fvm/src/as_parser.c

#include "as_parser.h"
#include "as_tokenizer.h"
#include "utils.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// BNF
// ===
//
// <prog> ::= <stmts>
// <stmts> ::= <stmt> newline | <stmt> newline <stmts>
// <stmt> ::= <label> <instr> | <instr> | <label>
// <instr> ::= <op> | <op> arg | <op> tag
// <label> ::= tag ":"
// <op> ::= "add" | "sub" | "mul" | "div" | "mod" | "eq"


Prog parseProg(Allocator alct, TokenStream ts) {
    Prog p = allocate(alct, sizeof(struct prog));
    p->stmts = parseStmts(alct, ts);
    return p;
}

Stmts parseStmts(Allocator alct, TokenStream ts) {
    Stmts ss = allocate(alct, sizeof(struct stmts));
    ss->stmts = allocate(alct, sizeof(Stmt));
    ss->stmts[0] = NULL;
    int capacity = 0;
    int len = 0;
    while (peekToken(alct, ts)->type != ENDOFFILE) {
        Stmt s = parseStmt(alct, ts);
        if (s == NULL) continue;
        if (len == capacity) {
            size_t newCapacity = capacity * 2 + 1;
            void* newStmts = allocate(alct, sizeof(Stmt*) * newCapacity);
            memcpy(newStmts, ss->stmts, sizeof(Stmt*) * capacity);
            ss->stmts = newStmts;
            capacity = newCapacity;
        }
        // expect newline
        if (peekToken(alct, ts)->type == NEWLINE) {
            nextToken(alct, ts);
        } else {
            fprintf(stderr, "%d:%d Expect NEWLINE.\n", peekToken(alct, ts)->line, peekToken(alct, ts)->col);
        }
        ss->stmts[len] = s;
        len++;
    }
    ss->stmts[len] = NULL;
    return ss;
}

Label parseLabel(Allocator alct, TokenStream ts) {
    Token t = nextToken(alct, ts);
    if (t->type != TAG) {
        fprintf(stderr, "%d:%d Expect LABEL.\n", t->line, t->col);
        exit(-1);
    }
    Label l = allocate(alct, sizeof(Label));
    l->name = t->sval;
    t = nextToken(alct, ts);
    if (t->type != COLON) {
        fprintf(stderr, "%d:%d Expect COLON.\n", t->line, t->col);
        exit(-1);
    }
    return l;
}

Stmt parseStmt(Allocator alct, TokenStream ts) {
    Token t = peekToken(alct, ts);
    Stmt stmt = allocate(alct, sizeof(struct stmt));
    stmt->label = NULL;
    stmt->instr = NULL;
    if (t->type == TAG) {
        stmt->label = parseLabel(alct, ts);
        if (peekToken(alct, ts)->type == NEWLINE) {
            return stmt;
        }
        t = peekToken(alct, ts);
    }
    if (t->type == OP) {
        stmt->instr = parseInstr(alct, ts);
        if (peekToken(alct, ts)->type == NEWLINE) {
            return stmt;
        }
    }
    if (t->type == NEWLINE) {
        return NULL;
    }
    fprintf(stderr, "%d:%d Expect lable + instruction, lable, or instruction.\n", t->line, t->col);
    exit(-1);
}

enum op parseOp(Allocator alct, TokenStream ts) {
    Token t = nextToken(alct, ts);
    enum op op;
    if (t->type == OP) {
        op = str2op(t->sval);
        if (op == OPEND) {
            fprintf(stderr, "%d:%d Invalid OP.\n", t->line, t->col);
            exit(-1);
        }
    } else {
        fprintf(stderr, "%d:%d Expect OP.\n", t->line, t->col);
        exit(-1);
    }
    return op;
}

Instr parseInstr(Allocator alct, TokenStream ts) {
    Token t = peekToken(alct, ts);
    Instr i = allocate(alct, sizeof(struct instr));
    i->tagName = NULL;
    i->arg = NULL;
    i->op = OPEND;
    if (t->type == OP) {
        i->op = parseOp(alct, ts);
        t = peekToken(alct, ts);
        if (t->type == ARG) {
            Arg a = allocate(alct, sizeof(struct arg));
            a->ival = t->ival;
            a->fval = t->fval;
            i->arg = a;
            nextToken(alct, ts);
        } else if (t->type == TAG) {
            i->tagName = t->sval;
            nextToken(alct, ts);
        }
    }
    return i;
}