diff options
| -rw-r--r-- | lib/pure/bitops.nim | 12 | ||||
| -rw-r--r-- | tests/stdlib/t21564.nim | 28 |
2 files changed, 37 insertions, 3 deletions
diff --git a/lib/pure/bitops.nim b/lib/pure/bitops.nim index a518c25d2..d19c3d248 100644 --- a/lib/pure/bitops.nim +++ b/lib/pure/bitops.nim @@ -63,6 +63,12 @@ macro bitxor*[T: SomeInteger](x, y: T; z: varargs[T]): T = type BitsRange*[T] = range[0..sizeof(T)*8-1] ## A range with all bit positions for type `T`. +template typeMasked[T: SomeInteger](x: T): T = + when defined(js): + x and ((0xffffffff_ffffffff'u shr (64 - sizeof(T) * 8))) + else: + x + func bitsliced*[T: SomeInteger](v: T; slice: Slice[int]): T {.inline, since: (1, 3).} = ## Returns an extracted (and shifted) slice of bits from `v`. runnableExamples: @@ -73,7 +79,7 @@ func bitsliced*[T: SomeInteger](v: T; slice: Slice[int]): T {.inline, since: (1, let upmost = sizeof(T) * 8 - 1 uv = v.castToUnsigned - (uv shl (upmost - slice.b) shr (upmost - slice.b + slice.a)).T + ((uv shl (upmost - slice.b)).typeMasked shr (upmost - slice.b + slice.a)).T proc bitslice*[T: SomeInteger](v: var T; slice: Slice[int]) {.inline, since: (1, 3).} = ## Mutates `v` into an extracted (and shifted) slice of bits from `v`. @@ -85,7 +91,7 @@ proc bitslice*[T: SomeInteger](v: var T; slice: Slice[int]) {.inline, since: (1, let upmost = sizeof(T) * 8 - 1 uv = v.castToUnsigned - v = (uv shl (upmost - slice.b) shr (upmost - slice.b + slice.a)).T + v = ((uv shl (upmost - slice.b)).typeMasked shr (upmost - slice.b + slice.a)).T func toMask*[T: SomeInteger](slice: Slice[int]): T {.inline, since: (1, 3).} = ## Creates a bitmask based on a slice of bits. @@ -96,7 +102,7 @@ func toMask*[T: SomeInteger](slice: Slice[int]): T {.inline, since: (1, 3).} = let upmost = sizeof(T) * 8 - 1 bitmask = bitnot(0.T).castToUnsigned - (bitmask shl (upmost - slice.b + slice.a) shr (upmost - slice.b)).T + ((bitmask shl (upmost - slice.b + slice.a)).typeMasked shr (upmost - slice.b)).T proc masked*[T: SomeInteger](v, mask :T): T {.inline, since: (1, 3).} = ## Returns `v`, with only the `1` bits from `mask` matching those of diff --git a/tests/stdlib/t21564.nim b/tests/stdlib/t21564.nim new file mode 100644 index 000000000..cb06155cf --- /dev/null +++ b/tests/stdlib/t21564.nim @@ -0,0 +1,28 @@ +discard """ +targets: "c js" +""" + +import bitops +import std/assertions + +proc main() = + block: # bug #21564 + # tesk `bitops.bitsliced` patch + doAssert(0x17.bitsliced(4..7) == 0x01) + doAssert(0x17.bitsliced(0..3) == 0x07) + + block: + # test in-place `bitops.bitslice` + var t = 0x12F4 + t.bitslice(4..7) + + doAssert(t == 0xF) + + block: + # test `bitops.toMask` patch via bitops.masked + doAssert(0x12FFFF34.masked(8..23) == 0x00FFFF00) + +main() + +static: + main() |