#include <ion.h>

uint32_t Ion::crc32PaddedString(const char * s, int length) {
  /* s is a char array. Its length in Bytes is not necessarily a multiple of 4.
   * However, crc32 method awaits input in a form of uint32_t table. To limit
   * the use of additional memory, we compute 2 crc32:
   * - one corresponding to s with a byte length truncated to be a multiple of 4
   * - the other corresponds to the remaining chars in s padded with 0 to be 4
   *   bytes long
   * The CRC32 of s is the crc32 of both. */

  // CRC32 of the truncated string
  uint32_t c[2] = {0, 0};
  size_t crc32TruncatedInputSize = length*sizeof(char)/sizeof(uint32_t);
  c[0] = Ion::crc32((const uint32_t *)s, crc32TruncatedInputSize);

  // CRC32 of the tail of the string
  uint32_t tailName = 0;
  size_t tailLength = length - crc32TruncatedInputSize*sizeof(uint32_t)/sizeof(char);
  strlcpy((char *)&tailName, s+crc32TruncatedInputSize*sizeof(uint32_t)/sizeof(char), tailLength+1); //+1 because strlcpy assures null termination
  c[1] = Ion::crc32(&tailName, 1);

  return Ion::crc32((const uint32_t *)c, 2);
}