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fix, tests: saturated on unsigned

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This commit is contained in:
Agnish Ghosh 2024-04-22 02:29:48 +05:30
parent 0f5abee01d
commit b78fe3e61a
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GPG Key ID: 7E927C221EBA4F6E
2 changed files with 51 additions and 13 deletions
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27
stew/intops.nim
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@ -59,19 +59,13 @@ func addOverflow*(x, y: SomeUnsignedInt, carry: bool):
func addSaturated*(x, y: SomeUnsignedInt): SomeUnsignedInt =
## Add the two integers using saturating arithmetic.
let r = x + y
if r > max(SomeUnsignedInt):
max(SomeUnsignedInt)
let
(p, r) = addOverflow(x, y)
if r:
SomeUnsignedInt.high
else:
r
p
func subSaturated*(x, y: SomeUnsignedInt): SomeUnsignedInt =
## Subtract y from x using saturating arithmetic.
let r = x - y
if r < min(SomeUnsignedInt):
min(SomeUnsignedInt)
else:
r
func subOverflow*(x, y: SomeUnsignedInt):
tuple[result: SomeUnsignedInt, overflow: bool] =
@ -94,6 +88,15 @@ func subOverflow*(x, y: SomeUnsignedInt, borrow: bool):
(c, d) = subOverflow(a, typeof(a)(borrow))
(c, b or d)
func subSaturated*(x, y: SomeUnsignedInt): SomeUnsignedInt =
## Subtract y from x using saturating arithmetic.
let
(p, r) = subOverflow(x, y)
if r:
SomeUnsignedInt.low
else:
p
func mulWiden*(x, y: uint64): tuple[lo, hi: uint64] =
let
x0 = x and uint32.high
@ -153,6 +156,6 @@ func mulSaturated*(x, y: SomeUnsignedInt): SomeUnsignedInt =
let
(a, b) = mulOverflow(x, y)
if b:
max(SomeUnsignedInt)
SomeUnsignedInt.high
else:
a

37
tests/test_intops.nim
View File

@ -23,6 +23,14 @@ template testSubOverflow[T: SomeUnsignedInt]() =
doAssert subOverflow(T.high, T.high, false) == (T(0), false)
doAssert subOverflow(T.high, T.high, true) == (T.high, true)
template testAddSaturated[T: SomeUnsignedInt]() =
doAssert addSaturated(T(100), T(1)) == T(101)
doAssert addSaturated(T.high, T(127)) == T.high
template testSubSaturated[T: SomeUnsignedInt] =
doAssert subSaturated(T(100), T(27)) == T(73)
doAssert subSaturated(T(13), T(127)) == T.low
template testAddOverflow() =
testAddOverflow[uint8]()
testAddOverflow[uint16]()
@ -37,6 +45,20 @@ template testSubOverflow() =
testSubOverflow[uint64]()
testSubOverflow[uint]()
template testAddSaturated() =
testAddSaturated[uint8]()
testAddSaturated[uint16]()
testAddSaturated[uint32]()
testAddSaturated[uint64]()
testAddSaturated[uint]()
template testSubSaturated() =
testSubSaturated[uint8]()
testSubSaturated[uint16]()
testSubSaturated[uint32]()
testSubSaturated[uint64]()
testSubSaturated[uint]()
template testMulWiden[T: SomeUnsignedInt]() =
doAssert mulWiden(T.low, T.low) == (T.low, T.low)
doAssert mulWiden(T(2), T(2)) == (T(4), T(0))
@ -47,7 +69,17 @@ template testMulWiden[T: SomeUnsignedInt]() =
doAssert mulWiden(T.high, T.high, T(0)) == (T(1), T.high - 1)
doAssert mulWiden(T.high, T.high, T.high) == (T(0), T.high)
# TODO testMulOverflow
template testMulSaturated[T: SomeUnsignedInt]() =
doAssert mulSaturated(T(100), T(2)) == T(200)
doAssert mulSaturated(T.high, T(10)) == T.high
template testMulSaturated() =
testMulSaturated[uint8]()
testMulSaturated[uint16]()
testMulSaturated[uint32]()
testMulSaturated[uint64]()
testMulSaturated[uint]()
template testMulWiden() =
testMulWiden[uint8]()
@ -59,7 +91,10 @@ template testMulWiden() =
template test() =
testAddOverflow()
testSubOverflow()
testAddSaturated()
testSubSaturated()
testMulWiden()
testMulSaturated
static: test()