mask

Date:

10-12-2011

NAME

_mask, _maskl, _maskr, MASK - Return a bit mask

SYNOPSIS

C

#include <intrinsics.h>

long _mask (long i);
long _maskl (long i);
long _maskr (long i);

Fortran

MASK ([I=]i)

IMPLEMENTATION

Cray Linux Environment (CLE)

STANDARDS

C extension

Fortran extension

DESCRIPTION

C

The _mask function forms a mask of bits set to 1, left-justified or right-justified. If 0 <= i <= 63, a left-justified mask of bits set to 1, i bits long, is formed. Otherwise, a right-justified mask of bits set to 1, (128 - i) bits long, is formed. Value i must be in the range of 0 through 128.

The _maskl function returns a left-justified mask of i bits set to 1. Value i must be in the range of 0 through 64.

The _maskr function returns a right-justified mask of i bits set to 1. Value i must be in the range of 0 through 64.

Because these are intrinsic functions, no externally visible library functions are available for them. The compiler generates inline code to produce the result.

Fortran

The MASK function returns a bit mask of 1’s.

It accepts the following argument:

i

In Fortran, this must be an integer argument, as follows:

  • If i is an 8-bit object, i must be in the range 0 <= i <= 16.

  • If i is a 16-bit object, i must be in the range 0 <= i <= 32.

  • If i is a 32-bit object, i must be in the range 0 <= i <= 64.

  • If i is a 64-bit object, i must be in the range 0 <= i <= 128.

MASK is an elemental function. The name of this function cannot be passed as an argument.

This is an outmoded routine. Refer to the Cray Fortran Reference Manual for information about outmoded features and their preferred standard alternatives.

RETURN VALUES

In C, the mask functions return a 64-bit object.

When i is a 64-bit object, the return values are of the following form:

  • If i is in the range 0 <= i <= 64, a left-justified mask of i bits is returned.

  • If i is in the range 65 <= i <= 128, a right-justified mask of (128 - i) bits is returned.

When i is a 32-bit object, the return values are of the following form:

  • If i is in the range 0 <= i <= 32, a left-justified mask of i bits is returned.

  • If i is in the range 33 <= i <= 64, a right-justified mask of (64 - i) bits is returned.

When i is a 16-bit object, the return values are of the following form:

  • If i is in the range 0 <= i <= 16, a left-justified mask of i bits is returned.

  • If i is in the range 17 <= i <= 32, a right-justified mask of (32 - i) bits is returned.

When i is an 8-bit object, the return values are of the following form:

  • If i is in the range 0 <= i <= 8, a left-justified mask of i bits is returned.

  • If i is in the range 7 <= i <= 16, a right-justified mask of (16 - i) bits is returned.

EXAMPLES

Fortran: The following section of Fortran code shows the MASK function used with several different arguments. The bit patterns of the results are given.

INTEGER I1, I2, I3
...
I1 = MASK(3)
I2 = MASK(64)
I3 = MASK(127)
 -----------------------------------------------------
| 1 | 1 | 1 | 0 | 0 | 0 | 0 |    ...    | 0 | 0 | 0 |
 -----------------------------------------------------
                        I1

 ---------------------------------------------
| 1 | 1 | 1 | 1 |    ...    | 1 | 1 | 1 | 1 |
 ---------------------------------------------
                    I2
 ---------------------------------------------
| 0 | 0 | 0 | 0 |    ...    | 0 | 0 | 0 | 1 |
 ---------------------------------------------
                    I3

SEE ALSO

For a complete list of C intrinsic functions, see the Cray C and C++ Reference Manual.