Added basic bit manipulation procs to bitops (#10338)

2 files changed, 116 insertions, 1 deletions

diff --git a/lib/pure/bitops.nim b/lib/pure/bitops.nim
index 3f213c5ea..d258a42de 100644
--- a/lib/pure/bitops.nim
+++ b/lib/pure/bitops.nim
@@ -8,7 +8,8 @@
 #
 
 ## This module implements a series of low level methods for bit manipulation.
-## By default, this module use compiler intrinsics to improve performance
+
+## By default, this module use compiler intrinsics where possible to improve performance
 ## on supported compilers: ``GCC``, ``LLVM_GCC``, ``CLANG``, ``VCC``, ``ICC``.
 ##
 ## The module will fallback to pure nim procs incase the backend is not supported.
@@ -32,6 +33,63 @@ const useICC_builtins = defined(icc) and useBuiltins
 const useVCC_builtins = defined(vcc) and useBuiltins
 const arch64 = sizeof(int) == 8
 
+when defined(nimHasalignOf):
+
+  import macros
+
+  type BitsRange*[T] = range[0..sizeof(T)*8-1]
+    ## Returns a range with all bit positions for type ``T``
+
+  proc setMask*[T: SomeInteger](v: var T, mask: T) {.inline.} =
+    ## Returns ``v``, with all the ``1`` bits from ``mask`` set to 1
+    v = v or mask
+
+  proc clearMask*[T: SomeInteger](v: var T, mask: T) {.inline.} =
+    ## Returns ``v``, with all the ``1`` bits from ``mask`` set to 0
+    v = v and not mask
+
+  proc flipMask*[T: SomeInteger](v: var T, mask: T) {.inline.} =
+    ## Returns ``v``, with all the ``1`` bits from ``mask`` flipped
+    v = v xor mask
+
+  proc setBit*[T: SomeInteger](v: var T, bit: BitsRange[T]) {.inline.} =
+    ## Returns ``v``, with the bit at position ``bit`` set to 1
+    v.setMask(1.T shl bit)
+
+  proc clearBit*[T: SomeInteger](v: var T, bit: BitsRange[T]) {.inline.} =
+    ## Returns ``v``, with the bit at position ``bit`` set to 0
+    v.clearMask(1.T shl bit)
+
+  proc flipBit*[T: SomeInteger](v: var T, bit: BitsRange[T]) {.inline.} =
+    ## Returns ``v``, with the bit at position ``bit`` flipped
+    v.flipMask(1.T shl bit)
+
+  macro setBits*(v: typed, bits: varargs[typed]): untyped =
+    ## Returns ``v``, with the bits at positions ``bits`` set to 1
+    bits.expectKind(nnkBracket)
+    result = newStmtList()
+    for bit in bits:
+      result.add newCall("setBit", v, bit)
+
+  macro clearBits*(v: typed, bits: varargs[typed]): untyped =
+    ## Returns ``v``, with the bits at positions ``bits`` set to 0
+    bits.expectKind(nnkBracket)
+    result = newStmtList()
+    for bit in bits:
+      result.add newCall("clearBit", v, bit)
+
+  macro flipBits*(v: typed, bits: varargs[typed]): untyped =
+    ## Returns ``v``, with the bits at positions ``bits`` set to 0
+    bits.expectKind(nnkBracket)
+    result = newStmtList()
+    for bit in bits:
+      result.add newCall("flipBit", v, bit)
+
+  proc testBit*[T: SomeInteger](v: var T, bit: BitsRange[T]): bool {.inline.} =
+    ## Returns true if the bit in ``v`` at positions ``bit`` is set to 1
+    let mask = 1.T shl bit
+    return (v and mask) == mask
+
 # #### Pure Nim version ####
 
 proc firstSetBit_nim(x: uint32): int {.inline, nosideeffect.} =
diff --git a/tests/stdlib/tbitops.nim b/tests/stdlib/tbitops.nim
index d8c6da1d4..b8b44703c 100644
--- a/tests/stdlib/tbitops.nim
+++ b/tests/stdlib/tbitops.nim
@@ -162,6 +162,63 @@ proc main() =
       doAssert( U64A.rotateLeftBits(64) == U64A)
       doAssert( U64A.rotateRightBits(64) == U64A)
 
+  block:
+    # mask operations
+    var v: uint8
+    v.setMask(0b1100_0000)
+    v.setMask(0b0000_1100)
+    doAssert(v == 0b1100_1100)
+    v.flipMask(0b0101_0101)
+    doAssert(v == 0b1001_1001)
+    v.clearMask(0b1000_1000)
+    doAssert(v == 0b0001_0001)
+    v.clearMask(0b0001_0001)
+    doAssert(v == 0b0000_0000)
+  block:
+    # single bit operations
+    var v: uint8
+    v.setBit(0)
+    doAssert v == 0x0000_0001
+    v.setBit(1)
+    doAssert v == 0b0000_0011
+    v.flipBit(7)
+    doAssert v == 0b1000_0011
+    v.clearBit(0)
+    doAssert v == 0b1000_0010
+    v.flipBit(1)
+    doAssert v == 0b1000_0000
+    doAssert v.testbit(7)
+    doAssert not v.testbit(6)
+  block:
+    # multi bit operations
+    var v: uint8
+    v.setBits(0, 1, 7)
+    doAssert v == 0b1000_0011
+    v.flipBits(2, 3)
+    doAssert v == 0b1000_1111
+    v.clearBits(7, 0, 1)
+    doAssert v == 0b0000_1100
+  block:
+    # signed
+    var v: int8
+    v.setBit(7)
+    doAssert v == -128
+  block:
+    var v: uint64
+    v.setBit(63)
+    doAssert v == 0b1000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000_0000'u64
+  block:
+    # Test if RangeError is thrown if indexing out of range
+    try:
+      var v: uint32
+      var i = 32
+      v.setBit(i)
+      doAssert false
+    except RangeError:
+      discard
+    except:
+      doAssert false
+
   echo "OK"
 
 main()