asn1_primitives_getters.h

/*
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Copyright (c) 2023-2025 Institute for Automotive Engineering (ika), RWTH Aachen University
 
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#ifndef ETSI_ITS_MSGS_UTILS_IMPL_ASN1_PRIMITIVES_ASN1_PRIMITIVES_GETTERS_H
#define ETSI_ITS_MSGS_UTILS_IMPL_ASN1_PRIMITIVES_ASN1_PRIMITIVES_GETTERS_H


inline std::vector<bool> getBitString(const std::vector<uint8_t>& buffer, const int bits_unused) {
 
  // bit string size
  const int bits_per_byte = 8;
  const int n_bytes = buffer.size();
  const int n_bits = n_bytes * bits_per_byte;
  std::vector<bool> bits;
  bits.resize(n_bits - bits_unused, 0);
 
  // loop over bytes
  for (int byte_idx = 0; byte_idx < n_bytes; byte_idx++) {
 
    // loop over bits in a byte
    for (int bit_idx_in_byte = 0; bit_idx_in_byte < bits_per_byte; bit_idx_in_byte++) {
 
      // map bit index in byte to bit index in total bitstring
      int bit_idx = bit_idx_in_byte + byte_idx * bits_per_byte;
      if ((byte_idx + 1) >= n_bytes && (bit_idx_in_byte + bits_unused) >= bits_per_byte) break;
 
      // extract bit from bitstring and set output array entry appropriately
      bool byte_has_true_bit = static_cast<bool>(buffer[byte_idx] & (1 << (bits_per_byte - 1 - bit_idx_in_byte)));
      if (byte_has_true_bit) bits[bit_idx] = true;
    }
  }
  return bits;
}
 
#endif  // ETSI_ITS_MSGS_UTILS_IMPL_ASN1_PRIMITIVES_GETTERS_H