/*
 * decn.h
 *
 *  Created on: Mar 21, 2019
 */

#ifndef SRC_DEC_DECN_H_
#define SRC_DEC_DECN_H_

#include <stdint.h>

#define DEC64_NUM_LSU 8
#define DEC80_NUM_LSU 10

//follow IEEE754 standard
#define DEC64_MIN_EXP (-383)
#define DEC64_MAX_EXP (384)

//allow full range, but reserve -16384 for special numbers
#define DEC80_MIN_EXP (-16383)
#define DEC80_MAX_EXP   16383

//decimal64 unpacked into 72 bits
typedef struct {
	int16_t exponent;
	uint8_t lsu[DEC64_NUM_LSU]; //lus[0] holds most-significant 2 nibbles
} dec64;

//decimal80 unpacked into 80 bits
// for computation
typedef struct {
	int16_t exponent; //MSBit is sign of dec80 number, bottom 15 bits are 2's Compl exponent
	uint8_t lsu[DEC80_NUM_LSU]; //lus[0] holds most-significant 2 nibbles
} dec80;

//remove sign bit, and return 15 bit exponent sign-extended to 16 bits
int16_t get_exponent(const dec80* x);

void dec64to80(dec80* dest, const dec64* src);
void dec80to64(dec64* dest, const dec80* src);

void copy_decn(dec80* dest, const dec80* src);

void build_dec64(dec64* dest, const char* signif_str, int16_t exponent);
//void build_dec80(dec80* dest, const char* signif_str, int16_t exponent);

void set_dec64_zero(dec64* dest);
void set_dec80_zero(dec80* dest);
void set_dec64_NaN(dec64* dest);
void set_dec80_NaN(dec80* dest);

void negate_decn(dec80* x);
int8_t compare_decn(dec80* a, dec80* b); //a<b: -1, a==b: 0, a>b: 1
void add_decn(dec80* acc, const dec80* x);

//buf should hold at least 18 + 4 + 5 + 1 = 28
#define DECN_BUF_SIZE 28
void dec80_to_str(char* buf, const dec80* x);
void dec64_to_str(char* buf, const dec64* x);

#endif /* SRC_DEC_DECN_H_ */