 |
HP OpenVMS DCL Dictionary
F$CVUI
Extracts bit fields from character string data and converts the result
to an unsigned number.
Format
F$CVUI (start-bit,number-of-bits,string)
Return Value
The integer equivalent of the extracted bit field, converted as an
unsigned value.
Arguments
start-bit
Specifies the offset of the first bit to be extracted. The low-order
(rightmost) bit of a string is position number 0 for determining the
offset. Specify the offset as an integer expression.
If you specify an expression with a negative value, or with a value
that exceeds the number of bits in the string, DCL displays the
INVRANGE error message.
number-of-bits
Specifies the length of the bit string to be extracted, which must be
less than or equal to the number of bits in the string argument.
If you specify an expression with a negative value, or with a value
that is invalid when added to the bit position offset, DCL displays the
INVRANGE error message.
string
Specifies the character string to be edited.
Example
|
$ A[0,32] = %X2B
$ SHOW SYMBOL A
A = "+..."
$ X = F$CVUI(0,4,A)
$ SHOW SYMBOL X
X = 11 Hex = 0000000B Octal = 00000000013
|
This example uses an arithmetic overlay to assign the hexadecimal value
2B to all 32 bits of the symbol A. The symbol A has a string value
after the overlay because it was previously undefined. (If a symbol is
undefined, it has a string value as a result of an arithmetic overlay.
If a symbol was previously defined, it retains the same data type after
the overlay.) The hexadecimal value 2B corresponds to the ASCII
character "+".
Next, the F$CVUI function extracts the low-order 4 bits from the symbol
A; the low-order 4 bits contain the binary representation of the
hexadecimal value B. These bits are converted, as a signed value, to an
integer. The converted value, 11, is assigned to the symbol X.
|
