/*
   * There are multiple 16-bit CRC polynomials in common use, but this is
   * *the* standard CRC-32 polynomial, first popularized by Ethernet.
   * x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x^1+x^0
   */
  #define CRCPOLY_LE 0xedb88320
  #define CRCPOLY_BE 0x04c11db7
  
  /* How many bits at a time to use.  Requires a table of 4<<CRC_xx_BITS bytes. */
  /* For less performance-sensitive, use 4 */
  #ifndef CRC_LE_BITS 
  # define CRC_LE_BITS 8
  #endif
  #ifndef CRC_BE_BITS
  # define CRC_BE_BITS 8
  #endif
  
  /*
   * Little-endian CRC computation.  Used with serial bit streams sent
   * lsbit-first.  Be sure to use cpu_to_le32() to append the computed CRC.
   */
  #if CRC_LE_BITS > 8 || CRC_LE_BITS < 1 || CRC_LE_BITS & CRC_LE_BITS-1
  # error CRC_LE_BITS must be a power of 2 between 1 and 8
  #endif
  
  /*
   * Big-endian CRC computation.  Used with serial bit streams sent
   * msbit-first.  Be sure to use cpu_to_be32() to append the computed CRC.
   */
  #if CRC_BE_BITS > 8 || CRC_BE_BITS < 1 || CRC_BE_BITS & CRC_BE_BITS-1
  # error CRC_BE_BITS must be a power of 2 between 1 and 8
  #endif