ton/tolk/constant-evaluator.cpp

/*
    This file is part of TON Blockchain Library.

    TON Blockchain Library is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation, either version 2 of the License, or
    (at your option) any later version.

    TON Blockchain Library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public License
    along with TON Blockchain Library.  If not, see <http://www.gnu.org/licenses/>.
*/
#include "constant-evaluator.h"
#include "ast.h"
#include "tolk.h"
#include "openssl/digest.hpp"
#include "crypto/common/util.h"
#include "td/utils/crypto.h"
#include "ton/ton-types.h"

namespace tolk {

// parse address like "EQCRDM9h4k3UJdOePPuyX40mCgA4vxge5Dc5vjBR8djbEKC5"
// based on unpack_std_smc_addr() from block.cpp
// (which is not included to avoid linking with ton_crypto)
static bool parse_friendly_address(const char packed[48], ton::WorkchainId& workchain, ton::StdSmcAddress& addr) {
  unsigned char buffer[36];
  if (!td::buff_base64_decode(td::MutableSlice{buffer, 36}, td::Slice{packed, 48}, true)) {
    return false;
  }
  td::uint16 crc = td::crc16(td::Slice{buffer, 34});
  if (buffer[34] != (crc >> 8) || buffer[35] != (crc & 0xff) || (buffer[0] & 0x3f) != 0x11) {
    return false;
  }
  workchain = static_cast<td::int8>(buffer[1]);
  std::memcpy(addr.data(), buffer + 2, 32);
  return true;
}

// parse address like "0:527964d55cfa6eb731f4bfc07e9d025098097ef8505519e853986279bd8400d8"
// based on StdAddress::parse_addr() from block.cpp
// (which is not included to avoid linking with ton_crypto)
static bool parse_raw_address(const std::string& acc_string, int& workchain, ton::StdSmcAddress& addr) {
  size_t pos = acc_string.find(':');
  if (pos != std::string::npos) {
    td::Result<int> r_wc = td::to_integer_safe<ton::WorkchainId>(acc_string.substr(0, pos));
    if (r_wc.is_error()) {
      return false;
    }
    workchain = r_wc.move_as_ok();
    pos++;
  } else {
    pos = 0;
  }
  if (acc_string.size() != pos + 64) {
    return false;
  }

  for (int i = 0; i < 64; ++i) {    // loop through each hex digit
    char c = acc_string[pos + i];
    int x;
    if (c >= '0' && c <= '9') {
      x = c - '0';
    } else if (c >= 'a' && c <= 'z') {
      x = c - 'a' + 10;
    } else if (c >= 'A' && c <= 'Z') {
      x = c - 'A' + 10;
    } else {
      return false;
    }

    if ((i & 1) == 0) {
      addr.data()[i >> 1] = static_cast<unsigned char>((addr.data()[i >> 1] & 0x0F) | (x << 4));
    } else {
      addr.data()[i >> 1] = static_cast<unsigned char>((addr.data()[i >> 1] & 0xF0) | x);
    }
  }
  return true;
}


static std::string parse_vertex_string_const_as_slice(V<ast_string_const> v) {
  std::string str = static_cast<std::string>(v->str_val);
  switch (v->modifier) {
    case 0: {
      return td::hex_encode(str);
    }
    case 's': {
      unsigned char buff[128];
      long bits = td::bitstring::parse_bitstring_hex_literal(buff, sizeof(buff), str.data(), str.data() + str.size());
      if (bits < 0) {
        v->error("invalid hex bitstring constant '" + str + "'");
      }
      return str;
    }
    case 'a': {  // MsgAddress
      ton::WorkchainId workchain;
      ton::StdSmcAddress addr;
      bool correct = (str.size() == 48 && parse_friendly_address(str.data(), workchain, addr)) ||
                     (str.size() != 48 && parse_raw_address(str, workchain, addr));
      if (!correct) {
        v->error("invalid standard address '" + str + "'");
      }
      if (workchain < -128 || workchain >= 128) {
        v->error("anycast addresses not supported");
      }

      unsigned char data[3 + 8 + 256];  // addr_std$10 anycast:(Maybe Anycast) workchain_id:int8 address:bits256 = MsgAddressInt;
      td::bitstring::bits_store_long_top(data, 0, static_cast<uint64_t>(4) << (64 - 3), 3);
      td::bitstring::bits_store_long_top(data, 3, static_cast<uint64_t>(workchain) << (64 - 8), 8);
      td::bitstring::bits_memcpy(data, 3 + 8, addr.bits().ptr, 0, ton::StdSmcAddress::size());
      return td::BitSlice{data, sizeof(data)}.to_hex();
    }
    default:
      tolk_assert(false);
  }
}

static td::RefInt256 parse_vertex_string_const_as_int(V<ast_string_const> v) {
  std::string str = static_cast<std::string>(v->str_val);
  switch (v->modifier) {
    case 'u': {
      td::RefInt256 intval = td::hex_string_to_int256(td::hex_encode(str));
      if (str.empty()) {
        v->error("empty integer ascii-constant");
      }
      if (intval.is_null()) {
        v->error("too long integer ascii-constant");
      }
      return intval;
    }
    case 'h':
    case 'H': {
      unsigned char hash[32];
      digest::hash_str<digest::SHA256>(hash, str.data(), str.size());
      return td::bits_to_refint(hash, (v->modifier == 'h') ? 32 : 256, false);
    }
    case 'c': {
      return td::make_refint(td::crc32(td::Slice{str}));
    }
    default:
      tolk_assert(false);
  }
}


struct ConstantEvaluator {
  static bool is_overflow(const td::RefInt256& intval) {
    return intval.is_null() || !intval->signed_fits_bits(257);
  }

  static ConstantValue handle_unary_operator(V<ast_unary_operator> v, const ConstantValue& rhs) {
    if (!rhs.is_int()) {
      v->error("invalid operator, expecting integer");
    }
    td::RefInt256 intval = std::get<td::RefInt256>(rhs.value);

    switch (v->tok) {
      case tok_minus:
        intval = -intval;
        break;
      case tok_plus:
        break;
      case tok_bitwise_not:
        intval = ~intval;
      break;
      case tok_logical_not:
        intval = td::make_refint(intval == 0 ? -1 : 0);
        break;
      default:
        v->error("not a constant expression");
    }

    if (is_overflow(intval)) {
      v->error("integer overflow");
    }
    return ConstantValue::from_int(std::move(intval));
  }

  static ConstantValue handle_binary_operator(V<ast_binary_operator> v, const ConstantValue& lhs, const ConstantValue& rhs) {
    if (!lhs.is_int() || !rhs.is_int()) {
      v->error("invalid operator, expecting integer");
    }
    td::RefInt256 lhs_intval = std::get<td::RefInt256>(lhs.value);
    td::RefInt256 rhs_intval = std::get<td::RefInt256>(rhs.value);
    td::RefInt256 intval;

    switch (v->tok) {
      case tok_minus:
        intval = lhs_intval - rhs_intval;
        break;
      case tok_plus:
        intval = lhs_intval + rhs_intval;
        break;
      case tok_mul:
        intval = lhs_intval * rhs_intval;
        break;
      case tok_div:
        intval = lhs_intval / rhs_intval;
        break;
      case tok_mod:
        intval = lhs_intval % rhs_intval;
        break;
      case tok_lshift:
        intval = lhs_intval << static_cast<int>(rhs_intval->to_long());
        break;
      case tok_rshift:
        intval = lhs_intval >> static_cast<int>(rhs_intval->to_long());
        break;
      case tok_bitwise_and:
        intval = lhs_intval & rhs_intval;
        break;
      case tok_bitwise_or:
        intval = lhs_intval | rhs_intval;
        break;
      case tok_bitwise_xor:
        intval = lhs_intval ^ rhs_intval;
        break;
      case tok_eq:
        intval = td::make_refint(lhs_intval == rhs_intval ? -1 : 0);
        break;
      case tok_lt:
        intval = td::make_refint(lhs_intval < rhs_intval ? -1 : 0);
        break;
      case tok_gt:
        intval = td::make_refint(lhs_intval > rhs_intval ? -1 : 0);
        break;
      case tok_leq:
        intval = td::make_refint(lhs_intval <= rhs_intval ? -1 : 0);
        break;
      case tok_geq:
        intval = td::make_refint(lhs_intval >= rhs_intval ? -1 : 0);
        break;
      case tok_neq:
        intval = td::make_refint(lhs_intval != rhs_intval ? -1 : 0);
        break;
      default:
        v->error("unsupported binary operator in constant expression");
    }

    if (is_overflow(intval)) {
      v->error("integer overflow");
    }
    return ConstantValue::from_int(std::move(intval));
  }

  static ConstantValue handle_reference(V<ast_reference> v) {
    // todo better handle "appears, directly or indirectly, in its own initializer"
    std::string_view name = v->get_name();
    const Symbol* sym = lookup_global_symbol(name);
    if (!sym) {
      v->error("undefined symbol `" + static_cast<std::string>(name) + "`");
    }
    const GlobalConstData* const_ref = sym->try_as<GlobalConstData>();
    if (!const_ref) {
      v->error("symbol `" + static_cast<std::string>(name) + "` is not a constant");
    }
    if (v->has_instantiationTs()) {   // SOME_CONST<int>
      v->error("constant is not a generic");
    }
    return {const_ref->value};
  }

  static ConstantValue visit(AnyExprV v) {
    if (auto v_int = v->try_as<ast_int_const>()) {
      return ConstantValue::from_int(v_int->intval);
    }
    if (auto v_bool = v->try_as<ast_bool_const>()) {
      return ConstantValue::from_int(v_bool->bool_val ? -1 : 0);
    }
    if (auto v_unop = v->try_as<ast_unary_operator>()) {
      return handle_unary_operator(v_unop, visit(v_unop->get_rhs()));
    }
    if (auto v_binop = v->try_as<ast_binary_operator>()) {
      return handle_binary_operator(v_binop, visit(v_binop->get_lhs()), visit(v_binop->get_rhs()));
    }
    if (auto v_ref = v->try_as<ast_reference>()) {
      return handle_reference(v_ref);
    }
    if (auto v_par = v->try_as<ast_parenthesized_expression>()) {
      return visit(v_par->get_expr());
    }
    if (v->try_as<ast_string_const>()) {
      return eval_const_init_value(v);
    }
    v->error("not a constant expression");
  }

  static ConstantValue eval_const_init_value(AnyExprV init_value) {
    // it init_value is incorrect, an exception is thrown
    return visit(init_value);
  }
};

ConstantValue eval_const_init_value(AnyExprV init_value) {
  // at first, handle most simple cases, not to launch heavy computation algorithm: just a number, just a string
  // just `c = 1` or `c = 0xFF`
  if (auto v_int = init_value->try_as<ast_int_const>()) {
    return {v_int->intval};
  }
  // just `c = "strval"`, probably with modifier (address, etc.)
  if (auto v_string = init_value->try_as<ast_string_const>()) {
    if (v_string->is_bitslice()) {
      return {parse_vertex_string_const_as_slice(v_string)};
    } else {
      return {parse_vertex_string_const_as_int(v_string)};
    }
  }
  // something more complex, like `c = anotherC` or `c = 1 << 8`
  return ConstantEvaluator::eval_const_init_value(init_value);
}

} // namespace tolk