iflBitArray(3) Image Format Library C++ Reference Manual iflBitArray(3)NAMEiflBitArray - limited subscriptable bit array class
INHERITS FROM
none, standalone object
HEADER FILE
#include <ifl/iflBitArray.h>
CLASS DESCRIPTION
This class implements a very limited functionality subscriptable bit
array that is used by the image data type converter (iflConverter). The
constructor requires a void* initializer, so a form such as
int from[1024], to[1024];
iflBitArray f = from, t = to;
declares bit "pointers" referencing the int arrays. The bit array can
then be accessed with contructs of the form
floatVal = (float)f[i];
and deposits made with statements such as
t[i] = floatVal; // no cast needed
CLASS MEMBER FUNCTION SUMMARY
Constructor
iflBitArray(void* dp)
Subscripted access
iflBitArray& operator[](int idx)
void operator=(long rhs)
operator long()FUNCTION DESCRIPTIONSiflBitArray()
iflBitArray(void* dp)
Constructs a bit "pointer" that accesses the bit array pointed to by
dp. Use the subscript operator to access elements of the array off
this pseudo-pointer on either the left-hand or right-hand side of an
assignment.
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iflBitArray(3) Image Format Library C++ Reference Manual iflBitArray(3)
operator[]
iflBitArray& operator[](int idx)
The subscript operator stores the byte and bit offsets needed to
access the element specified by idx. This function returns a self-
reference so the real work can be done with the cast and assigment
operators for this class. It works with certain restrictions noted
below.
operator=
void operator=(long rhs)
The assignment operator clears or sets the bit pointed to by the
left-hand side of the assigment. The bit is set if rhs is nonzero,
otherwise it is cleared. By only allowing a long for the right-hand
side, a bit subscript on the right is automatically extracted by
going through the cast operator. C++ converts other types such as
float and short to long without complaining.
operator long
operator long()
The cast operator extracts the (previously remembered) subscripted
bit. Again, C++ fills in all the other type conversions.
NOTES
Due to limitations of the implementation, the same bit "pointer" must not
occur twice in the same assignment (with different subscripts):
t[i] = ~(long)t[j]; // bogus result (depends on order of evaluation)
t[i] = f[j]; // ok even if 't' and 'f' point to same data array
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