rc/src/interpreter.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include "types.h"
#include "interpreter.h"
#include "parser.h"

void error(char *msg) {
    printf("Error at token %d ('%c'): %s\n", pc, tokens[pc].type, msg);
    exit(1);
}

void match(int type) {
    if (tokens[pc].type == type) pc++;
    else error("Unexpected token");
}

int find_local(char *name, int len) {
    for (int i = loc_cnt - 1; i >= 0; i--) {
        if (!strncmp(locals[i].name, name, len) && locals[i].name[len] == 0)
            return i;
    }
    return -1;
}

int find_func(char *name, int len) {
    for (int i = 0; i < func_cnt; i++) {
        if (!strncmp(funcs[i].name, name, len) && funcs[i].name[len] == 0)
            return i;
    }
    return -1;
}

int find_native_func(char *name, int len) {
    for (int i = 0; i < native_func_cnt; i++) {
        if (!strncmp(native_funcs[i].name, name, len) && native_funcs[i].name[len] == 0)
            return i;
    }
    return -1;
}

void skip_block() {
    int brace = 0;
    do {
        if (tokens[pc].type == '{') brace++;
        if (tokens[pc].type == '}') brace--;
        pc++;
    } while (brace > 0 && tokens[pc].type != 0);
}

void statement() {
    if (tokens[pc].type == '{') {
        pc++;
        while (tokens[pc].type != '}' && tokens[pc].type != 0) {
            statement();
            if (ax == -999) break;
        }
        match('}');
    }
    else if (tokens[pc].type == Int || tokens[pc].type == Char) {
        pc++;
        while (tokens[pc].type != ';') {
            while (tokens[pc].type == '*') pc++;
            Token *t = &tokens[pc];
            match(Id);

            int addr = sp;
            Symbol *s = &locals[loc_cnt++];
            strncpy(s->name, t->text, t->val); s->name[t->val] = 0;
            s->addr = addr;
            s->is_array = 0;

            if (tokens[pc].type == '[') {
                pc++;
                int size = (int)expression();
                match(']');
                s->is_array = 1;
                sp += size;
            } else {
                sp++;
            }

            if (tokens[pc].type == '=') {
                pc++;
                memory[addr] = expression();
            }
            if (tokens[pc].type == ',') pc++;
        }
        match(';');
    }
    else if (tokens[pc].type == If) {
        pc++;
        match('(');
        long cond = expression();
        match(')');
        if (cond) {
            statement();
            if (ax == -999) return;
            if (tokens[pc].type == Else) { pc++; skip_block(); }
        } else {
            skip_block();
            if (tokens[pc].type == Else) {
                pc++;
                statement();
                if (ax == -999) return;
            }
        }
    }
    else if (tokens[pc].type == While) {
        pc++;
        int loop_start = pc;
        match('(');
        long cond = expression();
        match(')');
        if (!cond) {
            skip_block();
        } else {
            while (1) {
                statement();
                if (ax == -999) return;
                int save_pc = pc;
                pc = loop_start;
                match('(');
                cond = expression();
                match(')');
                if (!cond) { pc = save_pc; break; }
            }
        }
    }
    else if (tokens[pc].type == Return) {
        pc++;
        if (tokens[pc].type != ';') ax = expression();
        else ax = 0;
        match(';');
        ax = -999;
    }
    else if (tokens[pc].type == Printf) {
        pc++;
        match('(');
        char *fmt = tokens[pc].text;
        match(Str);

        char *p = fmt;
        while (*p) {
            if (*p == '%' && (p[1] == 'd' || p[1] == 's')) {
                p++;
                match(',');
                long val = expression();
                if (*p == 'd') printf("%ld", val);
                else if (*p == 's') printf("%s", (char*)val);
                p++;
            } else {
                putchar(*p++);
            }
        }
        match(')');
        match(';');
    }
    else {
        expression();
        match(';');
    }
}

void scan_functions() {
    int i = 0;
    while (tokens[i].type != 0) {
        if ((tokens[i].type == Int || tokens[i].type == Char) &&
            tokens[i+1].type == Id && tokens[i+2].type == '(') {

            Func *f = &funcs[func_cnt++];
            Token *name = &tokens[i+1];
            strncpy(f->name, name->text, name->val); f->name[name->val] = 0;

            i += 3;
            int params = 0;
            while(tokens[i].type != ')') {
                if (tokens[i].type == Int || tokens[i].type == Char) {
                    params++;
                    i++;
                    while (tokens[i].type == '*') i++;
                    if (tokens[i].type == Id) i++;
                } else i++;
            }
            f->param_count = params;
            i++;
            f->entry_point = i;

            int brace = 0;
            do {
                if (tokens[i].type == '{') brace++;
                if (tokens[i].type == '}') brace--;
                i++;
            } while (brace > 0 && tokens[i].type != 0);
        } else {
            i++;
        }
    }
}