wsieee754.c File Reference

#include "wsint.h"

Go to the source code of this file.

Macros
#define	WS_IEEE754_SINGLE_EXP_SIZE   8
#define	WS_IEEE754_SINGLE_MANT_SIZE   23
#define	WS_IEEE754_SINGLE_BIAS   127
#define	WS_IEEE754_SINGLE_EXP_MIN   -126
#define	WS_IEEE754_SINGLE_EXP_MAX   127
#define	WS_IEEE754_POSITIVE_INFINITY   0x7f800000

Functions
WsIeee754Result	ws_ieee754_encode_single (double value, unsigned char *buf)
WsIeee754Result	ws_ieee754_decode_single (unsigned char *buf, double *value_return)
WsUInt32	ws_ieee754_single_get_sign (unsigned char *buf)
WsUInt32	ws_ieee754_single_get_exp (unsigned char *buf)
WsUInt32	ws_ieee754_single_get_mant (unsigned char *buf)

Variables
unsigned char	ws_ieee754_nan [4] = {0xff, 0xff, 0xff, 0xff}
unsigned char	ws_ieee754_positive_inf [4] = {0x7f, 0x80, 0x00, 0x00}
unsigned char	ws_ieee754_negative_inf [4] = {0xff, 0x80, 0x00, 0x00}

Macro Definition Documentation

WS_IEEE754_POSITIVE_INFINITY

#define WS_IEEE754_POSITIVE_INFINITY   0x7f800000

Definition at line 82 of file wsieee754.c.

WS_IEEE754_SINGLE_BIAS

#define WS_IEEE754_SINGLE_BIAS   127

Definition at line 77 of file wsieee754.c.

Referenced by ws_ieee754_decode_single(), and ws_ieee754_encode_single().

WS_IEEE754_SINGLE_EXP_MAX

#define WS_IEEE754_SINGLE_EXP_MAX   127

Definition at line 80 of file wsieee754.c.

Referenced by ws_ieee754_encode_single().

WS_IEEE754_SINGLE_EXP_MIN

#define WS_IEEE754_SINGLE_EXP_MIN   -126

Definition at line 79 of file wsieee754.c.

Referenced by ws_ieee754_encode_single().

WS_IEEE754_SINGLE_EXP_SIZE

#define WS_IEEE754_SINGLE_EXP_SIZE   8

Definition at line 75 of file wsieee754.c.

WS_IEEE754_SINGLE_MANT_SIZE

#define WS_IEEE754_SINGLE_MANT_SIZE   23

Definition at line 76 of file wsieee754.c.

Referenced by ws_ieee754_decode_single(), and ws_ieee754_encode_single().

Function Documentation

ws_ieee754_decode_single()

WsIeee754Result ws_ieee754_decode_single	(	unsigned char *	buf,
		double *	value_return
	)

Definition at line 199 of file wsieee754.c.

References WS_IEEE754_NAN, WS_IEEE754_NEGATIVE_INF, WS_IEEE754_OK, WS_IEEE754_POSITIVE_INF, WS_IEEE754_SINGLE_BIAS, ws_ieee754_single_get_exp(), ws_ieee754_single_get_mant(), ws_ieee754_single_get_sign(), and WS_IEEE754_SINGLE_MANT_SIZE.

Referenced by ws_bc_decode().

{
    WsUInt32 sign = ws_ieee754_single_get_sign(buf);
    WsInt32 exp = (WsInt32) ws_ieee754_single_get_exp(buf);
    WsUInt32 mant = ws_ieee754_single_get_mant(buf);
    double value;
    int i;

    /* Check the special cases where exponent is all 1. */
    if (exp == 0xff) {
        if (mant == 0)
            return sign ? WS_IEEE754_NEGATIVE_INF : WS_IEEE754_POSITIVE_INF;

        return WS_IEEE754_NAN;
    }

    /* Expand the mantissa. */
    value = 0.0;
    for (i = 0; i < WS_IEEE754_SINGLE_MANT_SIZE; i++) {
        if (mant & 0x1)
            value += 1.0;

        value /= 2.0;
        mant >>= 1;
    }

    /* Check the `unnormalized' vs. `normal form'. */
    if (exp == 0)
        /* This is a `unnormalized' number. */
        exp = -126;
    else {
        /* This is a standard case. */
        value += 1.0;
        exp -= WS_IEEE754_SINGLE_BIAS;
    }

    /* Handle exponents. */
    while (exp > 0) {
        value *= 2;
        exp--;
    }
    while (exp < 0) {
        value /= 2;
        exp++;
    }

    /* Finally notify sign. */
    if (sign)
        value = -value;

    *value_return = value;

    return WS_IEEE754_OK;
}

ws_ieee754_encode_single()

WsIeee754Result ws_ieee754_encode_single	(	double	value,
		unsigned char *	buf
	)

Definition at line 94 of file wsieee754.c.

References gw_assert(), WS_IEEE754_NEGATIVE_INF, WS_IEEE754_OK, WS_IEEE754_POSITIVE_INF, WS_IEEE754_SINGLE_BIAS, WS_IEEE754_SINGLE_EXP_MAX, WS_IEEE754_SINGLE_EXP_MIN, and WS_IEEE754_SINGLE_MANT_SIZE.

Referenced by read_float_from_exp(), and ws_bc_encode().

{
    int sign = 0;
    WsInt32 exp = 0;
    WsUInt32 mant = 0;
    int i;
    WsIeee754Result result = WS_IEEE754_OK;

    /* The sign bit. */
    if (value < 0.0) {
        sign = 1;
        value = -value;
    }

    /* Scale the value so that: 1 <= mantissa < 2. */
    if (value > 1.0) {
        /* The exponent is positive. */
        while (value >= 2.0 && exp <= WS_IEEE754_SINGLE_EXP_MAX) {
            value /= 2.0;
            exp++;
        }
        if (exp > WS_IEEE754_SINGLE_EXP_MAX) {
            /* Overflow => infinity. */
            exp = 0xff;

            if (sign)
                result = WS_IEEE754_NEGATIVE_INF;
            else
                result = WS_IEEE754_POSITIVE_INF;

            goto done;
        }

        /* The 1 is implicit. */
        value -= 1;
    } else {
        /* The exponent is negative. */
        while (value < 1.0 && exp > WS_IEEE754_SINGLE_EXP_MIN) {
            value *= 2.0;
            exp--;
        }
        if (value >= 1.0) {
            /* We managed to get the number to the normal form.  Let's
                      remote the implicit 1 from the value. */
            gw_assert(value >= 1.0);
            value -= 1.0;
        } else {
            /* The number is still smaller than 1.  We just try to
                      present the remaining stuff in our mantissa.  If that
                      fails, we fall back to 0.0.  We mark exp to -127 (after
                      bias it is 0) to mark this unnormalized form. */
            exp--;
            gw_assert(exp == -127);
        }
    }

    for (i = 0; i < WS_IEEE754_SINGLE_MANT_SIZE; i++) {
        value *= 2.0;
        mant <<= 1;

        if (value >= 1.0) {
            mant |= 1;
            value -= 1.0;
        }
    }

    /* Handle rounding.  Intel seems to round 0.5 down so to be
       compatible, our check is > instead of >=. */
    if (value * 2.0 > 1.0) {
        mant++;
        if (mant == 0x800000) {
            /* This we the really worst case.  The rounding rounds the
               mant up to 2.0.  So we must increase the exponent by one.
               This may then result an overflow in the exponent which
               converts our number to infinity. */
            mant = 0;
            exp++;

            if (exp > WS_IEEE754_SINGLE_EXP_MAX) {
                /* Overflow => infinity. */
                exp = 0xff;
                goto done;
            }
        }
    }

    /* Handle biased exponent. */
    exp += WS_IEEE754_SINGLE_BIAS;

done:

    /* Encode the value to the buffer. */

    mant |= exp << 23;
    mant |= sign << 31;

    buf[3] = (mant & 0x000000ff);
    buf[2] = (mant & 0x0000ff00) >> 8;
    buf[1] = (mant & 0x00ff0000) >> 16;
    buf[0] = (mant & 0xff000000) >> 24;

    return result;
}

ws_ieee754_single_get_exp()

WsUInt32 ws_ieee754_single_get_exp

(

unsigned char *

buf

)

Definition at line 262 of file wsieee754.c.

Referenced by ws_ieee754_decode_single().

{
    WsUInt32 value = buf[0] & 0x7f;

    value <<= 1;
    value |= (buf[1] & 0x80) >> 7;

    return value;
}

ws_ieee754_single_get_mant()

WsUInt32 ws_ieee754_single_get_mant

(

unsigned char *

buf

)

Definition at line 273 of file wsieee754.c.

Referenced by ws_ieee754_decode_single().

{
    WsUInt32 value = buf[1] & 0x7f;

    value <<= 8;
    value |= buf[2];

    value <<= 8;
    value |= buf[3];

    return value;
}

ws_ieee754_single_get_sign()

WsUInt32 ws_ieee754_single_get_sign

(

unsigned char *

buf

)

Definition at line 256 of file wsieee754.c.

Referenced by ws_ieee754_decode_single().

{
    return (buf[0] & 0x80) >> 7;
}

Variable Documentation

ws_ieee754_nan

unsigned char ws_ieee754_nan[4] = {0xff, 0xff, 0xff, 0xff}

Definition at line 86 of file wsieee754.c.

Referenced by ws_bc_encode().

ws_ieee754_negative_inf

unsigned char ws_ieee754_negative_inf[4] = {0xff, 0x80, 0x00, 0x00}

Definition at line 90 of file wsieee754.c.

Referenced by ws_bc_encode().

ws_ieee754_positive_inf

unsigned char ws_ieee754_positive_inf[4] = {0x7f, 0x80, 0x00, 0x00}

Definition at line 88 of file wsieee754.c.

Referenced by ws_bc_encode().