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cvt_ftof(3)
NAME
cvt_ftof - Converts a floating-point data type to another supported
floating-point data type.
SYNOPSIS
#include <cvt.h>
int cvt_ftof(
void *input_val,
int input_type,
void *output_val,
int output_type,
int options );
LIBRARY
Math Library (libm)
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_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 4 bytes
IEEE Little Endian S
Floating
CVT_IEEE_T 8 bytes
IEEE Little Endian T
Floating
CVT_IEEE_X 16 bytes
IEEE Little Endian X
Floating
CVT_BIG_ENDIAN_IEEE_S 4 bytes
IEEE Big Endian S
Floating
CVT_BIG_ENDIAN_IEEE_T 8 bytes
IEEE Big Endian T
Floating
CVT_BIG_ENDIAN_IEEE_X 16 bytes
IEEE Big Endian X
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).
___________________________________________________________________________
Status Condition Option Description
Applicable
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.
___________________________________________________________________________
___________________________________________________________________________
"FORCE" Options Description
Applicable
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.
___________________________________________________________________________
___________________________________________________________________________
Description
Applicable
Conversion
Options for Cray Format
Conversion
___________________________________________________________________________
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).
___________________________________________________________________________
___________________________________________________________________________
Description
Applicable
Conversion
Options for IBM Format
Conversion
___________________________________________________________________________
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
___________________________________________________________________
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 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.)
_________________________________________________________________
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) );
SEE ALSO
ANSII/IEEE Std 754-1985, IEEE Standard for Binary Floating-Point Arithmetic
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Alphabetical
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