(tokbuf, TOKEN_L_PAREN);
        node->while_stmt.cond = parse_expr(parser);
        expect_pop_tok(tokbuf, TOKEN_R_PAREN);

        node->while_stmt.body = parse_stmt(parser);
        node->type = NT_STMT_WHILE;
        break;
    }
    case TOKEN_DO: {
        /**
         * do stmt while (exp)
         */
        pop_tok(tokbuf);
        node->do_while_stmt.body = parse_stmt(parser);
        ttype = peek_tok_type(tokbuf);
        if (ttype != TOKEN_WHILE) {
            error("expected while after do");
        }
        pop_tok(tokbuf);
        expect_pop_tok(tokbuf, TOKEN_L_PAREN);
        node->do_while_stmt.cond = parse_expr(parser);
        expect_pop_tok(tokbuf, TOKEN_R_PAREN);
        node->type = NT_STMT_DOWHILE;
        break;
    }
    case TOKEN_FOR: {
        /**
         * for (init; [cond]; [iter]) stmt
         */
        // node->children.stmt.for_stmt.init
        pop_tok(tokbuf);
        ttype = peek_tok_type(tokbuf);
        if (ttype != TOKEN_L_PAREN) {
            error("expected ( after for");
        }
        pop_tok(tokbuf);

        // init expr or init decl_var
        // TODO need add this feature
        node->for_stmt.init = parse_expr(parser);
        expect_pop_tok(tokbuf, TOKEN_SEMICOLON);

        // cond expr or null
        ttype = peek_tok_type(tokbuf);
        if (ttype != TOKEN_SEMICOLON) {
            node->for_stmt.cond = parse_expr(parser);
            expect_pop_tok(tokbuf, TOKEN_SEMICOLON);
        } else {
            node->for_stmt.cond = NULL;
            pop_tok(tokbuf);
        }

        // iter expr or null
        ttype = peek_tok_type(tokbuf);
        if (ttype != TOKEN_R_PAREN) {
            node->for_stmt.iter = parse_expr(parser);
            expect_pop_tok(tokbuf, TOKEN_R_PAREN);
        } else {
            node->for_stmt.iter = NULL;
            pop_tok(tokbuf);
        }

        node->for_stmt.body = parse_stmt(parser);
        node->type = NT_STMT_FOR;
        break;
    }
    case TOKEN_BREAK: {
        /**
         * break ;
         */
        // TODO check 导致外围 for、while 或 do-while 循环或 switch 语句终止。
        pop_tok(tokbuf);
        expect_pop_tok(tokbuf, TOKEN_SEMICOLON);

        node->type = NT_STMT_BREAK;
        break;
    }
    case TOKEN_CONTINUE: {
        /**
         * continue ;
         */
        // TODO check 导致跳过整个 for、 while 或 do-while 循环体的剩余部分。
        pop_tok(tokbuf);
        expect_pop_tok(tokbuf, TOKEN_SEMICOLON);

        node->type = NT_STMT_CONTINUE;
        break;
    }
    case TOKEN_RETURN: {
        /**
         * return [exp] ;
         */
        // TODO 终止当前函数并返回指定值给调用方函数。
        pop_tok(tokbuf);
        ttype = peek_tok_type(tokbuf);
        if (ttype != TOKEN_SEMICOLON) {
            node->return_stmt.expr_stmt = parse_expr(parser);
            flush_peek_tok(tokbuf);
            expect_pop_tok(tokbuf, TOKEN_SEMICOLON);
        } else {
            node->return_stmt.expr_stmt = NULL;
            pop_tok(tokbuf);
        }
        node->type = NT_STMT_RETURN;
        break;
    }
    case TOKEN_GOTO: {
        /**
         * goto label ;
         */
        // TODO check label 将控制无条件转移到所欲位置。
        //在无法用约定的构造将控制转移到所欲位置时使用。
        pop_tok(tokbuf);
        // find symbol table
        ttype = peek_tok_type(tokbuf);
        if (ttype != TOKEN_IDENT) {
            error("expect identifier after goto");
        }
        expect_pop_tok(tokbuf, TOKEN_SEMICOLON);
        // TODO filling label
        node->goto_stmt.label = expect_pop_ident(tokbuf);
        node->type = NT_STMT_GOTO;
        break;
    }
    case TOKEN_SEMICOLON: {
        /**
         *  ;
         * empty stmt using by :
         *      while () ;
         *      if () ;
         *      for () ;
         */
        pop_tok(tokbuf);
        node->type = NT_STMT_EMPTY;
        break;
    }
    case TOKEN_L_BRACE: {
        /**
         * stmt_block like: { (decl_var | stmt) ... }
         */
        node->block_stmt.block = parse_block(parser);
        node->type = NT_STMT_BLOCK;
        break;
    }
    case TOKEN_IDENT: {
        // TODO label goto
        if (peek_tok_type(tokbuf) != TOKEN_COLON) {
            goto EXP;
        }
        node->label_stmt.label = expect_pop_ident(tokbuf);
        expect_pop_tok(tokbuf, TOKEN_COLON);
        node->type = NT_STMT_LABEL;
        break;
    }
    case TOKEN_CASE: {
        // TODO label switch
        pop_tok(tokbuf);
        error("unimplemented switch label");
        node->label_stmt.label = parse_expr(parser);
        // TODO 该表达式为const int
        expect_pop_tok(tokbuf, TOKEN_COLON);
        node->type = NT_STMT_CASE;
        break;
    }
    case TOKEN_DEFAULT: {
        // TODO label switch default
        pop_tok(tokbuf);
        expect_pop_tok(tokbuf, TOKEN_COLON);
        node->type = NT_STMT_DEFAULT;
        break;
    }
    default: {
        /**
         * exp ;
         */
    EXP:
        node->expr_stmt.expr_stmt = parse_expr(parser);
        flush_peek_tok(tokbuf);
        ttype = peek_tok_type(tokbuf);
        if (ttype != TOKEN_SEMICOLON) {
            error("exp must end with \";\"");
        }
        pop_tok(tokbuf);
        node->type = NT_STMT_EXPR;
        break;
    }

    }
    return node;
}