token.c

#include "10cc.h"

static char *user_input;

bool is_alpha(char c) {
  return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || c == '_';
}

bool is_alnum(char c) {
  return is_alpha(c) || ('0' <= c && c <= '9');
}

void error_at(char *loc, char *fmt, ...)  {
  va_list ap;
  va_start(ap, fmt);

  int pos = loc - user_input;
  fprintf(stderr, "%s\n", user_input);
  fprintf(stderr, "%*s", pos, "");
  fprintf(stderr, "^ ");
  vfprintf(stderr, fmt, ap);
  fprintf(stderr, "\n");
  exit(1);
}

bool startswith(char *p, char *q) {
  return memcmp(p, q, strlen(q)) == 0;
}

int len_of_lvar(char *p) {
  int len = 0;
  if (is_alpha(*p)) {
    len += 1;
    p++;
    while(is_alnum(*p)) {
      len += 1;
      p++;
    }
  }
  return len;
}

Token *new_token(TokenKind kind, Token *cur, char *str, int len) {
  Token *tok = calloc(1, sizeof(Token));
  tok->kind = kind;
  tok->str = str;
  tok->len = len;
  cur->next = tok;
  return tok;
}

Token *tokenize(char *p) {
  user_input = p;
  Token head;
  head.next = NULL;
  Token *cur = &head;

  while (*p) {
    if (isspace(*p)) {
      p++;
      continue;
    }

    if (strncmp(p, "return", 6) == 0 && !is_alnum(p[6])) {
      cur = new_token(TK_RETURN, cur, strndup(p, 6), 6);
      p += 6;
      continue;
    }

    if (strncmp(p, "if", 2) == 0 && !is_alnum(p[2])) {
      cur = new_token(TK_IF, cur, strndup(p, 2), 2);
      p += 2;
      continue;
    }

    if (strncmp(p, "else", 4) == 0 && !is_alnum(p[4])) {
      cur = new_token(TK_ELSE, cur, strndup(p, 4), 4);
      p += 4;
      continue;
    }

    int lvar_len = len_of_lvar(p);

    if (lvar_len > 0) {
      cur = new_token(TK_IDENT, cur, p, lvar_len);
      p += lvar_len;
      continue;
    }

    if (startswith(p, "==") || startswith(p, "!=") ||
        startswith(p, "<=") || startswith(p, ">=")) {
      cur = new_token(TK_RESERVED, cur, p, 2);
      p += 2;
      continue;
    }

    if (strchr("+-*/;=()<>", *p)) {
      cur = new_token(TK_RESERVED, cur, p++, 1);
      continue;
    }

    if (isdigit(*p)) {
      cur = new_token(TK_NUM, cur, p, 0);
      char *q = p;
      cur->val = strtol(p, &p, 10);
      cur->len = p - q;
      continue;
    }

    error_at(p, "cannot tokenize");
  }

  new_token(TK_EOF, cur, p, 0);
  return head.next;
}