Decode kmer from 64-bit integer

kmer2str.h

#ifndef KMER2STR_H
#define KMER2STR_H
#include "stdint.h"


#ifndef num2nuc
# ifndef NUM2NUC_STR
#  define NUM2NUC_STR "ACGTN"
# endif
# define num2nuc(x) NUM2NUC_STR[(uint8_t)x]
#endif

/*
 *Fill a buffer with the string for a kmer of a given k.
 *For performance, since the string length will be constant during
 *execution, you must null-terminate your string appropriately beforehand
 *so that you don't have to add it every single time.
 */
inline void kmer2str(uint64_t kmer, int k, char *buf) {
  buf += k;
  while(k) *--buf = num2nuc((kmer >> (2 * --k)) & 0x3u);
}

#endif