cvt_ftof - Converts a floating-point data type to another
supported floating-point data type.
#include <cvt.h>
int cvt_ftof(
void *input_val,
int input_type,
void *output_val,
int output_type,
int options );
Math Library (libm)
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_type Data Type Size
------------------------------------------------------------
CVT_VAX_F VAX F Floating 4 bytes
CVT_VAX_D VAX D Floating 8 bytes
CVT_VAX_G VAX G Floating 8 bytes
CVT_VAX_H VAX H Floating 16 bytes
CVT_IEEE_S IEEE Little Endian S 4 bytes
Floating
CVT_IEEE_T IEEE Little Endian T 8 bytes
Floating
CVT_IEEE_X IEEE Little Endian X 16 bytes
Floating
CVT_BIG_ENDIAN_IEEE_S IEEE Big Endian S 4 bytes
Floating
CVT_BIG_ENDIAN_IEEE_T IEEE Big Endian T 8 bytes
Floating
CVT_BIG_ENDIAN_IEEE_X IEEE Big Endian X 16 bytes
Floating
CVT_IBM_SHORT IBM Short Floating 4 bytes
CVT_IBM_LONG IBM Long Floating 8 bytes
CVT_CRAY_SINGLE Cray 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 Status Condition Option Description
Conversion
----------------------------------------------------------------------------
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.
All CVT_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.
All CVT_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.
All CVT_ROUND_TO_ZERO Round the output value toward
zero (truncate).
All CVT_ROUND_TO_POS Round the output value toward
positive infinity.
All CVT_ROUND_TO_NEG Round the output value toward
negative infinity.
----------------------------------------------------------------------------
----------------------------------------------------------------------------
Applicable "FORCE" Options Description
Conversion
----------------------------------------------------------------------------
All CVT_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 Options for Cray Format Conver- Description
Conversion sion
----------------------------------------------------------------------------
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 Options for IBM Format Con- Description
Conversion version
----------------------------------------------------------------------------
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
--------------------------------------------------------------------
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 Name Condition (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 Name Condition (Only reported if the
CVT_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.)
------------------------------------------------------------------
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) );
ANSII/IEEE Std 754-1985, IEEE Standard for Binary Floating-Point
Arithmetic
cvt_ftof(3)
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