path: root/src/pack2b.c

#include <stdio.h>
#include <ctype.h>
#include <stdarg.h>
#include <string.h>
#include <stdint.h>
#include <inttypes.h>
#include "pack2b.h"

/*
** pack754() -- pack a floating point number into IEEE-754 format
*/ 
uint64_t pack754(long double f, unsigned bits, unsigned expbits)
{
	long double fnorm;
	int shift;
	long long sign, exp, significand;
	unsigned significandbits = bits - expbits - 1; // -1 for sign bit

	if (f == 0.0) return 0; // get this special case out of the way

	// check sign and begin normalization
	if (f < 0) { sign = 1; fnorm = -f; }
	else { sign = 0; fnorm = f; }

	// get the normalized form of f and track the exponent
	shift = 0;
	while(fnorm >= 2.0) { fnorm /= 2.0; shift++; }
	while(fnorm < 1.0) { fnorm *= 2.0; shift--; }
	fnorm = fnorm - 1.0;

	// calculate the binary form (non-float) of the significand data
	significand = fnorm * ((1LL<<significandbits) + 0.5f);

	// get the biased exponent
	exp = shift + ((1<<(expbits-1)) - 1); // shift + bias

	// return the final answer
	return (sign<<(bits-1)) | (exp<<(bits-expbits-1)) | significand;
}

/*
** unpack754() -- unpack a floating point number from IEEE-754 format
*/ 
long double unpack754(uint64_t i, unsigned bits, unsigned expbits)
{
	long double result;
	long long shift;
	unsigned bias;
	unsigned significandbits = bits - expbits - 1; // -1 for sign bit

	if (i == 0) return 0.0;

	// pull the significand
	result = (i&((1LL<<significandbits)-1)); // mask
	result /= (1LL<<significandbits); // convert back to float
	result += 1.0f; // add the one back on

	// deal with the exponent
	bias = (1<<(expbits-1)) - 1;
	shift = ((i>>significandbits)&((1LL<<expbits)-1)) - bias;
	while(shift > 0) { result *= 2.0; shift--; }
	while(shift < 0) { result /= 2.0; shift++; }

	// sign it
	result *= (i>>(bits-1))&1? -1.0: 1.0;

	return result;
}

/*
** packi16() -- store a 16-bit int into a char buffer (like htons())
*/ 
void packi16(uint8_t *buf, int16_t i)
{
	uint16_t i2 = i;

	*buf++ = i2>>8; *buf++ = i2;
}

/*
** packi32() -- store a 32-bit int into a char buffer (like htonl())
*/ 
void packi32(uint8_t *buf, int32_t i)
{
	uint32_t i2 = i;

	*buf++ = i2>>24; *buf++ = i2>>16;
	*buf++ = i2>>8;  *buf++ = i2;
}

/*
** packi64() -- store a 64-bit int into a char buffer (like htonl())
*/ 
void packi64(uint8_t *buf, int64_t i)
{
	uint64_t i2 = i;

	*buf++ = i2>>56; *buf++ = i2>>48;
	*buf++ = i2>>40; *buf++ = i2>>32;
	*buf++ = i2>>24; *buf++ = i2>>16;
	*buf++ = i2>>8;  *buf++ = i2;
}

/*
** unpacki16() -- unpack a 16-bit int from a char buffer (like ntohs())
*/ 
int16_t unpacki16(uint8_t *buf)
{
	uint16_t i2 = ((uint16_t)buf[0]<<8) | buf[1];
	int16_t i;

	// change unsigned numbers to signed
	if (i2 <= 0x7fffu) { i = i2; }
	//else { i = -(int16_t)((uint16_t)0xffff - i2 + (uint16_t)1u); }
	else { i = -1 - (uint16_t)(0xffffu - i2); }

	return i;
}

/*
** unpacki32() -- unpack a 32-bit int from a char buffer (like ntohl())
*/ 
int32_t unpacki32(uint8_t *buf)
{
	uint32_t i2 = ((uint32_t)buf[0]<<24) | ((uint32_t)buf[1]<<16) |
	              ((uint32_t)buf[2]<<8)  | buf[3];
	int32_t i;

	// change unsigned numbers to signed
	if (i2 <= 0x7fffffffu) { i = i2; }
	else { i = -1 - (int32_t)(0xffffffffu - i2); }

	return i;
}

/*
** unpacki64() -- unpack a 64-bit int from a char buffer (like ntohl())
*/ 
int64_t unpacki64(uint8_t *buf)
{
	uint64_t i2 = ((uint64_t)buf[0]<<56) | ((uint64_t)buf[1]<<48) |
	              ((uint64_t)buf[2]<<40) | ((uint64_t)buf[3]<<32) |
	              ((uint64_t)buf[4]<<24) | ((uint64_t)buf[5]<<16) |
	              ((uint64_t)buf[6]<<8)  | buf[7];
	int64_t i;

	// change unsigned numbers to signed
	if (i2 <= 0x7fffffffffffffffu) { i = i2; }
	else { i = -1 -(int64_t)(0xffffffffffffffffu - i2); }

	return i;
}

/*
** pack() -- store data dictated by the format string in the buffer
**
**  c - 8-bit signed int     h - 16-bit signed int
**  l - 32-bit signed int    f - 32-bit float
**  L - 64-bit signed int    F - 64-bit float
**  s - string (16-bit length is automatically prepended)
*/ 
int32_t pack(uint8_t *buf, char *format, ...)
{
	va_list ap;
	int16_t h;
	int32_t l;
	int64_t L;
	int8_t c;
	float32_t f;
	float64_t F;
	char *s;
	int32_t size = 0, len;

	va_start(ap, format);

	for(; *format != '\0'; format++) {
		switch(*format) {
		case 'h': // 16-bit
			size += 2;
			h = (int16_t)va_arg(ap, int); // promoted
			packi16(buf, h);
			buf += 2;
			break;

		case 'l': // 32-bit
			size += 4;
			l = va_arg(ap, int32_t);
			packi32(buf, l);
			buf += 4;
			break;

		case 'L': // 64-bit
			size += 8;
			L = va_arg(ap, int64_t);
			packi64(buf, L);
			buf += 8;
			break;

		case 'c': // 8-bit
			size += 1;
			c = (int8_t)va_arg(ap, int); // promoted
			*buf++ = (c>>0)&0xff;
			break;

		case 'f': // float
			size += 4;
			f = (float32_t)va_arg(ap, double); // promoted
			l = pack754_32(f); // convert to IEEE 754
			packi32(buf, l);
			buf += 4;
			break;

		case 'F': // float-64
			size += 8;
			F = (float64_t)va_arg(ap, float64_t);
			L = pack754_64(F); // convert to IEEE 754
			packi64(buf, L);
			buf += 8;
			break;

		case 's': // string
			s = va_arg(ap, char*);
			len = strlen(s);
			size += len + 2;
			packi16(buf, len);
			buf += 2;
			memcpy(buf, s, len);
			buf += len;
			break;
		}
	}

	va_end(ap);

	return size;
}

/*
** unpack() -- unpack data dictated by the format string into the buffer
*/
void unpack(uint8_t *buf, char *format, ...)
{
	va_list ap;
	int16_t *h;
	int32_t *l;
	int64_t *L;
	int32_t pf;
	int64_t pF;
	int8_t *c;
	float32_t *f;
	float64_t *F;
	char *s;
	int32_t len, count, maxstrlen=0;

	va_start(ap, format);

	for(; *format != '\0'; format++) {
		switch(*format) {
		case 'h': // 16-bit
			h = va_arg(ap, int16_t*);
			*h = unpacki16(buf);
			buf += 2;
			break;

		case 'l': // 32-bit
			l = va_arg(ap, int32_t*);
			*l = unpacki32(buf);
			buf += 4;
			break;

		case 'L': // 64-bit
			L = va_arg(ap, int64_t*);
			*L = unpacki64(buf);
			buf += 8;
			break;

		case 'c': // 8-bit
			c = va_arg(ap, int8_t*);
			if (*buf <= 0x7f) { *c = *buf;}
			else { *c = -1 - (uint8_t)(0xffu - *buf); }
			buf++;
			break;

		case 'f': // float
			f = va_arg(ap, float32_t*);
			pf = unpacki32(buf);
			buf += 4;
			*f = unpack754_32(pf);
			break;

		case 'F': // float-64
			F = va_arg(ap, float64_t*);
			pF = unpacki64(buf);
			buf += 8;
			*F = unpack754_64(pF);
			break;

		case 's': // string
			s = va_arg(ap, char*);
			len = unpacki16(buf);
			buf += 2;
			if (maxstrlen > 0 && len > maxstrlen) count = maxstrlen - 1;
			else count = len;
			memcpy(s, buf, count);
			s[count] = '\0';
			buf += len;
			break;

		default:
			if (isdigit(*format)) { // track max str len
				maxstrlen = maxstrlen * 10 + (*format-'0');
			}
		}

		if (!isdigit(*format)) maxstrlen = 0;
	}

	va_end(ap);
}