Content-type: text/html Man page of cvt_ftof

cvt_ftof

Section: C Library Functions (3)
Index Return to Main Contents
 

NAME

cvt_ftof - Converts a floating-point data type to another supported floating-point data type.  

LIBRARY

Math Library (libm.a)  

SYNOPSIS

#include <cvt.h>

int cvt_ftof(
                 void *input_val,
                 int  input_type,
                 void *output_val,
                 int  output_type,
                 int  options);  

DESCRIPTION

cvt_ftof() converts one floating-point data type to another. Input_val points to the input value to be converted and output_val points to the converted result. The conversion is subject to the options specified in the options (bit field) argument. This function returns a bit field indicating any status conditions.

Input_type and output_type identify the floating-point data type of input_val and output_val as follows:


Input_type/Output_typeData TypeSize

CVT_VAX_FVAX F Floating 4 bytes
CVT_VAX_DVAX D Floating 8 bytes
CVT_VAX_GVAX G Floating 8 bytes
CVT_VAX_HVAX H Floating16 bytes
CVT_IEEE_SIEEE Little Endian S Floating 4 bytes
CVT_IEEE_TIEEE Little Endian T Floating 8 bytes
CVT_IEEE_XIEEE Little Endian X Floating16 bytes
CVT_BIG_ENDIAN_IEEE_SIEEE Big Endian S Floating 4 bytes
CVT_BIG_ENDIAN_IEEE_TIEEE Big Endian T Floating 8 bytes
CVT_BIG_ENDIAN_IEEE_XIEEE Big Endian X Floating16 bytes
CVT_IBM_SHORTIBM Short Floating 4 bytes
CVT_IBM_LONG IBM Long Floating 8 bytes
CVT_CRAY_SINGLECray Single Floating 8 bytes

Provide a zero (0) value to the options argument to select default behavior or choose one or more options (status condition option, rounding options, "FORCE" options, Cray and IBM options) from the tables below as the options argument. Specify only the options that apply to your conversion. A conflicting or incompatible options argument will be reported as an error (CVT_INVALID_OPTION).


Applicable
ConversionStatus Condition OptionDescription

All CVT_REPORT_ALL Report all applicable status conditions as the default. The reporting of recoverable status conditions is disabled by default when this option is not used.


Applicable
ConversionRounding Options Description

AllCVT_ROUND_TO_NEAREST The default rounding mode for conversions to IEEE data types. This IEEE Std. 754 rounding mode results in a representable output value nearest to the infinitely precise result. If the two nearest representable values are equally near, the one with its least significant bit zero is the result.
AllCVT_BIASED_ROUNDING The default rounding mode for conversions to non-IEEE data types. Performs "traditional" style rounding. This mode results in a representable output value nearest to the infinitely precise result. If the two nearest representable values are equally near, the output value is the closest to either positive infinity or negative infinity depending on the sign of the input value.
AllCVT_ROUND_TO_ZERO Round the output value toward zero (truncate).
AllCVT_ROUND_TO_POS Round the output value toward positive infinity.
AllCVT_ROUND_TO_NEG Round the output value toward negative infinity.


Applicable
Conversion"FORCE" Options Description

AllCVT_FORCE_ALL_SPECIAL_VALUES Apply all applicable "FORCE" options for the current conversion.
IEEE CVT_FORCE_DENORM_TO_ZERO Force a denormalized IEEE output value to zero. This option is valid only for conversions to IEEE output values.
IEEE CVT_FORCE_INF_TO_MAX_FLOAT Force a positive IEEE infinite output value to +max_float and force a negative IEEE infinite output value to -max_float. This option is valid only for conversions to IEEE output values.
IEEE or VAX CVT_FORCE_INVALID_TO_ZERO Force an invalid IEEE NaN (not a number) output value or a VAX ROP (reserved operand) output value to zero. This option is valid only for conversions to IEEE or VAX output values.


Applicable
ConversionOptions for Cray Format Conversion Description

Cray CVT_ALLOW_OVRFLW_RANGE_VALUES Allow an input/output exponent value > 60000 (8).
Cray CVT_ALLOW_UDRFLW_RANGE_VALUES Allow an input/output exponent value < 20000 (8).


Applicable
ConversionOptions for IBM Format Conversion Description

IBM CVT_ALLOW_UNNORMALIZED_VALUES Allow unnormalized input arguments. Allow an unnormalized output value for a small value which would normalize to zero.

The maximum representable floating-point values (max_float) for the IEEE_S_Floating, IEEE_T_Floating, IEEE_X_Floating, Big_Endian_IEEE_S_Floating, Big_Endian_IEEE_T_Floating, and Big_Endian_IEEE_X_Floating formats are:


Data Type max_float Value

S_FLOAT Decimal: 3.402823e38
T_FLOAT Decimal: 1.797693134862316e308
X_FLOAT Decimal: 1.189731495357231765085759326628007016196477e4932

 

EXAMPLES

This example converts the value pointed to by big_x which is of type IEEE Big Endian T Floating, to the IEEE Little Endian T Floating data type and stores the result in the location pointed to by little_x. No conversion options are specified.


    status = cvt_ftof( &big_x, CVT_BIG_ENDIAN_IEEE_T,
                       &little_x, CVT_IEEE_T, 0 );

This example converts the value pointed to by x which is of type VAX D Floating, to the IEEE Little Endian T Floating data type and stores the result in the location pointed to by y. Any special IEEE values which would normally be generated will be removed. That is, NaN and Denormalized results will be returned as zero and infinite results will go to +- max_float. In addition, all recordable status conditions will be reported.


    status = cvt_ftof(&x, CVT_VAX_D, &y, CVT_IEEE_T,
          (CVT_FORCE_ALL_SPECIAL_VALUES | CVT_REPORT_ALL) );

 

RETURN VALUES

The return value is a bit field containing the condition codes raised by the function. cvt_ftof() returns CVT_NORMAL; otherwise, it sets one or more of the following recoverable and unrecoverable conditions. Use the following condition names to determine which conditions are set:


Condition NameCondition (Always reported by default)

CVT_INVALID_INPUT_TYPE Invalid input type code.
CVT_INVALID_OUTPUT_TYPE Invalid output type code.
CVT_INVALID_OPTION Invalid option argument.



              
Condition (Only reported if the
Condition NameCVT_REPORT_ALL option is selected)

CVT_RESULT_INFINITE Conversion produced an infinite result. (For conversions to IEEE data types.)
CVT_RESULT_DENORMALIZED Conversion produced a denormalized result. (For conversions to IEEE data types.)
CVT_RESULT_OVERFLOW_RANGE Conversion yielded an exponent > 60000 (8). (For Cray data type conversions.)
CVT_RESULT_UNDERFLOW_RANGE Conversion yielded an exponent < 20000 (8). (For Cray data type conversions.)
CVT_RESULT_UNNORMALIZED Conversion produced an unnormalized result. (For IBM data type conversions and reported
CVT_RESULT_INVALID Conversion result is either ROP (reserved operand), NaN (not a number), or closest equivalent. Cray and IBM data types return 0. (For all data type conversions.)
CVT_RESULT_OVERFLOW Conversion resulted in overflow. (For all data type conversions.)
CVT_RESULT_UNDERFLOW Conversion resulted in underflow. (For all data type conversions.)
CVT_RESULT_INEXACT Conversion resulted in a loss of precision. (For all data type conversions.)

 

RELATED INFORMATION

ANSII/IEEE Std 754-1985, IEEE Standard for Binary Floating-Point Arithmetic delim off


 

Index

NAME
LIBRARY
SYNOPSIS
DESCRIPTION
EXAMPLES
RETURN VALUES
RELATED INFORMATION

This document was created by man2html, using the manual pages.
Time: 02:42:19 GMT, October 02, 2010