Unsigned-saturate
(unsigned-saturate n x) coerces the integer x into an
n-bit unsigned integer by unsigned saturation.
By unsigned saturation, we mean:
- If x is too small (less than 0) it becomes 0.
- If x is too big (2^n or more) it becomes 2^n - 1.
- Otherwise x is unchanged.
unsigned-saturate is actually a macro. Generally it expands into a
call of unsigned-saturate-fn. But, in the common cases where n is
explicitly 8, 16, 32, or 64, it instead expands into a call of an optimized,
inlined function.
Macro: unsigned-saturate
(defmacro unsigned-saturate (n x)
(cond ((eql n 8)
(cons 'unsigned-saturate8
(cons x 'nil)))
((eql n 16)
(cons 'unsigned-saturate16
(cons x 'nil)))
((eql n 32)
(cons 'unsigned-saturate32
(cons x 'nil)))
((eql n 64)
(cons 'unsigned-saturate64
(cons x 'nil)))
(t (cons 'unsigned-saturate-fn
(cons n (cons x 'nil))))))
Subtopics
- Unsigned-saturate-fn
- Logical definition of unsigned-saturate, and also its
executable implementation in the general case.
- Unsigned-saturate8
- Optimized implementation of 8-bit unsigned saturation.
- Unsigned-saturate64
- Optimized implementation of 64-bit unsigned saturation.
- Unsigned-saturate32
- Optimized implementation of 32-bit unsigned saturation.
- Unsigned-saturate16
- Optimized implementation of 16-bit unsigned saturation.
